Construction and Design
of Prestressed Concrete Segmental Bridges
Walter Podolny, Jr., Ph.D., P.E.
Bridgc Division
()Hicc
Ellgineering
h'dcr;ti II iglll\'d Y :\d millisl ratioll
L' .S. Depart illenl 01 Tr;lIls[Jortalioll
or
Jean M. Muller
(:llaillll;11I (lilhe Board
Figg alld ),[uJkr Ellgincers, [Ill.
BR1T"
LEM".
-9 AUG 1982
82/19656
A Wiley-Intersdence Publication
John Wiley & Sons
New York
Chichester
Brisbane
Toronto
Singapore
Copyright
©
1982 by john Wiley & Sons, Inc.
All rights reserved. Published simuhaneollsly in Canada.
Reproduction or translation of any part of this work beyond
that permitted by Section 107 or 108 of the 1976 United
States Copyright Act without the permission of the copyright
owner is unlawful. Requests for permission or further
information should be addressed to the Permissions
Department. john Wilt·)' & Sons, Inc
Library of Congress Cataloging in Publication Data:
Podoln)', Walter.
Construction and design of prestressed concrete
segmental bridges.
(Wiley series of practical construction guides
ISSN 0271-6011)
"A Wiley-Interscience publication."
Includes index.
I. Bridges, Concrete-Design and construction.
2. Prestressed concrete construction. I. Muller, jean M.
II. Title. III. Series.
81-13025
AACR2
TG355.P63
624.2
ISBN 0·471-05658-8
Printed in the United States of America
10 9
·d e
.
-------- .-------­
8
7
6
5 4
3
2
-- - ---­
..
...
Series Preface
The Wiley Series of Practical Construction Guides
provides the working constructor with up-to-date
information that can help to increase the job profit
margin. These guidebooks. which are scaled
mainly for practice, but include the necessary
theory and design. should aid a construction con­
tractor in approaching I\ork problems I\'it h more
knowledgeable confidence, The guides should be
useful also to engineers. architects. planners.
specification writers. project managers, superin­
tendents, materials and equipment manufacturers
and, the source of all these callings, instructors and
their students.
Construction in the United States alone will
reach $250 billion a year in the early I980s. In all
nations, the business of building will continue to
grow at a phenomenal rate, because the population
proliferation demands !1('I\ living. I\'orking. and
recreational facilities. This construction will have
to be more substantial. thus demanding a more
professional performance from the contractor. Be­
fore science and technology had seriously affected
the ideas, job plans, financing, and erection of
structures, most contractors developed their
know-how by field trial-and-error. Wheels, small
and large, were constantly being reinvented in all
St'C(ors. bccause there ,\as no interchange of
knmdedge. The current complexity of cOlIStru{'­
tion. even in more rural areas, has revealed a dear
need for more proficient. professional methods
and tools in both practice and learning,
Because construction is highly competitive. sOllle
practical technologv is necessarily proprietary. BUI
most practical day-to-day problems are common to
the whole construction industry. These are the
subjects for the Wiley Practical Construction
Guides.
M. D.
MORRIS.
P.E.
v
Preface
Prestressed concrete segmental bridge construc­
tion has evolved, in the natural course of events,
from the combining of the concepts of prestress­
ing, box girder design, and the cantilever method
of bridge construction. It arose from a need to
Qvercoml: construnion difficulties in spalIning
deep valleys and river crossmgs without the use of
conventional falsework, which in some instances
may be impractical, economically prohibitive, or
detrimental to environment and ecology.
Contemporary prestressed, box girder, seg­
mental bridges began in Western Europe in the
1950s. Ulrich Finsterwalder in 1950, for a cross­
ing of the Lahn River in Balduinstein, Germany,
was the first to apply cast-in-place segmental con­
struction to a bridge. In 1962 in France the first
application of precast. segmental, box girder COll­
struction was made by Jean Muller to the Choisy­
Le-Roi Bridge crossing the Seine River. Since then
the concept of segmental bridge construction has
been improved and rdined and has spread from
Europe throughout most of the world.
The first application of segmental bridge con­
struction in North America was a cast-in-place
segmental bridge on the Laurentian Autoroute
near Ste..\dele. Qllebec. in 1964. This was fol­
lowed in 1967 by a precast segmental bridge cross­
ing the Lievre River near ~otre Dame du Laus,
Quebec. In 1973 the first U.S. precast segmental
bridge was ope lied to traffic in Corpus Christi.
Texas, followed a year later by the cast-in-place
segmental Pine Valley Bridge near San Diego,
California. As of this date (1981) in the United
States more than eighty segmental bridges are
completed, in construction, in design, or under
consideration.
Prestressed concrete segmental bridges may be
identified as precast or cast in place and cat­
egorized by method of construction as balanced
cantilever, span-by-span, progressive placement,
or incremental launching. This type of bridge has
extended the practical and competitive economic
span range of concrete bridges. It is adaptable to
almost any conceivable site condition.
The objective of this book is to summarize in one
volume the current state of the art of design and
constrllction methods for all I ypc,; of segmelHal
bridges as a ready reference source for ellgillcer­
ing faculties, practicing engineers, contractors, and
local, state, and federal bridge engineers.
Chapter I is a quick review of the historical evo­
lution to the current state of the art. It bITers the
student an appreciation of the way in which seg­
mental construction of bridges developed, thc
factors that influenced its development, and the
various techniques used in constructing segmental
bridges.
Chapters 2 and 3 present case ,tudies of the pre­
dominant methodology oi constructing segmental
bridges by balanced cantilever in both cast-in-place
and precast concrete. Conception and design of
the superstructure and piers, respectively, are dis­
cussed in Chapters 4 and 5. The other three ba­
sic methods of constructing segmental bridges­
progressive placement, span-by-span, and incre­
mental launching-are presented in Chapters 6
and i.
Chapters 2 through i deal essentially with girder
type bridges. However, segmental construction
may also be applied to bridges of other types.
Chaprer 8 discusses application of thc segmcntal
concept to arch, rigid frame, and truss bridges.
Chapter 9 deals with the cable-stayed type of
bridge and Chapter 10 with railroad bridges. The
practical aspects of fabrication, handling, and
erection of segments are discussed in Chapter II.
In selected a bridge type for a particular site, one
of the more important parameters is economics.
Economics, competitive bidding, and contractual
aspects of segmental construction are discussed in
Chapter 12.
Most of the material presented in this book is not
vii
-
viii
Preface
original. Although acknowledgment of all the
many sources is not possible, full credit is given
wherever the specific source can be identified.
Every effort has been made to eliminate errors;
the authors will appreciate notification from the
reader of any that remain.
The authors are indebted to numerous publica­
tions, organizations, and individuals for their
assistance and permission to reproduce photo­
.."iiliiI...........
__•_ _ _ _ _ _ ---·--­
graphs, tables. and other data. Wherever possible.
credit is given in the text.
WALTER PODOLNY, JR.
JEAN M. MULLER
Burkt, 1'h-~i1/i(J
Pans, France
january 1982
Contents
1 Prestressed Concrete Bridges and
Segmental Construction
2.8
2.9
2.10
2.11
2.12
1
Introduction, 1
Development of Cantilever
Construction, 2
Evolution ()f Prestressed
1.3
Concrete, 4
1,4
Evolution of Prestressed Concrete
Bridges, 5
1.5
Long-Span Bridges with
Conventional Precast
Girders. R
1.6
Segmental Construction, 10
1.7
Various Types of Structures, 12
1.8
Cast-in-Place and Precast
Seg-mental Construction, 17
1.9
Various \Ici hods of
Construction, 18
1.10 Applications of Segmental
Construction in the Cnited
States, 26
1.11 Applicability and Advantages of
Segmental Construction, 28
References, 30
1.1
1.2
~,
13
2.14
2.15
2.lG
3
Precast BaLanced Cantilever Girder
Bridges
:U
3,2
:5.3
3.-1:
:~,5
2 Cast-In-Place Balanced Cantilever Girder
Bridges
2.1
2,2
2.3
2,4
2.5
2.6
2.7
Introduction, ~~ 1
Bendorf Bridge, German" 35
Saint Adele Bridge, Canada, 37
BOllguen Bridge in Brest and
Llcroix Falgarde Bridge,
France, 38
Saint Jean Bridge over the
Garonne River at Bordeaux,
France. 41
Siegtal and Kochertal Bridges.
Germany, 43
Pine Valley Creek Bridge,
U.S.A.,46
J.b
31
Gennevilliers Bridge, France, 52
Grand';"'fere Bridge, Canada, 55
Arnhem Bridge, Holland, 58
:-';apa River Bridge, C.S.A., 59
Koror-Babelthuap, C.S. Pacific
Trust Territon', 61
Vejle \'jord Bridge,
Denmark, 63
Houston Ship Channel Bridge,
C.s.A.,68
Other ~otable Structures, 71
Conclusion, 81
References, 81
;~,7
:L8
:t9
3.1 ()
;) .11
:U2
3.13
3.14
3.15
3.16
82
I III roclllU iOIl , 82
Choisy Le Roi Bridge and Other
Structures in Greater Paris,
France, 83
Pierre Benite Bridges near Lyons,
France, 89
Other Precast Segmental Bridges
in Paris, 91
Oleron Viaduct, France, 96
Chillon Viaduct, Switzerland, 99
Hartel Bridge, Holland, 103
Rio-~iteroi Bridge, Brazil, 106
Bear River Bridge, Canada, 108
J FK ;"'lell1orial Cause\\ay,
U.S.A., 109
Saint Andre de Cubzac Bridges,
France. 113
Saint Cloud Bridge, France, 114
Sallingsund Bridge,
Denmark, 122
B-3 South Viaducts, France, 124
Alpine ~Iotorway Structures,
France, 129
Bridge over the Eastern Scheidt,
Holland, 134
IX
Contents
x
3.17
3.18
4 Design of Segmental Bridges
4.1
4.2
4.3
4.4
4.5
4.6
4.7
4.8
4.9
4.10
4.11
4.12
4.13
4.14
4.15
4.16
4.17
4.18
4.19
5.4
5.6
5.7
Introduction, 225
Loads Applied to the Piers, 230
Suggestions on Aesthetics of Piers
and Abutments, 232
Moment-Resisting Piers and
Their Foundations, 234
........
iI' ...._ .. _._._ _ _ _ _ _
~.--~
-------­
5.8
5.9
148
Introduction, 148
Live Load Requirements, 149
Span Arrangement and Related
Principle of Construction, 149
Deck Expansion, Hinges, and
Continuity, 151
Type, Shape and Dimensions of
the Superstructure, 159
Transverse Distribution of Loads
Between Box Girders in ~1ultibox
Girders, 164
Effect of Temperature Gradients
in Bridge Superstructures, 170
Design of Longitudinal Members
for Flexure and Tendon
Profiles, 173
Ultimate Bending Capacity of
Longitudinal Members, 190
Shear and Design of Cross
Section. 193
Joints Between Match-Cast
Segments, 199
Design of Superstructure Cross
Section, 202
Special Problems in
Superstructure Design, 203
DeAections of Cantilever Bridges
and Camber Design, 205
Fatigue in Segmental
Bridges, 210
Provisions for Future
Prestressing, 212
Design Example, 212
Quantities of Materials, 219
Potential Problem Areas, 220
References, 224
5 Foundations, Piers, and Abutments
5.1
5.2
5.3
5.5
Captain Cook Bridge,
Australia, 136
Other Notable Structures, 139
References, 147
6
Progressive and Span-by-Span
Construction of Segmental Bridges
6.1
6.2
6.3
6.4
6.5
6.6
7
7.5
7.G
7.7
7.8
7.9
7.10
225
8.3
8.4
8.5
8.6
321
Illlrodunioll.321
Rio Carolli, Venezuela, 323
Val Resle! Viaduct, Italy, 327
Ravensbosch Valley Bridge.
Holland, 329
Olifant's River Bridge, South
Africa, 331
Various Bridges ill France. 333
Wabash River Bridge, U.S.A., 335
Other ~otable Bridges. 338
Design of Incrementall)
Launched Bridge~. 34::1
Demolition of a Structure by
Incremental La~nching, 352
References, 352
Concrete Segmental Arches, Rigid
Frames, and Truss Bridges
8.1
8.2
281
Introduction, 281
Progressive Cast-i n- Place
Bridges, 283
Progressive Precast Bridges, 289
Span-by-Span Cast-in-Place
Bridges, 293
Span-by-Span Precast
Bridges, 308
Design Aspects of Segmental
Progressive Const ruction, 314
References, 319
Incrementally Launched Bridges
7.1
7.2
7.3
7.4
8
Piers with Double Elastomeric
Bearings, 241
Piers with Twin Flexible Legs, 253
Flexible Piers and Their Stability
During Construction, 263
Abutments. 271
Effect of Differential Settlements
on Continuous Decks, 276
References, 280
Introduction, 354
Segmental Precast Bridges over
the Marne River, France, 357
Caracas Viaducts, Venezuela, 363
Gladesville Bridge, Australia, 371
Arches Built in Cantilever, 374
Rigid Frame Bridges, 382
354
xi
Contents
8.7
9 Concrete Segmental Cable-Stayed Bridges
9.1
9.2
9.3
9.1
9.5
9.6
9.7
9.8
9,9
11
Truss Bridges, 392
References. 399
Technology and Construction of
Segmental Bridges
Il.l
11.2
400
Introuuction,400
Lake Maracaibo Bridge,
Venezuela. 405
Wadi Kuf Bridge, Libya. 407
Chaco/Corrientes Bridge,
Argentina, 408
\lainbrticke, GermallV, 410
Tiel Bridge. ~etherlands. 412
Pasco-Kennewick Bridge.
C.S.A., 418
BrolOnne Bridge, France. 41!:l
Dalluhe Canal Bridge,
11.3
11.1
11.5
11.6
11.7
:\ll~lri;l, '1~7
9.10
10
~()table
Examples of
Concepls, 4:W
Referellces, 439
Segmental Railway Bridges
Illtl'OdllUioll 10 Panicubr
:\spects of Rail\Va~ Bridges and
Field of Applicatioll, 441
IO,':!
La VOlllte Bridge over the
Rholle Ri\'('l'. Frallct'. 4·12
10.:l
\Ior:llld Bridge III L\om,
Frallce,442
IO,,!
Cerg\ POlltoise Bridge Ileal'
":Iris, Frallce, ·'·H
10,5
:-'!allle La Vallee and Torn
Bridges for the ~e\V Express
Lille lIeal' Paris, Fl'allce, 444
!(Ui
Clichy Bridge Ileal' Paris,
Frallce, ·l!q
10.7
Oidaill's Bridge, SOllth
:\frica, '1:)2
1O.H
[ncremental" Lallllched
R;lil\\';!\ Bri(
for the
High-Speed Line, Paris to
Lmlls, France, 45:~
10.9
Segll1ental Raih,'av Brid~es ill
Japall,457
to, 1() Special Oe'iign A~ peets of
Segmenral Railwav Bridges, 458
10.11 Proposed Concepts for Future
Segmental Railwav Bridges, 404
11.8
441
12
IO.l
l~.l
12,,~
13
Scope and Introduction. 465
Concrete and Formwork for
Segmental Construction. 466
Post-tensioning Materials and
Operations, 470
Segment Fabrication for
Cast-In-Place Cantilever
Construction, 475
Characteristics of Precast
Segmellts and \Iatch-Cast
Epoxy Joints. 485
\1anufacture of Precast
Segments, 493
Handling and Temporan
:\ssclllhh of Preca,1
Segments, 507
Placing Precast Segments, 50!}
References. 517
Economics and Contractual Aspects of
Segmental Construction
12.2
1:3.4
LL")
13,6
Index
Index
Index
Index
518
Bidding Procedures, 518
Exam pies of Some Interest illg
Biddillgs alld Costs, 523
j lit I CI,C ill EITlticll(\ ill
Concrete Bridge~, 528
References, 535
Future Trends and Developments
1:3.1
1:),2
1:3,:~
465
536
Introductiol1,536
~!aterials, 536
Segmental Application to
Bridg;e Decks, 542
Se~l11enlal Bridge Piers and
Substructures, 543
Application to Existing or :\ew
Bridge I) pe~, ij·H
Summary, 548
References, ;")49
of Bridges
of Personal Names
of Firms and Organizations
of Subjects
551
555
557
559
1
Prestressed Concrete Bridges
and Segmental Construction
1.1
1.2
1.3
1.4
1.5
INTRODUCTION
DEVELOP!'v1ENT OF CANTILEVER CONSTRUCTION
EVOLUTION OF PRESTRESSED CONCRETE
EVOLUTION OF PRESTRESSED CONCRETE BRIDGES
LONG-SPAN BRIDGES WITH CONVENTIONAL PRE­
CAST GIRDERS
1.6 SEGMENTAL CONSTRUCTION
1.7 VARIOUS TYPES OF STRUCTURES
1.7.1 Girder Bridges
1.7.2 TnJsses
1.7.3 Frarn(>, with Slant I.(>~,
1.7.4 Concrete Arch Bridges
1.7.5 Concrete Cable-Stayed Bridges
1.8 CAST-IN-PLACE AND PRECAST SEGMENTAL CON­
STRUCTION
1.1
Introduction
The conception, development, and worldwide ac­
ceptance of seglllental c()n~trllcti()n in till' field or
prestressed concrele bridges represents one 01 the
most intere~ting and illlport;lIlt achievelllents in
civil engineering durillg the past thirtv \ears. Rec­
ognized to<i;l\ in all COlllltries ;111d particlilariv ill
the United States as a sale, praCTical, and econolllic
construction method, the seglllental concept prob­
ably owes its rapid growth and acceptance to its
founding, frOl1l the I)eginning, on sound construc­
tion principles sllch as cantile\'er construction.
Using this method, a bridge structure is made up
of concrete elements usually called segments
(either precast or cast in place in their final position
in the structure) assembled by post-tensioning. If
the bridge is cast in place, Figure 1.1, travelers are
used to allow the various segments to be con­
structed in successive increments and progressively
1.8.1
1.8.2
1.8.3
1.9
1.10
1.11
Characteristics of Cast-in-Place Segments
Characteristics of Precast Segments
Choice between Cast-in-ptace and Precast
ConstnJction
VARIOUS METHODS OF CONSTRUCTION
1.9.1 Cast-in-Place Balanced Cantilever
1.9.2 Precast Balanced Cantilever
1.9.3 Span-by-Span ConstnIction
1.9.4 Progressive Placement ConstnIction
1.9.5 Incremental Launching or Push-Out ConstnJction
.\PPUCATTONS OF SEGMDITAL CONSTRUCTTON
IN THE UNITED STATES
APPLICABILITY AND ADVANTAGES OF SEGMEN­
TAL CONSTRUCTION
REFERENCES
prestressed together. II the bridge is precast, seg­
Illent.s are Illanufactured in a special casting vanl
or factory, transported to their final position, and
placed ill the structure bv various tvpes or lallnch-
FIGURE 1.1
Cast-in place form traveler.
1
I
2
Prestressed Concrete Bridges and Segmental Construction
FIGURE 1.2. Olcron Vi'HIlIct, scgllH'llIal (ollSlrllclioll ill progress. 011\' t"pical
P)('CISI seglllt'llt placcd jll tile 01('1"011 Vi;,dllCl.
Ill).; equiplllent. Figure
l.~, while prestressing
.!lhincs the ;t;,-,;clIlhly al1d prmides the stnJcturai
strellgth.
\1ost carl\' seglllelltal bridges were huill as call'
tilc\'crs, where construction procceds ill a S\'l1lIIlet­
rical fashion from the bridge picrs ill sllccessi\(' ill­
('n'lIlcllts to cOlllplete each spall and lil1al!\ the
eillire superstructure, Figure 1.3. Later, olher COII­
,tructioll methods appeared in conjunction with
FIGURE 1.3. Cantil<'\er (omtrucliol1 applied to pre­
st ressed concrete bridges.
the scglllelital cOllCept to IUrlhcr it, !icld of appli­
C;1t io 11.
1.2
Developmerrt oj Cantilever Construction
The idea ofcalltile\'er (ollstrllctioJl is anciellt ill the
Oriellt. Shogun';, Bridge located ill thc cit\ of'
.'\'ikko, Japall, is the eadicst recorded GtlltileHT
bridge ,Illd dates b;lck 10 the fOlll'1!J CeIJtlIr~. The
Wall<iipol'c Bridge, Figure lA, was built ill tlte
sc\'clIteellth century in Bhutall, betweell lndia and
Tibet. It is constructed frolll great timbers that
arc corbeled OUt IowaI'd each othcr from mas·
si\e abut mellts and thc narrowed illlen al fillall\'
capped with a light beam. 1
FIGURE 104.
Wandipore Bridge.
Development of Call t ilever Constmdion
Tholllas Pope, a :\ew York Clrpenter, was ~() in­
spired b\' these structures that he used the concept
in his "Fhing Le\cr Bridge," In IH [0 he built a 50
ft ([5 rn) model on a scale of ~ in, to I It ([ to 3~ 111)
represellting half of a proposed IHOO ft (549 Ill)
span. It was to be a single wooden structure cr()sS~
ing the Hudson River near New York City, Figure
1.5. According to witnesses the 50 ft ([5 Ill) unsup­
ported arm withstood a [0 ton (9 1111) weight. Pope
puhlished the design of his daring and interesting
concept the following \'ear. Althollgh arched in
form. the optil1listic span was a calltilever beam in
principle. with the "fhing levers" projected from
great maSOIll'\' abutments, tined out on the :\ew
YOl·k side as apartlllents, Pope's presentation of
this desigll was anolllpatlied bv rile following
couplet":
3
ThaI half an arc ~hol!ld sund UPOIl rhe
ground
Without support while building, or a rest;
This caus'd the theorist's rage and 'iceptic's
jest.
Prefabrication techniques were successfullv
combined with cantilever construcriot1 in many
bridges near the end of the nineteenth century, as
exemplified by such notable structures as the Firth
of Forth Bridge, Figure 1.6, and later the Quebec
Bridge, Figure 1.7, mer the Saint Lawrence River.
These st.rllClU res bear witness to the engineering
genius of an earlier generation. Built more re­
cently, the Greater :\ew Orleans Bridge over the
\Iississippi River, Figure 1.8, represelJls 11lodcm
cOlHemporan' long-spall ,Iecl clI1filevcr cOllslrnc­
I [()Il.
Lei the broad arc the spaciolls Hudso[J stride
And spall Columbia's rivers far [JJore wide
COll\ince the world ,\lllcricl hegins
To fo'nn Arts. the ;lIlCiClll \\()rk of killgs,
Stupendous plan! which llone belorc c'cr
j'otlild.
FIGURE 1.6.
-
Firth of Forth Bridge.
Because the properties and behavior of pre­
stressed concrete are related more closetv to those
of structural sleel than those of comelttional rein­
rorced cOllcrete. the applicatiotl of this material to
cllllileH:r construction W~IS a logical step ill the
COil! iIwing developmetlt or bridge cngllleeriJlg,
FIGURE l.i.
(~uchec
FIGURE l.8.
Greatcr :-.lew Orleans Bridge.
Bridgt:.
4
Prestressed Concrete Bridges and Segmental Construction
This applicatioll has eyol\'ed over many years by
the slIccessive de\'e!opment of mallY concepts and
innovations. III order to see how the present slate
olthe art has beel1 reached, let us briefly trace the
devcloplllelll of presu'essed concrete and in par­
ticular its applic<ltioll to bridge construction.
1.3
Evolution of Prestressed Concrete
The in\'cllIioll of reinforced concrete stirred the
Illlagination 01 t'llgilleers in 11I;JJl\ countries. Thev
envisiolled IlIa tat relllcndoll s ad va 11\,1 ge could be
achie\cd, if the steel could he lensioned to put the
,qrllctllrc in a pennallclli state 01 compression
g-1'Catcr thall all\ tellsile stresses g-clleraled by the
<tpplied loads. The pre~ellt state of the art of pre­
stressed concrete has C\ohcd froll1 the erfort and
('x]lericlln' of lIIall\' ell~ille('rs and scielltists o\'cr
lhc past nillet\' \cars" I 1OW('\'('I' , lire concept of pre­
stressing is centllries old. Swiss imcstigators ha\'c
shown tl1;lt as earh as :!70(l H.C. thc :tnciellt Egyp­
tians prestressed their s(,;lgoing \'('sscls long-itlldi­
nail\'. This h;IS 1)(,(,1l detenl1illcd from pictorial
represcntations fOlllld in Fifth Dynast\' tOIllI)s.
The hasic principle or prestressing was used in
the era It of cooperage WhCll the cooper wound
ropes or !!letal hands aroulld wooden staves to
forlll harrels.: l When thc I)ands were lightened,
thcv were under tensile prestress, which created
cOlllpression betwecn the SWH'S and enabled thelll
\0 rcsist Iroop tCllsiol1 produced by internal liquid
pressure. I II other words, the hands and staves
wcre hot h prest ressed hefore thev \\'(Te subjected
to all\ sel\'i('(' loads. The woodell cartwheel with ils
shrunk-Oil iroll rim is al10ther example of pre­
stressed cOl1struction.
The (irst all(,lIlpt to introdllcc internal stresses in
reinforced (OllCl'('te mel1lbers iJy tensioning the
steel reinforcement was made about 1886 whell
P. H. Jackson, all engineer ill San Francisco, obtained
a Ullited St;ltes patent ()r tightenin~ stcel rods in
concrete nJ(:lIliJers serving as Hoor slabs. ] n 1888,
C. E. \N. Dilhrillg of Berlin secured a patent for the
Illallufacture of slabs, battens, and small beams for
structural engineering purposes by embedding
tensiollcd wire in concrete in order to reduce
cracking. This was the first attempt to provide pre­
cast concrete units wit h a tensioned reinforcement.
Several structures wcre constructed using these
concepts; IHlWe\'er, ollly mild steel reinforcement
was available at the time. These structures at first
hehaved according to predictions, but because so
little prestrcss force could be induced in the mild
steel, the\' lost their properties because of the creep
and shrill kage of the concrete. I n order to recover
some 01 the losses, the possibilitv of retightening
the reinforcing rods after some shrinkage and
creep of the concrete had taken place was
suggested in 190f\ by C. R. Steiner of the L'nited
States. Steiner proposed that the bond of em­
bedded steel hars be destroyed b\· lightly tension­
ing the bars while the concrete \\'as still voung and
then tellsioning them to a higher stress when the
concrete had hardened. Steiner was also the first to
suggest the lise of cuned tendons.
In 19:25, R. E. Dill of :\ebraska took a further
slep t()\\'anl freeing cOllcrete beams of any lensile
stresses In tensioning high-tensile steel wires after
the concrete had hardened. Bonding was to he
prevented 1)\ suitahh' coating the wires. He
explicith llI{'llliollCd the ;!(h';llltage of lIsing st('eI
with a high elastic lilllit alld high strength as COll1­
pared to onlinan reillforcing hal'S.
In 19:21'1, E. Freyssillct of France, who is credited
wit h the !llOdtTll dc\('loplllellt of prest rcssed COI1­
nete, started min,!.!; high-strellgth steel wires
prestressil1g. Although Frnssillct also tried tile
lIlethod oj pretcllsiol1lllg, where the steci was
bOl1ded to the cOl1crete without elld al1chorages,
the lirst 1)l;lctlcd applicatioll of this method \\"as
ll1ade 1)\ E. H(lH'! ai;olll I ~nH. Wide applicatioll 01
the prestressil1g tcchlJiqlle was 1l0! possible ulltil
reliahle al1d ecollol11icailllt'thods (If tellsionillg alld
elld allchorage were dc\·ised. From approximately
1939 OIL E. Fn'\ssillet, "fagllt'l, awl othelS d('­
\'cloped differcllt 1ll(,tl\()(ls alld procedures. Prc­
st ress hegall to gail1 SOlllC importallce ahow 1945,
while allernatin' prestressing lllethods were beillg
devised 1)\, ellgilleers ill \'arious coulltries.
During the past thirty \'ears, prestressed con­
crete ill the Cllited States has growll from a
hrall<!-IH':W idea illto all an:cpted lllethod or COI1­
crete construction. This growth. it result of a l1ew
applicatioll of existing l1latelials and theories, is in
itsel f phellolllenai. I II Europe the shortage of ma­
terials and the cllforced economies in construction
gave prestressed concrete a substantial start. De­
veloplllent in the Cnited States, however, was
slower to
underway. Designers al1d contractors
hesitated mainly because of their lack of experi­
ence and a reluctance to abandon more familiar
methods of construction. Contractors, therefore,
bid t he first prestressed concrete work conserva­
tively. Moreover, the equipmcnt available for pre­
stressing and related techlliques was essentially
new and makeshift. However, experience was
gained rapidly, the quality of the work improved,
ror
..
._
",
1\1
{'I
Evolution of Prestressed Concrete Bridges
..........
5
"
~~'T
.---- ---:::
""~~
.....
,
\
FIGURE 1.9.
River.
~
Frevssinet\ Esbh Bridge on the '.larne
and prestressed concrete became more :md more
competitin: with other Illaterials.
1.4
Evolution of Prestressed Concrete Bridges
Although France lOok the lead ill Ihe de\Tlopmenl
of prestressed concrete. Ill;Ul\ European COUllt ric:;
SIKh as Belgilllll. England, (~erlllall\. Switzerland.
and Holl;llld quickh showed interest. As earl:: as
1948. Frcnsinet llsed prest ressed coneret e for I he
constructioll
fi\'e bridges o\'er the \larne River
,near P;lris, \\ith ~W ft (7t Ill) spans or all excep­
tiollally light ;l()pC;lrance. Figure 1.9, ,\ Sllne\
made ill (;erlll;lll\ .showed I hat between IIJ49 ;lIld
1953. out 01 ;)00 bridges built. 350 \\ere pre­
stressed.
or
FIGURE 1.10
(COllrtt"\'
\\'allllll Lane Bridge. Philadelphia
of the Portland Cement :\ssociation),
Prestressing in the Lnited Slates followed a <Iii
ferent course, Instead of linear prestressing. cir­
cular prestressing as applied to storage tallks took
lhe lead. Lillear prestressillg as applied to be;tllls
did [lOl sian until 1949. The first strllcture of tiJis
tYlw W;l~ a hridge ill \LtdisOlI COllll(\', Telll]essee.
followcd ill I~);)() In the well-known HiO ft HH.HO
Ill) spall Walilut LlIle Bridge in Philadelphia, Fig.
lire 1.10. Ih the middle or 1951 it was estimated
that 17:'1 brid!.{cs alld 50 buildillgs had heel] Cllll·
strllClcd ill Ellrope ;lIld 110 !llore thall 10 strllClure~
ill the Lilited State~. III 1952 the Portlalld Cellleill
.\sS()Ciatloll cOllducted a SUnle\' ill this COUllln'
silowill!.{ 100 or Illorc structurcs cOlllpleted or
.r.--TI
=:
L
f2"
IV
~
I'
~--------~
!
.....'
I
...
\...:.i
• I
~I
L
I.
2'· 4"
.1
V
FIGURE 1.11.
m
.-\:\SHTO·PCI I-girder c!'Oss sections.
I
'I
6
Prestressed Concrete Bridges and Segmental Constme/ion
under construction. In 195:1 it was estimated that
there were is bridges in Pennsyh'ania alone.
After the Walnut Lane Bridge, which was cast ill
place and post-tensioned, precast pretensioned
bridge girders e\'oh'ed, taking ach'antage of the in­
herent economies and qualin' control achievable
with shop-fabricated members, With few excep­
tions, during the 1950s and early 1960s, most mul­
tispan precast prestressed bridges built ill the
Cnited States were designed as a series of simple
spalls. The\' were designed with standard
AASHTO-PCI* girders of various cross sections,
Figure Ll1. for spans of approximately 100 ft
(~O,S m), hut more cOlllmonh for spans of 40 to 80
It {I:! 10 :!4 IIlL The a<!\'alltages of a continuous
cast-ill-place st ruet ure were ab;lI1doned in I;l\or of
the simpler constructioll offered bv plallt­
produced st;tJ1(brdizcd units.
AI thi~ lillIe, plecast prctensiollcd lll(,llIl)er~
found all outstandillg application in the Lake
Pontchartraill crossing Ilorth of ;\cw Orleans,
Louisiana. The crossillg consisl eel of more t hall
:!:!()O idelltical S(i It (Ii 111) spalls, Figures I,I:!
through I. H. Each SP,lll \\'a~ Illadc of a sillgle ~()()
tOil 1I1011olith with pretensioned longitudillal gird­
State High"';l\ "11(1 TL'"'i'or!.llioll
Offlci"b (1"'CVlOU,h known ", AASIIO. Amcrican A"ocialloll
of Slall' IIlghw;l\ Offlci;lIs) "lid Presln'"ed (;OIl(T('I(' illSlitlltC,
"\ltl(,l ;(;]It ;\,,,,,'1011;011 01
FIGURE 1.13.
r
FIGURE 1.12.
Lake l'olltchartraill Brid!-\c. C.S.A.
crs all d a reill/()J'Ccd (,Ollcre1 e dec k cast ill tegrall\'.
resting ill turn Oil a prccast cap alld two pre­
stressed 'PUll piles. The speed of erectioll \\'as ill­
credihle. oftell Illore thaI! eight (,()]llpiell' spam
pi;.ccd ill a sillgle da\.
III the middle 19GOs a growIllg COlK('rll \\;IS
'ihoWIl about the s;det\' of highw,tys. Tile
AASHTO Traffic Safel\' COllllllit!ee called ill ;1
1~)(ii rcporr1 for the ", , , adoptioll and llSC of t\\O­
Sp;1l1 hridges for overpasses lTOSSillg dilided Illgh­
\\'<I\,S , . . to elilllillate the bridge piers nonllalh
placed adjacellt to the ,houlders." Figllrc LIS.
terstat{' high"',l\'s tOd;1\ reqllire oHTpasses witl;
two, tl1r('e, aud /<lllr 'pallS of II» to 1HO II (54.9 Ill)
or 101lger. III the case of ri\er OJ strealll (Tossings.
Lake POlltchartrain Bridge, U,S.A.
It;­
........
..."".."".,
'
<,,~.-'
(a)
33'-0"
..~--------------------
18'-9"
(b)
FIGCRE 1.14.
\erse sectioll.
Lake Ponlch;lItrain Bridge. C.5..-\. (11) Longilwlinal ,e.-lion. (Ii) Trans­
7
tt
Prestressed Concrete Bridges and Segmental Construction
8
STANDARD 4-SPAN INTERSTATE CROSSING
Span tor Skewed Brldge$
Span
Skew
30­
144'
4!5­
60"
177'
2!50'
FIGL'RE 1.15. Standard four-span illlcrstatc clOssing
(COllrleS\ of lilt' POrlbnd Cemcnt .\sso(iat ion 1.
longer spans in the range of 300 rt (9].5 111) or
longer may be required, and there is a very distinct
lrend toward l()llger-~pan bridges. I t soon became
apparent that the conventional precast pretell­
,jollC'd AASHTO-PCI ginlers were limited In their
transportable lellgth and weight. TrallSportation
mer the higlm<l\s limits the precast girder to a
length or 100 to 120 It C~O.5 to :)G.()), depending
upon local regulatiolls.
1.5
Long-Span Bridges with Conventional
Precast Girders
As a result of longer spall requirements a study was
conducted I)\' the Prestressed Concrete Institute
(PCI) in cooperatioll with the Portland Celllel1l As­
sociation (peA).:' This study proposed thai simple
spans up to 140 It (42.7 Ill) and continllous spallS
up to ]60 ft (48.H m) be constructed of stalldard
precast girders lip to 80 ft (24 111) in length joined
1)\· splicing. To obtain longer spans the use of in­
clined or haullched piers was proposed.
The following discussion and illustratiollS are
hased 011 the grade-separalion studies conducted
In PCI and PCA. Actual structures will be illus­
trated, where possible. to emphasize the particular
design concepts.
The design stud), illustrated in Figure 1.16 uses
cast-in-place or precast end-span sections and a
two-span unit with AASHTO I girders. s Narrow
median piers are maintained in this design, but the
abutments are extended into the spans by as much
as 40 ft (12 m) using a precast or cast-in-place
frame in lieu of a closed or gravity abutment.
\\'hen site conditions warrant, an attractive type of
bridge can be built with extended abutments.
A similar span-reducing concepl is developed in
Figure] .17, using either reinforced or prestressed
COl1crele for cantilever abutlllents. An aesthetic
abutment design in reinforced concrete was de­
n.-loped for a grade-separation structure on Ihe
Tram-Canada Highway near Druml1lolldvilJe in
the Province of Quebec, Figure 1.18. This 1'1'0­
\ided a :)2~ It (9.9 Ill) span reduction that led 10 Ihe
lISe of t\Ve IV Standard AASHTO I girders 10
SP;1I1 97~ It (29.7 111) to a simple, llarrow median
pIer.
:\ c<lsi-in-placc reinlorced cOllcrete frame wilh
olliward-:-.loping legs provides a stahle. ccnter sup­
porring struclure that reduces spall lellgth by 29 It
(H.H 111). Figure].1 Y. This enables either standard
box secriolls or I seclions 84 ft (25.6 Ill) IOllg 10 be
w,cd ill Ihe two main spans. This hn'out was used
(()J the Hohbema Bridge in Alberta. B.C.. Canada,
shown in Figure 1.20. This bridge was builr with
precasl challuel girder sectiolls, but could be buih
wilh AASHTO I girders or hox secriollS. The me­
diall frallle with inclined legs was cast ill place.
'I'll(' schematic and photograph in Figures 1.21
and 1.22 show the Ardrossan Overpass in Alberta.
I t is similar to the Hobbema Bridge except that the
spans are longer and, with the exception of a
casi-in-place footing, the median frame is made up
of precast units post-tensiolled together, Figure
1.2 I. The finished bridge, Figure ] .23, bas a
64'
Af:
II
\. Precosl
or
CO$t-m~ploce Frome
L_~h=::;::::==:;=t:;::===;:::j
E.LE.VATION
SECTION A-A
FIGURE 1.16.
from reI. G).
Extended abutments (courtesy of the Prestressed Concrete Institute,
...... -0
_
"
0
9
Long-Span Bridges with Conventional Precast Girders
AF'F'ROX . • ,' ..- - - - - '
ELEVATION
nz:
GIROEA
SECTION
FIGURE 1.17. Call1iincred
!ll,lilllte, rrolll rd. 6).
abulllH.'lIb (coulleS\ u["
the
Pre~lresse{l
Concrete
pleasing appearance. The standard units were
channel-shaped siringers 64 in, wide and 41 in.
deep (1.6 III bv I.tH m). The use of precast ullits
allowed erection or the entire superstructure, in­
cluding the median rrame. in onlv three weeks.
The bridge was opened to trafficjusr eleven weeks
after construction began in the early sumlller of
196(),
or
FIGURE 1.18. DIll1l11l101Hhille Bridge (collrtesv
the Portland (:CIIlI'11l :\"'ociatlOn).
or
lh lise
lemporan bents. Fii-iure 1.21.
standard units t)O It (18.3 Ill) long can be placed
over Ihe median pier alld connected to main span
1I11ih with cast-in-place reinforced concrete splices
located near the poim of dead-load contrallexure.
FIGURE 1.19. Median frame cast in place (courtesv of the Prestressed
CotHTl'tc Institute. from ref. 6).
Prestressed Concrete Bridges and Segmental Construction
10
FIGURE 1.20,
l<ollncs\'
HolJhem,l Bridge. completed structure
of the
Ponland CCIl1Cllt Association).
from the side pier o\'er the maill pier to the hinge­
support for the suspended span.
The t\'pe of construction that uses long,
standard, precast, prestressed lIllits never quite
achieved the recogllition it deserved. As spans in­
creased. designers turned toward post-tensioned
GIst-in-place box girder construction. The Califor­
nia Division of H ighwa;s, for exallIple, has been
quite successful with cast-in-place, multicell, post­
tensioned box girder construction for multispall
structures with spans of 300 It (91.5 lll) and even
longer. However, this t\'pe of construction has its
own Iilllilations. The extensive fOrInwork used
during casting often has undesirable effects on the
em'ironlllclit or the ecology.
1.6
This design is slightly morc expensive than PI'('\,I­
ous oncs but it prO\ides the mosl open t\'IK' tW()­
span structure.
The structural arrangement of the Sehastian
Inlet Bridge in Florida consists
a three-span \I!lit
o\'er the lllain challnel, Figure J .~5, The ell<lspall
of this three-spall ullit is 100 It (30.5 lll) IOllg and
cantileH:rs 30 ft (9 Ill) beyond the piers to support
a l~O ft (3G.G Ill) precast prestressed drop-in spall,
Figure I.~(). The end-spall seClioll was huilt in two
seglllellts witlI a cast-in-place splice with the help 01
a falsework bent. The :\apa River Bridge at V,t1­
kjo, California (not to be confused with the \:apa
River Bridge described in Section 2.11), used a
prccast concrete calltile\,cr-suspended spall COll­
cept silllilar to the Sebastian bllet Bridge, at about
the same tillle. The olll" differellce was that the
cantile\'er girder was a sillgle girder extcllding
or
Segmental Construction
Sq~melltal
constructioll lias hecn delilled 7 as a
Illcdtod of COllst ruct ion in whieh primar\' load­
supporting lIlclllhers arc composed of indi\'idual
lllemhers called segmcllts post-tellsiolled together.
rile cOlJcepts dncloped ill the pel-peA studies
and desnibcd ill the prcC(:dillg scctioll cOllie under
this delillitioll. alld wC' Illight call theln "longitudi­
nal" seglilelltal cOllstruction becallse the indi\'idual
clelllcilts arc IOllg with respect to their width.
III Europe, llleanwhile, sel{lllelltal constructioll
proceeded ill a sligl1th differellt malltler ill COlJ­
jUllctiotl with box girder dcsil{ll. SCI{InCllts wcre
cast ill place ill r<:lathclr short lellgths hut in flll1­
loadw;I\ width and depth. T()(bv segmclltal COIl­
struction is uSllally understood to hc the type de­
\clojJcd ill Europe, Howc\cr, as will be shown
lalcr, tlte segllH'llts lIced lIot he of full-roadw;l\'
ELEVATION
16'-6'
Lf7-----L---'---'-;..;;;......I----r1-. e llI:
48
AASHO-PCI
eox SECTION
SECTIONS A-A
FIGURE 1.21. Median frame precast (collrtes\,
InstifUle, hom reI'. G),
-- .,
or
the Prestressed Concrete
Segmental Construction
FIGURE 1.22. Ardross<ln Overpass preca~t llledia II
frame (counes\ of the Portbnd Ccment Association).
width and can become rather IOllg in the 1011­
gitudill<l I d ircctioll of t he bridL{l\ dependi Ilg OIl the
constrlluioll S\stelll lllilized.
Eugene Frevssinet. ill It.H5 to 1941:). was the lil-st
to use precast segmental constructioll for pre­
stressed COIlClTte bridge;., :\ bl'idge at LUZallL\
over the \bnH: Ri\ ('I' ahout :iO llliles east or Paris.
Figure I. '27, \\;IS followed In a groll p or lin~ precast
bridges mer tlrat rin:!'. Shorth thereafter, Urich
Finsterwal<it:r applied Gist-in-place seglllelltal pre­
stressed cOllstructioll in a babllced cantilever
fashion to;1 bridge (l'n-;,illg the Ltl1ll Rin:r at Bal­
duinsteill. Cenll;lIl\. rhis S\stelll or c<lntile\er
segmental COIlst rllct iOll rapidlv gained wide ac­
ceptal1l:e ill (~enllall\. arter cOIlstructioIl of a
bridge U'os.,ing the Rhillc at Worllls ill 195:2. as
shown ill Figun.: I.~H.' \\ith three spam or :):)0.
371, and :~,iO II (100. 11:~. :111<1 HH Ill). :\Iore thall
300 such slrucllllT'i, with spalls ill excess of ~51) It
(76 m), werc constl'llued bctweell 19:,)() al1d 1965
11
FIGURE 1.23. Completcd
Ardrossan
Ovcrpass
(courtesy of the Portland CClllent Association).
in Europe.:l Since thell the concept has spread
throughollt the world,
Precast seglllenr,ll construction also was evolving
during this period, In 1952 a single-span COUllt:
bridge near Sheldon. :\cw York. W;15 designed hv
the Frey'isillet COlllpam. Although tbis bridge W;IS
constructcd
longitudinal Luher than the Euro­
peall transversc seglllents, it represents the hrst
practical applicatioll of lllatch castillg, The bridge
girders were divided into three IOllgitudinal seg­
lllelits that were cast end-to-etld, The center seg­
IIlelll. wa, cast first aiid then the end segments were
cast directh agaillst it. Ke\'s were cast at the joints
so that the three precast eieIllcnts could be joined
at the site ill tbe S,lIlle positioll they h;id in the pre­
casting \;tnL Lpon shipment to the job site the
three eleillcllts of a girder were post-tensioned to­
gether with cold joints. HI,It
The first major application of lllatch-cast. pre­
cast segmelltal cOllstruction was no[ consummated
or
FIE:...D SPLICE
SCCTIO~
A-A
FIGCRE 1.24. Field splice for cOlltinuity (courtesy of the Prestressed COll­
crete lmtitute, from ref. 6),
12
Prestressed Concrete Bridges and Segmental Construction
FIGURE 1.25. Sebastian Inlet Bridge (courtesy of the
Portland Cement Association),
'I'
35'
I, ~<L.r
The ultimate use of the bridge-that is, high­
way or railwa\' structure or combination
thereof. Although man\' problems are com­
mon to these two categories, the considerable
increase of live loading in a railway bridge
poses special problems that call for specific so­
lutions.
2.
The type of structure in terms of statical
scheme and shape of the main bending mem­
bers. Many segmental bridges are box girder
bridges, but other types such as arches or
cable-stayed bridges show a v..·ide \'arietv in
shape of the supporting members.
The use of cast-in~place or precast segment~ 01
a combillation thereof.
The method of construction.
3.
ulltil ]962. This struClure, designed by Jeall r-.luller
and built by Entreprises Campenon Bernard, was
the Choisy·Ie-Roi Bridge over the Seine Rin'r
south of Paris, Figure 1.29. This concept has been
refined and has spread from France to all parts of
the wodd.
The technology of casl-in-place or precast seg­
mental hridges has advanced rapidly in the las!
decade. During its initial phase the balanced
cantilever method of construction was used. Cur­
relltly, other techniques such as spall-b:/-span, in­
cremental laullching, or progressive placelllent
also arc available. Any of these cOl1struction
methods iliaI' call on either cast-in-place or precast
segments or a combination of both. Consequently,
a variety of design cOIJcepts and cOllstruction
lllethods are now available to economically pro­
duce segmental bridges for almost anv site condi­
tion.
Segmental bridges mav be classified broadh' b\
four criteria:
100'
C65'
1.
4.
The sections that follow will deal brie/l\ with til('
last three classifications.
1.7
Various Types of Structures
hOlll the point or view of their statical schellle.
there ale essentialh' five categories of structures:
(I) girders, (2) trusses, (3) rigid frames, (4) arch
frallJes. and (5) cable-staved bridges.
1.7.1
GIRD':lm J5WJ)U-:S
Box girders in the JJl;~jorit\ of cases are the most
ef'ficient and economical design for a bridge. Whell
constructed in balanced GlIltile\'er, box girder
derks were initially made integral with the pier~
while a special expansion joint was provided at the
center of' each span (or every other span) to allow
180'
1~9'
.._3_0'.· 35'
100' ......
65'
~------.~-----
~
SeClIOn A·A
FIGURE 1.26. Sebastian I nJet Bridge (courtesy of the Prestressed Concrete I fl­
stitute, from ref. 6) .
..
..
Various Types of Structures
FIGURE 1.29.
FIGURE 1.27.
Luzane\( Bridge over the Marne Ri\'cr
n
& Widmann).
:iii
~;,s "3':"'.":
..
_ ..
13
Choisv-Ie-Roi Bridge.
for volume changes and to control differential
deflections between individual cantilever anTIs. [t is
now recognized that continuitv of the deck is desir­
able. and l110st structures are now continuous over
several spans, bearings being provided between
deck and piers for expansion.
Todav, the longest box girder bridge structure
that has been built in place in cantilever is the
Korol' Babelthuap crmsing in the Pacific rrust ter­
ritories with a center span or 790 ft (24 [ m), Figure
1.:)0.12 A box girder bridge has been proposed for
I~'-O"
J
i
FIGURE 1.30.
Koror-Babclthuap Bridge. elevation and cross section (rcf. 12).
14
Prestressed Concrete Bridges and Segmental Construction
longitudinal section
100'
I
100'
r-----~
I
,I.­
c-~
DO
Typical sections at span center
and over main piers
..
FIGURE 1.3 I.
FIGURE 1.33.
Tht' (;n'at Belt I'If>jl'ct.
the Creal Belt pJ(~jecl ill Denlllark \\'ith a J OiO fl
(:126 111) clear main spall, Figure I.;~ I, The box
girder design has bcell applied wilh equal suc­
c('ss 10 Ihe cOllstruction of difficult and spectacular
stl"ll(:lurcs such as the Saint Cloud Bridge o\('r
the Seine Ri\cr lIcar Paris, Figure J ,3:!, or 10 I he
constructioll 01' c!e\';tted structures in \('1'\ CO!l­
gestcd urban areas slIch as the B<) \'iaducls Ileal
Paris, Figure 1.:1:).
1.7.2
B-3 \'iaduCls, France.
The cantilever method ha" potential applications
hel\\'een the optimum spall length'. Ollvpical hox
girders for the low ranges and of SI;l\Td hridges for
the high ranges.
1.7."3
/-/(A,\1/-;S JrlrJI SI..·/'\']" U~(;.'·;
Whcll tile configuration of the sitc allows, the lise
01 inclillcd legs reduce" the dfcctin' span length.
lRl'SSFS
Whcll spall lellglh illcreases, Ihe I\']lied box girder
hecollles hea\"i' ami diHicult 10 build. For Ihe pur­
pose or rcdu~:illg dead weighl while silllplir\"illg
casl ing or VtT\' dccp wch sect ions. a t russ wit h opell
webs is a \cr:-' saiisraCl0rV type that call he C()ll\"C­
!Iiellth' huilt ill call1ilever, Figure J ,;)4. The tech­
llological lilllilatiolls lie ill the complication
COIl­
!IectiolJs between prestressed dia~()lIals and
chords. An otllslanding example is the Rip Brid~c
in Brisb;lIIC, Australia, Figure 1.;):1.
or
FIGURE 1.34.
Long-spall
COliC!
el(" lillSSCS.
'.'.6ii''',;
.... _,,'otl
__ .
•
I
"0<........
FIGURE 1.32.
'
~
Saint Cloud Bridge. France.
FIGURE 1.35.
Rip Bridge, Brisbane, Australia.
.....
...
_
,oj
n
----------~
15
Various Types of Structures
~
I
;1
,I .:
I{~
~
I
.::
; __ I
I
~
/
~~
'"
FIGt:RE 1.36.
Pro\·isiollal Ilack ,!;t\"S or ;t tClllporan pier ;1I-e
lleeded 10 permil cOllslructioll III LIlltilcHT. Figure
1.3(). ["his requircllIcllt 111;1\ ,olllclill1cS presclIl
diflindl\ .. \11 illtercstillg c,ample
,tiel! a ,chcme
is (hc BOllhollllllC Bridge oycr 1/](' BL!\ct RiV"tT ill
Frallce. Figme 1.:17.
The sciIeme is a trallsilioll hClweell the bo,
girder with \enied picrs alld Ihe true arch. where
the load is clrried Il\ 1he drch rill, ;tiOllg I he pres­
sure lille with lIlinillllllll hClldillg while the deck is
supporlcd In spandrel col ti III II s.
or
,~
'I
I' ...-
/
I" __
!
-~
, , ~- 1/ :;
Lung-spall fratlle.
1.7.1
(.'O.W.RI:TF . INCH IWI/)(;/:·S
COllCITte arches are an ecollolllicti w;!\, to Iransfer
loads to the ground where foundation cOl1ditiol1s
are adequate to resist horil.ollul loads. Eugene
Fre\ssinet prepared a design for a 100{) meter
(:~2HO ft) clear span 40 v"{'ars ago. Because of con­
struction difficlllties. however. the maximulTI span
built to date (1979) has been no IIlore than I ()O() II
C~()() Ill). Construction Oil falsework is made
difficult and risb bv the effect of strong winds
d II ri ng construct ion.
flle lirst outstanding concrete arch was built at
PIOllg~lstei bv Freyssinet ill 1928 with three fiOO ft
(I H;) Ill) spans. Figure 1.:~H. Real progress was
achie\"ed only when free calltilever and provisional
,Ll\ llIelhods were applied to arch constrtKtion.
Figure 1.39. The world record is pn:sentlv the Kirk
Bridge ill Yugoslavia. Imilt in cantilever and COl1l­
~;~:~~~~ .......-=<!I!'.;~~:~§~".
"':,.~,:."l:n­
~'*:~r-:~:i'~., . .
FIGURE 1.37.
Nt;
BOllholl1tlle Bridge.
FIGURE 1.38.
P!ougastel Bridge. France.
16
Prc'stressed Concrete Bridges and Segmelltal Construction
,
.:
FIGURE 1.39.
pkted ill 1979 with
Figure lAO.
1.7.5
<l
dear ~pall of 1:!HO It (:190 Ill).
CO'\"CNEn. LWH.-Sr.1l1.1> filUj)(;},) '"
\\'!Jcn a span is i>eyolJ(l 1he reach of <l COllE'Il1 iOJl,iI
i~ to suspend the deck
1)\ a s\'slem oC pdons alld Sla\'S, Applied 10 sted
Sf rUClures Cor the last t wellt \' \cars. t his approach
g'aillcd illlll1ediate acceptallce ill thc field of COIl­
crete brid ges wilcli cOllq ruCl ion bcca lIIe possihle
girder bridge. a logical stcp
FIGt:RE lAO.
Kirk BridgTs.
Yllg()sl;n'i~L
l..4sr
ItfCLOS(./'U'
1­
FIGURE 1.41.
Long-spall concrete cablc-sta yed bridges.
SECOI'fO
_~C40SI.lPil'
17
Cast-in-Place and Precast Segmental Construction
the structure's deformability. particularlv durin/.{
cmi'S'i'lw:tion, DeAections of a typical cas!:ln:,>Sce
GlIltile\'cr are often two or three times those of the
same camilever made of precast segments.
The local effects of concentrated forces behind
the anchors of prestress tendons ill a young con­
crete (two or four days old) are always a potential
source of concern and difficulties,
/.8.2
FIGURE 1.42.
Ihotollllt' Bridge. Frallct',
and ecolloll1iGlI ill balallced calltilevel' with a larg-e
nUlllber of sta\'s 1IIlifol'lllh' di~tril)ljted ;dollg- the
deck. Fig-ure IAI, I'lIe long-cst 'ipall or this type is
the Brotolllle Bridge ill Fraw" with a 10;)0 It ctW
01) dear Illaill'ip,lll mer the Seille River. Figlll'('
1.42, Single In lOllS alld olle lillc of Sla\s :IIT iOCllCd
along the centl'rlllll' 01 !Ill' hl'ld;..il',
1.8
1,8,1
Cast-in-Place and Precast Segmental
C()ns/ruction
Cfl,W, ! CT/JUS TICS OF L1SI',/\',/JI..I<:F
S /·:C.\I F,\
r\
In cast-in-pl:ln: U)lISlrllctioll. \('gTlll'Ili'i ;IlT c;t'il olle
after another illliteir fill:d InelltO!l ill lite stl'llctllt't',
Special equipnll'lll is llSed for Ilti" pllrpme. '>11(11 as
traveler's (for c;lIltilcn~1' COIl'ilrllctioll) or f()l'I11work
units I1l<)\'ed ;dollg ,t stlpporting g;lllIl'\ (for spall­
b~'-spat1 cOllstrllctiOI1), btl'll seg!!l('nt is rcild'ol'ced
with cotH'entional lIntcnsiol1cd steel ;I!ld 'iOllle­
times by trans\'(:rsc or \crucd pn:'itres'iing or hot h.
while the assel!,lbl ~ of>eglllclllS i'i ;1,~~!il'\Td h_:: J~?~l:
-tellSioning.
-'--''''''~-'---'--''''-:-----~~cg'I;ll;~;,re cast end-to-end. it is
not difficult to placc IOllgitlldin.d reilll'on:illg steel
across the joillls betweell SCg-lllClllS if the desigll
calls for colltinltolls reinforcemctll. Joints !Il<lV be
treated as reqllired for safe trallsfer of all bending
and shear stresses alld for water tightlless ill ag­
gressive eli mates. COllnection betweell ind i\'idual
lengths of longitlldillal posHellsiollitlg dllns lll;t\
be made easih' at each joillt alld for each telldon.
The method\ essential limitation is that the
strength of the concretc is alw<\\s 011 thc critical
path of cOllstruction and II <t!~0it~!ll~,=-Il('csgre,;t~\~_'"
C/I,/IUCTERISnCS OF PREC.iST
[n precast segmelltal constrllction. segments are
manufactured ill a plant or near the job site. then
transported to their final positioll for asselllblY.
I nitialh'. joints between segments were or comen­
tional t>Ve: either concrete poured wel joints or
dn mortar packed joints. :Vlodern seglllcntal COI1­
st ruct ion calls for the lllatch-castillg techllique. as
mcd for the Choisv-Ie-Roi Bridge ~lI1d further de­
\'eloped and refilled. \\'hcreb:; thc seglllents are
precast against each other. preferabh in the same
"ciati\'(: order thev will have ill the final strllctllrc,
\:0 ;uIjllstlllent is therefore llccessarv between
,cgmcnts before assembly. The joints arc cithcr
left <In' (ill ;Ireas where climate permils) or made of
a vel'\' thin fillll of epox:: resin or mineral complex.
which docs not alter the lIlatch-casting properties.
.l'here is llO lIecd for allv waiting period ror joint
lllre. and final asselllbly of segments bv prest res­
~illg 111:1\' proceed as bs! as practicable,
Becausc the joints are or negligihle thickness.
1 here is u-;uallv no mechanical cOllllect iOIl bet wecn
thc illdi\iduallellgths of tendoll ducts at thejoillt.
L'ql:tlh' no attempt is Inade to obtain cOlltinllitv
of the longitudinal con\'entional steel through the
joints. ,tithollgb se\'eral methods are ~I\'aibhle ~II}(I
han: heen applied slIcccssfulh (as ill the Pasco
Kellilewick cable-sl<l\ecl bridge, for exalllplc).
Segillellts Illay be precast 10llg ellough ill advallce
01 their asselllbh in the structure to reach
'iufficiellt strellgtll and maturitv and to miuilllize
both the deHecriol1S during construction alld the
elfeets of cOllcrete shrinkage and creep ill the lill~d
5t ruct u re.
If erection of precast segments is to proceed
smoothl\,. a high
of geometry control is re­
quir'ed during match casting to ensure accuracv.
1.1-1.
CH01CE BETWEE.V CAST-IX-PLACE ./XD
PRECAST CO,VSTRL'CTIO.v
Both cast-in-place methods and precast methods
h;l\e been successful!:' lIsed and produce suhstall­
(/
s
SE(;,\l/~'\TS
I
18
Prestressed Concrete Bridges and Segmental Construction
tially the same final structure. The choice depends
on local conditions, includillg size of t he project,
time allowed for constructioll. restrictiolls on ac­
cess and environment, and the equipment available
to the successful contractor. Some items of interest
are listed helm\':
1. SjJ(w/ of COlis/ruction Basical"', cast-in-place
calltile\'er construction proceeds at the rate of one
pair of segments 10 to 20 It (:1 to 6 m) long even
fOllr to se\'en d;l\s. On the average. Olle pair of
travelers permits the completioll of 150 f't (46m) of
hridge deck per 111011th, excluding the transfer
from pier 10 pier and fabrication of the pier table.
Oil the otlier hand, precast segmental cOllstructioll
allows a cOl1siderablv /'aster erectiol1 schedule.
a.
For the Oleron Viae! lIct, the average speed of
collJpletion of tlw deck was 750 It C22H 1Tl) per lIlont h
for more than a year.
h, For both the B-:1 Viaducts ill Paris and the
Long Kev Briclge ill Florida, a typical 100 to I f)() It
(:10 to 4:) Ill) spall was erected ill two working cla\s,
repres('l1til1g a construction of I :10() It HO() Ill) of
fillished bridge per lIlollth,
c. Saillt Cloud Bridge llear Paris, despite t hl' ('x­
cept iOllal di fficlilt y of its geolllet n and design
schellle. was COllstructed ill exactlv Olll' \Tar, its
total area anloullting to 250,()OO sq It (~;L()()() sq
III ).
It is evident, then. that cast-in-place GllJlile\'er COlJ­
struction is basically a slow process, while precast
seglllental \"ith lllatching jOlllls is ,lI11011g the las­
test.
2. 1117.'('.111111'111 ill Sf'(,Cla/ Equil'lI/f'IIt f lere t hl'
situation is usuallv reversed. Cast-in-place requires
usually a lower investment. which IlIa kes it COIlJ­
petitive on short structures \\ith long spa ns [ for
example, a typical three-span structure with a
center span in excess qj approximately :150 f't (J 00
m)].
III long, repetitive structures precast ~egl11elltal
may he 1I10re economical than cast-ill-place. For
the Chillon Viaducts with twin structures 7000 n
(2134 111) long in a d i I'ficu 11 environmcllt, a detailed
com parative estimate showed the cast -ill-place
method to be 10% more expensive than the pre­
cast.
3. Size alld Weight of S('gmerlts Precast seg­
JIlemal is limited by the capac:it y or transportation
and placing equipment. Segmellts exceeding 250
tons are seldom economical. Cast-ill-place con­
struction does not ha\'(' the same limitation, al­
though the weight alld cost of the travelers are di­
rectly proportional to the ,,'eight of the heaviest
segment.
4, Ell1!lromnfJlI Rfslricliolls BOI h precast and
cast-in-place segmelltal permit all work to he per­
formed from the lOp, Precast. however. adjusts
more easily to restrictions such as allowing work to
proceed over traffle or allowing access of workmell
ami materials to the various piers.
1.9
Variou.~
Methods of Construction
Probahh Ihe most signihcant classification of seg­
lllental hridges is In llll'1 hod or cOllslrUClioll. Al­
though cOllstruction mel hods ma\' be as varied as
the ingenuit\
Ihe designers alld contractors,
thn Ldl into 10111' hasic categories: (J) halall(ed
c<lntiienT, (~) spall-I>\ -span cOllstructioll. (:I) pro­
gressive placclIlellt COllst ruet iOIl. alld (4) 111 ('r('­
lIlcl)tal launchillg or push-oUl construction.
or
1,9,1
c.'ISr·/.\'·j'j.,l(J, li.1LJ.\'CUl C/.\T/UJUI
The h;li;lllccd or frce calli iI('\('1 COllst run ion CO)l­
(ejlt \\'as origillalh dcn'loped to elilllilJate
Lllsework, TClIJporan sllOrillg Ilot ollh is ('XPCIl­
si\'(' hUI call he ;1 hazard ill tile Lise of suddcll
floods, as cOlJfirllJed 1)\ lll;tm f;tilllles. (her Ila\'iga­
ble waterways or Iran·led highwa\'s or railways,
lals('\\ork is either not allowed or ;,('\eIT" re­
strictcd. Cantiien:r cOllstructiol], \\hetlier cast ill
place or precast, clilliinates slIch difficulties: C()IJ­
structiolJ ilia\, pro(ced from Ihe permallellt piers,
and the Slrllcture is sell-supportillg at all sLtges,
The hasic prillciple of the lIIethod \\as outlincd ill
Section 1. J (Figme l.~i).
In cast-ill-place COllst ructioll the jonn\\'ork is
sllpported from a 1ll00ahie form carrier, Figure
1.1. Detaib of the lorlll Iran·lers arc showll ill Fig­
lire 1.43. The forllltra\'eier 1IJ00es forward 011 rails
attached to the deck of the completed structure
and is anchored to the deck at the rear. With the
form tr;J\e!er ill place, a ncw segmellt is formed,
cast, and strcssed to the IHe\'iolish constructed
segment. I n some instances a covering m<l\ be pro­
vided on the form carrier so that work m<ly pro­
ceed during inclelllent weather, Figure 1.44.
The opcration sequence in cast-in-place bal­
anced cantilever construction is as follows:
1.
Selling lip and <l(Uustillg carrier.
2.
Selling up and aligning forms.
Various Methods of Construction
19
CENTERJACt<
,,
FRONTAL UPPER
WORKING PLATFORM
REA~
GANG-BOARD
FIGURE 1.43.
BOTTOM
FRAME WORK
Forlll I r;I\\:I('I' IC()t!rtl";\
or D\ckcrhofT &
!
FRONTAL LOWER
WORKING PLATFORM
Widmallll),
COIlCl'Cling,
cOllStl'llnioll time for a full cycle below two work­
ing da~s, ;lIHI this ollly for ;1 very simple structure
5,
lllscriing plt'SlleSs IClldollS illlhc segmcnl and
stres'iing
or reinforcillg' and
6,
7.
RCll1millg I he IOl'll1work,
3.
4.
Placing reinlorcclIlcl1l and tendoll ducts.
~[()\'illg I hI.' lorm carrier
and slarling ;1 new C\cle,
(0
the
llCXI
position
Initia!!\', Ihe normal cOl1slruClion time for a
segmellt W;IS olle week per fOl'1nwork lIni!. Ad­
vances ill precast sq';ll1enul construction ha\c bcen
applied ret'el)t!\' 10 the cast-ill-pbce method in
order to reduce the nde 0[' operaliolls and in­
crease the eificiellc\ of the travelers. \'.'jth todav's
techllologY' it does Hot seem possible to reduce the
FIGURE 1.44. Bendorf Bridge form tra\-e!er (cour­
tesy of DvckerholT & Widmann).
with constant cross section and a moderate a1l10UIlI
prestress. For a structure with
\;triahle deplh and longer spans, say ;Ibove 250 ft
(75111), the typical nell' is more realistically three to
lour working' <la\·;;.
\Vhe!e a IOllg viaduct type structure is 10 be COIl­
strllcted of cast-ill-place segmellts, an auxiliary
stee! girder may be used to support the f()rmwork,
Figure 1 A5, as on the Siegtal Bridge. This equip-
FIGURE 1.45. Siegtal Bridge, use of an auxiliary truss
in cast-in-place construction.
20
Prestressed Concrete Bridges and Segmental Construction
i
ment may also be used to stabilize th~ free-standing
pier by the anchming of the auxiliaiy<~teel girder
to the completed portion of the structure. Nor­
mally, in construction using the form traveler pre­
viously described, a portion of the end spans (near
the abutments) must be cast on falsework. I f the
auxiliary steel girder is used, this operation may be
eliminated. As soon as a double typical camilever is
completed, the auxiliary steel girder is advanced to
the next pier. Obviously, the economic justification
for use of an auxiliary steel girder is a function of
the number of spans and the span length.
1.9.2.
PRECAST BALA.\'CED C;/]\'TILEVER
For the first precast segmental bridges in Pal'is
(Choisy-le-Roi, Courbevoie, and so on, 1961 10
1965) a floating crane was Itsed to transfer the pre­
cast segments from the casting yard to the barges
that transported them to the project site and was
used again to place the segments in the structure.
The concept of sell-openlling launching gantries
was developed shortly thereafter for the COllst ruc­
tioll olthe Oleron Viaduct (1964 to 1966). Further
refined and extellded in its potential, this concept
has heen used ill many large structures.
The ereclioll optiollS available Gill be adapted to
almost all construction sites.
I. Crane Placing Truck or cr,l\vler cranes are
used on land where feasible; float.ing cranes Illay
be used for a hridge over navigable water, Figur'c
1.46. Where site cOllditions allow, a portal crane
may be used Oil the fulllengtb or the deck, prefer­
ably with a castillg yard aligned with the deck near
one abutment to minimize the number of handling
operations, Figure 1.47.
2. Beam and Winch A1c1hod If access by land or
water is available under the bridge deck, or at least
around all permanent piers, segments may be
lifted inlO place by hoists secured atop the previ­
ously placed segments. Figure 1,48. At first this
method did not permit the installation of precast
pier segments upon the bridge piers, but it has
been improved to solve this problem. as will be ex­
plained later.
3. Launching Gan/rip.I There are essentially
two families of launching gantries, Ihe details or
which will be discussed in a later chapter. Here we
briefly outline their use.
In the first family developed lor the Oleron Via­
duct, Figures 1.49 and 1.50. the lalllKhing gantrY
is slighth more than the typical span length, alld
t he gantry's rear support reaction i;. applied ncal
the far end of the last completed cantilever. All
segments are brought onto the finished deck alld
placed bv the launching gant!'y ill balanced can­
tilever; after cOlllpletion of a calltilever, alter
placing the precast segment over the new pier. the
launching gantry launches itsclllO the next span to
start a new cycle of operations.
In the second family. developed for the De­
venter Bridge in Holland and for the Rio Niteroi
Bridge in Brazil, the launching gal1lrY has a length
approximately twice the tvpical span, and the reac·
tioll of the legs is always applied abo"e the perIna­
nent concrete piers, Figures 1.51 amI 1.52.
Placing segments with a launching gamry is now
in most cases the Illost elegant ane! efficient
method, allowing the least disturbance to the envi­
ronment.
1.9.3
SPAN-ln'-SPAN COSSTRUC710.\'
'The balanced cantilever construction method was
developed primarily for long spans, so that con­
struction activity for the superstructure could be
accomplished at deck level without the use of ex­
tensive falsework. A similar need in the case of
long viaduct structures \\·ith relatively shorter
spans has been filled by the development of a
span-by-span methodology using a form traveler.
The following discussion explains this methodol­
ogy.13,14,15.16
FIGURE 1.46. Segment erection by barge-mounted
crane, Capt. Cook Bridge, Australia (courtesy of G. Be­
lofr, Main Roads Department, Brisbane, Australia).
In long viaduct structures a segmental span-by­
span construction may be panicularly advanta­
geous. The superstructure is executed in one direc­
...
.. "
~~
21
Various Methods of Construction
rt
1:'1 ~::
r:
I 11
COUPE TRANSVERSALE
o
FIGURE 1.47.
.\liLt!JC;llI
tion, span In span. bv Illeans of a forll1 traveler,
Figure 1.5:~, with construuion joints or hinges lo­
cated at the point or cOIltr:lllexllre. The forlll car­
rier in effect provides a tvpe of factory operation
transplanted to the jol) site. It h;lS lllany or the ad­
vantages of 1ll;ISS production C011111101lIy associated
with precast plant operations as well as the added
advantage of permitting ver~;1Ii1e adjustment, ill
FIGURE 1.48.
France.
Hoist placing at Pierre Benile Bridges.
Bridge
,II
r()urs. Fra[]ce.
the field. The form traveler 111;1\' be supported on
the piers, or frolll the edge of the previously COlll­
pleted construction, at the joint location, and at the
forward pier. In some instances, as in the ap­
proaches of Rheinbrticke, Dusseldorf-Flehe, the
movahle formwork may he supported from the
ground. Figure 1.54. The forlll traveler consists of
a steel superstructure, which is lI10ved from the
co111 pleted portioll of the structure to the next span
to be cast. For an above-deck carrier, large
form work elements are suspended from steel rods
during concreting. After concreting and post-ten­
sioning, the forms are released and rolled forward
by means of the structural steel outriggers on hoth
sides of the form traveler's superstructure. For a
below-deck carrier, a similar procedure is followed.
l\lany long bridges of this type have been built in
Germany, France, and other countries. Typical
construction time for a 100 ft (30 m) span
superstructure is five to eight working days, de­
pending upon the complexity of the structure.
Deck configuration for this type of construction is
usually a monolithic slab and girder (T beam or
douhle T), hox girder, or a mushroom cross sec­
22
Prestressed q:oncrete Bridges and Segmental Construction
,/
(a)
:r;~::~M'
L~oO m~~~J.1.Qjt
~~~_ ..._.~~..... 106.00
,
en
:400 m-.--l8QfL_+
~_...~~_.~
3~. _ _
(b}
FIGURE 1.51.
S(,({)lJ<i [alllih 01 [;\lIlll'hillg galltri('s.
Rio :\itcloi Bridge.
Ie)
FIGURE 1.49.
rOll
Fir.s! Llllli'" 01 bUllchillg g;lll!ric, (Ole­
\·iaduCl).
lioll. This llIethod has heell lIsed rce<:nlh
III
the
lhe l)el1l1\' Creek pr<~ieci
1lI
lhe
l'lliled States
Oil
stale of Washinj.;IoIl.
III ils illitial fOrIll. as described above, the spall­
b\'-spall lllelhod is a casi-ill-place techllique. The
sallle principle has heell applied in conjullction
wit h precasl segmental (,'Ollst ructiolJ for I wo \'ery
larj.;c st me' '.Ires ill tile Florida Ke\'s: LOIlj.; Key
Bridge alld SevelJ \lile Bridge, \\·ilh SIXlllS of I 1 Hit
(36 Ill) and 135 ft (40 Ill), respectively. Segmellts
are assembled Oil a steel truss to make a complete
spall. Prestressillg telldol1s t hell asslIre 1he <[sselll­
1>1\. of the various segments ill Olle spall while
achieving full cOlltinuity with the precedillg spall,
Figw'es 1.55 alld 1.5G. The lIoatinj.; crane lIsed [0
place the segmellts over Ihe trll~S also 1Jl()\'es the
[rllss (rolll spall to spall. The contractor lor the
Sevcn I\1ilc Bridge modified the erection scheme
frolllihat lIsed for LOllg Key Bridge bv sllspending
a spall of scgments 11'0111 an O\('r1)(.';ld fabc\\'ork
tntss. This is lite first application of' a method that
seellls to have a great potelltial for treslle struc­
tllres ill tcrms
speed of cOllstructioll and e(OIl­
or
(}Ill L
1.9.4
Progressive placement is similar 10 the span-IJ\­
span method ill that construction starts at olle end
Ihe structure and proceeds cOlltinuously 10 the
or
,.,:....1...- Il.._
•
FIGURE 1.52. Rio :'\iteroi laullching girder.
....
FIGURE 1.50.
Ion Viaduct.
.,
IT
db
Placing pn:<.:ast segments on the Ole­
PIWGRL'iS/I'E PL-ICE,HF,,\'T COXSTIWCT/(),\'
...\ ... ,
~,
'
.'.
-
Various Methods of Construction
h
~;~iiil ~
23
,
i
FIGURE 1.53. Span-by-span construction using a
form traveler (courtesv or elI'ieh Finsterwalcler),
FIGURE 1.54. Form traveler supported from the
ground. Dtisseldorf-Flehe Bridge.
-
PRINCIPE
DE
POSE
FIGURE 1.55. Span-bv-span assembly of precast segments.
.,
7
FIGURE 1.56. Placing segments on assembly truss for
Long Key Bridge.
other end. It derives its origin, however, from the
cantilever concept. In progressive placel1lellt
the precast segments are placed from one end of
the structure to the other in successive cantilevers
on the same side of the various piers rather than
by balanced cantilevers on each side of a pier. At
present, this method appears practicable and
economical in spans ranging from 100 t" 300 ft
(30 to 90 m).
Because of the length of cantilever (one span) in
relation to construction depth, a movable tempo­
rary stav arrangement must be used to limit the
cantilever stresses during construction to a reaSOll­
able level. The erection procedure is illustrated in
Figure 1.57. Segments are transported over the
completed portion of the deck to the tip of the
cantilever span under construction, where they are
positioned by a swivel crane that proceeds from
one segment to the next. Approximately one-third
of the span from the pier mav be erected bv the
free cantilever method, the segments being held in
position bv exterior temporary ties and final pre­
stressing tendons. For the remaining two-thirds of
the span, each segment is held in position by tem­
porarv external ties and by two stays passing
through a tower located over the preceding piers.
Al! stavs are continuous through the tower and an­
chored in the previously completed deck structure.
The stavs are anchored to the top Aange of the box
girder segments so that the tension in the stavs can
be adjusted by light jacks.
U sed for the first time in France on several
structures, Figure 1.58, progressive placement is
being applied in the United States for the con­
struction of the Linn Cove Viaduct in ~orth
Carolina. In this bridge the precast pier construc­
tion proceeds also from the deck to solve a difficult
problem of environmental restrictions.
24
Prestressed Concrete Bridges and Segmental Construction
TOWER
FIGURE 1.57.
Progl'e~si\'e
The progressive placement method may also be
applied to cast-in-place construction.
1.9.5.
INCREMENTAL LAUNCHING OR PUSH-OUT
COl,'STRUCT/ON
This concept was first implemented on the Rio Ca­
roni Bridge in Venezuela, built in 1962 and 1963
by its originators, Willi Baur and Dr. Fritz
Leonhardt of the consulting firm of Leonhardt
and Andra (Stuttgart, Germany).17
placement ereClion procedure.
Segments of the bridge superstructure are cast
in place in lengths of 30 to 100 ft (10 to 30 m) in
stationary forms located behind the abutment(s),
Figure 1.59. Each unit is cast directly against the
previous unit. After sufficient concrete strength is
reached, the new unit is post-tensioned to the pre­
vious one. The assembly of units is pushed forward
in a stepwise manner to permit casting of the suc­
ceeding segments, Figure 1.60. Normally a work
cycle of one week is required to cast and launch a
segment, regardless of its length. Operations are
-
- ...
.
-
--­
•
25
Various Methods of Construction
FIGURE 1.58.
(onstruuiol1.
Fontenm' Bridge. progressl\'c placing
scheduled so that the concrete can attain sufficient
strength over a weekend to allow laullching at the
beginning of the next week. Generally. fabrication
in the oil-site f~tctorv can be done in the open, al­
though in inclement weather a protective covering
mav be provided.
Bridge alignlllent in this type or cOllstruction
mav be either straiglll or cUlTed; however, the
curve lIlust have a COllstatlt radius. This rcquire­
ment of constant rate of curvature applies to bot h
horizontal and vcrtical curvature. The Val Ristel
Bridge in Italv. which was incrementally bunched
on a radius or ·1<):2 It (ISO Ill). is illu"tr~lted ill Fig­
ure 1.61. Roaclw;\\ gco III et n tluts is dictated by
construction. as opposed to I he present practice in
the Cniled Slates. in which cOI1<;trllctioll is dictated
by geolllctrv.
To allow the supcrstructurc to movc forward,
special low-friction sliding bearings are provided at
the various piers with proper lateral guides. The
main problcm is to imure the rcsistance or the
•
----~
_i_F_#'l~~_ ________________
===~\
FIGURE 1.60.
Incremental
launching
sequence
(murre,\, of Prof. Fritz Leonhardt).
superstructure under its own weight at all stages of
launching and in all sections. Four methods for this
purpose are used in conjullction with one another.
I.
2.
3.
jIl
FIGURE 1.59. Casting bed and laul1<.:hing arrange­
ment (counes\' of Prof. Fritz Leonhardt).
-
r.
4.
A first-stage prestress is applied concentrically
to the entire cross section and in successive in­
crements over the entire length of the
superstructure.
To reduce the large negative bending mo­
mellts ill the fronl (particularly just before the
superstructure reaches a new pier) a fabricated
structural steel launching nose is attached to
the lead segment, Figure 1.62 .
Long spans may be subdivided by means of
tem porary piers to keep bending moments to a
reasonable magnitude, This construction
technique has been applied to spans up to 200
ft (60 m) without the use of temporarv
falsework bents. Spans up to 330 ft (l00 m)
have been built using temporary supporting
bents. 'rhe girders must have a constant depth.
which is usually one-twelfth to one-sixteenth of
the longest span.
Another method has been used successfully in
Fmnce to control bending moments in the
26
I
Prestressed Concrete Bridges and Segmental CQnstructiQn
-.j
FIGURE 1.61.
I ncrcmcnlal launching on a curve
(courtCSY of Prof. Fritz Leonhardt).
FIGURE 1.62. Stccllaum:hing nose (mul!csv of Prof.
Fritz Leonhardt).
deck in the forward pan of the superstructure.
A system using a tower and provisional stays is
attached 10 the front part of the superstruc­
ture. The tension of the stays and the corre­
sponding reaction of the tower on the deck are
automatically and continuously controlled
during all launching operations to optimize the
stress distribution in the deck, Figure 1.63.
ft (1035 111). The incremental launching technique
was used successfully for the {il'st time in the
United States for the construction of the \Vabash
River Bridge at Covington, Indiana.
After launching is complete, and the opposite
abutment has been reached, additional prestress­
ing is added to accommodate moments in the final
structure, while the original uniform prestress
must resist the varying moments that occur as the
superstructure is pushed over the piers to its final
position.
Today, the longest incrementally launched clear
span is over the River Danube near Worth, Ger­
many, with a maximum span length of 550 ft (168
m). Two temporary piers were used in the river for
launching. The longest bridge of this type is the
O!ifant's River railway viaduct in South Africa with
23 spans of 147 ft (45 m) and a IOtal length of 3400
The state of the art of designing and constructing
prestressed concrete segmental bridges has ad­
vanced greatly in recent years. A wide variety of
structural concepts and prestressing methods are
used, and at least a thousand segmental bridges
have been built throughout the world. We may
conclude that segmental prestressed concrete con­
struction is a viable method for building highway
bridges. There are currently no known major
problems that should inhibit utilization of seg­
mental prestressed concrete bridges in the L'nited
States. They have been successfully consummated
in other countries and are increasingly being em­
ployed in the L'nited Slates.
1.10 Applications of Segmental Construction
in the United States
WD
.'
27
Applications of Segmental Construction in the United States
(aJ
(bJ
FIGURE 1.64. Three Sisters Bridge.
(c)
(dJ
(e)
FIGURE 1.63.
sional tower and
IIHH'lllcnlai
bunching with
provi­
'iU\ ,.
One of the earliest projects for which segmental
constructioll was considered was the proposed I n­
terstate 1-266 Potomac River Crossing in Wash­
ington, D.C., Figure 1.64, otherwise known as the
Three Sisters Bridge. This structure contemplated
a 750 ft (229 Ill) center span with side spans of 440
ft (134 m) 011 reyerse hve-degree curves, huilt wilh
cast-in-place segmental construction. Because of
environmental objections. this project never
reached fruition.
The JFK \[emorial Causeway (Intracoastal
Waterway), Corpus Christi, Texas, Figure 1.65,
represents the hrst precast, prestressed, segmental,
balanced cantilever construction completed in the
United States. I t was opened to traffic in 1973. De­
signed by the Bridge Division of the Texas High­
way Department, it has a center span of 200 ft (61
m) with end spans of 100 ft (30.5 m).
The first cast-in-place, segmental, balanced can­
tilever, prestressed concrete bridge constructed in
the United States is the Pine Valley Bridge in
California, on Interstate 1-8 about 40 miles (64 km)
east of San Diego. Designed by the California De­
partment of Transportation, the dual structure,
Figure 1.66, has a total length of 1716 ft (53,6 m)
FIGURE 1.65. JFK
Christi, Texas.
FIGURE 1.66.
CALTRANS).
;"'femorial
Causeway.
Corpus
Pine Valley Bridge (courtesy of
28
Prestressed Concrete Bridges and Segmental Construction
FIGURE 1.67.
Rendering of Houston Ship Channel Bridge.
with spans of 270, 340,450, 380, and 276 it (82.3,
103.6, 137.2, 115.8, and 84.1 m).
As indicated previously, numerous segmental
bridge pntiects have been constructed or are con­
templated in the United States. Many of them will
be discussed in detail in the following chapters.
Among the most significant are the Houston Ship
Channel Bridge with a clear span of 750 ft (228 m),
which will be the longest concrete span in the
Americas, Figure 1.67, and the Seven Mile Bridge,
which will be the longest segmental bridge in
:\'orth America, Figure] .58.
FIGURE 1.68.
Rendering of Seven Mile Bridge.
1.11
Applicability and Advantages of Segmental
Construction
Segmelltal construction has extended the practical
range of spall lcngths for concrete hridges. Practi­
cal collsiderations of handling and shipping limit
the prestressed I-girder type of bridge construc­
tion to spans of about ]20 to ISO ft (3710 45 Ill).
Bevond this range, post-tensioned cast-in-place
box girders on falsework are the only viable con­
crete alternative. At many sites, however, falsework
is not practical or evcn feasible, as when crossing
deep ravilles or large navigable waterways.
Falsework construction also has a serious impact
upon environment and ecology.
Prestressed concrete segmental construction has
been developed to solve these problems while ex­
tending the practical span of concrete bridges to
about 800 ft (250 m) or even 1000 ft (300 m). With
cable-stayed structures the span range can be ex­
tended to 1300 ft (400 m) and perhaps longer with
the materials available today.13 Table 1.1 sum­
marizes the range of application of various forms
of construction by span lengths.
Although the design and construction of very­
long-span concrete segmental structures pose an
important challenge, segmental techniques may
29
Applicability and Advantages of Segmental Construction
TABLE 1.1
Range of Application of Bridge Type by Span Lengths"
Bridge Types
0- 150
100- 300
100- :~OO
250- 600
200-1000
800 -1500
a1
ft
I-type pretensioned girder
Cast-in-place post-tensioned box girder
Precast balanced cantilever segmental, constant depth
Precast balanced cantilever segmental, variable depth
Cast-In-place cantilever segmelllal
Cable-stay with balanced cantilever' segmental
ft
II
ft
fI
ft
ft
O.:\o4il
Ill.
find even more important applications in moderate
span lengths and less spectacular structures. Espe­
cialh in difficult urban areas or ecologv-sensitive
sites', segmenlal structures h;I\'e proven to be a val­
uable asset.
Tod<l\' 111m I ~iles for new bridges can be adapted
for segmental cOllcrete construction. The principal
advantages of segmcl1Ial cOllstrllctiol1 ma\' be
summarized as follows:
1. Seglllelllal COllsrru('Iion is ;tIl efficient and
economical met hod lor a large range of span
lengths and I\pes of structllre. Structures with
sharp cllrves and \'ariable superelevation mav he
easily accol1lll1odated.
2. COllcrete seglllellLtl cOllstruction often pro­
vides for I he lowcst ill\CSll1lCtlt cost. Savitl!-{s of 10
to 20o/c· ovcr comentional mcthods have been
realized In competitive bidding 011 alterllate de­
signs or b\' realistic cost comparisolls.
3. Segmelltal cOIl!'trtlcrioll permits a reduction
of construction time. This is particularly true for
precast methods, where segments may be man­
ufactured while substructure work proceeds and
be assemblcd rapidly thereafler. Further cost sav­
ings ensue from the lessenillg of the influence or
inflation on total const ructioll costs,
4. SegJl1ental construction protects the envi­
ronment. Segmental viaduct-type bridges Gill
minimize the impact of highway construction
through em'ironmentalh sensitive areas. \Vhereas
conventional cllt-antl-fill nVe highway construc­
tion can scar the cllvil'Onlllellt and impede wildlife
migration, an elevated viaduct-type structure re­
quires onh a relatively narrow path along the
alignment to provide access for pier construction.
Once the piers have been constructed, all con­
struction activit\' proceeds from above. Thus, the
impact on the environment is minimized.
5. Interference with existing traffic during
construction is significant!;· reduced, and expen­
sive detours call be eliminated. Figure 1.69 indi­
cates how precast segments may be handled while
traffic is maintained with a minimum disturbance.
6. Segmental construction contributes toward
aesthetically pleasing structures in many different
sites. A long approach viaduct (Bl'Otonne, Figure
1. 70), a curved bridge over a ri\'cr (Saint Cloud,
Figure 1.7l), or an impressive viaduct over a deep
valley (Pine Valley, Figure 1.66) are some examples
where nature accepts human endeavor in spite of
its itllperfcctiom.
7. Materials and labor arc lIslIal! y available 10­
callv for segmental construction. The overall labor
requirelllcilt is less than for cOllventional con­
struction methods. For the precast option a m~jor
part of the work force on site is replaced by plant
labor.
8. As a consequence, quality control is easier to
perform and high-quality work may be expected.
9. Segmcntal bridges when properly designed
and when constructed by competent contractors
under proper supervision will prove to be practi­
cally free of maintenance for mallv veal's. Only
bearillgs and ex pansion joints (usuallv very few for
continuous decks) nced to be controlled at regular
intervals.
.
":;;;.
....
FIGURE 1.69.
ovel' traffic.
.
Saint Cloud Bridge, segments placed
30
. Prestressed Concrete Bridges and Segmental Construction
6. Anon., "Long Spans with Standard Bridge Gii'ders,"
PCI Bridge Bulletin, March-April 1967, Prestressed
Concrete Institute, Chicago.
7. "Recommended Practice for Segmental Construc­
tion in Prestressed Concrete," Report by PCI Com­
mittee on Segmental Construction, journa/ of the
Prfltrflsed Concretr Institute, Vol. 20, :\0. 2, March­
April 1975.
8. Clrich Finsterwalder, "Prestressed Concrete Bridge
Construction," jounla/ of the A mrriwlI COllcrrte Illsti­
tute, Vol. 62, 1\0. 9, September 1965.
FIGURE 1.70.
Brotonne Bridge approach.
10. During construction, the technique shows
an exceptionally high record of safety.
Precast segmental construction today is compet­
itive in a wide range of applications with other
materials and construction methods, while it adds a
further refinement to the recognized advantages
of prestressed concrete.
9. F. Leonhardt, "Long Span Prestressed Concrete
Bridges in Ellrope,"jouT/w/ of the Prr'strr,l.lrd COllcretr
I II.Ititute , Vol. 10, No. I, Februarv 1965.
10. Jean Muller, "Long-Span Precast Prestressed Con­
crete Bridges Built in Cantilever," Fint Intnllatiolla/
SYllljlO.lium, COllcrrte Bridge Desigll, ACI Publicatioll
SP-23, Paper 23-40, American Concrete Institute,
Detroit. 1969.
II . .lean Muller, "Ten Years of Experience in Precast
SegJllen tal Const ruct ion ," j ourlla/ oj' thf' Prr.l/rrs.lf'r!
COllrrf'/f' Institute, Vol. 20, ,,",0. I, January-Februan
1975.
12. \fan-Chung Tang, "Kmor-Bahelthllap Bridge-A
World Record Span," l'reprint Papn 3441. ASCI-:
Convention, Chicago. October 16-20, 1978.
1:-\.
A. Ballinger, W. Podolny, Jr., and M . .J. Ah­
ralIallls, "A Report on the Design and Construction
of Segmelltal Prestressed Concrete Bridges ill West­
erll Ellrope-1977," International Road Federa­
tion, Washington, D.C., June 1978. (Also a\'ailable
f!'Olll Federal Highway Administration, Offices of
Research alld Development, \\'ashillgtoll, D.C., Re­
po1'l :\0. FHWA-RD-78-44.)
c.
14. Clrich Fillsterwalder, ":\ew De\'Clopmellts in Pre­
stressing Methods and Concrete Bridge COllstruC­
tioll," Ihwir/ag-Bf'Tich/e, 4-1967, September 1967,
D\'ckcrhofl & Widmann KG, Munich, Germany.
FIGURE 1.71. Saint Cloud Bridge, France, curved
bridge over a river.
References
I. H. G. Tyrrell, History of Bridge Engineering, Henry G.
TYITell, Chicago, 1911.
2. Elizaheth B. Mock, The Archi/ec/ure of Bridges, The
Museum of Modern Art, New York, 1949.
3. T. Y. Lin, Design of Prestressed Concrete S/ruclurcs.
John Wiley & Sons, Inc., New York, 1958.
4. Anon., "Highway Design and Operational Practices
Related to Highway Safety," Report of the Special
AASHO Traffic Safety Committee, February 1967.
5. Anon., Prestressed Concrete for Long Span Bridges, Pre­
stressed Concrete Institute, Chicago, 1968.
15. lJlrich Fillsterwalcler, "Free-Cantile\'er COllstructioll
of Prestressed COIIC\'ete Bridges alld \1ushroolll­
Shaped BI'idges," First Ill/al/ationa/ SpnjlOsiulll, COI/­
rrr/r Bridgf' Df'sigll, ACI Publication SP-23, Paper SP
23-26, AlIlerican Concrete Institute. Detroit, 1969.
16. C. A. Ballinger and W. Podol ny, Jr., "Segmental
Construction in \\'estern Europe-Impressions of
an IRF Stud\, Team," Procredings, Conference con­
ducted by Transportation Research Board, National
Academy of Sciences, Washington, D.C., TRR 665,
Vol. 2, September 1978.
17. Willi Baur, "Bridge Erection by Launching is Fast,
Safe, and Efficient," Civi/ Engineering-ASCE, Vol.
47, No.3, March 1977.
18. Walter Podolny, Jr., and J. B. Scalzi, "Construction
and Design of Cable-Stayed Bridges," John Wiley &
Sons, Inc., New York, 1976.
2
Cast-in-Place Balanced Cantilever Girder Bridges
2.1
2.2
2.3
2.4
INTRODUCTION
BENDORF BRIDGE, GERMANY
SAIl'<T ADELE BRIDGE, CANADA
BOUGUEN BRIDGE IN BREST Al'<D LACROIX FAL­
GARDE BRIDGE, FRAl'<CE
2.5
SAINT JEAN BRIDGE OVER THE GAROl'<NE RIVER
AT BORDEAUX, FRAl'<CE
2.6
SIEGTAL AND KOCHERTAL BRIDGES, GER\t:ANY
2.7 PINE VALLEY CREEK BRIDGE, U.S.A.
2.8 GENNEVILLIERS BRIDGE, FRANCE
2.9
GRAND'MERE BRIDGE, CANADA
2.10 ARNHEM BRIDGE, HOLL-\ND
2.11 NAPA RIVER BRIDGE, U.S.A.
2.12 KOROR.BABELTHUAP, U.S. PACIFIC TRUST
TERRITORY
2.13 VEJLE FJORD BRIDGE, DENMARK
2.i
introduction
Developed initiallv for steel structures. cantilever
construction was lIsed for reinforced concrete
bridges as earh as fift\ veal's ago. In 1928. Frevs­
sinet used the cantilever cO!lcept to construct the
springings of the arch rib in the Plougastel Bridge.
Figure 2.1. The reactions and overturning 1l10­
melHs applied bv the faisework to the lower part of
the arch ribs were balanced bv steel ties connecting
the two short cantilevers..-\ provisional prestress
was thus applied bv the ties to the arch ribs with the
aid of jacks and deviation saddles.
The first application of balanced cantilever con­
struction in a form c1oseh' resembling its present
one is due \0 a Brazilian engineer, E. Baumgart,
who designed and built the Herval Bridge over the
Rio Peixe in Brazil in 1930. The 220 1£ (68 111)
center span was constructed by the cantilever
method in reinforced concrete with steel rods ex­
tended at the various sIages of construction by
threaded couplers. Several other structures 1'01­
2.14 HOUSTON SHIP CHANNEL BRIDGE, U.S.A.
2.15 OTHER NOTABLE STRUcrURES
2.15.1
Medway Bridge, U.K.
Rio Tocantins Bridge, Brazil
2.15.2
Puente Del Azufre, Spain
2.15.3
2.15.4
Schubenacadie Bridge, Canada
2.15.5
Incienso Bridge, Guatemala
Setubal Bridge, Argentina
2.15.6
2.15.7
Kipapa Stream Bridge, U.S.A.
2.15.8 Parrots Ferry Bridge, U.S.A.
2.15.9
Magnan Viaduct, France
2.15.10 Puteaux Bridge, France
2.15.11 Tricastin Bridge, France
2.15.12 Eschachtal Bridge, Gennany
2.16 CONCLUSION
REFERENCES
lowed in varioLls countries, particularly in France.
Albert Caquot, a leading engineer of his time, built
several reinforced concrete bridges in canlilever.
Shown in Figures 2.2 through 2.4 is Bewns
Bridge over the River Seine ncar Paris, with a dear
center span of 31 () ft (95 m), being constructed
in successive cantilever segments with auxiliarv
trusses. 'This bridge design was prepared in 1942.
The method was not widely used at that time,
because the excessive amount of reinforcing steel
Overturning
moment due
to centering
FIGURE 2.1. Cantilever construCLion of arch spring­
ings for Plougastel Bridge, France.
31
L
32
33
Introduction
I,'
¥J""'...... ~.~
~'f/I'III(,.;.A,
ttY....
ft ,.,,.
flh ~t<,
1.4..Nf/~
I. NJIItI
f,ltw",*"
FIGURE 2.3.
BezoJls Bridge, constructioll procedure.
required to balanlt: the calltilevcr moments pro­
duced the tendency toward cracking inherent in
an oH.'ITei nl'orced slab suhject to permanent tell­
sile stresses.
The introduction of prestressing in conuete
stnldllrcs dralllatically changed the situatioll.
Cscd successfully in 1950 and 1951 by Fillsterwal­
der with the German firm of DyckerhofT & \Vid­
mann for the construction of the two bridges of
Balduillstein and :\eckarrews, balanced cantilever
construction of prestressed concrete bridges ex­
perienced a continuous popularity in German\'
-~
•
FIGURE 2.4.
Bezons Bridges under construction.
34
FIGURE 2.5,
Cast-in-Place Balanced Cantilever Girder Bridges
La Voulte Bridge. France.
and surrounding countries. !'\icolas Esquillan de­
signed and built a large bridge by the cantilcvcr
mcthod over the Rhine River in France, La Voulte
Bridge (J 952), where an overhead truss was lIsed
during construction, Figure 2.5.
Betwcen 1950 amI 1965 more than 300 such
hridges were constructed in Europe alonc. Initially
all structurcs were prestresscd by high-strength
bars, and hinges werc provided at the center of the
various spans. Later other prestressing methods
with parallel wire or strand tendons were also used.
More important, a significant improvement in
structural behavior and long-term performance
was made possible b\ the achievement of deck
continuity between the various cantilever arms.
The first cantilever bridges with continuous deck~
were designed and built in France in 1962: the
Lacroix Falgarde Bridge and Bougllen Bridge.
Figures 2.6 and 2.22. Subsequently, the a(hantage~
of continuity were recognized and accepted in
many countries.
From 1968 to 1970 cantilever construction was
considered for the Three Sisters Bridge in Wash­
ington, D.C., Figure 1.64. This pn~iecl never
reached the construction stage. The hrst cast -in­
place balanced cantileYer segmcntal bridge built in
the United States is the Pine Valley Creek Bridge
ill California (1972 to 1974), Figure '2.7. To dalc.
all segmcntal bridges constructed in the U niled
States have been eit hcr prccast or cast -in-place
cant ilever const ruction, wit h thc following cxcep­
tions:
\-"abash Ri\'cr Bridge. illcremelltallv launched
(Chapter 7)
Dcnny Creek alld Florida Ke\'s Bridgcs, spall-In.
span constructioll (Chapter 6)
FIGURE 2.6. BOllguen Bridge in Brest, France. First continuous rigid-frame structure
built in balanced cantilever.
Bendorf Bridge, Germany
FIGURE 2.8.
35
Bendorf Bridge (courtesy of Dyckerhofl
& Widmann).
;:
.
~
,;;"Y
•
FIGURE 2.7.
,
r­
,>
.... ~
"", ......
1
t
Pinc Valin Creek Bridge,
,
Lilln COH? Viaduc\. progressive placement
stmelioll (Chapler ())
COll­
or
The bal;lIlCed clillilever lllethod
C()ll~trlleliol!
has alreadv been briefly described. III Ihis chapter
we shall see how this 1l1ethod has beel! i111­
plelllcll1cd OIl v~lri()lIs structures bcfore we go Oil
to cOllsider specific design ;tI1d technological as­
pects.
2.2
(west.) are the river spans consisting of a symmetri­
cal seven-span colltinuOlls girder with an overall
length of 1721 ft (524.7 Ill). In part two (east) are
the' nine-span contilluous a ppro:Jch girders wit.h
the spans ranging froJl1 134.5 ft (41 111) to :WH rt (~H
Ill) and havillg an o\eralllellgth of 1657 h (505 m),
Figures 2.9 and 2.10.
The continuous, seven-span. malt1 river stnlC­
lure consists of twin, independent, single-cell hox
girders. Total width of Ihe hrid[.ie cross SCUiOll is
I() I 1'1 (30.S() 111). Each single-cell box has a lOp
lbnge width 01 43.;~ rt (13.2 Ill), a hottOlll Jlange
width of 23.6 ft (7.2 m), and wehs wilh a constant
thickness or 1.2 h (().~)7 Ill). Girder dept h is 3-t.2H h
(10.45 m) at the pier and 14.44 ft (4.4 111) al
midspan represellting, with respect to the main
span, a depth-tn-span r;lIio of 1120 and U1:7. re­
specti\'eh'. Girdcr depth of t.he cnd or this se\CIl­
spall unit reduced to 10.H ft (3.3 Ill). The main
n~l\igation spall has a hinge at midspan that is deHinge
Bendorf Bridge, Germany
Longitudinal section
An earh alld outstanding example of the casl-il1­
place balanced (;1I11ile\er bridge is the Bendorf
autobahn bridge O\'er the Rhine River about 5
miles (8 km) north of Koblenz, West Germ<1ll\'.
Built in 1964, this structure. Figure 2.8, has a total
length of 337S ft (1029.7111) with a navigation span
of 682ft (20S m). The design competition allowed
the competing firms to choose the material,
configuration, and design of the structure. Navi­
gation requirements 011 the Rhine River dictated a
328 ft (100 111) wide channel during construction
and a final channel width of 672 ft (205 m). The
winning design was a dual structure of cast-in­
place concrete segmental box girder construction.
consummated in two distinct portions. In part one
Plan
Cross section at
river pier
Cross section
at pier G
FIGURE 2.9. Bendorf Bridge, Part One (West), lon­
giwdin<ll section. plan, and cross sections at the ri\'er
pier and pier G, from ref. 1 (courtesy of Beton- lind
Stahlbetonball).
l
Cast-in-Place Balanced Cantilever Girder Bridges
36
'~-~!.
I
=Y~,-=t-'-'R' d~··:~,···
~ ,~- . ,';. - ...,..~\
9
,m"L __ "to _..~7_ _ sc,o __ L- __ ,,8,0 ---~-~ cao
II,
'
a,roa
-----.!...-.- sz.o--f!...-¥I,S-_1-
~l,O'!
·--·--.·-.----·---·-----SOS,Om - - - - - - - -----;-,-,.--------.----- -.-_.---._.--, ~
Longitudinal section
Federal
Plan
FIGURE 2.10. Bendorf Bridge, Part T\w (East). longitudinal section and plan. from
ref. I (courtesy of Beton- und Stahlbetonbau).
signed to transmit shear and torsion forces only,
thus allowing the superstructure to he cast
l11011olit hically with the rnai n piers. 1 •2 After con­
struction of the piers, the superstructure over the
navigahle portioll of the Rhille was completed
within one year. The repetition of the procedure in
240 sCi-illlcnts executed one aftcr the other offered
numcrous occasions to mechanize and improve the
erection Illet hod. 3.4
Thc dcck slah has a longitudinally varying thick­
ness from II in. (279.4 O1m) at midspan to 16.5 in,
(419 Illlll) at the picrs, The bottom flange varies ill
thickncss from fi in. (152 mm) at midspan to 7.87 ft
(2.4 Ill) at the piers. To reduce dead-weight
bending-moment stresses in the bottom flange
concrcte, compression reinforcement was used
extensivel\' in regions away from the piers.
Thicknesses or the various elements of the cross
seClioll are controlled partly by stress requirements
and partly by clearance requirements of the ten­
dons and anchorages.
The structure is three-dimensionally pre­
stressed: longitudinal prestressing uniformly dis­
tributed across the cross section; transverse
prestressing in the top flange; and inclined pre­
stressing in the webs. A total of 560 Dywidag bars
1! in. (32 mm) in diameter resists the negative bend­
ing moment produced by a half-span, Figure 2, I L
The maximum concrete compressive stress in the
bottom flange at the pier is IS00 psi (12.4 MPa). As
a result of the three-dimensional prestress tbe ten­
sile stresses in the concrete \\'cre negligiblc. The
longitudinal prest ressing is incrementalh' de­
creased from the pier to the hinge at midspan ami
to the adjacent piers: thus, shear stresses in the
webs on both sides of the main picrs are almost
constant. Therefore, the web thickness l-emalIlS
constant and the diagonal prest ressing remains
ycrv nearly constant.
Const ruction began on March 1, 1962. After
completion of the foundations and piers, balanced
calltilever operations began from the west river
pier in July 1963 and were com pleted at the' end of
that year. Segments were 12 ft (3.65 m) in Icngth in
the river span and 11.4 ft (3.48 Ill) in the remaining
spans, Segments \\'ere cast on a \\'eekh cycle. As the
segments becal1le shallower, the construction cvcle
was adyancecl to two segments per week. During
winter months, to protect operations from inclem­
ent weather, the form traveler was provided with
an enclosure, Figure 2.12,
FIGURE 2.11. BendOl-f Bridge, cross section showing
tendons in the deck, ref. 2. (courtesy of the American
C()!l(Tete Institute).
FIGURE 2.12. Bendorf Bridge, protective covering
for form traveler (courtesy of Ulrich Finsterwaider),
Saint Adele Bridge, Canada
37
---·1------~---'-26.5' - - - - - - - .j'-"-'--132'-6~-"--"-.1.-55'~'"
'
I ,
,
FIGURE 2.13.
SIC. ;\dcle Bridge, elevation, from ref. 5 (courtesy of Engineering News-Rf'corrl).
III the comtrllctioll of the approach spans, the
n\'c spans from the east abutl]lent were built in a
rOllline manller with the assistatlce of faisework
bents. The rour spans over water were cOllstructed
bv a pro,L\"ressi\'e placell1en t cantilever fllet hod (~ee
Chapter 6), which elllplm'ed a telllpOl'ar:' cab1e­
stay arrangement to reduce tht: calltilever stresses.
2.3
Saint Adele Bridge, Canada
;
This sttllCllln:', buill in 19G·l (the same year as the
Bendorf Bridge), represents the lirst segmental
bridge, in the COlltelllpOran' sense, cOllstruLied ill
North America. [I crosses the River of the :'vlules
near Ste. . \dele, Quebec. alld is part of the
Laurential) .\lliOrtlllie. II is a single-cell box girder
contillllolis three-span dual strllcllIre with a cellter
span of265 tr (~().~ Ill) and end spansof I:~~ ft () in.
(40.4 m), Figure 2.13. ,\t one elld is a prestressed
concrete :'):) t't (If).H m) simple spall. The bridg-e has
a Ion ft CW,;')!Il) \Trtical clearance oyer the river ill
the GlIIVOIl helow,
FIGURE 2.14. Ste, Adele Bridge, view of variable­
depth box girder (COllrtes\" of the Portland Cement As­
sociation),
"
The \'ariable-depth girder is 16 ft 3 ~ in. (4.96 Ill)
deep at the piers and 6 ft (1.83 tTl) deep at midspan
and its extremities, Figure 2.14. Each dual struc­
ture consists of;} single-cell rectangular box 23 ft (7
Ill) wiele with the top fiang-e cantilevering- on each
side 9 ft (2,75 m) for a total width of 41ft (12.5 m),
Fig-ure 2.15, pr()\iding three traffic lanes in each
direnioll. Thickness of bottom flange, webs, and
top flange are respectively I ft It in, (0.35 m), I ft 6
in. (0.46 Ill), and I ft (0.3 rn).5
A (Otal of 70 prestressi Ilg tendons were required
in each girder. Each tendon of the SEEE system
cOllsists of seven strands of seyen 0.142 in. (3.6
!llln) wires, The se\'en strands are splayed out
through a steel ring ill the anchorage and held in a
circular pattern by steel wedges between each of
the strallds. The number of tendons anchored off
at each seglllent end varies with the distance from
the pier, increasing- from an initial six tendons to
eig-ht tendons at the eighth segment, then de­
creasing to two tendons at the eleventh segment at
midspan. There are an additional 44 positive­
mOlllellt tendons ill the center span located in the
bouolll flange. 5
Ste. Adele Bridge, view of end of box
girder segment (counesv of the Portland Cement As­
sociation),
38
Cast-in-Place Balanced Cantilet!er Girder Bridges
counterweighted with iO tons (63.5 !Ill) of concrete
hlock, which was gradualh' diminished as COI1­
struction proceeded and the depth of the segments
decreased. The first pair of segments (at the pier),
each with a length of21 ft 2~ in. (6.4i m), were cast
on a temporary scaffolding braced to the pier,
Figure 2.1 H, which remained fixed in position
throughout the erection process. s
Construction of four segments per week, one at
each end of a cantilever from two adjacent piers,
was attained 1)\ the following fi\'e-d,1\ cOllstruction
cycle'>:
FIGURE 2.16. Ste. Adele Bridge, dual structure
under constructioll bv the balanced cantilever method.
frOll! ref. j (courtesv of EligillN'rilig Sl'll',I-RI'(Orrl).
Forty-sevell segments are required for each
strtlCture, eleven cantile\'ered each side of each
pier, a closure segment at midspan of the cellter
span, and a segment cast in place on each abut­
lllent. Segments cast hy t he form tr,l\'e!er were 10
It n in, C~.24 Ill) in lellgth.' Four traveling forllls
were used 011 the pr<~ject: olle pair 011 each side of
the pier for each of the dual structures, Figures
2.16 and 2.li.
The forllls \\'ere supported bv a pair of 42 ft
(12.8 111) long, 36 in. (914.4 Illlll) deep structmal
steel beams spaced 15 f't (S.Si m) 011 centers, that
cantileyered beyond the completed portion of the
structure. Initially the cantileyered beams were
Fir,11 day: Travelillg forms moved, hottOlll flallge
fOrilled, reillforced. alld cast. In the parallel span
there was a olle-dav lag such that cre\\'s could shih
back alId forth between adjacent structures,
S('(ond dO)':
top /lange.
Reinforcement placed for wehs and
Concrete placed for webs alld top
lIallge. cure hegun.
Third d(l\':
Fllurlh do)': TendOlls placed ,llld prest ressi llg
jacks positiollcd while COlJcrete was ctlring.
FijI" doy: Prest ressin g aCCOlll pi is lIed. Forms
stripped: preparatiolls lllade 10 repeat ndc.
rile ncle begaq Oil :-tolJday. Since there was a
lag of ()ne day 011 the parallel structure. a six-!!;!\'
work week was required. U pOll completioll of the
ele\'en t h seglllellt ill each ca I1tih:\'Cr the cont raet or
installed telllporan' blsework to support the
abutlllent end amI then cast the closure segment at
midspall. Counterweights were imtalled at the
abutmellt cnd to balallce the weight of thc closure
forms alld seglllent weight. After installation and
stressing of the contilluity tcmlons. ai>utmelll seg­
ments were cast and expallsioll joillts installed."
2.4
Bouguen Bridge in Brest and Lacroix Falgarde
Bridge, France
The Bouguen Bridge in Brittany, West Province in
France, is the lirst rigid-frame continuous struc­
ture built in balanced calltilever (1962 to 19(3).
The finished bridge is shown in Figure 2.6, while
dimensions are given in Figure 2.19. It carries a
three-lane highway over a valley 145 ft (44 m)
deep-Le Vallon du Moulin Poudre-and pro­
\'ides a link between the heart of Brest city and Le
Bouguen, a new urban development.
The total length of bridge is 684 It (208 Ill). The
main structure is a three-span rigid frame with
a
FIGURE 2.17.
Ste. Adele Bridge, view of form travel­
ers c<lntile\'(:ring from completed port ion of the st rtle­
tllre, from ref. 5 (courtesy of Enginl'fring A'('u·s-Rf(Ord).
Sf
39
Bouguen Bridge in Brest and Lacroix Falgarde Bridge, France
FIGURE 2.18. Ste. Adele Bridge. schematic of construction sequence. from
ref. ;) (courtesy of EngiW'Pring News-Record).
box girder is 10 ft (3 Ill); web thickness also is CO[l­
stant throughout the deck and is equal to g~ in.
(0.24 111).
Piers consist of two square box COIUllllIS I() ft by
10ft (3 x 3 m) with wall thickness of 91 ill. (0.24 m)
located under each deck girder. Two walls 8~ in.
(0.22 111) thick with a slight recess used for ;11'­
chitectural purposes connect the two COIUIIIIlS.
Both piers are of conventional reinforced concrete
construction, sli p-formed at a speed reaching 14 ft
(4.25 m) per day in (JIle continllolls operation,
piers elasticall\' built-in on rock foundations with
span lengths of 147, 268, and 147 ft (45, 82, and 45
m). At one end the deck rests on an existing
masonry wall properh strengthened; at the other
end a shorter rigid frall1e with a clear deck span of
87 ft (26.5 111) p1'Ovides tire approach to the main
bridge.
'The deck cOllsists of two box girders with vertical
webs of variable height, varving frolll 15 ft 1 in.
(4.6 m) at the support to 6.5 ft (2 m) at midspan
and the far ends of the side sp,~ns. vVidth of each
(a)
1
~
I
~\
.
,
Midspan section
!
~
~
(\
"
'.00
Pier section
J
i
;
J-I"I~ ~
II
---r
p,;
'_00
.00
Plan section at pier
(b)
FIGURE 2.19. Bouguen Bridge. France, general dimensions. (a) Longitudinal section.
Cross sections.
(Ii)
100
40
Cast-in-Place Balanced Cantilever Girder Bridges
FIGURE 2.20. Bouguen Bridge. construction of east
cantilever.
The superstructure box girders are connected to
the pier shaft bv transverse diaphragms made in­
tegral with both elements to insure a rigid connec­
tion between deck and main piers. Construction of
the deck proceeded in balanced cantilever with 1()
ft (:1 m) long segments cast in place in form travel­
ers with a one-week cycle, Figures 2.20 and 2.21.
High-early-strength concrete was used and no
steam curing was I·equired. Concrete was allowed
to harden for 60 hours before application of pre­
stress. The following cube strengths were obtained
througboUl the project:
60 hours (time of pre­
stress)
i days
28 days
90 days
3700 psi (25.5 I\fPa)
5500 psi (37.9 MPa)
7000 psi (48.3 MPa)
8200 psi (56.5 MPa)
Only one pair of form tra\'elers was used for the
entire project, but each traveler could accommo­
date the construction of both girders at the same
time.
,
,/
.i!i~
. ...~
FIGURE 2.21. Bouguen Bridge, view of the traveler.
During construction of the deck, much attention
was given to the control of vertical deflections.
Adequate camber was gi"en to the travelers to fully
compensate for short- and long-term cOllcrete
deflections. The cumulative deflection at midspan
of the first cantilever arm was H in. (40 mm) at
time of completion. Concrete creep caused this
deflection to reach 3 in. (75 mm) at the time the
second cantilever arm reached the midspan sec­
tion. Proper adjustment of the travelers allowed
both cantilever arms to meet within i in. (3 mm) at
the time continuity was achieved. flat jacks were
provided over the outer supports to allow for am'
further desired adjustment.
The structure is prestressed longitudinally b,
tendons of eight 12 111m strands:
76 tendons over the top of the pier segment,
32 tencions at (he bottom of the crown section,
20 tendons in the side spans,
and transversely bv tendons of seven 12 111m
strands.
The Lacroix Falgarde Bridge over Ariege
River in France, built in 1961 and 1962, is similar
to the Bouguen Bridge and represents (he first
continuous deck built in balanced cantilever (see
(he photograph of the finished bridge, Figure
2.22). It consists of three continuous spans 100,
200, and 100 ft (30.5, 61, and 30.5 111). The single
box girder has a depth varying between 4 ft 5 in.
and 10 ft 6 in. (1.35 to 3.2 111). Dimensions are
given in Figure 2.23. The superstructure rests on
both piers and abutments through laminated
bearing pads.
The deck was cantilevered and the construction
started simultaneously from the two piers with
four travelers working symmetrically. During COI1­
FIGURE 2.22. Lacroix-Falgarde Bridge, view of the
structure during construction.
Saint Jean Bridge Over the Gardonne River at Bordeaux, France
41
~L~~-~I
_
30 25
j
60.00
I
30 2 ~
[
2.50
FIGURE 2.23.
I
l.;[croix-Fal~arde
structioll. the deck was telllpOLlri!v fixed to the
piers b\' vertical prestress. rhe structure is pre­
stressed longitlldinalh h\' tendolls of tweln~ H IllIll
strands alld tLlIlS\er'iel\ 1)\ tendons of tweh'e 7
mill strallds.
2.5
Saint Jean Bridge over the Garonne River at
Bordeaux, France
Completed ill .\pril l~l!j:i. the Saint Jean Bridge ill
Bordeaux is a remarkable application of the new
concepts deH'loped at that time in cast-in-place
cantilever cOllstructioll. l'he main structure has all
over~ililellglh or !5!i() t't (47:') Ill) and is continuous
with expallsionjoilll'i ollh on:r the ahutments. The
deck is free to expand on neoprene hearings lo­
cated Oil all ri\'('r piers. Figl1l'e 2.2·1. .'\ very
efficient method of pier and fOllndatioll constl'llC­
lioll was also (h~\'l'loped, which will he described in
more detail ill ChaplCl' 5.
The bridge was built in the heart of the cit\' of
Bordeaux O\'er the Caroline Ri\'er between a 175­
year-old multiple-arch stone structure and a 120­
year-old railwav bridge designed by Eiflel, the en­
gineer who designed the EifTel Tower.
The main structure includes six continuous
spans. The central spans are :253 h (77 111) long and
allow a navigation clearance of 38 ft (11.60 m)
abm'e the lowest water level, while the end spans
are only :2:22 ft (67.80 111) long. Short spans at both
ends. 50ft (15.40 m) long, provide end restraint of
the side spans over the abutments. The overall
width of the bridge is RR ft (26.RO m), consisting of
six traffic lanes, twO walkways, and two evde lanes.
Super'structure dimensions are shown in Figure
2.25,
Bridge. e\e\;ttion and cross seniol1.
The deck consists of three box girders. The COIl­
stant depth of 10.R ft (3.30 m) has been increased
to 13 ft (3.90 lll) over a length of 50 It (15 111) on
each side of the piers to illlprme the bending
capacit\' of the pier section and reduce the amollnt
of cantilever prestress. :\0 di~lphragms were used
except O\'er the supports. '['he results of a detailed
a 11 a lysis performed to <fetermi ne the transverse
hehavior of the deck con firmed this choice (see
detailed description ill Chapter 4).
Longitudillal prestressing consists of tendons
with t we!ve H 111111 and twehe } ill. st rands. Trans­
verse prestressillg consists
tendons with twelve R
nllll strands at 2.5 ft (0.75 m) illtervais. Vertical
prestressing is also provided ill the wel)s near the
supports.
As indicated in Figure 2.26. three separate pier
colulllns support the three deck girders. 'They are
capped with large prestressed transverse dia­
phragms. The piers are founded in a gravel bed lo­
cated at a depth 0[,15 ft (14 Ill) below the river level
bv means of' a reinforced concrete circular caisson
or
FIGURE 2.24. Saint Jean
completed structure.
at
Bordeaux, view of the
:
::
COUPE LONGITUOINALE
(a)
FIGURE 2.25.
Saini Jean al Bordeaux.
(a)
Longitudi1lal and
~t
t--.
1
1\(DI
/
(,.
':0
.,
If •
(/I) (TOSS
seniollS.
J
1
f\
i
I
t'3ali
!
i
II
¢1
29'(>'
FIGURE 2.26.
42
's' ,
29'(>'
Saint Jean Bridge at Bordeaux, typical section at river piers.
Siegtal and Kochertal Bridges, Germany
FIGURE 2.27. Saint Jean Bridge at Bordeaux, work
progress on piers and deck.
18.5 ft (5.60 1l1) in diameter and 10ft (3 m) high,
tloated and sunk to the river bed and then open­
dredged to the gravel bed. Precast circular match­
cast segments prestressed vertically make up the
permanent walls of caissons, while additional seg­
ments are used temporarily as cofferdams and
support for the deck during cantilever construc­
tioll. A lower rrel11ie seal allows (It:w~terillg alld
placi llg of plain concrete fill inside the caisson ..
reinforced concrete fOOling and pier shaft are
finally cast ill one ([;\\'.
The superstructure box girders were cast in
place in 10 ft C3.05 Ill) long segments using twelve
form travelers, allowing simultaneous work on the
three parallcl cantilevers at. two different piers.
The 20 fl (0.1 111) long pier segment was cast on the
temporary supports provided bv the pier caissons.
allowing the form travelers to be installed and can­
tilever construction to proceed. Six working days
were necessarv for a complete cycle of operations
Oil each traveler. Work prog-ress is shown ill Fig­
lues 2.27 and 2.28. Total construction tillle for the
entire 130,000 sq It (12,000 m 2 ) was approximatelv
n.e
FIGURE 2.28. Saint Jean Bridge at Bordeaux. can­
tilever construction on tvpical pier.
43
one year, as shown on the actual program of work
summarized in graphic form in Figure 2.29. To
meet the very strict construction deadline or the
contract, it was necessary to bring to the project site
another set of three travelers to cast the last can­
tilever on the left bank and achieve continuity with
the southern river pier cantilever. Altogether.
meeting the two-year construction schedule was
recognized as an engineering achievement.
Exactly one hundred years earlier, Gustave Eif­
fel had built the neighboring railway bridge in
exactly two years-food for thought and a some­
what humbling reHection for the present genera­
tion.
2.6
Siegtal and Kochertal Bridges, Germany
The Siegtal Bridge near the town of Sieger, north
of Frankfort, Germany, represents the first indus­
trial application of cast-in-place cantilever con­
struction with an auxiliary overhead truss. This
method was initially developed by Hans Wittfoht
and the firm of Polensky-und-Zollner amI sub­
sequently used for several large structures in Ger­
many and other countries. One of the 1110St recent
and rcmarkablc examples of this technique is the
Kochenal Bridge between Nuremberg and Heil­
bron, Germany. Both structures will be briefly de­
scribed in this section, while a similar application ill
Denmark is covered in another section of this
chapter.
Siegtal Bridge is a twelve-span strllctUl'e 3450 rt
(1050 m) long resting on piers up to 330 it (lOO Ill)
high, with maximum span lengths of 344 ft (105
m). Figure 2.30. Two separate box girders carr"
the three lraflic lanes in each direction for a total
width of 100 ft (~~O.5 m). Figure 2.:31. Structural
height of the constant-depth box girder is 19 ft (5,8
Ill), corresponding to a span-to-depth ratio of 18.
The deck is continuous throughout its entire
length, with fixed bearings provided at the three
highest center piers and roiler bearings of high­
grade steel for all other piers and end abutments.
Piers have slip-formed reinforced concrete hollow
box shafts with a constant transverse width of 68
ft (20.7 m) and a variable width in elevation with
a slope of 40 to 1 on both faces.
The superstructure was cast in place in balanced
cantilever from all piers in 33 ft (10 m) long seg­
ments with an auxiliary overhead truss supporting
the two symmetrical travelers, and a cycle of one
week was obtained without difficulty for the con­
struction of two symmetrical 33 ft (10 m) long seg­
,I
PONT OESCHAMPS
I~
l\!
~
z
.~
i
'MAl
!
!
~~IN
l
I?',AOUT
1PlEUXO
,
jPIEU
t=:h
.,.-.i
DEC
BfT~
JANV
I
~~
BETON
[t:1AR5
: AVRIL
~ JUIL
'AovT •
I
NOV
I 1
DEC
IJ')
-c;
g:
"-­
FEV
~.-,
MARS
I­
/
L
~illl
-"'.1
~~
~4
~
AM<»lCE
/
/ \
1i
!:!
\.
--­
~
~~
i
il!:~
-'
L...J
-
!\
1_\
A
"­
L
:=::::::::::::­
iBE11lN
P'PHASE
'ij i!i
~
-I.
CL
~~
~~
!l
ICLAVAGf
---­
I BArTAGE
1PlfUX
lil
~~
:7::--"
r-
~
~
":'"
!
;;
~ '"
E,,­
A.
---
~U\'ES.2.M!lJJ.
FIGURE 2.29.
::
~I~
~I--~£:---~
~~
~jij
~
-~
JIf2
\
•.
.!Q
~l~
illl:'
.J~
"'\.
BETON
•
.J~l~.
.W1iL
~~
J!~
B.
..L ,.\
I
OCT
~1i5
.1.1
L \
1 _\.
J \
:,)EPT
.~
~
~ i!i
i:i~
~~~~
1'1,.
~IJUIN
~oo.~ ..
j
~ i«
t-l~,'f,t
'"
.~
,;U
!;l
~
j
IMAI
JANV
~
.",
~
d
7~
w
~tTI
~
;t
·f
17.00
~: BATTAGf
i
l-
~
j
.L.:...!
NOV.
~
I
!
I JVIL
'OCT.
g
83.16
' L
:6:---­
~T
~
L
,
I
'"
1
93.21
IAVRIL
1
~
.L
fl' !'­ ~ tTl'
1 J !
7'
/
1965
to
"­
(
L
--==-­
FINn.
Sailll Jean Bridge at Bordeaux. actual program
/
..
1
\
I
'\
~.i
\
-
-­
i~i1i~SE
or \\ork.
Elevation
Cross section 1
Longitudinal section
Cross section 2
Top view
Horizontal section
FIGURE 2.30.
44
SiegtaI Bridge, general dimensions.
Siegtal and Kochertal Bridges, Germany
JI
! 00
375
'00
FIGURE 2.31.
Sicgtal Bridge. tvpical cross section.
mellls. The auxilian truss was also first used to cast
the pier segment abo\e each pier, Figure 2.32, be­
fore cantilever const ruct ion could pnx:eed, Figu re
2.33. Because the pier shafts are lIexible and have
limited bellding capacil:', il was inadvisable to sub­
ject thelll to ullsnnlllelrical loading conditiolls
during deck cOllStruction. rims, the merhead
truss also served the purpose of stabilizillg the GIll­
tilever arms beli)j'C conlillllit\, was achieved with
the previolls cantilever.
The auxilian steeitruss is made of high-strength
steel (50 ksi vieid strength). Prestressing is applied
to the upper chord, which is subjected to high tell­
sill' stresses in order to reduce t he weight of the
equipment. 'I 'he overall lellgt h of the truss is 440 n
(135 !Il) long to ;tCCOllllllodate the maximulll span
length of 3,H ft (105 lll). rhe total weight of' the
truss and of tile two sllspended travelers, allowillg
castillg of two :$:$ (\ (I() Ill) long .'leglllCrtlS, was 6{)() t
(600 lilt). DeckcOllCl'ete was pUlIlped to the \'ariolls
segments through pipes carried from thc finished
deck bv tlte allxiliarv truss, Figures 2.~~4 alld ~,:.\5.
\Vork cOllllllelKcd on the superstructure in
l\larch 1966, The first box girder was completed ill
FIGURE 2.32.
45
Siegtal Bridgc, pier segment casting.
April 1968. The truss and travelers were illl­
lllcdiateh transferred to the second box girder,
which was completed ill Septelllber 1969. Thus,
the average rate of casting was as follows:
3450 ft (1050 1l1) in '25 months, or 140
per momh
First bridgl':
ft (4 ~
Ill)
Sl'(olld bridgr': ;H50 It (l050 m) in 17 mOllths, or
~()() rr ({)2 111) pCI' mOllt h
Both bridges: G900 It ('2100 111) in 42 months, or
100 ft (50 m) per mont h
An otIlstanding contemporary example of the
sanle technique is lhe KochertaI Bridge in Ger­
Illany, shown ill fill a I progress ill Figure '2.36. Gen­
eral dilllellsions of the project arc givcn in Figure
~.:)7, Total length is 3700 ft (1128 Ill) with typical
spam of 453 fl (138 Ill) supported on piers up to
f)OO ft (183 Ill) ill height. The single box girder
superstructure with precast outriggers canies six
t raJ'fic lanes for a lotal widt h of 101 ft (30.7G Ill).
Box [Jiers wcre cast ill climbing forms with 14.~ ft
(~Ls3 1II) high lilts. The top sectioll is COllstant for
all piers with olltside dimensions or 16.4 by 2H.'2 1't
FIGURE 2.33.
Siegtal Bridge, cantilever construction.
46
Cast-in-Place Balanced Cantilever Girder Bridges
\
FIGURE 2.34.
Sicgtal Bridgc. elcvation
(5 hv 8.6 m). The f6ur faces are sloped to increase
the dimensions at foundation level to a maximum
of 31.2 by 49.2 It (9.5 by 15 m) for the highest
piers. Wall thickness varies progressiveh' from top
to bottom, to follow the load stresses, from 20 in.
(0.5 m) to 36 in. (0.9 01).
The constant-depth superstructure is cast in two
stages, Figure 2.38: (l) the single center box with a
width of 43 ft (13.1 111) and a depth of 23 ft (7 m),
and (2) the two outside cantilevers resting on a se­
ries of precast struts. To meet the very tight con­
struction schedule of22 months it was necessary to
llse two sets of casting equipment. working simul­
taneously from both abutments toward the center.
Each apparatus was made of an overhead truss
FIGURE 2.35.
and travelers.
Siegtal Bridge. typical section of truss
or O\'Crhead truss and
travelers.
equipped with a launching nose to move from pier
to pier and two suspended travelers working in
balanced cantilevers, casting segments on a one­
week cycle. Figure 2.39.
2.7
Pine Valle), Creek Bridge, U.S.A.
The first prestressed concrete cast-in-place seg­
mental bridge built in the United States was the
Pine Valley Creek Bridge on Interstate 1-8 between
San Diego and El Centro, Calif6rnia. Figures 1.66
and 2.7, opened to traffic late in 1974. This struc­
t tire is located approximately 40 miles (64 km) east
of San Diego and 3 miles (4.8 km) west of the
FIGURE 2.36.
project.
Kochertal Bridge, general vIew of
Pine Valley Creek Bridge, U.S.A.
o
I
5
-~;
ft
,""" ."'"..,,
-'~
~"tI",r ~u"h'l ••lk ----~
--'-
.'
-jJ~:
.----
,
II
,!
'II
---~~U,I'h('l
.....
Kocher
47
I
l,
- "._.-_
~_
_._---_.-------_ .. --.--.-----------------~---~--
Unl'''' Musch.lk.lk
Obtrfr Buntsands t ~tn
/~~ Herlbronn
Nurnb"g
c.--:C>
'\'"
- 81,00
IliaD
l38GG
[J6,00
1]3,00
1128.00
Il8,00
Il8.00
~~
I
,I
FIGURE 2.37.
ero,s sect iOIl.
1l8,OO
-
61,00
U"
'
Kochenal Bridge. e\nation. plan and
commutlit\ of Pine Valle\ and within the Cle\e­
land :'\ation,Il Forest. Interstate 1-8 crosses over a
sell1i,lrid l-cgion that is highly erodible when the
ground c()\'Cr is disturbed; consequenth' strillgent
controls were imposed on access roads and
ground-c()\'cr disturbances. Structure type was
influenced 1)\ the following factors: site restric­
tions. ecollomics. ecological considerations. and
Forest Sel'\ice limitatiolls. After com paring \arious
possible schemes sllch as steel arch, deck truss, or
steel. box girder. the California Department of
Transport,ltion selected a concrete box girder
bridge predicated on the use of cantilever seg­
­
(1/)
58J
JO,7&
13.10
8.83
(b)
FIGURE 2.38. Kochertal Bridge. typical cross sec­
lions. (Il) First stage casting. (b) Final stage.
48
Cast-in-Place Balanced Cantilever Girder Bridges
...
•
FIGURE 2.39.
lion.
Kocherral Bridge, cantilever construc­
mental construction, particularly well suited to the
site because the depth and steep slopes of the "allev
made the use of falsework impractical. Also, the
cantilever method minimized scarring of the
natural em'ironment, which was a major consider­
ation [or a prC!iect located in a :\:ational Forest.
The bridge has an average length of 1716 ft (523
m) ane! consists of twin two-lane single-cell,
trapezoidal box girders each 42 ft (12.8 m) out-to­
out. The deck is 450 it (137 m) above the creek
bed. The superstructure consis~s of five spans of
prestressed box girders 19 ft (5.8 m) deep. The
center span is 450 ft (137 Ill) in length, Ranked by
side spans of340 fl (103.6 lll) and 380 ft (115.8111),
with end spans averaging 270 ft (82.3 Ill) and 276 ft
(84.1 11l). The bridge was constructed with four
cantilevers. Pier 2 has cantilevers 115 ft (35.1 m) in
length. piers 3 and 4 have 225 ft (69.6 m) cantile­
vers, and pier 5 has 155 ft (47.2 m) cantile­
vers,6.7.R Figure 2.40. Provisions were made in the
design 10 permit the portions of spans I and 5 ad­
jacent to the abutments to be constructed segmen­
tally or un falsework at the contractors' option. The
later option was exercised by the contractor. !I. 10
CANTu.evtR
ABUT. 6
,.,.
PIER Z
PitR
~
PltR 3
PIER"
ELEVATION
TYPICAL SECTION
FIGURE 2.40.
Pine Valley Creek Bridge, ele\'ation and typical senion, from ref. 8.
I
Pine Valley Creek Bridge, V.SA.
Hinges were prodded in spans 2 and 4 at the
end of the main cantilevers. In the preliminarv de­
sign, consideration was given 10 the concept of a
continuous structure for abutment to abutment
without any intermediate joints. Continuity has
mallV advantages insohlr as t his particular struc­
ture is concerned. Howner, it has the significant
dis<I(hantage of large displacements uncler seismic
loading conditions. Because of the extreme dif­
ference in height and stiffness between piers, it was
determined that all the horizontal load was being
trallsmillecl to the shoner piers, which were not
capable of accepting it. H
The pier foundations posed sOllle interesting
cOllStruniOll problems. The top ~() ft (f) tll) of the
rock material at the ~tructure ;;ite 'was badlv
fissured, with sOllJe tissuring as deep as 40 ft (12
m). :\'arrow footings onlv 1 ft (0.3 Ill) wider than
the pier shafts, tied dowII wit h rock anchors, were
preferred to the conv(:,lHional spread footings to
minimize the amount of eXGl\·;lIion.
Although the piers are ~pectaclilar because or
their sizc, thc\ are no! ulliqllc in concept. The two
main piers, :1 and ..t:, are approximatelv 370 It (I U
Ill) in height and are made up or two vertical cellll­
lar sectiol1s intercollnected with horizontal tics. III
a trallsVerse directioll the piers h,l\e a constant
width to ElCilita!e slip-form cOllstructioll. while in
the IOllgituciin;d directioll the sectioll varies
parabolicalh. with a llIinimul11 width or 16 1'1 (4.9
m) approximateh olle-third down h'olll the top. At
this point the\ flare out 10 ~:\ n In 24 ft (7 In 7.3 m)
at the soffil. The pier wall t hicklless is a cotlstan! 2
ft (0.6 m).6.!)
Earthqllake cOllsiderations produce the critical
design load Ii)!' the piers. rile 1940 EI Centro earth­
quake was used as the forcing function in the de­
sign anahsis. Design criteri;l re<luired that the
c.omplcted strllctural fLlIne withstand this force
level \\'ithmll exceeding stress levels of 75c;{ of
yield. The picr struts arc all important clement in
the seisIlIic design of rhe piers. They provide duc­
tility to the piers h\' pmviding energy-absorbing
joints alld an increased stabilit\" against buckling
for the PI'illcipal shaft elements. Because of the size
of the struts in relation to the pier legs, the major­
ity of the rotatioll in the 5t rut-Iegjoint occurs in the
strut. Thus, ;t yelT high percentage of tranS\'erse
confinillg reinforcemellt was required in the strut
to insure the ductility at this location. 6 •9
Although preliminan design anticipated the
slip-forming technique for construction of the
piers, the contractor tinalh elected to use a self­
climbing forllJ system. Steel forms permitted 22 ft
49
(6.7 m) high lifts, and they were given a teflol1
coating to facilitate stripping while producing a
high-guality finished concrete surface.
COllstruction of the pier caps was especially
challenging. The pier caps, Figure 2.41, consist of
two arms 60 ft (18.3 m) in height, which pntiect
outward at an approximate angle of 60 0 from each
stem of the pier shafts. These arms are constructed
in four lifts in such a manner that the forms for
each lift are tied into the previous lift. Upon com­
pletion of the pier cap arIllS they are tied together
and the top strut is formed, reinforcement placed,
and cast.. The pier cap is prestressed tra!lsversely in
order to overcome side thrust from the super~
structure.
The superstructure consists of two parallel
trapezoidal box girders 42 ft( 12.8 m) wideand 19 It
(5.R 1l1) deep with a 38 ft (11.6 111) space between
the boxes, sllch that all additional box girder may
be cOllStructed for future widening, Figures 2.40
and 2.4~. The boxes. in addition to being post­
tensioned longitudinalh-, have transverse prestress­
ing in the deck slab, together with sufficient mild
st eel rei n forcemcllt to l'esist nom ina I construct.lOll
loads, allowing the transverse prestressing opera­
tions to be relllO\'cd fmIll the critical path. The
'NCUNED
COL......
!~
!
110'
280'
PIER SfiAFT
280'
lCct.......1
&CI
tJ-"---'-"-':
!'l-J:~ION
=-~-±i' FOOTING
OF PIER
SECT. X:L
{e'ER s_n
FIGURE 2.41. Pine Vallev Creek Bridge, elevation.
side vie\\". and cross section of pier. from ref. 7 (courtesy
of the Portland Cement :\ssociation).
50
Cast-in-Place Balanced Cantilever Girder Bridges
STEEL TAUSS USED FOR ACCESS
TO CANTILEVER CONSTRUCTION
AB.6
?'STEfL TOWERS
FOR LAUNCHING
AUXIUARY BRIDGE
BARRIER RAILING
PIER 5
AUXIUARy BRIDGE
SUPPORTEO AT PIE.R CAP
COlJNTERltltiGHT
FIGURE 2.42. Pille Valle\ Creek Bridge, t\'jlical hox
girder cross section, from reI". 7 (courtesy of the Ponland
Cement Association),
sloping webs and large deck ()\'Crhallgs \,'ere lIsed
to minimize the slab spans and the number of
gi!'der webs and to accentuate a longitudinal shad­
ow line. thus redllcin~ the apparet1l depth. The web
thickness of 16 in. (406 mm) was selected to permit
side-by-side placement of the largest tendon I hell
being used ill bridge construction alld to keep the
shear reinforcement to a reasonable size and
spacing, Figure 2.42. The bottom slah al lllidspan
is 10 in. (254 mm) thick and flares out to 6.5 ft (1.98
111) at the pier. 6,7.9 Construction of the superstruc­
ture proceeded in a balanced cantilever fashion.
Figures 2,i and 2.43.
As shown in Figure 2.44. the erectioll scheme
proposed by the contractor allowed all super­
structure work to be performed in a continuous
sequence, essentially from the top. Four forlll
travelers were used for the cantilever construction
of t his project, one at each end of each cantile\'er
arm. Basically, one tni\'eler consisted of an o,'el'­
head steel truss used to support the £'onnwork for
the typical 16.5 It (5111) long segments. The truss is
anchored, af the rear. to the previoush' cast seg­
ment, while the front end is equipped with hr­
draulic jacks used for grade adjustment. High­
dellsit y plywood was used for all formed surfaces.
A total of 1i2 cast-ill-place segments ,,"ere required
for the entire structure. Falsework was required
close to abutments 1 and 6 to complete the side
spans beyond the balanced cantilever arms,
Fonnwork used in that portion of the structure
could be reused above each intermediate pier cap
to construct the 35 ft (l 0.7 Ill) long pier segl1lent
before the actual cantilever construction pro­
ceeded.
The cross section of the superstructure allowed
STEEL SAODLE
AUXILIARY
BRIOGE
SUPPORTED BY SUPERSTRUCTURE
FIGURE 2.43. Pillc Valin Crcck Brid~('.allxilial'\
bridge. froJl] rd. 7 ((Jurtes\ of the Portland Ccment As­
sociatioll).
an auxiliar\' truss 10 he located between the t\\'()
concrete box girders, Figut'e 2.43, This auxiliary
bridge consisted of a st rucIU ral steel t russ I() It
(3.05111) square in cross section and :120 ft (97.5 m)
in length. In a stationan positioll it was supported
at the leading end on the pier cap strut and at the
rear end of a steel saddle between the two concrete
boxes, I twas desiglled such that the frollt end
could be cantilevered out 225 It (68.6111), \,'hich is
one-half the main span, Electric winches allowed
longitudinal launching between the concrete box
girders. When pier 5 was completed, the auxiliary
bridge was erected in spall 5-6, utilizing tempo­
rary Sll ppon towers near abutlllent 6. Subsequent
30 ft (9. I m) lengths of auxiliary truss were attached
at the abutment amI incrementallv launched to­
ward pier 5, umil its frotH end was supported on the
pier cap. The pier table was thell constructed and
cantilever construction commenced until the
structural hinge in span 4-5 was reached. Upon
completion of the closurejoint in span 5-6 the aux­
iliary truss was launched forward until the front
end reached pier 4. The form travelers were dis­
mantled from the tip of the cantilever and
reerected on the pier table at pier 4. and cantilever
FIGURE 2.44. (Opposite) Pine Vallev Creek Bridge,
erection scheme proposed by the contractor. from ref.
10.
c
~
construction on
conventional
falsework
Cantilever
Construction
from pier 5
4
auxiliary
"
@
bridge
/
G)
3
I"
0
0
auxiliary
bridge
(i)
Stage 4
from pier 2
I
CD
Stage 5
completion
n
G)
CD
51
52
Cast-in-Place Balanced Cantilever Girder Bridges
construction was started again. This cycle was re­
peated until closure was achie"ed in span 1-2.
The use of the auxiliary truss had the following
advantages 1o:
1.
2.
3.
Men and materials for the superstructure
could reach the location of construction from
abutment 6 over the auxiliary bridge and the
already completed portion of the superstruc­
ture without interfering with the valley below.
The construction equipment (tower cranes and
hoists) at the piers was required only for the
actual construction of the piers and could be
relocated from pier to pier without waiting for
completion of the superstructure.
Except for construction of abutment 1 and
pier 2, site installation for the entire project
was located at one location, near abutment 6.
Concrete was supplied from a batching plant lo­
cated approximately.2 miles (3.2 km) from the site.
Ready-mix trucks delivered the concrete at abut­
ment 6. The concrete was then pumped through 6
in. (152 mm) pipes down the slope to the foot of
piers 5 and 4. The concrete for the superstructure
was pumped through a pipeline installed in the
auxiliary truss right into the forms. A second
pump with a similar installation was located at
abutment 1 to supply concrete for abutment 1 and
pier 2.10
A 5000 psi (35 MPa) concrete was specified for
the superstructure, presenting no unusual prob­
lems. However, to maintain a short cycle for the
construction of the individual segments it was nec­
essary to have sufficient strength for prestressing
30 hours after concrete placement. This was
difficult to achieve, since the specifications did not
allow type III cement and certain additives. A so­
lution was to prestress the individual tendons nec­
essary to support the following segment to 50 per­
cent of their final force. The form carrier could
then be advanced and the remainder of the pre­
stressing force applied after the concrete reached
sufficient strength and before casting the next
segment. to
Prestressing was achieved using It in. (32 mm)
diameter Dywidag bars. Longitudinal tendons
were provided in 33 ft (10 m) lengths and coupled
as the work progressed. Temporary corrosion
protection of the bars was obtained by blowing
"VPI" powder into the ducts and coating each bar
with vinyl wash or "Rust-Van 3 10."8
2.8
Gennevilliers Bridge, France
The Gennevilliers Bridge, Figures 2.45 and 2.46, is
a five-span structure with a total length of 2090 ft
(636 m). At its southern end it is supported on a
common pier with the approach "iaduct from the
port of Gennevilliers. It crosses successively an en­
trance channel to the port, a peninsula situated
between the channel, and the Seine River itself,
Figure 2.47. It is part of the Al5 Motorway, which
traverses from the Paris Beltwav through Gen­
nevilliers, Argenteuil, the valley d'Oise, and on to
the city of Cergy-PonlOise. The present structure
provides a four-lane divided highway with provi­
sion for a future twin structure.
The superstructure is a variable-depth two-cell
box girder with spans of 345, 564, 243, 564 and
371 it (l05, 172,74, 172 and 113111). Depth varies
from 29.5 ft (9 m) at intermediate piers to 11.5 It
(3.5 m) at midspan of the 564 ft (172 m) spans and
its extremities, with a depth of 23 ft (7 m) at
midspan of the short center span, Figure 2.46.
Depth-Io-span ralios of the 564 ft (172 m) spans al
midspan and at the piers are respectiveh' 1/49 and
1119. The curved portion of the structure has a
radius, in plan, of 2130 ft (650 m). The longitudI­
nal grade is a constant 1.5 percent within the zone
of cUrYature. Because the short center span is sub­
jected to negative bending moment over its entire
length, the structure behaves much as a continuous
three-span beam.
In cross section, Figure 2.48, the two-cell box
girder has a bottom Range \'aning in width from
42.2 It (12.86 !TI) at midspan to 30.5 ft (9.3 m) at
the pier, for the 564 ft (172 m) span. Thickness of
the bottom Range varies from 47 in. (1.2 m) at the
pier to 8 in. (20 cm) at midspan. The top Range has
FIGURE 2.45. Gennevilliers Bridge, view of curved
five-span structure.
=
==
53
Gennevilliers Bridge, France
.,;~"
"lfz
..
$
o
FIGURE 2.46.
Cenm:vil!iels Bridge. plan and dev'ation, from ref. II.
an overall width of 50.!) ft (18.48 111) with a 6 ft
(Ut~ Ill)
overhang 011 one side and 1),2 ft (l.88 111)
on the olher. Thickness of the top flange is a con­
stant 8 ill. (20 cm). The center web has a constant
thicKness of It) in. (400 mll1). Exterior webs, which
are inclined tHO to the venical, varv in thickness
FIGURE 2.47.
from 16 in. (400 !TIm) at the pier to 12 in. (300 mm)
at midspan. Diaphragms, Figure 2.49, are located
at the su pports. The superstructure is prestressed
in three directions, with strand tendons being
utilized longitudinally and transversely and bar
tendons utilized for the webs. I nterior anchorage
Gennevilliers Bridge, aerial view of the completed bridge.
54
Cast-in-Place Balanced Cantilever Girder Bridges
At Support
FIGURE 2.48.
At Mid Span
Genne\'ilIiers Bridge. cross section, from rei. II.
blocks for the longit udinal prestressing are located
at t(,P slab level.
FIGURE 2.49.
Genne\'illicrs Bridge. interior vie\\'
showing diaphragm.
The superstructure is fully continuous over its
total length of 2090 ft (636 Ill) between the nonb­
ern abutment alld the southern transition pier \\'ith
the approach viaduct. The deck rests upon the
four main piers supported Iw large elastollleric
pads. The superstructure was cast in place using
the balanced cantilever method according to the
step-by-step scheme shown in Figure 2.50, Seg­
ments over the piers (pier segments) were COII­
structed first on formwork, in a traditional man­
ner, except for their unusual length [26 ft (1.9m)]
and weight [850 t (770 mt)].
Four travelers were used for casting the t\piGd
11 ft (3.35 m) long segments varying in weight
from 242 t (220 mt) near the piers to 110 t (100 mt)
at midspan. ll The travelers were specially designed
to achieve maximum rigidity and prevent the usual
tendency to crack a newly cast segment under the
deflectiolls of the supporting trusses of COI1\'ell­
tional travelers. The framework used for this pur­
pose was made of self-supporting forming panels
assembled into a monolith weighing 120 t (110 Illt)
and prestressed to the preceding part of the
superstructure to make the unit substantially
deflection free, Figure 2.51. Stability, especially
uncleI' wind loads or in the event of an accidental
failure of the travelers during the construction pc­
riml, was maintained by a pair of cables on each
Grand'mere Bridge, Canada
55
~
L
Jr
K
~
~
···········0
82
t
81
~-LL
---
A1
A2
:-f
A;
M
-
~
""
:if
9
I
B'
!l
I
E
FIGURE 2.50.
t
82
0
t •
t
r
S2
B2
to
Grand'lV1ere Bridge, Canada
I
~0
B
A2
I
I
I
I
i
;
1_
&
(;ennl'villicrs Bridge, erectioll seqlll'l1Ce,
This three-lane ClSI-ill-p!;Ke segmelltal bridge is
located Oil Quebec .\Uloroule ;,)5 and crosses the
SI. .\Lmrice Ri\er ;1J)proxil11;ueh :) miles (4,8 kill)
llorth of Grand'.\lere, Quebec. Figure 2,52. Water
depth at the bridge site is (Her Ito ft (35.5 lll), with
all additional 150 rt (ri,15 111) depth of sand, sill,
\
Al
B2
r
side of the pier cOllllening the superstructure
pier base,
2.9
~
A281
~
II
l
8'
t
Al
gO-- I
1
-
g
I-
Ii
A~
,"
t----­
B2
81
------r
JL
I
it 1--
Bl
!
a
fWIll
iiIi[
0
A2
~
ML
0
42
Lti:mL
~
r
L
0
CD
CD
@
reI. II.
and debris above bedrock. The river liow at the
bl'idge site is 3,6 ftlsee ([, I rn/sec),
During the preliminary design stage ill 1973 and
1974, several structural solutiolls were considered,
The use of short spans of precast concrete
A:\SI-ITO sectiolls or structural steel girders re­
quiring a number of piers was il11l11edi;nely aban­
doned because of river depth and cnrrent velocity
at the site. Site conditions required the develop­
ment of all economical long clear span with as few
piers as possible in .(he river. Options available
"'. -,
FIGURE 2.51. Gellnevilliers Bridge, supersrructure
under const ructioll,
FIGURE 2.52. Grand'Mere Bridge. general view
showing' parabolic soffit of center span, (courtesy of the
Portland Cement Association),
Cast-in-Place Balanced Cantilever Girder Bridges
56
were structural steel, post-tensioned precast seg­
mental, and several options of cast-in-place pre­
stressed concrete, varying in span, cross section,
and pier requirements. The design finally selected
for preparing the bid documents was a concrete
cantilever single-cell box with a center span of 540
ft (165 rn), a 245 ft (75 m) western land span, and a
150 ft (46 rn) eastern land span for a IOtal length of
935 ft (285 m). The design actually used for con­
struction, Figure 2.53, for the same total length,
has a main span increased to 595 ft (181 m) and
two equal 170 ft (52 m) long side spans. The corre­
sponding slight increase in cost of the superstruc­
ture was far more than offset by eliminating the
need to build a caisson in 48 ft (15 m) of water 98 ft
(30 111) above bedrock for the west pier. This rede­
sign, developed in cooperation with the contractor,
allowed an overall saving of approximately 20~ of
the project cost.
The two identical 170 ft (51.9 m) long land spans
cantilever from the main piers and act as counter­
weights for the main span. From a depth of 32 ft
(9.8111) at the main piers they taper to a depth of 28
It (3.5 m) at a point 130 ft (39.6 m) from the maill
FIGURE 2.53. Grand'Mere Bridge, center span
parabolic arch soffit (courtesy of the Portland Cement
Association).
piers, where they are supported b~' a secondary
pair of 4 It by 4 It (1.2 by 1.2 m) bearing capped
pier~. The 40 It (12.2111) wedge-shaped shore ends
of the land spans taper from t.he secondary piers to
grade at the top of the abutment. The abutments,
which are just 16 ill. (406 mill) thick, are designed
to support the approach slab onl\', Figure 2.54.
-
I
ELEVATIOti
\
!
TY PICA L
7(
SECT 10M
OETIlIL OF ABUTMENT
FIGURE 2.54. Grand'Mere Bridge, general arrangemem,
(11) Typical section. (c) Detail of abutment.
(a)
Elevation.
Grand'mere Bridge, Canada
Modular, confined rubber expansion joints are
provided in the roadway above the abutments. The
wedge portions of the land spans are solid con­
crete, helping counterhalance the weight of the
main span under service conditions as well as dur­
ing the construction stage. The land spans have a
web thickness of 2 ft (0.6 111), a 3 ft (0.9 m) thick
bottom slab, and a 15 in. (381 mrn) thick top flange.
A 2 h (0.6 m) thick diaphragm is located 78 ft (23.8
57
m) outboard of the secondary piers to form a
chamber between the solid wedge end and the
diaphragms. This chamber was incrementally hlled
with gravel in three stages to counterbalance the
main span as it was progressively constructed. The
bottom soffit of the west land span was supported
on temporary steel scaffolding. However, because
of the terrain slope, the east land-span bottom
soffit was plywood-formed on a bed of sand spread
----~ ....---~------------------------------------'
Plan
(a)
- - - - ....
---~-------------------,
'{
='
~.
-""""--~.
Elevation
(b)
FIGURE 2.55.
Arnhern Bridge.
(II)
Plan. (b) Ebation.
Cast-in-Place Balanced Cantilever Girder Bridges
58
over the mck. l:pon completion of concreting and
curing, the sand was hosed out from under the
formwork, allowing it to be stripped. 12
2.10
Arnhem Bridge, Holland
The Arnhem Bridge, Figure 2.55, is a cast-in­
place. lightweight concrete, segmental bridge cross­
ing the Rhine River with a center span of 448 ft
(136 m), a south end span of 234 ft (71 Ill), and a
north end span of 238 ft (72 m) connecting to ap­
proach ramps. It is a dual structure composed of
two-cell box girders. Figure 2.56a. The western
structure has two 30 ft (9.1 111) roaclw<J\"s for au­
tomobile traffic. The eastern structure has a 23 ft
(7 m) roadw<l\ reserved [or bus traffic, a 17 ft (5.3
m) roadway for bicycles and motorcycles, and a 7 ft
(2.1 111) pedestrian walkwa\. Ramp structures are
of prestressed flat slab construction, Figure 2.56b.
The main three-span ri\"er cmssing with an
overall width of 122.7 ft (37.4 111) consists of two
double-cell box girders that vary in depth from 6.5
ft (2.0 m) at midspan to 17 ft (5.3 m) at the piers.
The western rectangular box girder has a width of
49 ft (14.8 m) with] 0 ft (3 m) top flange canrilevers
for an overall width of 68.4 ft (20.84 m). The east­
ern rectangular box girder has a width of 35.4 ft
(l0.8 111) with top flange cantilevers of 8.6 1't (2.62
m) for a total width of 52.6 ft (16.04 111), Figure
2.56a.
Construction of the main spans is bv the conven­
tional cast-in-place segmental balanced cantilever
method with form travelers. The form travelers
are owned by the Dutch Government and leased to
the contractors. Strand tendons were used for
post-tensioning, and the lightweight concrete had a
weight of about 110 Ib/ft 3 (1780 kg/m 3 ), Figure
2.57.
Temporary supports at the pier were used for
unbalanced loading during constructioll, Figure
2.58. Precast exposed aggregate facia units were
used for the entire length of the structure and its
approaches, Figures 2.59 and 2.60.
2110
auto's
1630
auto's
openbaar vervoer
r t
f'etsers
~l
0'
050
0)3
+:.
050
050
302
(a)
Q13
(b)
FIGURE 2.56. Arnhcm Bridge, typical cross sections of main bridge and Rat-slab
ramp. (Il) Main structure. (b) Prestressed flat-slab ramp.
VOf!tgangers
ij
]
,d
Napa River Bridge, U.S.A.
59
-----.~
FIGURE 2.57.
erg,
Arnhem Bridge, center-span canli!c\'­
FIGURE 2.59. Arnhem Bridge. vIew of prestressed
f1at-slah ramp structure,
--=--'
FIGURE 2.58. Arnhem Slidge, temporal'v pier sup­
ports for unbalanced !1l0!Tle I l!:, ,
2.11
FIGURE 2.60. Arnhem
aggregate facia units,
Bridge,
precast
exposed
Napa River Bridge, U.S.A.
The ~apa River Bridge, Figure ~,61, is located Oil
Highwav 29 just south 01 the city of :\apa. Califor­
nia, and pr{)\'ides a four-lane. 66 ft (20 111) wide
roadway over the :\apa River to bypass an existing
two-lane lift span and several miles of city streets,
The 68 ft (20,7 111) wide, 2230 ft (679,7 111) long
bridge consists of 1:~ spam varying in length from
120 to 250 ft (36,58 to 76,2 111) and a two-cell
trapezoidal box girder van'illg from 7 ft 9 ill, (2,36
m) to 12 ft (3,66 m) in depth, Figure 2,62, Three
hinged joints were provided at midspan in spans 2,
6, and 10. These joints involved elaborate connec·
tions incorporating e1astomeric bearing pads and
hard-rubber bumper pads to withstand severe
movement and shock during an earthquake, Fig­
ure 2,63, All other joints between the cantilevers
were normal cast-in-place closure joints,13 The
superstructure is fixed to the piers, primaril~' for
seismic resistance,
The Structures Division of the California De­
partment of Transportation (CALTRA::--IS) de­
veloped plans and specifications for three alterna-
:,.
FIGURE 2.61.
Napa River Bridge, aerial view,
tive types ot construction, Figure 2.62. as follows:
A.
B,
C.
A conventional continuous cast-in-place pre­
stressed box girder bridge of lightweight con­
crete.
A continuous structural-steel trapezoidal box
girder composite with a lightweight concrete
deck.
A cantilever prestressed segmental concrete
box girder bridge allowing either cast-in-place
Cast-in-Place Balanced Cantilever Girder Bridges
60
PROFILE GRADE
6<3150'-0"
.....
~
..
120'-0"
-~-
Abul
Pier 2
ELEVATION
Conlde-,er Segmenlol PIS
LHJh!welqht Cone 80x Glrder
Welded
ALTERNATIVE B
A
FIGURE 2.62.
ALTERNATIVE C
l\apa River Bridge. profile grade, elevation, and alternate sections.
or precast segments. Erection was allowed on
faJsework or bv the free cantilever method.
Rubber
Bumper - + - - - - - '
Bump_.e:r_-I----.
Rom ­
lfii¥zq---
FIGURE 2.63. Nap<l River Bridge, mid-span hinge
joint wid1 seismic bumbers.
Because of poor foundations and a readily avail­
able aggregate supph. all alternatives utilized
lightweight concrete in the superstructure. Alter­
nati\'e C utilized trans\-erse prestressing in the deck
to reduce the number of webs to three. as com­
pared to seven webs required in alternative A. Of
seven bids received and opened on :-\()\'ember 6,
1974, six were for alternati\'e C and the seventh
and highest was for alternati\'e B. :-\0 bids were
submitted for altemative A.
Design of the superstructure required light­
weight concrete with ,1 com pressive strength of
4500 psi (316 kg/clll 2 ) at 28 days and 3500 psi (246
kg/cm 2 ) prior to prestressing. The three-web win­
ning alternative required a minimum of formed
surfaces and forced the majority of longitudinal
prestressing into the flanges, resulting JI1
maximum prestress eccentricity, and therefore an
economical solution.
Contract plans showed the minimum prestress
force required at each section and permitted the
use of either 270 ksi (1862 MPa) strand or )50 ksi
(1034 MPa) bar tendons. Prestressing force dia­
grams were provided for both materials. The con­
tractor had the option of balancing segment length
against prestress force to achieve the most eco­
nomical structure. In addition, the plans provided
the contractor with the option of a combination of
diagonal prestressing and conventional reinforce­
Koror-Babelthuap, U.S. Pacific Trust Territory
ment in the wehs for shear reinforcement or the
utilization of conventional stirrup reinforcement
only. The design was based upon a 40,000 psi (276
MPa) prestress loss for the 270 ksi (1862 MPa)
strand and 28,000 psi (193 ~fPa) loss for the 150
ksi (1034 MPa) bars. Because the loss of prestress is
a function of the type of lightweight aggregate
used, the contractor was required to submit test
values for approval concerning the materials to be
used and relevant calculations.14
The contractor elected to use the cantilever
cast-in-place alternative supported on falsework
until each segment was stressed, Figure 2.64.
Falsework bents with ten 70 ft (21.3 m) long, 36 in.
(914 111m) deep, wide-Mange girders support each
balanced cantilever. The falsework was then
moved to the next pier, leaving the cantilever
free-standing, Figure 2.65. The entire formwork,
steel girders, and timher forms were lowered by
winches from the cantilever girder after all nega­
tive post-tensioning was completed. Positive post­
tensioning followed midspan closure pours. 13
The 250 ft (76.2 m) long navigation span was
constructed with a complicated segment sequence
because of a U.S. Coast Guard requirement that a
70 ft (21.3 m) wide by 70 ft (21.3 m) high naviga­
tion channel be maintained. Approximately 60 ft
(18.3 m) of span 4, over the navigable channel, was
constructed in three segments on suspended
falsework by the conventional cast-in-place seg­
mental method. 13
All transverse and longitudinal post-tension­
ing tendons consist of tin. (12.7 mm) diameter
strands. Longitudinal tendons are twelve! in. (12.7
mm) diameter strand, with anchorages located in
the top and bottom flanges such that all stressing
was done from inside the box girder. Loops are
used for economy and efficiency, as shown in Fig­
ure 2.66. The longest span over the navigation
channel is prestressed by 50 (twelve ~ in. strand)
tendons. Transverse prestress in the top flange al­
lowed a 10 ft (3 m) cantilever on each side of the
two-cell box girder. Transverse tendons consist of
four ~ in. diameter strands encased in nat dUGS
2.251>y 0.75 in. (57 by 19 mm) with proper splay at
both ends to accommodate a Rat bearing at the
edge of the deck slab.
2.12
:\"apa River Bridge, free-standing can­
tilever and supporting bents for false work
~apa River Bridge, falsework bents
(courtesy of Phil Hale, CALTR.~:-.JS).
61
Koror-Babelthuap, U.S. Pacific
Trust Territory
This structure currently represents (1979) the
longest concrete cantilever girder span in the
world. It connects the islands of Koror and Babel­
thuap, which are part of the Palau Island chain of
the Caroline Islands located in the United States
Trust Territory some 1500 miles (2414 km) east of
the Philippines, Figure 2.67.
FIGURE 2.66.
tendons.
Napa River Bridge, longitudinal loop
62
'a: ;
.... ..'
PHlliPPINES~
j
"
'if
.ucu
II"
!>:~1I
{
'ill.
~
Cast-in-Place Balallced Calltilever Girder Bridges
t,
.
PI'tlLlPPINE
SEA
.·~"'l""'H
~
--.~'I~'~
_ ~(;.::.t.!,,~u~
....
13;~'~
(j!JSa
"'~
,,;(,y/
"~
... lttt>IHLI>W
' I l t fiE" !.f A
••
~,
CAQOUNE
l'SlAI'oIOS
~
f
!I'oIOOf>lfSIA
FIGURE 2.67.
Koror-Babelthuap
Bridge,
location
map, from ref. L'i.
In elevation this structure has a center span of
790 ft (241 111) with sicie spans of 176 ft (53.6 m)
that cantilever another 61 ft (18.6 111) to the abut­
ments, Figure 1.30. Depth of this single-cell box
girder superstructure varies parabolica'Uy from 46
it (14 m) at the pier to 12 ft (3.66 m) at midspan of
the main span, Figure 2.68. The side span de­
creases linearly from the main pier to 33 ft 8 in.
(10.26 m) at I he end piers ancithen to 9 ft (2.74 Ill)
at the abutments. The structure has a symmetrical
vertical curve of 800 ft (243.8 m) r~dius from
abutment to abutment with the approach roadways
at a 69t grade. I5
Superstructure cross section, Figure 1.30, is a
sillgle-cell box 24 ft (7.3 m) in width with the top
flange cantilevering 3 ft 9~ in. (1.16 m) for a total
top flange width of 31 ft 7 in. (9.63 m), providing
two traffic lanes and a pedestrian path. The webs
have a constant thickness of 14 in. (0.36 m). Bot­
tom Bange thickness varies from 7 in. (0.18 m) at
midspan of the center span to 46 in. (1.17 m) at the
FIGURE 2.68.
Koror-Babdthuap Bridge, parabolic
soffit of main span (courtesy of Dr. Man-Chung Tang,
DRC Consultants, Inc.).
main pier and then to 21 in. (0.53 01) at an inter­
diaphragm located in the end span. This
diaphragm and the one at the end pier form a bal­
last compartment. Another ballast compartment is
located between the end-pier diaphragm and the
abutment. The bottom flange under the ballast
compartments is 3 ft (0.9 m) thick in order to sup­
port the additional load of ballast material. Top
flange thickness varies from 11 in. (0.28 m) at
midspan of the main span to 17 in. (0.43 m) at the
main pier and has a constant thickness of 17 in.
(0.43 m) in the end spans. 15
The superstructure is monolithic with the main
piers, with a permanent hinge at midspan to ac­
commodate concrete shrinkage, creep, and ther­
mal movements. The hinge can only transfer verti­
cal and lateral shear forces between the two
cantilevers and has no moment-transfer capacitv. 15
T~le superstructure was constructed in segme;1ts
~,ltb the end spans on falsework and the main span
111 the convenLional segmental cantilever manner,
using form travelers. Aftcr foundations were com­
pleted, a 46 ft (14 m) deep by 37 ft (11.3 m) pier
segr:lent was constructed, Figure 2.69, in three op­
erallons; first the bottom Bange, then thc webs and
diaphragm, and finally the top Bange. Upon com­
pletion of the pier segment, form travelers were
installed and segmental construction begun. Two
form travelers were used to simultalleously ad-
rr~ediate
"
FIGURE 2.69. Koror-Babelthuap Bridge, pier seg­
ment (courtesy of Dyckerhoff & Widmann).
Vejle Fjord Bridge, Denmark
FIGURE 2.70.
Koror-Babelthuap Bridge, main-span
c<lntile\ers adyancing (counesy of Dvckerhoff & Wid­
mann).
vance the main-sp;1l1 c<lll1ilc\'ers, Figure 2.70. Seg­
ments ror this project were 15 ft (4.57 111) ill
length. ls
On this project. each segment took slightly more
than olle week to construct. .-\ tvpical cn:le was as
10110\\'s: I.;
l.
\Vhen the cOllcrete strength in the last segment
cast reached 2500 psi (l7.2 MPa), a specihed
llumber of tendo!]s, ranging frOI11 six to 12,
were stressed to :j() percent or their final force,
thus enabling the form traveler to advance in
preparation t()l' the following segment.
Advancin,Li the form tr;l\c!er also brought for­
ward the Olllside forms or the box. The forms
were cleaned while rough adjustments of ele­
\'<ltion were made.
3.
4,
5.
6.
I.
Reinforcement and prestressing tendons were
placed ill the bottom llange and webs. The in­
,.,ide forllls were advanced and top flange reill­
I'on:ell1ellt alld tendons placed.
.\fter the prc\iou, segment COlKrete had
reached;! ,trength of 3500 psi (24.1 \IPa), the
remaining- tendons were stTessed. The previ­
ous segment had to be fully prestressed before
concrete for the subsequent segment could be
placed.
Fine adjustment of the forms for camber and
ml~' required correction was made.
:"Jew segment concrete was placed and cured,
\Vhen the new segment reached a concrete
st rength of 2500 psi (I i.2 MPa), the cycle was
repeated.
The stmcture was prestressed longitudinallv,
transversely. and verticallv. Three hundred and
63
two longitudinal tendons were required at the pier
segment. As the cantilever progressed, 12 10 16
tendons were anchored otT at each segment, with
eight longitudinal tendons remaining for the last
segment in a cantilever at midspan. As the stnK­
ture has a hinge at midspan, there were 110 con­
tinuity tendons in the bottom flange. Transverse
tendons in the top flange were spaced at 22 in.
(0.56111) centers. Vertical tendons were used in the
webs to accommodate shear. Spacing for the verti­
cal web tendons was 30 in. (0.76 111) in the center
span and 15 in. (0.38 111) in the end spans. All ten­
dOllS were l:'r in. (32 mm) diamcter bars.ls
Side spans were constructed on falsework resting
on compacted hi!. The sequcnce of segmental con­
struction in the side spans was coordinated with
that in the lllain~pan. so that the unbalanced mo­
ment at the main pier was maintained within pre­
scribed limits.
2.13
Vejle Fjord Bridge, Denmark
This structure crosses the Vejle Fjord about 0.6
mile (I kl11) cast of thc V cjle Harbor. I t is part of
the East Jutland \lowrway, which will provide a
In'pass around the city of Vejle, Denmark. A total
lenglh of 56 II ft (1710 m) makes it the second
longest bridge in Denmark.
Bid documents indicated two alt.ernative designs,
on(' in steel and one in concrete. The steel alterna­
tive called for a superstructure composed of a
central box girder with cantilevered outriggers
slIpporting an orthotropic deck and Ijonl spans of
413 It (126111). The second alternative required a
prestressed concrete superstructure with a central
box girder to be constructed by the balanced can­
tilever method utilizing either precast or cast-in­
place segmelHs, with Ijord spans of 361 ft (110 111),
The successful alternative was the cast-in-place
segmental prestressed concrete box girder.
The bridge, in plan, is straight without any hori­
zontal curvature. It does have a constant grade of
0.5% falling toward the north. :"Javigation re­
quirements were a minimum 131 ft (40 m) vertical
and 246 ft (75 111) horizontal clearance. Water
depth in the fjord is generally 8 to 11.5 ft (2.5 to
3,5 m) except at the navigation channel, where the
depth increases to 23 ft (7 m). Under the fjord bed
are !avers of ver\, soft foundation mat.erials, vary­
ing in depth From 26 to 39 ft (8 to 12 m). There­
fore, the piers in the tJord are founded on 8 in. (0.2
m) square driven reinforced concrete piles varying
in length from 100 to 130 ft (30 to 40 m), Figure
2.7 L Piers on the sOllth bank are founded on
64
Cast-in-Place Balanced Cantilever Girder Bridges
s;.OIllCR[TE 90X-G1RDER
TOP or
c:ASTlt·.,
VIER
fiXED FORM WORK
r;====,~ ~'
~pYr" Tl-iICKN£SSES $"1OWN
Co><'l{$PONC TO AvtRAGl
SITUATION AT PIEFl.S to-U
Mue
lA-E:'~"'C1A~
GRAVl:llV SAND
FIGURE 2.71. Vejle Fjord Bridge, ~j()rd
founded on driven reinforced concrete piles.
piers
bored reinforced concrete piles, 59 in. (1500 mm)
in diameter, Figure 2.72. On the north bank one
pier is founded on driven reinforced concrete piles
and one is supported directly on a spread footing.
The cross section of the bridge, Figure 2.73,
which carries four traffic lanes with a median bar­
rier, is a variable-depth single box with a vertical
web and prestressed transverse ribs. Total width
between edge guard rails is 87 ft (26.6 m). Box
girder width is 39.4 ft (12 m), with a depth vary­
ing from 19.7 ft (6 m) at the pier to 9.8 ft (3 m)
at midspan. Each segment is cast with a length of
11.3 ft (3.44 m). Transverse top flange ribs are
spaced at 22.6 ft (6.88 m) centers-that is, every
other segment joint.
The total bridge length is divided into four sepa­
rate sections by three expansion joints located at
t he center of spans 4-5, 8-9, and 12-13. Lon­
gitudinal prestress is achieved by Dywidag (twelve
---'-- .----...........
FIGURE 2.72,
on bored piles.
V~ile
Fjord Bridge, land piers founded
0.6 in. diameter strand) tendons, as are the trans­
verse prestress in the top slab and the continuity
prestress in the bottom slab.
A 492 ft (150 m) long steel launching girder and
two special form travelers were used for casting in
place the full width of the 11.3 ft (3.4 m) long seg­
ments in balanced cantilever. Insulating forms
followed the form travelers in order to prevent the
formation of fissures due to adverse temperature
gradients. I n addition, the steel girder stabilized
the concrete structure during construction and was
used for the transportation of materials, equip­
ment, and working crew. The total weight of the
girder including the two travelers was approxi­
mately 660 t (600 mt). A typical longitudinal sec­
tion of a cantilever is shown in Figure 2.74, along
with the structure erection procedure.
Work on the bridge started in the summer of
1975 and was scheduled for completion in 1980.
,.j
"".
j
~
'
0:
UJ
0
0
CL
0: :::
W .::
N
..­
> :::
o :..;;:
Z
;:;
0
I­
U
W
0
.Q
.Q
N
lfl(Jlr1C>{S
(j)
(j)
(j)
dlM1S
3aln!)
iiS
0
~
o
U
0
1.1)
'"
~a:
~
tI
S3Nvl ::u
-JvMl l
I-
«:..;
1"­
.N
~
"::2
;:l
"'"lS
30 In")
gI
....
]N\l1
' " ~3!)~3Vl]
iiSt~1noHS
z
j
11.
65
C'>
C'>
or
SPAN
J
o{l.tl\..lt'l
CAST ON SCMfCt-O'NG
[N;)
FIGURE 2.74.
SUPERSTRUCTURE, PRINCIPLE OF EXECUTION
C[NTR[ lIN(
LONGITUDINAL SECTION
Fjord Bridge.
@
©
®
ACCESS fOR
l,.,'OR1UN(~
CRrH
F:QUlr~'f'ENT
_1
or !'IER
~lli\FTS.
@
®
®
CD
CD
s('(t ion a lid erect ion seq!!!' 11('.
--.~
COS'CRFTI~:G
SLIP FORti
PIERS.
CA~TIl.F.VF;:':EP :;CAFfOUHNG
FOR CA.STl~G OF SUPERSTRUCTURE srCTION ON Tor Of?
CARRIAGFS FOR CONCRETlNG, WEICHT 1 SO ~1p PER
CARRIAGE
I.fITH rORM FOR CI\STl~G Of SUI'F:RHRUC­
SECTroN5 Of ),U H [~
FULL h'1])T1I or
THf RRIDGr
TllE GIRDER
Ll\lmcm:n SLlCCr::SS1Vf:LY AccOROINr;
TO PROGRF;SS FRO}! PIER TO PIER.
-
- TRANSPORTING OF HATFRlfiLS AND
llIO-Sf'AN. SECTIONS OF' ].44 H LENGTH cAST
TIlE SIlPFRSTf{UCT1!RE lS
lwnn
SHftn,TA­
!IF CONCRrTk 5TRl1CTIlRE AS OESCR Iltt:U
CANTU.EVER SFCTWN,
AtONG TIlE LAlfNClllll:G
1'HP EDGE REMIS OF TilE BRIIlGE nECK ARE FWAI.LY t•..(JN­
CRf'Tr::D TN A ~EPARAn: HORKTNC OP!~RATI0N.
THE N()RTIlERN ANn THF: SOUTllERN nm OF
nY W::ANl1 or InFNTlCAL EQU1N!F.NT Mm THF
SAltF: CilNSTRllCTHlN PRfNC1PLF:S.
l,At'NClll t~C
SUd\ A}lll Im[pm~ DF:eK {CPNfJ~U11Y-TENDONS)
1'(1 l'RFlnntlSLY ESTAl\U SHED f.lR IDCE SECTION flY
OF CF.NTRt: $1',(;'1"1(1;1 iN tHD-SPAN AND PRE­
STfWSS1Nf. AflDTTIONAL TENI'ONS IN ClRDF.R BOTT()H~
C(')~lCRETTN(;
TENDONS. REHOVAL
INC, SECTION.
t)ORK lNG cYeLl]S PER
TO ALTERNATE CASTTNG Of
tn ANIl UNSti PPORTU)_
TO~,;ARu~
C()NCRETING OF $Yl'lHETRICAL SECTIONS FRm{ rrr:R
Q)
THE
liAS THE F0LLOmNG FUNCTIONS:
- :;TARlt,TZTNG THE CONCRErr STl{!.lCTt1RE Dt!lUNr. cor:rGIRUeT toN
)00
LAUNCIIING GrRnER. LENGTH 105 ~1, 'r.'F.rCHT APr.
@
,,-CHHRE UNE Of SPAN
TE N DON S
CONSTRUCTION PRINCIPLES
POSI TlON Of PRESTRESSING
AUXILIARY EQUIPMENT ETC.
BOX-TYPE GIRDER
Vejle Fjord Bridge, Denmark
FIGURE 2.75.
Vejlc Fjord Bridge. launching girder.
FIGURE 2.77.
diaphragm.
67
Vejlc Fjord Bridge. pier segment \\itll
FIGURE 2.78. \'ejlc Fjord Bridge. «)Il\truction \ic\\.
spring 197H (courtes\ of H. A, Lindberg).
~7.:· '~~".J
.
FIGURE 2.76.
.(
.~
\'ejlc Fjord Bridge. tranS\'erse ribs.
Construction progress ill the spring of 1978 is il­
lustrated in Figures 2.75 through 2.78. Figure 2.79
is an aerial view showing the structure nearing
completion. To keep within the construction
schedule, it was hnalh necessan' to use two com­
plete sets of launching girders and twill travelers
working simultaneousl \ frol11 both ends of the
bridge.
FIGURE 2.79.
the north\\·est.
Vejle Fjord Bridge. aerial vIew from
68
Cast-in-Place Balanced Cantilever Girder Bridges
2.14
Houston Ship Channel Bridge, U.S.A.
shrinkage, superimposed dead loads, and !i\'e
loads). They are, therefore, heavil\' reinforced;
their dimensions are:
This bridge, a rendering of which is shown in Fig­
ure 1.67, includes a main structure over the Ship
Channel ill HOllston, Texas, and two approach
viaducts. The main structure is a three-span con­
tinuous box girder, cast in place in balanced can­
tile\·er. Span lengths are 375,750, and 375 ft (114,
229, and 114 111). The navigation channel is 700 ft
(213 111) wide at elevation 95 ft (29 m) and 500 it
(752 Ill) wide at elevation 175ft (53.4 m), Figu re
2.80.
The three-web box girder carries four traffic
lanes separated hy a 2 ft 3 in. (0.7 111) central bar­
rier and has two 3 It 9 in. (1.14 111) parapets. The
box girder is fixed to the top of the main piers to
make the structllre a three-span rigid frame. Sup­
port for the box girder is prm'ided by ebstomeric
bearings on top of the transition piers, where it is
separated frolll the approach \'iaducts 1n expan­
sion joints.
Total heigh I (from top of footing to bottom of pier
segments): 160 ft 10 in. (49 m)
Length (parallel to centerline of highwav): 20 ft
constant (6.1 m)
Width: variable from 38 ft at the bottom to 2i ft i
in. at the top (11.6 to 8.4 111)
Pier cross section: rectangular box, with 2 ft (0.6 m)
constant wall thickness
The transition piers support the last segment of
the main structure side span and the last span of
the approaches. The pier shaft is a rectangular box
with I ft 4 in. (0.4 111) thick walls. Their heights are
152 ft (46 m) at olle end and 164ft (50 111) at the
other end of the bridge. The length, parallel to the
centerline of the highway, varies from 18 to 8 ft
(5.5 102.4 m); the width is 38 ft (11.6 m) constant.
Atop the pier, a 6 ft 8 in. (2 111) cap carrics the per­
manent elastomeric hearings and all the temporary
jacks and concrete blocks t hat will be used at the
time of the side-span closure pour. All four piers
are slip-formed.
Box Girder SUjJers/ruc/ure Dimensions of the
variable-depth box girder were dictated by \'ery
stringent geometry requirements. Vertical align­
ment of the roadway was determined by the
maximum allowable grade of the approach via­
ducts and the connection thereof with the roadway
system on both banks. The clearance required f'or
the ship channel left, therefore, only a structural
depth of 21.8 ft (6.6 m) at the two points located
250 ft (76 m) on either side of the midspan section.
The soffit is given a third-degree parabolic shape
to increase the structural depth near the piers in
order to compensate for the very limited height of
FOUlidfi/iol/,\
The two center piers and two tran­
sition piers rest Oil 24 in. (610 111m) diametel'
dri\'cn steel pipe piles. The center piers each rest
upon 255 piles with a unit pile capacity of 140 t
(127mt). Foolingsare 81 ft (24.i m)wide, 85 ft (26
Ill) long, aud 15 h(4.6 m) deep. These footings are
surrounded by a sheet pile coilerdam and are
poured Oil a 4 ft (1.2 m) thick sub/'ooting seal con­
crete. The transition pier footings are 50 ft (15.2
m) wide, 35 ft (10.7 111) long, and 5.5 it (1.7 m)
thick and rest on iO piles each of lOO t (90 111t)
bearing capacil\.
Pins The main piers prmide for the stability of
the cantilevers during construction (unbalanced
constructioll loads and wind loads) and participate
in the capacil\' and behavior of the structure under
service loads (long-term loads due to creep and
"<u
C:,
'j
;/
)
.5.00'/.
FIGURE 2.80.
)
Houston Ship Channel Bridge, longiludinal section.
Houston Ship Channel Bridge, U.S.A.
the center portion of the main span. Maximum
depth at the pier is 47.8 ft (14.6 m), with a span­
to-depth ratio of 15.3. Minimum depth at midspan
is 15 ft (4.6 m), with a span-to-depth ratio of 49.
O\'er the 500 ft ( 152 m) center portion of the main
span the span-to-depth ratio is 23, compared to a
usual value between 17 and 20. Typical dimensions
of the box section are shown in Figure 2.81. Post­
tensioning is applied to the box section in three
dimensions:
69
Longitudinal prestress is provided by straight­
strand tendons (twelve 0.6 in. diameter or nineteen
0.6 in. diameter strands), as shown schematically in
Figure 2.82.
Transversely, the top slab is post-tensioned by ten­
dons (four 0.6 in. diameter strands) in flat ducts
placed at 2 ft (0.6 m) centers.
Vertically, the three webs are also post-tensioned as
prescribed in the specifications to a minimum
1-0 to I-I,
'"
'11
I
~ Bndg~
I
i
II I
I
\
rransv~rs~
I
I
I
\
0/
I
-
I
I
I
I
I
~'
\.. __ -;:~ ___J !L________ J
---'~~~
I~___­
III
FIGURE 2.81.
n
I
: I I~I,'!
IT
II
I I
I
\
III\
I
I
Houston Ship ChanIlel Bridge. box section.
Canti/~ver
teodons I,xO.6'/J
prestress over main
pl~S
/
/
T
} \,
t1
• • ~.-.nnroT'
\
[
\ I
V~rtjcal
\
\
r
\
--"---r~ndons (I2x O·6·dia.and (I9xO·6"dia. )
FIGURE 2.82.
Continuity prestress at mid· span
Houston Ship Channel Bridge. longitudinal prestress.
70
Cast-in-Place Balanced Cantilever Girder Bridges
FIGURE 2.83.
Houston Ship Channel Bridge. details of tr;l\clcrs.
cOlllpressi\e stress equal to 3f~; that is, 230 psi (1.6
MPa) for a concrete strengthf~ = 6000 psi (41.4
\fPa).
Details of the form traveler are shown in Figure
2.H3.
Pier segments over the main piers are of unusual
size alld posed a \'ery interesting design problem,
arising from the transfer of the superstructure Ull-
balanced moments into the pier shafts. Additional
vertical post-tensioning tendons are provided in
the two 2 ft (0.6 Ill) thick pier diaphragms lar this
purpose. End segments over the transition piers
were designed to allow either the approaches or
the main structure to be completed first, as these
are two separate contracts.
It is possible to make an adjustment at the end
piers to compensate either for differential settle­
71
Other Notable Structures
(a)
2,15,1
JHEDWAY BRIDGE, UK
One of the first very long-span calltilever bridges
was the :\Iedway Bridge, This structure used a se­
ries of temporary falsework bents to provide sta­
bilit\ during construction, Figure 2.84.
2./5.2
','
RIO TOCL\TINS BRIDG};. BRAZIL
This structure h<Js a center span of 460 ft (140 m)
and two side spans of only 174ft (53 m), Figures
2,85 and 2,86,
-.,,,;
. " , . ")!,
. (hi
.f'" "". , •
2,15.3
tiiI.;i!·
FIGURE 2.84. :-"led\\;tv BridgT. LK, «(I) [\-pical con­
struction ;,cqHl'ml', (b) Vic\\' of f1nishcd bridge,
Illems 01' for al1\ deviation of the deflectiolls from
(lie asslll1led call1ber diagram llsed for construc­
tion,
Provisions ha\"c been lIlade for unexpected ad­
ditiollal concrete shrinkage and creep problems;
empn' ducts have been placed in the pier segment
diaphragms and at midspan to allow for future
possible installation of additional tendons located
inside the box girder but outside the concrete sec­
tion, should the need for such tendons arise.
This bridge is located very high over a deep canyon
of the Rio Si!. Cantilever cast-in-place was the ideal
answer to allow construction with a minimal con­
tact with the environment, Figures 2,87 and 2.88,
2.1 H
SCflL'BEX.1CADIE BRIDGE. C.'1.VADA
This three-span bridge with a center span of 700 ft
(213 111) crosses the Schubenacadie River, near
Truro, :\ova Scotia, High tidal range. swift cur­
rents, ice, and adverse climatic conditions made
the construction of this structure very challenging,
Figures 2.89 and 2,90.
2./5.5
2.15
PCEXTE DEL AZUFRE, SPAI,V
/,VCIEXSO BRIDGE, GUATEA-lALA
Other Notable Structures
There are so mam' outstanding and interesting
cast-in-place cantilever bridges in the world today
that it is impossible to discuss the subject ade­
quately in the space available here. :'vlention should
be made, however, of several notable structures
not vet covered by a detailed description.
The main three-span rigid frame structure with a
center span of 400 ft (122 m) is of cast-in-place bal­
anced cantilever construction, and the approach
spans are of precast girders, Figures 2.91 and 2.92.
The very severe 1977 earthquake left the center
structure completely undamaged, while the usual
damage took place in the approach spans.
...
72
Cast-in-Place Balanced Cantilever Girder Bridge'S
~~
II~
~·~II
+'-1-'-"-+"-''-+'''''-if-'''''+'''''-1..~-~5:,-3-____T_ ..._ _~._1.l!!""'-0_ _ _-+1_-"5:,,c3_-..-""'4~_~~-+'~~~~
+-__._--""'Q2'--_ _+-_..~.~_. ___. 256 .
..::5::::32::.;•.:...:70::....-_ _ .. _ _ _..
FIGURE 2.85. Rio Tocantins Bridge. Brazil, tvpical elevation and cross section.
2.15.6
SETL'BAL BRlJJGE, ARGENTINA
This three-span structure with a main span of 460
It (140 111) rests on two main river piers with [win
\'ertical ......alls and piles, with a transition footing at
water elevation, Figures 2.93 and 2,94.
2.15.7
KIPAPA STREAM BRIDGE, U.S.A.
This bridge is located in the Island of Oahu in the
State of Hawaii, The dual structure has an overall
width of 118 It (36 m) to accommodate six traffic
lanes, three in each direction, and consists of two
double-cell box girders of constant depth with
interior spans of 250 ft (76.2 m), Figures 2.95 and
2.96. Construction was by cast-in-place cantilever
with segments 15 ft 3 in. (4.65 m) long. The bridge
has pleasant lines, which blend aestheticall\' with
the rugged deep-valley site.
2,15.8
PARROTS FERR}, BRIDGE, U.S.A,
This structure, built in California for the Corps of
Engineers, represents a major application of light­
weight concrete for cast-in-place cantilever con­
struction, Figure 2.97.
2.15.9
FIGURE 2.86. Rio Tocantins Bridge, Brazil, view of
the finished bridge.
MAGNAN VIADUCT, FRANCE
Located just off the French Riviera in Southern
France, this four-span continuous structure rests
on 300 ft (92 m) high twin piers of an I-shaped
section. Superstructure was cast in place in two
stages (first the bottom slab and webs and then the
top slab) to reduce the weight and cost of travelers.
Figures 2.98 and 2.99 show the principal dimen­
sions and views of one cantilever and the finished
structure, Figure 2.100 .
Other Notable Structures
6500
73
13000
RIO
'500
SIL
13.70
.-h-f=t
I
310
~
"I"'!i
:I
I
I
I
L
J-:
9'
I
I
----------
I
I
I
I
~
-1--4
:-----+­
J[
--,,,- j -----.J-50---t--12iL-~
FIGURE 2.87.
2.1 ill)
PUl'lltl'
dd Al.ufre. Spain. tvpical dc\ation and sections.
1'( Tr:. /IX liIUf)C/:". FR./SCE
These ;lre t\\in bridges <Tossillg Ihe Seine River
Ile;!r Paris. Bcc;tllse of \Tn' stril1gent clearance and
gconletn rcqllirements. the ayaibble structural
de]>1 h \\,;IS ollh 5.~) It (I.S m) for Ihe cle;n' 275 l't
(S:l.S 111) sp;ln ;lIHI4.S It (1.-+7111) for the clear 21-+
fI (G5.3 111) span. ll1aking both structures very slen­
der. Figures 't.l0l alld 2.102. StitT "V" piers in
both structures help reduce the flexibility of the
deck.
2.15.11
TRIC/SnV RRII)(;E, FR. LVCt:
This structure spam the Rhone River with no piers
in the river, which necessitates a long center span
and two yerv short side spans anchored at bOlh
ends against uplift. The center portion of the main
span is of lightweight concrete, while the two zones
over the piers where stresses are high are of con­
ventional concrete, Figures 2.103 and 2.104.
2.15.12
FIGURE 2.88.
Puente del Azufre. Spain.
ESCH-ICHTAL BRlDGE, GERMANY
This bridge is located near Stuttgart, Germam'.
The superstructure consists of a large single-cell
box girder with large top flange cantilevers sup­
ported by precast struts. Because of the weight in­
volved, the central box was cast in one operation;
struts were installed and flanges cast subsequently,
Figures 2.105 and 2.106.
..
TO WINDSOR
TO TRURO
"EST
--­ ----------------­ --' 'I
EXISTING RIVER SOTTOM
Elevation
It.
I
I
1
I~
, I
11:5
Section at Midspan
Section over Piers
FIGURE 2.89.
Shubcllacadic
Brid~e,
FIGURE 2.90. Shubenacadie Bddge, support system
for unbalanced cantilever moment at pier (courtesy of
the Portland Cement Association),
74
de\<ltioll and seC! ions, hom leI. I (j,
FIGURE 2.91.
the structure,
Incienso Bridge. Guatemala, view of
390.00
,25.00
6.00
I
122.00
64.00
ELEVATION
MAIN
111
FIGURE 2.92.
79.00
SECTION
ON SUPPORT
BRIDGE
1/2 SECTION
ON SPAN
IIKiel1'o Bridge. Guatemala. dimensions.
..Z.Q.. ~{L .•.___
DIC~CI
~---FIGURE 2.93.
lr
-~'\
Setubal Bridge. Argentina, dimensions.
75
...
FIGURE 2.94.
bridge,
205'
250'
.. T
250'
~~++-.-------r---
i
I
:
;
1,1,
~:::::J
Abut 1
:
Setubal Bridge. Argentina, \'ie\, of the
"
Ir
r
I~
r_:::::r==i
.--~--.
3
2
--I
5
4
Elevation
.
~.
.
Abut 2
7
6
'"
14"
12"
.,
>,
'"
~
14"
';::
12"
Cross Section
FIGURE 2.95.
Kipapa Stream Bridge. elevatioll and cross section.
FIGURE 2.96. Kipapa Stream Bridge, construction
view (courtesy of Dyckerhoff & Widmann).
5
FIGURE 2.97.
Ferry Bridge,
ref. 17,
Parrots
dimensions,
COUPE
(!)
LONGITUDINALE
0)
FIGURE 2.98.
(!J
I..f AAllLOH
:-­
~Iagnan
Viaduct, \Ol1giludill,d ;,enioll.
FIGURE 2.99.
:\[agnan ViaduC[, view of a cantilever.
FIGURE 2.100. :-"Iagnan Viaduct, aerial view of [he
completed bridge.
ii
...
FIGURE 2.101.
Putcaux Bridge, aerial "iew of the completed bridge.
COUPE LONGITUDIIILE
P2
Ct
C4
P3
i
---~.--
i
---------_.--­
.'Ul'--_ _ _ __
J.
-----~ --------~--
II...
!
,a.II.tJ
~-'
IJU.."
".
/_1
/
" !­
."
2 . . . , US
...........
nu
FIGURE 2.102.
78
Puteaux Bridge. longitudinal section.
PlRIII - PIll '1111
n
r
\
I
I
i
203 DO
30.25
25.25
"~
<',
"­
~
-
-~I
3025
142.50
Silon
I
.~~~.:
/.
.
...
.,
~
Ii qtr
,250.
.'
--
-
2525
1
..
,750
~-:,I\/'
,,~~"*""
I~
~
o
U"l
(\J
2 60
240
FIGURE 2.103.
2 60
5.20
240
fricastin Bridge, dimensions,
79
FIGURE 2.104.
FIGURE 2.105.
cantilevers.
80
Eschachtal
Tricastin Bridge, view of finished bridge.
Bridge, casting
flange
FIGURE 2.106.
struts,
Eschachtal Bridge, view of outrigger
References
2.16
Conclusion
The man\' structures described above show the
versatilitv of cast-in-place babnced cantilever COIl­
struction, particularly in the held of very-long-spall
bridges with few repetitive spans. The design as­
pect of these structures will be discussed in Chap­
ter 4 and construction problems in Chapter 11.
References
L H. ThuL "Briickenbau," Bf'/otl-
111111 S/ablhf/ollbau, 61
Jahrgang, Hetl 5, :-'lai 19i16.
:!.. ell'jeh Fills!erwalder, "Prestre,sed COlltTele Bridge
ConSI ruction." JOlin/III oj IiiI' .i ltil'nmll COllal'l/' 11I.,li­
1111,'. Vol. ():?, :-':0.9. Seplember 1965.
:1.
Llrich Finsterwalder, ":-':ew Developments ill Pre­
stressing \'lethods and Concrete Bridge Construc­
t i( HI," [)w ,idtlg-Bpnch/r , ·t-I <)0 i, September 19t;i,
Ihl kerholl &: Widlll,lnll KG, 'dUlliLil, Cel'lllam.
4. Llrich FillSlen,',ddel', "Free CalltileH'I' COIlSII'uctioll
01' Prest !'cssed COllcrete Bridges and \Iush roolll­
Sh;lped Bridges," Fir.lIIIl/!·l'IIflllllllll! SHII/JIi.'/llIIl, CI)II­
ITI'II' Bodg!' D".,igll. AC1 Publication SP-2:L Paper
SP2:~-2t), American COllcrete Institute, Detroit.
196~J.
5. "Brid),ic Built :\top the SCCIlCI\ With CtlltileYCI'ed
l'I'an'ler"" FII,~illl'l'Iil/g Snl'.l-Rt'((}rrl, JUllC IH, 19(i4.
t). Dale F. Downing, "Cantiit'\'Cr Segmcnt~:l Prestressed
i.
Clst-ill-l'lan' Construction 0(' the Pine Valle\' Creck
Bridge." presentcd to thc .\ASHO Anllu;ti \'lecting,
Los ,\ngeles. California, :-':o\elllber II I;"), IlJi3,
"Pine \';dle\ Crcek Bridgc, California:' Bridgc Re­
(101'1 SR It)!.lll E, Portland Ccment Association,
Skokie, 111., 19i4,
81
8, Richard A. Dokken, "CALTRA:-':S ExpericlH.:e in
Segmental Bridge Design," Bridgf' Noles, Division or
Structures, Department of Transportation. State or
California, Vol. XVII, :-':0. I, March IY75.
9. A. P. Bezzonl:', "Pine Valley Creek Brid).!;e­
Designing for Segmental Construction," ;vleeting
Preprim 1944. ASCE National Structural En­
gineering \1eeting. A pdl 9-13, 1973, San Francisco.
10. Richard Heinen, "Pine Valley Creek Bridge: Use 01
Canrilever Construction," \teeting i'reprint 19H I,
ASCE :-':;ltional Srruclllral Engineering Meeting,
April Y-I3, 19i3, San Francisco.
II. ".'1..15 et A.H6 raccorde!l1ent aurorOllticr dans Ie
nord <lu departetllcllt des hams-de-seine," \iinisrerc
de \.'Equipc1l1ent DireClioll Departcmelltal dc
L'Equipement des Hauts-de-Seine, Paris, September
1976.
12. "Bridge Has 595 l't Post-tensioned Span," HNI!'Y
COlls/ruc/ioll ,Vews, August:!, 1976.
I:), ":-':apa River Bridgc, :-':apa, California," Portland
Cement Associatioll, Bridge Report, SR 194.01 E,
19i7.
H. ".\lternale Bidding for California's :\apa River
Bridge WOI1 bv C~tst-il1-Place Prestressed COl1crete
Segmental Construction," Prestressed Concrete in­
s! itll! e. Post-Tensioning Division, Special Brid ge
Report,
15, \lau-Chung Llllg, "Koror-Babelthuap Bridge-A
World Record Span," Preprint Paper 3441, ASCE
COIl\Tntion, Chicago, October 16-20, 1978.
16. D. W, MacIntosh and R, A. Whitman, "The
SlllIht'llacadie Bridge, ~laitlal1d, :\ova Scotia," All­
Illlal Conl'erence Prcpl'ints, Roads and Trallsporta­
tioll Association or Canada, Olla\\'a, 1978.
17. "Concrete Alternate Wins Competitive Bidding
Comest [I)r Long SP,Hl Califo1'l1i~l Bridge," Bridge
Rcport, Post-Tensioning Institute. A.pri I 1977.
3
Precast Balanced Cantilever Girder BTidges
3.1
3.2
3.3
3.4
1l\.'TRODUCfION
CHOISY-LE-ROI BRIDGE AND OTHER STRUC­
TURES IN GREATER PARIS. FRANCE
PIERRE BENlTE BRIDGES NEAR LYON. FRA1':CE
OTHER PRECAST SEGMENTAL BRIDGES IN PARIS
3,14
3.15
3.16
3.17
3.18
3.4.1 Paris Belt (Downstream)
3.4.2 Paris Belt (Upstream)
3.4.3 Juvisy Bridge
3.4.4 Twin Bridges at Conflans
3.18.1
3.18.2
3.1S.3
3.18.4
3.18.5
3.18.6
3.1S.7
3.lS.8
3.18.9
3.18.10
3.18.11
:~.5
OLERON VIADUCT. FRANCE
CHILLON VIADUCT. SWITZERLAND
3.6
3.7
HARTEL BRIDGE, HOLLAND
3.8
RIO-NlTEROI BRIDGE. BRAZIL
BEAR RIVER BRIDGE. CANADA
3.9
3.10 JFK MEMORIAL CAUSEWAY, U.S.A.
3.II SAINT ANDRE DE CUBZAC BRIDGES, FRANCE
3.12 SAINT CLOUD BRIDGE, FRANCE
3.13 SALLlNGSUND BRIDGE, DENMARK
3.1
Introduction
;\s indicated ill Chapter I. precast sq..; mental coJ)­
stnluioll had its origins (in the cOl1temporalT
sense) in France in 1962 as a logical ahernati\'e to
the cast -in-plac~ met hod of const ruction. To the
advantagc oj' segmental cantile\cr cOllstructioll.
primarily the elimination of (ol1\'cl1tional false­
\\'ork. thc technique adds the rcfinel1lellts im­
plicit in t he use of precasling.
The characteristics or precast segmental con­
struction arc:
I.
2.
82
Fabrication of the segments can be accom­
plished while the substructure is ullder con­
st ructioll, thus enhancing erection speed of the
superst rU(ture.
lh virtue of precasting and therefore mawritv
of the cOllcrete at the time of erection. the lime
required for strength gain of the concrete is
H'IIl()\'cd from the construction critical path.
B·3 SOUTH VIADUCfS. FRANCE
ALPINE MOTORWAY STRUCTCRES. FRANCE
BRIDGE OVER THE EASTER]\; SCHELDT. HOLLAND
CAPTAIN COOK BRIDGE, AUSTRALIA
OTHER NOTABLE STRUCTURES
Calix Bridge, France
Vail Pass Bridges, U.S.A.
Trent Viaduct. U.K.
L-32 Tauernautobahn Bridge. Austria
Kishwaukee River Bridge. U.S.A.
Kentucky River Bridge. U.S.A.
1-205 Columbia River Bridge. U.S.A.
Zilwaukee Bridge. U.S.A.
Ottmarsheim Bridge. France
Overstreet Bridge, Florida, U.S.A.
F-~ Freeway, Melbourne, Australia
REFERENCES
3.
4.
:\.S a result of the maturit\, of the concrete at
the time of erection. the effects of concrete
shrinkage and (Teep arc Illinil1lizecl.
Superior qualin' cOl1trol call be achie\'ed for
factory-produced precast concrete.
i-Jom,'\cr, geometric cOlltrol during fahrication of
segments is es~ell!ial. and corrections during erec­
tion are more difficult than f()r cast-in-place seg­
mental construction. In addition, the connection
of longitudinal ducts for post-tensioning tendons
and the COlltillUit\ of reinforcing steel. if the\' are
required in the de~ign. are less easilv achieved III
precast than in cast-in-place methods.
Although precast segmental had been used as
early as 1944 for the Luzanc\ Bridge O\'er the
\1arne Ri\'er, Figure 1.'27, \\'ide acceptance began
when match-casting techniques \,'ere developed.
Basicallv, the principle of fabrication of precast
segments is to cast them in a series one against the
other in the order in which they are to be assem­
Choisy-le-Roi Bridge and Other Structures in Greater Paris, France
hied in the structure. The front face of a segment,
thus. seryes as a bulkhead for casting the rear face
of the subsequent segment. Methods of fabrication
of precast segments will be discussed in Chapter
11.
Seglllents are erected in balanced cantilever
starting from a segment over the pier, which is the
first to be placed. \-Ioditications to the initial prin­
ciple have further increased the fiexibility of erec­
tion procedures. Two major modifications are (1)
temporarv prestress ties to secure two or more suc­
cessive segments and thus free the erection equip­
ment, and (2) cantilever prestressing tendons an­
chored illside the box sections instead of at the
segment face as on early structures. These refi ne­
lIlents mean that the placing of segments and the
threading and stressing of tendons becollle illde­
pelldem operations.
Efficient application of this method has resulted
in the use of cantilever construction in moderate­
to small-span strnctures where it had preyiollslv
been considered utleconomical. Examples are the
15-;) South \'iaduet (Sectioll 3.14) composed of
spans ranging from 9H ft (30 111) to 164 ft (50 Ill)
and the .-\Ipine \Iotorwav Bridges (Sectioll ;).15)
where the spans range between 60 ft ( I H Ill) to 100
ft CW Ill).
It is interestillg to note a constant evolution to­
\\anl increased transverse dimensions alld weight
of precast seglllellts. Problems in precasting,
transportillg, and placing segments that are COIl­
stallll\' becoll1ing heavier and wider are being
progressively resolved. Chapter 4 will deal with this
progressive e\'ollltiOI1 as applied to some French
precast segmental bridges and will discllss typical
cross sect iOlls of sOllie precast segmental bridges
constrllcted or ill the design stage ill the Cllited
States.1.2
In cont inuous structures expansioll joilHs mav
be spaced verv far apart. Continuous bridges lip to
;3:)00 ft (I (jOO 111) in length hale been constructed
\\'ithollt intermediate joints: however. this may not
be an upper limit, provided that the design of
bearings and piers is correctly integrated into the
total design of the structure. Free longitudinal
movement of the bridge due to creep and temper­
ature change is allowed for by placing the structure
on eiastomeric or sliding (teflon) bearings. We can
also use pier Hexibi!ity to accommodate these
movements by fixing the superstructure to the
piers. In this case, flexibility can be obtained either
bv pier height or by the use of single or double
thin-slab walls, thus reducing the piers flexural re­
sistance.
83
The first precast segmental bridge to be built on
the North American Continent was the Lievre
River Bridge on Highway 35, 8 miles (13 km) north
of Notre Dame du Laus, Quebec. with a center
span of 260 ft (79 m) and end spans of 130 ft (40
m), built in 1967. It was followed in 1972 by the
Bear River Bridge, Digby, Nova Scotia (Section
3.9), with six interior spans of 265 ft (81 m) and
end spans of 204 ft (62 m). The JFK Memorial
Causeway, Corpus Christi, Texas (Section 3.10),
opened to traffic in 1973, was the first precast seg­
mental bridge to be constructed in the United
States. In the United States, as of this writing, the
authors are aware of more than 30 precast seg­
mental bridge projects that are either completed,
uncler construction, or in the design stage. Some
are listed in Table 3. I."
3.2
Choisy-le-Roi Bridge and Other Structures in
Greater Paris, France
The first bridge to lise the precast segmental cal1­
tilever technique with epoxied match-cast joillts
was built at Choisv-Ie-Roi near Paris between 1962
and 1964. It carries \iational Highway 186. a part
of the Paris Great Belt system, over the Seine River
just east of Orly Airport, Figu re 3.1. This structure
is a three-span continuous bridge of constant
dept II with end spans of 12:1 ft (37.5 m) and ;1
center span of 180 ft (55 m). Figures 3.2 and 3.3.
This bridg-e replaced one constructed in 187(),
which had a superstructure of six steel girders with
five spans of approximately 75 ft (23 111). This
structure, determined to be no longer adequate as
earlvas 1939, was se\erely damaged during World
\Var II. It in turn had replaced an ancient bridge
of five 66 !"t (20 m) oak a1"ch spans designed by
the famolls mathematician Claude-Louis-Marie
~avier"
In 1961, a stud, bv the Administration of
Bridges and Roads allowed two options, one in
prestressed concrete and the other in steel, each
having three continuous spans of 123 ft (37.5 mi.
180.1 ft (55 m), and 123 ft (37.5 m). Four pre­
stressed concrete solutions were considered. The
successful solution is illustrated in Figure 3.2.
The overall width of the superstructure for this
dual bridge is 93.2 ft (28.4 m), Figure 3.3. Each
bridge consists of two single-cell rectangular box
girders. Tlte superstructure accommodates dual
two-lane roadways of 23 ft (7 m), two 13 ft (4 m)
sidewalks, and a 10 ft (3 m) median.4.3 Individual
box girders have a constant depth of 8.2 ft (2.5 m),
84
Precast Balanced Cantilever Girder Bridges·
TABLE 3.1.
Name and Location
Lievre River, NOire Dame
du Laus, Quebec
Bear River, Digby,
Nova Scotia
JFK Memorial Causeway,
Corpus Christi, Texas
Muscaluck River, U.S. 50,
North Vernon, Indiana
Sugar Creek, State Route 1620,
Parke County. Indiana
Vail Pass, 1-70 V,est of Denver,
Colorado (4 bridges)
Penn DOT Test Track Bridge,
Penn Sate C niversity,
State College, Pa.
Turkey Run State Park
Parke County, Indiana
Pasco-Kennewick. Columbia
River between Pasco
and Kennewick, Washington
(cable-stay spans)
Wabash River, U.S. 136,
Covington, Ind.
Kishwaukee River, Winnebago Co.
near Rockford. III.
(dual structure)
Islington Ave. Ext., Torollto,
Ontario
Kentucky River, Frankfort, Ky.
(d ual structure)
Long Key, Florida (contract let
late 197H)
Linn Cove, Blue Ridge
Parkway, N.C.
(contract let late 197H)
Zilwaukee, Michigan
(dual structure)
(bids opened late 1978)
Precast Segmental Concrete'Bridges in North America
Date of
Construction
Method of
Construction"
Span Lengths.
It (m)
1967
B.C.
1972
B.C.
1973
B.C.
1975
B.C.
1976
B.C.
1977
B.C.
1977
O.F.
130 260 130
(39.6 - 79.2- 39.6)
203.75 ­ 5 @ 265 203.75
(62.1 - 6 @ HO.77 - 62.1)
100 200 ­ 100
(30.5 - 61 30.5)
95 190 95
(29- 5H ­ 29)
90.5 ­ 180.5 90.5
(27.6 55 27.6)
134 - 200 ­ 200 ­ 134
(40.8 51-61-40.H)
134 - 2()() 200 ­ 145
(40.H - 51 - 61 - 44)
151-155210-210-154
(46 47.2-64-6cJ 47)
1;)3 210 210- 154
(46.6 64 64 47)
124
(37.H)
1977
B.C.
1978
B.L
19/H
1.L.
1979
H.C.
1979
B,C,
1979
B.C.
S.S.
P.P.
B.C.
180 - IHO
(:)4.9 - 54.9)
406.5 981 - 406.5
(124 - 299 ­ 124)
93.5 4 We I Hi - 93.5
(28.5 - 4 @ 57 28.5)
170 :-1 ((1 250 ­ 170
(51.8 3 ((1 76.2 - 51.8)
2 ((I 16 I 2()0 - S (ii 272
(2@49-61-50 H3)
22H.5 - 320 22H.5
(69.6 97.5 ­ 69.6)
113 - 101 ((i 1 18 - 113
(34,4 101(~36-34,4)
98.5 ­ 163 - 4 @ 180 163 - 98.5
(30-49.7 4 @ 54.9-49.7 30)
26 :-.; .B. spans total length
8,087.5 (2,465)
25 S.B. spans total length
8,057.5 (2,456)
maximum span 392 (119.5)
------------------------------------------------------------"Method-or-construction notation; B.C.-balanced cantilever, LL-incrementallaunching, OJ,'.-on falsework, P.P.-progressive
placement, S.S.-span-by-span.
top Range width of 21.65 ft (6.6 m), and a bottom
flange width of 12 ft (3.66 m). Webs have a con­
stant thickness of 10i in. (0.26 m), and the top
flange is of constant section throughout its length
with a minimum thickness of 7 in, (0.] 8 m) at its
crown, Figure 3.3. The bottom Range thickness is
6 in. (0,15 m), except near the river piers where
the thickness increases to 15.75 in. (0.4 m) to ac­
commodate cantilever bending stresses. The
downstream half of the bridge (consisting of two
~---.
Choisy-le-Roi Bridge and Other Structures in Greater Paris, France
85
Precast Segmental Bridges
1 Choisy-le-Roi
2 Courbevoie
3
4
5
6
7
@J
8
9
113
A4
,.\'''."
10
II
12
Ring Motorway
Ring Motorway
St Cloud
Juvisy
Conflans
St Maurice Interchange
B-3 South Viaduct
Marne la Vallee
Torey RR
Clichy RR
1962-64
65-66
66-68
67-68
72-74
66-68
70-72
78
71 72
75-77
78
78
Cast-in-Place Segmental Bridges
13
14
15
16
• 17
18
19
20
FIGURE 3.1.
Location map of segmental bridges in greater Paris. FI'ancc.
box girders) was constructed first, alongside the
existing bridge. :\fter removal of the existing
bridge. the second or upstream half was con­
structed. Each dual structure was constructed by
the balanced cantilever method utilizing Freyssinet
tendons for the longitudinal prestressing. Box
girder segments were 8.2 ft (2.5 m) in length and
weighed 22 tons (20 mt), except the pier segments
FIGURE 3.2.
Gennevilliers
1974-76
North West A-86 Interchange
78
Clichv High\"ay
73-75
Puteaux Bridges
75-77
71 7·1
Issy les :'vloulineaux
Cravelle
H-75
74-76
Joinville
Neuilly sur \'-Iarne
h6-68
Choisv-Ie-Roi Bridge.
which were 16.4 ft (5 m) in length and weighed
60.6 tons (55 1m), The pier segments also con­
tained two diaphragms which provided continuity
with the inclined wall piers, Figure 3.3,
The segments were fabricated in a precasting
vard on the left bank of the Seine approximatelv a
mile (1.6 km) upstream of the project site, Figure
3.4. Although this bridge might be considered of
moderate importance with respect to span lengths,
its importance lies in the method of fabrication. It
was the first to use segments precast by the match­
casting technique. Segments were cast in the pre­
casting yard as a series of 8.2 ft (2.5 m) long units,
one against the other, on a continuous soffit form
which had been carefully adjusted to the intrados
profile of the bridge with allowance for camber.
This came to be known as the "long-line" method
(see Chapter 11). Two sets of steel forms riding the
soffit form and overnight steam curing allowed the
production of two segments per working day. To
prevent bonding of the segments to each other in
the casting form, a special peel-off bond breaker
was sprayed over the end of the segment before
the adjacent segment was cast. The segments were
86
Precast Balanced Cantilever Girder Bridges
Elevation
2lHO
7J.)O
120
;(0' •
.. :\0
~
;
~!
Fm -,- _F~--
I
:.
lL ..... _ ' )
!
«("
•
,
.
L
••
•
j
1HI2
"""
Elevation and cross section of river piers
Cross SEction of superstructure
FIGURE 3.3. Choi~y-le-Roi Bridge. dimensions: ele­
vatioll. elevatioll and (TOSS section of River piers, cross
section of superstructure.
suhsequently stripped from the soffit form at their
match-cas! joints and reassembled at the bridge site
in balanced cantilever on each side of the river
piers. 4
A floating crane handled the segments at the
casting yard. After the u nits were loaded on barges
and transported to the project site, the same crane
placed the segments over a retractable jig rolling
inside the box girder in the completed portion of
the bridge and was thus freed for another segment
placing operation. A platform mounted on jacks
on the jig, Figure 3.5, allowed for adjustment of
the segment at the desired position. 4 A I ft (0.3 m)
wide gap was temporarily maintained between the
faces of the segments to allow workmen to apply
Choisy-le-Roi Bridge and Other Structures in Greater Paris, France
FIGURE 3.4.
FIGURE 3.5.
87
Choisv-Ie-Roi Bridge, view of the precasting yard.
Choisv-Ic-Roi BI'idge, retractable erection jig.
the epoxvjoinl material. Thejig \Vas then retracted
and prestressing tendons were placed and stressed
to connect the two sym metrical segments on each
side of the previousl\' completed portion of the
cantilevers on either side of the pier."
Placing of the precast segments in a call1ilever
fashion OIl each side of the pier progressed step by
step. as indicated in Figure 3.6. Tendon layout is
illustrated in Figure 3.7. Cpon completion of the
two twin cantilevers from the river piers. a cast-in­
place closure pour was consummated at midspan
and a second series of prestressing tendons were
placed in the bottom flange to achieve continuity
between the two center-span cantilevers. These
tendons were given a draped profile to allow the
locati<,>Tl of tendon anchorages in the top flange of
the box girder. Both series of tendons, cantilever
and coIllinuity, overlap each other and cOIllribute
FIGURE 3.6. Choisy-Ie-Roi Bridge. segment placing
,dth floating crane.
....
88
Precast Balanced Cantilever Girder Bridges
FIGURE 3.7.
Choisy-le-Roi Bridge, tendon lavout.
to a substantial reduction in the shear forces in the
webs as a result of the vertical component of the
prestress. The side spans were constructed in a
similar manner. The three precast segments adja­
cenl to the abutments were assembled on
falsework. After a closure pour between these
segments and the cantilever from the river pier,
positive-moment tendons were placed and stressed
in the end span to achieve continuity. Because the
midspan area of the center span had little capacity
to withstand moment reversal under ultimate load,
additional short tendons were located m the top
flange to achieve full reinforcement continuity
with the longest cantilever tendons. 5
The same construction technique used for the
Choisy-le-Roi Bridge was used for the Courbevoie
Bridge, built bet ween 1965 and 1967, which also
crosses the Seine in the northwest suburb of Paris,
Figure 3.1. The bridge has three symmetrical
spans of 130, 200, and 130 ft (40, 60, and 40 m) for
a tOlallcnglh of 460 ft (140 m), Figure 3.8. Four
box girders of constant depth carry the 115 ft (35
4.o(1Q. _ _ .. _~
NEUILLY
35.70
I
NIVEAU NORMAL DE LA SEINE 23.50
FIGURE 3.8.
Courbevoie Bridge, elevation.
I
Pierre Benite Bridges near Lyon, France
m) wide deck, Figure 3.9. The available depth of
only 7.5 ft (2.28 m) made necessary a very slender
structure; depth-to-span ratio for the main span is
1126. 5 •6
Each river pier is an assembly of two half-piers,
Figures 3.9 and3.10, which are fixed at the level of
the foundation. Each half-pier consists of a rectan­
gular shaft 9 by 26 ft (2.8 by 8 m), which supports
two pairs of prestressed concrete walls, above the
normal water level, in the form of a parallelogram
of 18 in. (0.45 m) thickness and 10.5 ft (3.2 m)
width. The walls are arranged in a "V" in the
transverse direction of the bridge and have a di­
mension of 6.7 ft (2.05 m) out-to-out of walls in the
longitudinal direction. 6 The girders are fixed at the
piers and supported on elastomeric bearings at the
abutments. A total of 148 precast segments of 12.5
ft (3.8 m) length were required for the super­
structure. They were fabricated in four months at
the rate of two segments per day, in two sets of
steel forms, electrically heated and insulated with
polyurethane lining:'
Erection at the site was accomplished by a float­
iug crane. After careful (lcljustment of the pier
segments, they were erected at the rate of four per
day. The temporary jig used at Choisy-le-Roi for
adjustment of the segments was replaced in this
project by two temporarv steel beams bolted to the
top of each segment and connected to the com­
plett:d section of the cantilever bv prestressing
bars:;
The girder was prestressed longitudinally and
tra nsversely. th rough three longitudinal cast-in­
place strips between the top flange cantilevers of
the box girders. The completed structure is shown
in Figure 3.10.
3.3
89
FIGURE 3.9. Courbe\oie Bridge, cross section at river
pier and abutment.
~:;"'i>
\."..
.. ::­,
.
--~
\ 0::::: ' ....
\ '!o.
~\
FIGURE 3.10.
bridge.
Courbevoie Bridge. view of completed
Pierre Benite Bridges Near Lyon, France
These two large bridges carry the rnotorway from
Paris to the Riviera south of Lyon near the Pierre
Benite hydroelectric plant, Figure 3.11. There are
two separate bridges, one over the draft channel of
the power plant and the other over the Rhone
River. Both structures are twin bridges, each
bridge consisting of two single-cell box girders.
Typical dimensions in longitudinal and cross sec­
tions are shown in Figures 3.12 and 3.13. The same
constant depth of 11.8 ft (3.6 m) is used for all
spaf}S of the two bridges. However, a haunch
under the intracios of the box girders increases the
,
FIGURE 3.11. Pierre Benite Bridge, view of the
finished bridge.
Precast Balanced Cantilever Girder Bridges.
90
~
___ ~_~ ____ . ._~_________ ,~L~ __·________ i--~-------------~~!~n=,o=o~(~~~IQ~x~.~)__________
~,~2·
Bridge over draft channel
«(1 )
(hJ
FIGURE 3.12. l'icrn' lknil{, Bridge. longitudinal s('((iollS. (({) Bridg(, ()\er draft
Hel. (h) Bridge owr Rhone Rin'r.
'.
1
16.92
,
. 3,26.~
+.
1
'n
(han~
,
,t
-l--~0;.~~=~~~=:::rr=9=::::::V~
~
FIGURE 3.13.
Pierre Benile Bridge, t\'Pica]
structural depth over the piers to a maximum of 14
ft (4.28 m) for the 276 ft (84 m) span. All piers rest
on com pressed-air caissons and are made of solid
cylindrical columns 6.5 ft (2 m) in diameter which
support the cast-in-place pier segment, including
skew diaphragms between the two individual box
girders of each bridge. This pier segment served as
the starting base for precast segment placing in
balanced cantilever for the superstructure.
The 528 segments were precast near the southern
hank of the draft channel. This application of pre­
cast segmelltaJ construction was the occasion to
conceive and develop for the first time the short­
ClOSS
section.
linc precasting Illethod, whereby the segments are
cast in a formwork located in a stationary position.
Each segrnent is cast between a fixed bulkhead and
the preceding segment, in order to obtain a perfect
match. After a learning curve of a few weeks, each
of the two short-line-method casting machines was
used to cast one segment every day. Details and
specific problems of the short-line method will be
described in Chapter II. Figure 3.14 shows the
precast segments as they were fabricated, tem­
porarily stored, loaded on barges by a very simple
portal structure equipped with winches, and finally
transported to the construction site.
I
I
I
~-
Other Precast Segmental Bridges in Paris
91
construction site with segment placing in progress
is shown in Figure 3.16.
Both precasting and placing operations were
carried out successfully. All the segments were
placed in the structures in 13 months. The only re­
gret was that this erection system did not provide
for precast pier segments. The geometry of the
cast-in-place pier segments was further compli­
cated by the skew of the bridges, such that the
contractor expended as much labor on this aspect
of construction as in precasting and positioning all
the precast segments.
3.4
Other Precast Segmental Bridges in Paris
The first two match-cast bridges, Choisy-le-Roi and
Courbevoie, were followed by a series of other
crossings over the Seine River. All contracts for de­
sign and construction were obtained on a competi­
tive basis with other types of materials or construc­
tion methods.
The next two structures were for the construc­
tion of the Paris Belt :'lotorway which crosses the
Seine at two locations, one downstream of the city
and one upstream; see the location map, Figure
3.1. They were followed by several others, which
are briefly described in this section.
3.4.1
PARIS BELT (DOIV.\STllE,1!H)
These twin bridges, Figure 3.17, carry four traffiC
FIGURE 3.14. Pierre Benile Bridge. precasting yard
and loading portal. ((Ii {'recasting vanL (h) Loading portal. lanes. Dimensions are shown in Figures 3.18 and
Placing of all segments in the two twin structures
. was achieved in balanced cantilever. using the
cast-in-place pier segments as a starting base. This
project used the newlv developed "beam-and­
winch" erection system, illustrated in Figure 3.15
together with J close-up view of a typical seg­
ment-placing operation. Electric winches are sup­
ported in a cantilever position from the com­
pleted part of the deck to allow each segment to be
lifted oFf the barge and placed in its final position.
Because of high-velocity river currents on one
structure, it was considered advisable to transfer
the segments from the barge to the winch system
close to the piers to allow temporary anchorage of
the barge. Therefore, segments had to be moved
longitudinally from the barge position to their final
10GJ.tion. A special trolley carried the winches and
the suspended segment while riding along rails
fixed to the finished deck. A general view of the
3.19. Ylaximul1l span length is 302 ft (92 m) and
the structural depth of the four box girders is 11 ft
(3.4 m), increased toward the piers to a maximum
of 21.3 ft (5.5 m) bv straight haunches. Because of
the skew between the axis of the bridge and the
How of the Seine. the pier shafts were given a spe­
ciallozenge shape. which proved very efficient for
the hydraulic flo\\' and is of pleasant appearance.
The limited bending capacity of the shafts called
for temporary supports during cantilever COIl­
struction operations.
Precast segments were manufactured on the
bank of the Seine with two casting machines
(short-line method). For the part of the bridge
superstructure located over the river, segments
were placed with a floating crane, Figure 3.20. In
fact, almost half the bridge length was placed over
land au t of reach of the floating crane. The beam­
and-winch equipment used at Pierre Benite Bridge
was substituted for the crane to place these seg­
ments. There was also need of additional falsework
on one bank to compensate for the unusually long
-"
1f '
FIGURE 3.16.
FIGURE 3.15. Pierre Benite Bridge, segment placing
scheme (hft and tllP right).
92
Pierre Benite Bridge, under construction.
FIGURE 3.17. Paris
finished bridge.
Belt
(Downstream),
view of
1.10
1..0
90
CRA"
67...,7
P'~
P>LE 1
d5,~J!
J
~:.-.
l.
::
35Q
J
1'1AHt.rs
'"
__2%_
~~
AU.~~
312,506
_L!J
~~--~
__
81.<46
__"-:::- .._~.
... ~
1~OO
FIGURE 3.19.
'e
'
MOO
900
Paris Belr (Dowllstrealll),
•
.oJ
l
~I
, =~
.J
cross sect iOIl.
'FI'
I
"'2,.D.1
'N
7'1,65
t
r.53
800
_<t'*>o.-
l.
3lo
J
90
,
~
~
]
.
Lb
CtA.£E RO.
" ,
,~,
sectioll.
CRAtE
PILE}
"r,," ,,'~"N_
Al:;,..SLAi
"~<',,,;_
l\'pi(alloll~illldillal
!t1,(.(I'
'1<20'
<i1q6
I'ari, Bell (Dowmlrc;tlll),
92,00
H N \2<l-3'!
FIGURE 3.18.
11Q,SO'
! I
': ~Q
zeD
.
I "
. r.3~1?
CVLE£ RD
Precast Balanced Cantilever Girder Bridges
94
FIGURE 3.20.
placing.
segment
FIGURE 3.21. Paris Belt (Upstream), vIew of the
finished bridge.
end span, which could not be changed because of
stringent pier location requirements.
direction, Figure 3.21. The twin bridges have di­
mensions similar to those of the downstream
bridge, and each structure has two parallel bo;-:
girders connected by transverse prestress. Dimen­
sions are shown in Figures 3.22 and 3.23. A circu­
lar intrados profile was used in lieu of the straight
haunches. All segments were precast on the river
bank in the immediate vicinity of the bridge, using
3.4.2
Paris
Belt
(Downstream),
P,4RIS BELT (UPSTREAM)
On the other side of Paris another segmental
structure, also carrying the Beit Motor-way over the
Seine, was designed for five traffic lanes in either
65.m
56,62
d ~ut,.uil
FIGURE 3.22.
Paris Belt (L'pstrcam), longitudinal section.
E
o
N
o
...
3.50 m
3.50m
3.50m
3.50 m
FIGURE 3.23.
_--_._--_.
.
3.50m
3.50 m
3.50 m
3.50m
Paris Belt (Upstream), typical cross section.
3.5Om
3.50m
Other Precast Segmental Bridges in Paris
PHASES D'EXECUTION DU T AllllER
SEQtll!NCES OF
95
nu:
Dl!'.CK COIISTRUCTlctI
Right Bank
Quay of Bercy
FIGURE 3.24.
P;ll'is Bell (l'pstream), typical segment placing scheme.
the sallie two casting machines lIsed previously for
the downs! ream bridge.
Placing segments in the struClure posed some
interesting problems, as shown in the sequence
diagrams of Figure 3.2-!-. Pier segments were too
heavv to be handled as one unit and were sub­
divided into two segments, assembled upon the
pier shaft before cantilner placing could start. A
crane, either on crawlers or on a barge, together
with the beam-and-winch equipment handled all
segment placing,
3.4.3 JUVISY BRIDGE
This bridge, Figure 3.25, is also on the Seine just
somh of Choisy-Ie-Roi; see the location map. Fig­
ure 3,1. Dimensions are shown in Figure 3.26.
Segments were cast by the short-line method near
the site and placed with a floating crane, An aux­
iliary falsework on both banks allowed segment
placing and assemblv beyond the reach of the
floating crane,
3.4.4
FIGURE 3.25. Juvisv Bridge. completed structur:.
nnv BRIDGES AT CONFL4NS
These twin bridges, Figure 3.27, placed about 320
ft (100 m) apart to allow for interchange ramps on
both banks, are upstream of Paris where the Seine
and Marne Rivers merge; see the location map, .
Figure 3.1. Dimensions and construction methods
were similar to those of the Courbevoie Bridge al­
ready described.
Precast Balanced Cantilever Girder Bridges'
96
t
I
24-3
EL 133
, .,
24-3
"
V
I
I
/1\
I
I
IO~6"
I
I
I
1
i
1~133
EL 133 i
:
I
10'
~
~65
=t==
.,..
I
/
f--.I
I
EL.122
•
l
!
I.
j
:
7
I
I
EL.69
•
FIGURE 3.26. Ju\'isy Bridge, cross seclion.
Balanced cantilever construction was accom­
plished utilizing a launching gantry for erection.
In the approach spans the superstructure has a
constant depth of 8.2 ft (2.5 m). Depth of the
center spans varies from 14.9 ft (4.5 m) at the piers
to 8.2 ft (2.5 m) at midspan, Figure 3.29. The rec­
tangular box segment has a bottom flange width
of 18 ft (5.5 m) and a top flange width of 34.8 ft
(10.6 m). Webs ha,'e a constant thickness of 12 in.
(0.3 m), while the top and bottom flanges are 8 in.
(0.2 m) and 7 in. (0.18 m) thick, respectively, Fig­
ure 3.30. Typical segment length is 10.8 ft (3.3 m).
Expansion of the deck is provided in every
fourth span by a special stepped (ship-lap) joint
with horizontal elastomeric bearing pads, Figure
FIGURE 3.27.
hridge.
3.5
Twin Bridges at Conflans, finished
Oieron Viaduct, France
The Oleron Viaduct provides a link between the
mainland of France and the resort island of Oleron
off the Atlantic West Coast 80 miles (128 km) north
of Bordeaux, This structure has a total length be­
tween abutments of 9390 ft (2862 m). In the navi­
gable central part of the structure are 26 spans of
260 ft (79 m), Figure 3.28. Approach spans consist
of two at 194 ft (59 m), sixteen at 130 ft (39.5 m),
and two at 94 ft (29 m). The superstructure is sup­
ported by 45 piers and was assembled by pre­
stressing match-cast segments, using epoxy joints.
FIGURE 3.28.
OJeron Viaduct, cQmpleted structure.
97
Oleron Viaduct, France
1
i
I
I
I
'1
•
~.
"~
\r
_./
18'
FIGURE 3.29. Olcron Viaduct. typical cross section. from ref. :> (courtesy of
American Concrete l!lStitute).
I he
3,30. Throughout the total length of structure
there are ten expansion joints: one at each abut­
ment and eight intermediate ones. The latter are
located at points or cOlltraftexure in a tvpical
interior span subjected to a continuous uniform
load.~ The segments with the expansion joint have
the same length as typical segments and are in fact
two hair-segments that are temporarily preassem­
bled with bolts. with a special lavout of temporary
and permanent prestressing tendons. It is then
possible to maintain the balanced cantilever erec­
tion procedure beyond the expansion joint to
midspan. Later on, when continuity has been
achieved in the adjacent spans, the expansion­
joint segment is "unlocked" to perform in the in­
. tended manner.
I-;:V'"
"
I
The precasting plant was located in the vicinity
of the mainland abutment. Production in this plant
was scheduled so that the 24 segments required for
a typical 260 ft (79 m) central span could be fabri­
cated in nine working days. Segments were pro­
duced by the long-line method, described in
Chapter 11. Four sets of steel forms rode a bench
that was carefully aligned to the longitudinal
profile of the roadway and the variable-depth soffit
with due provision for camber. Segments were
match-cast in the same relative order in which they
were subsequentlv assembled at the site.;; An aerial
view of the casting yard is shown in Figure 3.31.
Handling of segments in the casting and storage
yard was accomplished by a special railwav­
mounted gantry capable of handling loads varying
r:
I
!
1
I
!Il.JI!L
'2­
I
I
FIGt:RE 3.30. Oleron Viaduct, typical center span elevation, from ref. 5 (cour­
tesy of the American Concrete Institute).
98
FIGURE 3.31.
\·ard.
Precast Balanced Cantilever Girder Bridges'
Olemn Viaduct. aerial "iew of casting
from 45 tons (42 I11t) for the center-span segment
to HO tons (i3 111t) for the pier segment. A lowboy
dolly riding on rails or the finished bridge and
pmhed by a farm tractor transported the segments
from stor:tge to their 10catiol1 for assembly.
Cantilever erection at the site was accomplished
by a launching gantry, Figure 3.32. This gantry
was the key to the successful operation of this proj­
ect. Although the structure is erected oyer water,
the use of floating equipment would have been
difficult, expensive, and subject to uncertainty be­
cause of the great tidal range and the shallowness
of water in most of the area traversed by the
structure. Floating equipment would have been
able to reach the approach piers only at high tide.
During low tide the marsh area, which is the loca­
ti011 of France's famed Marennes oyster beds,
could not accept any tire-mounted or crawler­
mounted equipment. Consequently, it was decided
to work entirely from above with a launching
gantry. This new technique was developed for the
first time for this structure and was later refined
for other structures. For the typical central spans
the erection cycle required between eight and ten
working days.f'
Construction began in May 1964, three months
after design work had started. The first segment
was cast in July and placed in August 1964. Side
spans laid on a cu I've were completed in December
and the launching gantry was then modified for
construction of the center spans. The last of the
8iO precast segments was in place in March 1966,
alld the bridge opened to traffic in May, after an
overall construction time of two years~; see the
summary of the work program in Figure 3.33. A
FIGURE 3.32. OleHln \'iarluct. cOllStruClioll yic\\
showing camilcHT span. from ref. :> (counes\, or lhe
American
COf1cr('lC
InslillHc).
view of the final structure is shown in Figurcs 3.28
and 3.34.
The Olcron Viaduct was thc first applicJtiolJ of
the launching-gantry concept for placing segments
in cantilever. Se\'craJ structures were later de­
siglled and huilt \\'ith the same construction
method. \iention should be lIlade here of three
special bridges:
I. Blois Bridp,f min tlt(, Loir(' Hit'('r The princi­
pal dimensiolls are given in Figure 3.35. The
superstructure box girders rest on the pier shafts
through twin elastomeric bearings, which allow
thermal expansion while prm'iding partial re­
straint for bcnding-moment transfer between deck
and piers. Consequently, sa\'illgs are ohtained both
in the deck and in the foundations. All segments
were placed in the bridge wit h an improved ver­
sion of the launching gantry first designed for the
Oleron Viad uct. High-strength steel and stays
were used to provide minimum weight with a sat­
isfactory stillness during operations, Figure
3.36. High-strength bolt connections were used
throughout to make the gantTv completely capable
of dismantling and easily transportable to other
construction sites.
2. Aramon Bridge over the Rhone River This was
the next structure where the same gantry could be
used, Figure 3.37.
3. Seudre Viaduct Located just a few miles
south of Oleron over the Seudre River, this 3300 ft
(1000 m) long viaduct was also of precast segmen­
tal construction and used the same launching gan­
Chillon Viaduct, Switzerland
99
CONTiNENT
OLERON
PIERS ON FOOTINGS
PIERS ON FOOTINGS
FIGURE 3.33.
Olcl'OlI Viaduct, program of work,
tn. The linished structure is shown in Figure 3.:HL
Foundations foJ' the cellter spalls were built Illside
sheet pile cofferdams in spite of verv swift tidal
currents.
3.6
Twin rectangular slip-formed shafts were used
for the piers. varying in height from 10 to 150 ft (3
to 45 m). Stability during construction was excel·
lent and required little temporary bracing except
between the slender walls to prevent elastic insta·
bility.! With the exception of three piers in each
Chillon Viaduct, Switzerland
The 7251 ft (2210 111) long dual structures of the
Chillon Viaduct are part of European Highwav E-2
and are located at the eastern end of Lake Geneva
passing through an environmentallv sensitive area
and very close to the famed Castle of Chillon, Fig­
ure 3.39. In addition, the structures have verv
difficult geometrical constraints consisting of 3%
grades, 6% superelevation, and tight-radius curves
as low as 2500 ft (760 m). Each structure has 23
spans of 302 ft (92 m), 322 ft (98 m), or 341 ft (104
m). The variable spans allowed the viaduct to be
fitted to the geology and topography, providing
minimum impact on the scenic forest. The viaducts
are divided bv expansion joints into five sections of
an approximate length of 1500 ft (457 m),
FIGURE 3.34.
bridge.
Oleron Viaduct, aerial view of finished
Precast Balanced Cantilever Girder Bridges
100
CD
ELEVATIOn - ELEVATION
9.100
9\00
PI
91,00
P?
P 3
61,50
p,
CI) (DUPE TfiAnSVERSALr
CROSS SECTION
to
4~ 79
m at midspan
FIGURE 3.35.
Blois Bridge. elevation and t\'pical cross section,
\'iaduct, all piers are hinged at the top. The piers
that are less than 72 ft (22 m) high are hinged at
the base; taller piers are fixed at their base, being
sufficiently flexible to absorb longitudinal move-
FIGURE 3.36. Blois
Bridge,
operating on the superstructure.
launching
ment of the superstructure.
The superstructure consists of a single-cell rec­
tangular box with a cellular cantilever top flange,
Figure 3.40, and with a depth varying from 18.5 ft
gantry
FIGURE 3.37.
Aramon Bridge, launching gantry.
Chillon Viaduct, Switzerland
FIGURE 3.38.
FIGURE 3.39.
Seudre Bridge, finished structure.
(5.64 m) at the longer-span piers to 7.2 ft (2.2 m) at
midspan. Widths of top and bottom flange are re­
spectively 42.7 ft (13 m) and 16.4 ft (5 m). Dimen­
sions of the two typical cantilevers are noted in
Figure g.41. :\laximum segmem weight was 88 tons
(80 mIl. :\ cellular cantilever top Bange was used
because the overall width of the top flange ex-
101
Chillon Viaduct, aerial vie\\'.
ceeded 40 ft (approx. 12 m) and the cantilever
length was 13.15 ft (4 Ill). An altemative would
have been to provide stiffening ribs as used in the
Saint Andre de Cubzac Viaducts (Section 3.11) and
the Sallingsund Bridge (Section 3.13).
Segments were precast in a yard at one end of
the structure with five casting machines, allowing
Over supports
(a)
1300
1300
5.00
At mid-span
(b)
FIGURE 3.40.
Chilion Viaduct, cross sections. (a) Over supports. (b) At midspan,
=
III
102
91
Hartel Bridge, Holland
103
Sections I, II, and V, conventional cast-in-place
prestressed concrete box girders
Sections III and IV, precast prestressed concrete
segmental box girders
Two steel bascule bridges.
FIGURE 3.42.
Chillon Viaduct, precasting yard.
an average production of 22 to 24 segments per
week (see aerial view, Figure 3.42).
Erection was by the conventional balanced can­
tilever method with a launching gantry designed to
accommodate the bridge-deck geometry in terms
of curve and variable superelevation. The overall
length of the gantry was 400 ft (122 m) and the
total weight 2,50 tons (230 mt). Special features of
this gantry will be discussed in Chapter 11. Can­
tilever placing of precast segments is shown in Fig­
ure 3.43.
This structure is truly an achievement of mod­
ern technology with emphasis upon the aesthetic
and ecological aspects of design.
3.7
Hartel Bridge, Holland
The 1917 ft (584.5 m) long Hartel Bridge crosses a
.canal in Rotterdam, Figllre 3.44, and consists of
the following elements:
FIGURE 3.43. Chillon Viaduct, cantilever construc­
tion with launching gantry.
The original design contemplated that the total
structure would be constructed as conventional
cast-in-place box girders on falsework. Substitution
at the contractor's request of cast-in-place seg­
mental construction by precast segmental con­
struction for sections III and IV saved the exten­
sive temporary pile foundation system necessary to
avoid uneven settlement of false work because of
initial soil conditions. The redesign proposed two
single-cell rectangular box girders as opposed to
one three-cell box girder, Figure 3.44, omitting the
center portion of the bottom flange and providing
thinner webs and a thicker bottom flange.
In the segmental box girder design the climen­
sions of the deck slab are constant over the entire
length, girder depth varies from 4.92 ft (1.5 m) to
17 ft (5.18 m), the webs have a constant thickness
of 13.8 in. (0.35 m), and the bottom flange thickness
varies from 10 in. (0.26 m) to 33 in. (0.85 m). Up to
a depth of 9.35 ft (2.85 m) the segments have a
length of 15.8 ft (4.8 m); over 9.3 ft (2.85 m) the
length decreases to 12.3 ft (3.75 m).
The vertical curvature of the bridge was made
constant for the full length of sections III and IV
by increasing the radius from 9842.,5 ft (3000 111) to
J9,029 ft (,5800 m), which resulted in a repetition
of eight times half the center span. This repetition
justified precast segments.
A long-line casting bed (see Chapter 11) was con­
structed on the centerline of the bridge box girders
at ground level, Figure 3.45. Thus, a portal crane
was able to transport the cast segments to the stor­
age area and also erect them in the superstructure,
Figure 3.46. The end spans have three more seg­
ments than half the center span; these were sup­
ported on temporary falsework until all the pre­
stressing tendons were placed and stressed, Figure
3.46.
The first segment cast was the pier segment;
each of the remaining segments was then match­
cast against the precedi.ng segment. The pier seg­
ment was positioned on bearings on top of the pier,
Figure 3.47, and the two adjoining segments were
positioned (one after the other) and the joints
glued with epoxy resin. Temporary high-tensile
bars located on the top of the deck slab and in the
bottom flange were stressed to prestress the three
Precast Balanced Cantilever Girder Bridges
104
._v ~
84.1
117.4
Elevation
I I
r~
F
"• no
'"
I
I I
0
I
-
A
HALF CROSS SleTtON _ B
'"
~,
l....-­
HALF CROSS SECTION ­
~
Cross sections of the redesign
~---
.---.
Cross section of the
original design
FIGURE 3.44. Hartd Bridge. typical dimensions: c!('yatioll, cross sections of the origi­
nal design. noss sections of the redesign (coune,\" or Brice Bender, BV:\ISTS).
segments together. After the epoxy had hardened,
the permanent tendons were placed and stressed.
The two segments adjoining the pier segment were
supported during erection on Hat jacks on the top
of the outside struts of a steel scaffolding bearing on
the pier foundation. Thus, the flat jacks were used
for adjustment of the segments to achieve proper
geometry control. The remaining segments were
FIGURE 3.45. Hanel Bridge. method of casting segments (courtesy of Brice
Bender, BVN/STS.
Hartel Bridge, Holland
FIGURE 3.48.
FIGURE 3.46.
dling segments.
105
Hartel Bridge, completed structure.
Hartel Bridge, portal crane for han­
erccted in thc cOT1\'enlional balanced Glnlilever
met hod. Thc cOl11pleted struclurc is shown in Fig­
ure 3.4H.
Othcr slructures using prccast scgmental con­
strllction wcre suhscquentl\' designcd and built in
the \iclhcrlands. Shown in Figurc 3.49 is the
Ilridgc o\'cr the ljssel at Deventcr, where segments
in thc 2·n It (74 111) SP;Il1S were placed with a
launching gallln. The overall Icngth of the gantry
was S2() ft (i:')ti 111), allowing the legs to bear on the
permanent concrete piers and impose no loading
on the deck during construction. Figure 3.50 .
FIGURE 3.49. Dnenler Bridge,
\\'ith the launching gantry.
. . . . --f--..--._-.. ---f
.___._____._%_n__ n_______ :~~[
FIGURE 3.47. Hartel Bridge, erection sequence and detail of tempo­
ran- pier bracing (courtesy of Brice Bender, BVN/STS).
placing segments
106
Precast Balanced Cantilever Girder Bridges
156 m (520 It)
74 m
ttl
Max bridge span 74 m (247 ttl
FIGURE 3.50.
Deventer Bridge. elevation of gantry.
3.8 Rio·Niteroi Bridge, Brazil
The Rio-Niteroi Bridge crosses the Guanabara Bay
connecting the cities of Rio de Janeiro and Niteroi,
thereby avoiding a detour of 37 miles (60 km). This
structure also closes the gap in the new 2485 mile
(4()OO km) highway that interconnects north and
south Brazil and links the towns and cities on the
eastern seaboard, Figure 3.51. Although the route
taken by the bridge across the Bay seems somewhat
indirect, it was selected because it avoids very deep
water and is clear of the flight path from Santos
Dumont Airport.
Total project length is approximately 10.5 miles
(17 km). of which about 5.65 miles (9. I km) is {)\"er
water. The alignment begins at the Rio side with a
3940 ft (1200 m) radius curve, then a straight sec:
tioll. \\·itl1in which are located steel box girder
na\'igation spans totaling 2872 ft (848 m) in length.
This is followed by an island, where the viaduct is
interrupted by a road section of604 ft (184 ml. and
finally <lIlother 3940 ft (1200 m) radius curve ar­
riving at Niteroi.
The precast ~egmental concrete viaduct sections
have a lOlal length of 27,034 ft (8240 m) repre­
senting a total deck area of 2,260,000 sq ft (210,000
-"-\---+--~ JoooPeuaa
___
7'1Reci~
Cuiobo
F'-~- ~
iteroi
Paulo
,u"uno
pol'
"
FIGURE 3.51.
.
•.
The
Rio·Niteroi
Bridge
Rio Nileroi Bridge. site location map.
Rio-Niteroi Bridge, Brazil
m 2 )", making this bridge the largest structure of its
type. An aerial view of the crossing under traffic is
shown in Figure 3.52. The superstructure has 262
ft (80 m) continuous spans with an expansion joint
at every sixth span, Figure 3.53. It consists of two
rectangular box girders for a total width of 86.6 ft
(26.4 m) and a constant depth of 15.4 ft (4.7 m). A
2 ft (0.6 m) cast-in-place longitudinal closure joint
between the top Range cantilevers provides con­
tinuity between the two box girder segments. Typi­
cal segments have a length of 15.75 ft (4.8 m) and
weigh up to 120 tons (110 mt). The pier segments
are 9.2 ft (2.8 m) in length. Special segments are
used for expansion joints.
Longitudinal prestressing tendons consist of
twelve! in. (13 mm) diameter strands in the top
and bottom Ranges with a straight profile, while
the resistance to shear stresses is obtained by verti­
cal web prestress, Figure 3.54.
All segments were manufactured in a large pre­
casting yard on a nearby island. Ten casting
machines (eight for the typical segments and two
for the pier and hinge segments) were laid in two
independent parallel lines, each equipped with a
portal crane for carrying the segments to the stor­
age area and the loading dock. More than 3000
segments were subsequently barged to their loca­
tion in the structure and erected by four launching
gantries working simultaneously on each of the two
parallel box girders and on either side of the bay,
Figures 3.55 and 3.56. The rate of segment placing
was remarkable. A typical span was assembled and
completed in five working days. Between the
months of February and July 1973, an average of
FIGURE 3.52. Rio-Nileroi Bridge, view of the com­
pleted ;,lrurture.
Cross
section
i
IJQaJ
Elevation
(h)
FIGURE 3.53.
Elevation.
107
Rio-Nileroi Bridge, cross section and elevation. (a) Cross section. (b)
108
Precast Balanced Cantilever Girder Bridges'
t .. t
80
7
8
(I
8
ELEVATION
BARRE5 MACALLOY 0 25~
.
I
PLAN
CABLAGE SUPERIEUR
PLAN
CABLAGE
.
-
INFER'EUR
lij
I
1:JJl~~~L-"1:J---:I1
FIGURE 3.54.
Rio-Niteroi Bridge, typical span dimensions and tendon layout.
278 precast segments per month were installed in
the structure by the four launching gantries, rep­
resenting an area of 180,000 sq ft (17,000 m 2 ) of
finished bridge per month. At the same speed,
OIeron Viaduct could have been built in two
months. Such is the measure of the determination
and enthusiasm of engineers and constructors of
the New World.
3.9 Bear River Bridge, Canada
The Bear River Bridge is about 6 miles (9,7 km)
east of Digby, Nova Scotia, on trunk route 101
between Halifax and Yarmouth, near the An­
napolis Basin; it replaces an 85-year-old structure,
Preliminary studies showed, and construction bid
prices verified, that precast segmental was more
economical than sted construction by nearly 7%.7.8
JFK Memorial Causeway, U.S.A.
FIGURE 3.55.
Ri()-~ilcroi
Bridge. cantilever con­
struction.
rotal structure length is 1998 ft (609 m) with six
interior spans of 265 ft (80.8 m) and end spans of
204 ft (62.1 111), Figure 3.57. The layout has very
severe geo1llctrv constraints. In plan, the east end
of t he bridge has two sharp horizontal curves con­
l1(~cted to each other ami to the west end tangent bv
two spiral curves; minilllum radius is 1150 ft (350
III). In elevation, the bridge has a 2044 ft (623 m)
vertical curve with tangents of 5.5 and 6.0 percent.
Two sets of short-line forms employed by the con­
tractor to Gist the segments met the variable
geoll!etry requirements admirably. The accuracv
of casting was stIch that only nominal elevation
adjustlllents were required at the abutments and
the center-span closure pours. R
The single-cell box girder su perstructure is con­
tinuous for the total length of the bridge. Typical
(Toss-section dimensions are indicated in Figure
:>.58. Prestressing tendon layout is illustrated ill
. Figure 3.59 for a tvpical luterior span. Fiftv-hve
tendons were required for negative moments and
22 for positive-moments. The majority of nega-
FIGURE 3.56. Rio-\iiteroi Bridge, launching gan­
tries.
109
tive-moment tendons were inclined in the web
and anchored at the face of the segments. Anchor­
age of six tendons at the face of the first segment
acUacent to the pier segment (three in each web)
produced a large upward shear force at the face of
the pier segment, which was not overcome until
therrection of several additional segments. The
midspan positive-moment tendons are continuous
through the cast-in-place closure joint at midspan.
These tendons, indicated by capital letters in Fig­
ure 3.59, were placed in preformed ducts upon
completion of erection of the segments in a span
and the closure pour consummated. All positive­
moment tendons were anchored in the top flange.
The precast segments are typically 14 ft 2 in. (4.;>
m) in length and the closure pour at midspan is 4­
ft 4 in. (1.3 m) long. 7 •H
The precast segments are reinforced with pre­
fabricated mild steel reinforcement cages, in addi­
tion to the primarv longitudinal prestressing ten­
dons, Figure 3.60, and transverse prestressing in
the top Hange. Web shear reinforcement varies
depending on the location of the segment. The 145
precast segments were cast in a plant located Ilear
the bridge. This plant was equipped with two cast­
ing molds, each producing one segment per day. A
12-hour steam curing perioe! was used and a con­
crete strength at 28 clays of 5000 psi (34.5 MPa)
was achievecJ.7
Because of the curved layout of the bridge and
its relative shortness, the use of a launching gantry
would have been uneconomical. Segments were
placed by a 200 ton (180 Illt) mobile crane on land,
or on a barge over water, Figure 3.61. Construc­
tion of this bridge started in Mav of 1971. and it
was opened to trafflc on December 18, 1972 .
3.10 JFK Memorial Causeway, U.S.A.
A portion of the JFK :\fellloriai Causeway repre­
sents the first precast. prestressed, segmental box
girder completed in the United States. Opened to
traffic in 1973, this 3280 ft (1000 m) long structure
spans the Gulf Intercoastal Waterway in Texas to
connect Corpus Christi and Padre Island. It was
designed by the Bridge Division of the Texas
Highway Department under the supervision of
v'layne Henneberger. The Center for Highway
Research, University of Texas at Austin, under the
supervision of Prof. John E. Breen, assisted in the
design and also built and tested a one-sixth scale
mode! of the bridge to check design requirements
and construction techniques. 9
,
o
7>
f4C<t«",,.r»»>hv
»p .... «V?
>p>
M.w. L, EL. 00.0
ft
.,~
,.,,""
P'ER 2
ELEVATION
~
127
CONC, PARAPET WALL
._----­265"0"
EXISTING
RIvER BED
PIER 3
PIER 1
UNITS NO.7, 21,47,67, B1.107, 121 AND 147
ARE CAST IN PLACE (DECK CLOSING UNITS)
Ii:.
,,,,'.)l'Ol71 )12175)1<)10
m"o"
'. .C;.'$O'.' ("'ne..,•• ,..,
I
.I"'
Ii:.
FIGURE 3.57. He,ll RivCl' Brid~c, elcvation, from reI'. H (courlesv of the Prestressed
COllcrete Institute).
c«::;;O"",,(tt<
i'"~''''' '·'·'"l''~l''''' ''''''1''1''
~o~
265"0"
~ BRGS.
I
.I
iPIER4
'--<l.
ROADWAY
39' -6"
2-6" b.
16'-0"
15'-0'
I'_~_"
I
I
l
:
o
~
r<l.
PRECAST
UNIT
I
la"
10"
-­ -
-
/
(
4'-3" 4'-6"
6'-0"
I'-a~
I'-a"
4'-6" 3'-10 3'-10' 4'-6"
~
I
a"
~
,
l'
1'-0"
./"
6'-a"
1'-4'~ ~
6'-a"
1'-0"
'-- r.-I'- 4"
la'-o"
,
FIGURE 3.58. Bear Riyer Bridge, typical cross section, from ref. 8 (courtesy
of the Prestressed Concrete Institute).
HALF INTERIOR SPAN TENDON ELEVATION
£ACH TENOON UT'LiZES
,
12~!/2IN
270 K
DIAMETER
STRANDS ______
'\
. ."
-
" I
t!f~
UIl'
uu~~ 14 IS!III, /,. \\'1..
.
11
• _01 l1,iW •
77 .:~,:
.,
13 11
i
I
II T£NOONS
,
1~"
HA~F
9tH"
SECTION AT MIDSPAN
/'
.I,
HA~F
.
SECTION AT PIER
TENDON DISTRlaUTION
FIGURE 3.59. Bear Ri\'er Bridge, typical center-span tendon elevation and
distribution. from ref. 8 (courtesy of the Prestressed Concrete Institute).
111
112
Precast Balanced Cantilever Girder Bridge;
,
'.
balanced
,
FIGURE 3.62. JFK Memorial Cause\\'av,
cantileH'i' construction (courtesy of J. E. Breen).
FIGURE 3.60. Bear River Bridge, longitudinal pre­
stress ducts in forms (courtesy of thc Pl'csll'essecl COll­
<Tele I nstitllle).
FIGURE 3.61. Bear River Bridge, erection by
barge-mounted crane (counesy of the Prestressed Con­
crete I IIstitu Ie).
The structure consists of thirty-six 80 ft (24.4 m)
long approach spans of precast, prestressed bridge
beams and the 400 ft (122 m) total length segmen­
tal bridge spanning the Intercoastal Waterway.
The segmental portion of this structure has a
center span of 200 ft (61 m) with end spans of 100
ft (30.5 m). The segments were precast, trans­
ported to the site, and erected by the balanced
cantilever method of construction using epoxy
joints, Figure 3.62. The precast, segmental super­
structure consists of constant-depth twin box
girders with a 2 ft (0.61 m) cast-in-place longitu­
"'"
dinal closure strip, Figure 3.63. Segments are
10 ft (3.05 m) in length and in cross section, are 8 (t
(2.44 m) in depth, and have a nominal top flange
width of 28 ft (8.53 m). The top Range or deck is of
constant dimension longitudinally but of variable
thickness in a transverse direction. The bottom
flange is of constant dimension transversely but
varies longitudinally from lOin. (254 mm) at the
pier to 6 in. (152 mm) at 25 fl (7.62 m) from the
pier center.
Segments were cast with male and female align­
ment keys in both the top and bottom flanges as
well as large shear keys in the webs, Figure 3.64.
I ntegral diaphragms were cast with the pier seg­
ments, Figure 3.65. Both matching faces of the
segments were coated with epoxv, and temporary
erection stressing at both top and bottom of the
segments precompressed the joint before installa­
tion of the permanent post-tensioning tendons.
The segments were erected by a barge-mounted
crane. As each segment was erected. it was tilted 21
degrees from the in-place segment. so that a pair of
hooks in the top of the segment being erected en­
gaged pins in the segment previously erected. The
new segment was then pivoted down by the sling
until its shear key slipped into the mating shear key
of the previously erected segment. 9 Figure 3.66
shows a permanent tendon being tensioned and
the temporary working platform.
The design concept on this project utilized pre­
stressing tendons in the top flange for dead-load
cantilever stresses; after closure at midspan, con­
tinuity tendons were installed for the positive mo­
ment, Figure 3.67. Research on the model testing
of the bridge is documented in references 10
through 15 with particular emphasis in reference
14 on lessons learned during construction that
might facilitate or improve similar projects.
Saint Andre de Cubzac Bridges, France
Sym.
28 ft. (8.53 m)
E
6fl.(1.83ml
@<tl
6'-8" (2.03
E
E
113
m)1
1=0,
E
M
.
0
• N
00_
"
,I,"
2ft. (0.6.1 m)
pour striP
I
,
•
12"
(305 mm)
00
i____ L;.....;....~~~:.:.=~~
17ft
. (2.13 m) :
• 'E
1
J
!t
13ft. (3.96 m)
I'
)I. '(
i
I
I
i
7'-10" (2.39 ml
:.r!
~lemoriaJ Causeway. typical cross section. Bottom slab
thickness varies from 10 in. (254 111m) at pier to 6 in. (152 mill) at 25 ft (7.62
Ill) from pier center.
FIGURE 3.63. JFK
FIGURE 3.66. JFK Memorial Causeway. prestressing
permanent tendon (courtesy of J. E. Breen).
FIGURE 3.64. JFK Memorial Causeway. precast seg·
ment in casting vanl (courtesv ofJ. E. Breen).
.:.;.~
FIGURE 3.65. JFK :YlemOl'ial Causeway. construction
\iew showing pier segments with diaphragms (courtesy
ofJ. E. Breenl.
3.11 Saint Andre de Cubzac Bridges, France
Opened to traffic in December 1974 after a con­
struction period of 29 months, this important
structure crosses the Dordogne River north of
Bordeaux on the South Atlantic Coast. A view of
the finished bridge is shown in Figure 3.68. The
main river crossing has a total length of 3800 ft
(1162 m) with approach land spans of 190 ft (59 m)
and main river spans of 312 ft (95.3 m), Figure 3.69.
Two intermediate expansion joints located at the
point of contraAexure in the transition spans sepa­
rate the deck into three sections for concrete vol­
ume changes. The center section has a length of
1920 ft (585 m). The main piers have rectangular
hollow box shafts supported by circular open­
dredged caissons 30 ft (9 m) in diameter. Ap­
proach piers have an I section.
Another structure, constructed under the same
contract, consisted of twin bridges 1000 ft (307 m)
in length with typical 162 ft (49.5 m) spans in an
114
Precast Balanced Cantilever Girder Bridges
\
Centr~pan
Main pier
FIGURE 3.67. JFK '\lelllOlial
Call~l'\\a". slstell)
..
-.
FIGURE 3.68. Saint Andre de Cubzac Bridge. "iew of
the finished bridge over the Dordogne Riler.
area north of the main crossing where poor soil
conditions did not permit stability of an embank­
ment. Altogether the deck area is 97,000 sq ft
(29,500 m 2 ), entirely of precast segmental COI1­
struction. The typical cross section is a single box
54.4 ft (16.6 m) wide with transverse ribs both in
the side cantilevers and between webs, Figure 3.69,
to provide structural capacity to the deck slab
under traffic loads. A casting yard located along
the bank of the Dordogne River produced the 456
segments for both bridges (main crossing and
north viaducts) in three casting machines (two for
the typical segments and one for the special seg­
ments such as pier, hinge, or end segments). Mod­
erate steam curing at 86°F (30°C) for 12 hours in a
movable kiln enclosing the newly cast segment and
its match-cast counterpart allowed a one-day cycle
and proved very efficient in avoiding any geomet­
ric corrections.
of I)l'{'stlTssing tendolls.
Segments were placed in the structure by the
heam-and-winch method either on land (for the
northern viaducts or the approach spans or the
lI1ain river crossing) as shown in Figure 3.70 or
over water for the main spans as shown in Figure
3.71. This prc~ject was the occasion for a further
improvement in the placing scheme by beam and
winch, whereby the pier segments could he precast
and placed with the same type of equipment as
shown in principle in Figure 3.72. A provisonal
tower prestressed against the pier side face allowed
the pier segment to be installed upon the pier cap,
with the beam and winch later used for cantilever
placing. To keep the segmellt weight to a
maximum of 110 t (100 I11t) the pier segment, rep­
resenting the starting base of each cantilever, had
been divided into two halves placed successively,
Figure 3.73. Figure 3.74 shows the lifting of the
last closure segment.
3.12
Saint Cloud Bridge, France
A connection between the peripheral Paris Ring
Road and the Western Motorway (A-I3) required
the construction of a bridge over the Seine ex­
tended by a viaduct along the left bank leading to
the Saint Cloud Tunnel, Figures 3.75 and 3.76.
This structure has two traffic lanes in each direc­
tion. It will be duplicated later by a similar adjoin­
ing structure when the congested Saint Cloud
Tunnel is duplicated. Original design of this
bridge contemplated a steel structure. However, an
alternative design utilizing precast segments and
....
at ANDRE
BORDEAUX
"~~ ______" _ _',",,6,,",::::6C,,-_
FIGURE 3.69.
DE
CUBZAC
-+
-,
Saint Andre de Cubzac l)ridge, elevation and cross section.
FIGURE 3.71. Saint Andre de Cubzac Bridge, beam­
and-winch segment placing over water.
-.
--4
FIGURE 3.70. Saint Andre de Cubzac Bridge, beam­
and-winch segment placing over land.
115
PROVISIONAL
TOWER
CD
i
,
..
FIGURE 3.72.
!
REMOVE
TOWER
Saint Andre de Cubzac Bridge. placillg precast pier segments.
I
I
I
I
I
FIGURE 3.73. Saint Andre Cubzac Bridge, lifting
second half pier segment.
116
FIGURE 3.74. Saint Andre de Cubzac Bridge, placing
closure segment in last span.
Saint Cloud Bridge, France
FIGURE 3.75.
117
Saint Cloud Bridge, overall view.
the balanced cantilever met bod of construction.
submitted by the contractor, permitted substantial
sa\'in~s and was accepted bv the authorities.
The brid~e has a total length of 3618 ft (1103 m)
with a constant-depth superstructure. It includes
two sectiolls: the bridge over the Seine. which is a
1736 ft (529 111) long cuned structure; and a 1883
ft (57.t Ill) lon~ viaduct. which follows a straight
lavout along the bank of the Seine and then crosses
the Place Clemenceau. on a 2260 ft (690 Ill) radius
curve, by an access ramp to the Saint Cloud Tun­
nel. It includes 16 spans divided as follows (refer to
}'igure 3.76):
Seine Bridge: 160.8.288.7.333.8,296.0, 150.9, and
two 219.5 ft spans (49,88, 101.75,90.25, .t6, and
two 66.9m)
Common area: 66A ft (20.2.t m) up to the ex pansion
joint, and then 153.1 ft (4.t.66 m), total 219.5 ft
(66.9 m)
Viaduct: five 219.5: 285.4, 210.0. and 137.8 ftspans
(five 66.9; 87,
and 42 m)
Architectural considerations led to the choice of
a 11.8 ft (3.6 m) constant-depth three-cell box
girder with sloping external webs with no overhangs,
Figure 3.77. Segments are 7.4 ft (2.25 111) in length
with,a record width of 67 ft (20A m), their average
weight varying from 84 to 143 tons (76 to 130 mt).
Since the superstructure has a constant depth, the
bending capacity is adjusted to the moment dis­
tribution bv varying the bottom fbnge thickness.
which decreases from 31.5 in. (800 mm) at the ri\'(~r
piers to 7 in. (180 mm) at midspan. To accommo­
date the curvature of the bridge the segments in
this area are cast, in plan, in a trapezoidal shape. "'\
4.5~:f superelevation is obtained bv placing the
units over the piers in an inclined position.
Three-dimensional prestressing was used in the
superstructure: the main longitudinal prestress.
transverse prestress in the cleck, and a vertical pre­
stress in the webs to accommodate shear. .-\fter the
closlIre joint at midspan was cast. additional IOll­
gitudinal prestress tendons were installed to pro­
\'ide continuitv.
Superstructure segments were precast in a plant
on the right bank of the Seine. Two casting molds
were used for fabrication of the se~ments. Each
mold had an external forrnwork and an internal
retractable formwork. The adjacent, previoush' cast
segment was used as a bulkhead to achieve a
match-cast joint.
For erection, segments were transported on a
trolley to a cable-stayed launching gantry of un­
usual size and capacity. It was of high-vield steel
construction, 402 ft (122.5 m) in length and
weighing 250 tons (235 mt), with a maximum load
capacity of 143 tOilS (130 mt). The constant-depth
gantry truss was supported on central and rear
legs, which were runnel shaped to allow passage of
the precast segments endwise. At the central sup­
port, a 52.5 ft (16 m) high tubular tower topped
118
1,
7_"\.
,,1.{$
,
'.f.lI.I:::::=_
L•
. I,
119
120
,[
Precast Balanced Cantilever Girder Bridges
with a saddle provided a large eccentricity to
the three pairs of cable stays, which improved the
negative-moment capacity at this support location.
At the forward end of the gantry an additional leg
was used as a third support poillt dllring launching
and pier segment placing. Figure 3.78. The
Iaullching girder was moved forward on rails
mounted on the completed superstructure. by
sliding on pads placed at the central and rear legs.
The launching girder, in cross section, was trian­
gular in shape. The base of this triangle incI~ded
two structural steel I sections, which served as
tracks for the segment transportation trolley. The
diagonal bracing of the launching girder consisted
of tubular steel members. The girder was fabri­
cated in ten sections, approximately 39 ft (12 m)
'
i
FIGURE 3.78.
Saint Cloud Bridge, segment placing.
MISE EN PLACE
DES
VOU550IRS SUR P1L£,J..L_ _ _ _ _ _---''--'-''--_ _ _ _,_ _ _ _J..O-_''_ _ _ , _ _ _- ' - '_ _
.~_
__
PLACING OF PILE UNITS
, 820
AVANCEMENT
DU
.,PORTIQUE
DE
fL_______
__
L l L -_ _ _ _ _ _ _U -_ _ _ _ _ _ _-LJ._ _ _ __
LANCEMENT.
MOVING THE
MISE
TRUSS
EN PLACE
~VO~Uf2S§:;:;Jl!!~~UlC00:U~RAN~TS~,-~-:-.::-:::--_ _ _
PLACING THE
UNITS
-.l..L_ _ _ _
~ I]_____-....I.l. . .- - - ­
_ ,....
IN CANTELIVER
FIGURE 3.79. Saint Cloud Bridge. sequence of operations in moving launching girder.
!
1
I
I
Saint Cloud Bridge, France
in length, so as to be transportable over the highways. These units were assembled at the job she by
prestressing bars.
The sequence of operatiom in moving the
launching girder forward is illustrated in Figure
3.79 and included the following operations:
Placing pier segment: The gantry was supported on
three points: the rear leg, the central leg placed­
near the end of the completed cantilever, and the
121
temporary front leg supported just in front of the
pier.
Launching of the gantry: The gantry slid on rails at
the rear leg and rolled over an auxiliary support
placed atop the pier segment. The central leg,
during this travel, crossed the gap between the
cantilever end and the pier unit.
Placing typical segments in cantilevl'r: In this phase
the gantry was supported at two points: the central
leg placed over the pier and the rear leg anchored
A
B
PRECONTRAINiE 'l'ERTICAU
-----
."
c
o
FIGURE 3.80.
the ri\er.
Saint Cloud Bridge. sequence of operations of launching gantry over
122
Precast Balanced
FICURE 3.81.
Canti~ver
Girder Bridges .
Angfu Bridge, longitudinal section.
at the end of the last completed cantilever. The
segments were lifted by the trolley at the rear end
of the girder, moved forward, after a rotation of a
quarter turn, and then placed alternatively at each
end of the cantilevers under construction.
As a rf''>ult of the horizontal curvature 01 the
structure, the transverse positioning of a segment
was accomplished both by moving the segment
transportation trolley sideways relative to the
girder [possible side travel of 3 ft (0.9 m) on ei­
ther side] and by moving the launching gantry it­
self sideways relative to its bearing support on the
bridge. Thus, the construction of a cantilever re­
quired one, two, or three different positions of the
gantry, according to the curvature radius and
length of span, as shown in Figure 3.80. Work
started in October 1971 and was completed in De­
cember 1973. Placing the 527 precast segments in
the 3600 ft (1097 m) long superstructure took
exactly one year.
In terms of erection speed, a more interesting
project was successfully carried out on a precast
segmental bridge awarded to Campenon Bernard.
A unique set of circumstances arose where a bridge
over the Loire River at Angers could be fitted to
use simultaneously the dimensions and casting
machines of Saint Andre de Cubzac Bridge, which
had recently been completed, and the gantry of
Saint Cloud Bridge.
The 2577 ft (786 m) long structure rests on 10
piers and has 280 ft (85.1 m) typical spans, Figures
3.81 and 3.82, using a single box girder with ribbed
deck slab units identical to the sections used at
Saint Andre de Cubzac. The construction contract
was signed in August 1974 and the superstructure
was completed in May 1975. All segments were
placed between January and Mar 1975, in a little
less than five months, corresponding to an aver­
age erection speed of 26 ft (8 m) per day of fin­
ished deck.
3.13
Sallingsund Bridge, Denmark
Sallingsund in Northern Jutland between Arrhus
and Thisted is a site of great natural beauty. Con­
struction of a bridge in such an environment was
the object of careful study, which concluded, after
an international competition, in the selection of a
precast segmental structure, Figure 3.83, resting
on piers of a unique design.
This structure has two end spans of 167 ft (51 m)
and 17 interior spans of 305 ft (93 m). '[here are
18 piers between the two abutments. The level of
the roadway reaches 100 ft (30.5 m) above the
water at the center span and 82 ft (25 m) at the
abutments. The two center spans are navigation
spans requiring 85 ft (26 m) vertical clearance over
a width of 197 ft (60 m). The bridge deck accom­
modates two traffic lanes, approximately 13 ft (4
m) each, two cycle paths, and two sidewalks for a
total width of 52.5 ft (16 m), Figure 3.84. The
po:>
FIGURE 3.82. Angers Bridge, view of the completed
structure.
FIGURE 3.83. Sallingsund Bridge, view of the com­
pleted structure.
~
1." .­::
~
\
:.\\
ag-.,
Ogog
~tn'l\
!lg
123
124
Precast Balanced Cantilever Girder Bridges
su perstructure consists of precast concrete box
girder segments 11.7 ft (3.57 Ill) in length, with
epoxy match-cast joints, which are prestressed to­
gether. Segment depth varies from 8.2 ft (2.5 m) at
midspan to 18 ft (5.5 m) at the pier.
The precast superstructure segments were
match-cast by the short-line method (see Chapter
11). There are altogether 453 segments varying in
weight from 86 t (78 mt) to 118 t (107 mt). The
typical segment shown in FigUl'e 3.85 has web cor­
rugated shear keys together with top and bottom
flange keys. Hinge segments equipped with a
roadway expansion joint for thermal movement of
the superstructure are placed every other span
near the point of contraAexure. A hinge segment
with its diaphragm is shown in Figure 3.86.,seg­
ments are placed in the structure in cantilever with
a cable-stayed launching gantry. Transfer from the
casting area and the storage yard to the construc­
tion site and the launching gantry is achieved by a
low-bed dolly pushed by a tractor, Figure 3.87.
The gantry shown in Figure 3.88 should look
familiar to the reader, as it was previously used at
the Saint Cloud and Angers Bridges.
Each pier in the v,ater consists of the followjng,
~s shown in Figure 3.89:
FIGURE 3.85. Sallingsund Bridge. "iew of a typical
segment.
FIGURE 3.87. Sallingsund Bridge, segment trans­
Twenty-four pipe piles filled with reinforced con­
crete after driving
A guiding template and a tremie concrete seal
A precast substructure block and precast ICe
breaker
A cast-in-place hollow box shaft with cap for re­
ceiving the superstructure
Chapter 5 gives a detailed description of the foun­
dation principles in design and construction.
3.14
-.
•
B-3 South Viaducts, France
The South Viaducts or the B-3 Motorway, Figure
3.90, east of Paris, are 1.25 miles (2 km) in length
port.
"
.1'''''''' /-.
FIGURE 3.86. Sallingsund Bridge, hinge segment
with diaphragm.
.•
FIGURE 3.88. Sallingsund Bridge, launching gantry.
;
8-3 South Viaducts, France
125
Figure 3.91 presents a plan of this pf(~iecl and
shows a subdivision in accordance with the type of
cross sections used. It includes the following main
subdivisions:
1.
2.
3.
4.
FIGURE 3.8iJ.
Sallingsund Bridge, elevation of main
piers in water.
and have 860,000 sq ft (80,000 m 2 ) of bridge deck.
The project is in a congested area that required the
crossing of railway tracks, canals, and more than 20
roads; its diverse structural geometry contains
curves, superelevation ranging from 2.5 to 6% and
grades up to 5%.
FIGURE 3.90.
B-3 South Viaduct, overall view.
The main viaduct VP I-A through VP I-J.
The main viaduct VP 2-A and VP 2-B.
The viaducts VI and V2, which are access
ramps to the main viaduct VP 2.
The viaducts V3 and V4, which are access
ramps to the \iational Road R:\3.
The original design for this project, prepared by
the French authorities, was based on conventional
cast-in-place construction of the superstructure in
complete spans using movable formwork. The
contractor proposed a more economical design
based on the use of precast segmellts. The alterna­
tive design had advantages in erectioll, wherein
parts were erected by a launching truss and parts
by a mobile crane in conjunction with an auxiliary
truss and winch. The use of precast units allowed a
deeper and thus a more economical superstruc­
ture, because the space required for formwork did
not have to be deducted in the clearance require­
ments over existing roads and other facilities.
The superstructure has a constant depth of 6.5 ft
(2 m), consisting of three different cross sections,
Figure 3.91. Different width and transitions were
accommodated bv varying the width of the east­
in-place median slab connecting the top Aanges of
the precast segments. Only the V3 and V 4 access
ramps were of conventional cast-in-place construc­
tion.
The webs of the precast segments have a con­
stant thickness of 12 in. (310 mm), increased in
some cases to 2'0 in. (500 mm) near a pier. Webs are
stiffened by an interior rib, which also serves to an­
chor the longitudinal prestressing inside the box
rather than in the web at the end of a segment.
Where the webs are not thickened near a support,
they are prestressed vertically by bars to accommo­
date shear forces. The top Aanges of the segments
are cantilevered 10 ft (3 m). In the case of segment
types 2 and 3, Figure 3.91, the top flange cantilever
between box sections is 9 ft (2.75 rn). The top
Aange follows the superelevation of the roadway.
The thickness of the cast-in-place longitudinal slab
between box girders varies from 7.9 to 13.8 in. (200
to 350 mm), depending upon its width.
The total superstructure is supported on neo­
prene or sliding bearings. Expansion joints are
spaced at distances up to 1970 ft (600 m) and are
Precast Balanced Cantilever Girder Bridges
126
I
200Ct
I,
9,50
18.75
200~
•
1
,I
22.00
1
795 V0U5S0IRS L.1,50 ou 2,50m
TYPE
2
1014 VOUS50lRS L. 2,50 ou 3,.mm
TYPE
3
m
'-1
J ! t:l
:;.;;;r .
T YP E
L.--UW
m
2.00[ 31:::'£ ., 1
15mrw
N:JRD
N:JRTH
'" \.'4
SUD
SOUTH
....
A1
RN3
t
FIGURE 3.91.
B-3 South Viaducl, plan showing segment type location.
located in special hinge joints near a pier.
Superstructure spans vary from 89.6 to 174 ft (27
to 53 m), with 90% of them being in the range of
III to 125 ft (34 to 38 m).
This project required 2225 precast segments, all
manufactured by the short-line method (see
Chapter 11), which involved the following opera­
tions:
I.
2.
3.
4.
5.
6.
7.
Subassembly of mild steel reinforcing on a
template.
Storage of subassembly units.
Assembly of complete reinforcement cages in­
cluding tendon ducts.
Placing of the cages in the forms.
Concreting and curing of the segments.
After concreting and curing, transportation of
the segment by a dolly to a position where one
end would act as a bulkhead for the casting of
the next segment. At the same time its position
was adjusted to conform to the proper
geometric configuration of the superstructure.
Transfer of the segment that had previously
acted as the bulkhead to temporary storage for
further curing.
8.
9.
Transfer of the segment, eight hours after
curing, to a more permanent storage until re­
quired for erection.
Return of the mold bottom, after temporary
storage, to the casting area for reuse.
Curing of the segments was accomplished with
low-pressure steam in the following 44-hour cycle:
I.
2.
3.
An initial 14-hour curing period at 35°C.
A two-hour temperature rise reaching 65"C.
A one-hour curing period at a level of 65"C.
The short curing cycle can be accomplished if the
following conditions are satisfied: use of a proper
cement, preheating of the materials to 35"C, rigid
forms, and proper supervision. Casting of a seg­
ment required nine hours, allowing two segments
per day per form; the four forms used produced a
total of eight segments per day.
Erection of precast segments by the launching
gantry shown in Figure 3.92 is schematically illus­
trated in Figure 3.93. After being rotated 90",
segments V2 and V'2 were placed at the same time
by means of two trolleys suspended from the bot­
tom chord of the launching girder, Figure 3.94.
B·] South Viaducts, France
FIGURE 3.92.
in operation.
127
V2 and V' 2 were then attached to the previously
erected segments by temporary prestressing.
During the erection operation of V2 and V'2 a
transport dolly delivered segment V' 3, then V3,
and so on. In this manner the erection of segments
could be carried out without being delayed by
transportation of the segrIJents from the storage
area. In addition, the tfueading and stressing of
the permanent prestressing tendons were inde·
pendent of the erection cycle. since the tendons
were anchored in the internal ribs and could be
prestressed inside the box girder.
Where the span length was less than 125 ft (38
m), the pier segments were placed by the gantry in
its normal working position. The pier segment po·
sition was adjusted from a platform fixed to the top
of the pier to avoid delaying the placement or can­
tilever segments at the preceding pier. For the few
B-3 SOllth Viaduct. launching gantry
The matching faces of the segments being erected
and the previouslv erected segments, V 1 and V' 1,
were coated with epoxy joint material. Segments
(a)
PI
P2
FIGURE 3.93. B-3 South Viaduct. erection sequence. (a) Placin.g the units: The two
trolleys bring the units V2 and V'2 which will be placed, after rotation at 90°, against
the units VI and V' 1. During this time, the lorry carries the units V'3. then V3, and so on.
(b) Laullching the truss: The rear and the central
are lifted abo\'e the piers PO and PI.
the tmss is supported by trestles and trolleys ill 1 alld P2 and moves forward by the
action of the trolley motors until the legs reach PI and P2. Thus the truss has advanced
along one span length and can place the pile-unit in P3 and the cantilevers from P2.
128
Precast Balanced CantiLever Girder Bridges
_....
FIGURE 3.94. B-3 South Viaduct, placing two seg­
ments in balanced cantilever.
larger spans, the pier segment was placed after clo­
sure of the preceding completed spans and ad­
vancement of the launching gantry. The center leg
was advanced out onto the last completed half­
span cantilever, but it remained in the proximity of
tlte pier. Launching of the gantry to the next span
was achieved b\· using the two segment transporta­
tion dollies temporarily fixed on the completed
superstructure by two auxiliary steel trusses. The
high degree of mechanization of the gantry to­
gether with the repetitive nature of the project al­
lowed speedy erection. A typical 130 ft (39 m) span
was erected and completed in two working days.
To maintain the construction schedule and
minimize required erection equipment, the super­
structure segments wel'e placed simultaneously
by two different methods. The launching gantry
previously described placed 57% of the seg­
ments and a mobile crane in conjunction with a
movable winch frame erected the remaining ones.
The latter method was used where access was
available for a truck-mounted crane and the seg­
ment transportation dolly. The truck-mml11ted
crane could easily be used along the centerline of
the structure to place segments at outboard can­
tileyer ends. However, its use became complicated
in the midspan area, particularly when it was used
to place the closure segments. To solve this prob­
lem, an auxiliary truss equipped with a winch was
used in conjunction with the mobile crane. This
truss was supported at one end over the pier where
cantilever construction proceeded and at the other
end over the last completed cantilever arm, which
might or might not require a temporary support.
pier, Figure 3.95. The segments were lifted by a
trolley-mounted winch traveling along the truss.
This truss was also used to stabilize the cantilevers
during erection, since it was fixed to the pier and
the completed ponion of the superstructure. After
the pier segment was positioned by the m()bile
crane, the frame was launched with the trolley in a
counterweight position at the rear of the frame.
\Vhen the span exceeded 65 ft (20 m), the front of
the frame was held by the crane~
This structure exemplifies an innovative appli­
cation of precast balanced cantilever segmental
construction to a difficult urban site and shows its
adaptability to almost any site conditions.
FIGURE 3.95. B-3 South Viaduct, auxiliary truss for segment assembly (crane placing).
(1) Auxiliary truss, (2) winch for segment lifting, (3) precast segment, (4) possible tempo­
rary support (as required), and (5) concrete cantilever stability device.
Alpine Motorway Structures, France
3.15
Alpine Motorway Structures, France
The new Rhone-Alps Motorway system in South
East France includes 220 miles (350 km) of toll­
ways, of which 60 miles (100 km) are an optional
section, between the cities of Lyons, Grenoble,
Geneva, and Valence in order to improve com­
munications between Germany and Switzerland on
one hand and South France and Spain on the
other. The motorway is situated among the beauti­
ful western slopes of the Alpine mountain range
(see the location map, Figure 3.96). The first 160
miles (250 km) include the following structures:
Ten viaducts varving in length between 500 and
1300 ft (150 to 400 m)
Two hundred overpass bridges
Fifty underpasses
Such a project afforded an exceptional occasion
to
129
optimize the structures in terms of initial invest­
ment and low maintenance costs.
The underpasses had to accommodate a variable
and often considerable depth of fill to reduce the
constraints of the longitudinal profile in this
mountainous region. The ideal answer was found
in the use of reinforced concrete arch structures,
which proved extremely well adapted and had a
cost approximately half that of conventional girder
bridges.
Apart from the first section of the motorway
(East of Lyons), which had to be built immediately
and therefore called for conventional solutions
(cast-in-place prestressed concrete slab), and ex­
cept for certain special situations (excessive skew,
railroad crossing, and so on), a careful study
showed that the remaining 150 overpass bridges
should be of precast concrete segmental construc­
tion, which were 20% more economical than other
methods and practically maintenance free. The
study further showed that segmental construction
-
"
Alpine Motorway, location map.
130
Precast Balanced Cantilever Girder Bridges
should be extended to viaduct structures and that
all segments for both overpasses and viaducts
could be economically built in a single factory lo­
cated near the center of gravity of the motorway
network. The maximum carrying distance was 110
more than 75 miles (120 km) and the average was
40 miles (60 km). Figures 3.97 and 3.98 are views
of a typical viaduct and a typical overpass in the
motorway network.
The two-span and th ree-span overpass bridges
have spans ranging from 59 to 98 ft (18 to 30 m). A
variety of standardized precast cross sections were
developed for this project, depending upon span
and width requirements. The first structures used
single and double-cell trapezoidal box sections, al­
though later on voided slab sections were pre­
ferred, as illustrated in Figure 3.99a. This solution
proved aesthetically pleasing and very simple to
manufacture and assemble. The viaducts had to
satisfy a wide range of environmental require­
ments. It was found that span lengths could be
limited at all sites to a maximum of 200 ft (60 m),
~oo~
o
(a)
f'4vr
b~ttusn
ptll.'1.lIlrH
gi
~,
I
'00
FIGURE 3.99. Alpine \10torll'<I). t'pied ~e((i()ns or
overpass and Yiaducts. (a) Chcrpass segments. (b) Via­
duct segments.
FIGURE 3.97.
FIGURE 3.98.
Alpine Motorway. view of a viaduct.
Alpine Motorway, view of an overpass.
which allowed a constant-depth superstructure
with precast segments, Figure 3.99b.
Segment manufacture was carried out in a fac­
tory close to the new motorway with eas), access to
the existing highway system, which was used to
haul all segments to their respective sites. The fac­
tory had two parallel bays, Figures 3.100 and
3.101, one for the overpass segments and one for
the viaduct segments. Segments for the overpasses,
Figure 3.100, were match-cast by the short-line
method with their longitudinal axis in a vertical
position. The bottom segment was a previously cast
unit. The segment at the top was then match-cast
against the segment on the bottom. After the unit
being cast had reached the required strength, the
bottom unit was removed for storage, and the en­
;; :
. !i
:~ ~
I
(bi
(e)
FIGURE 3.100.
Alpine Motorway, precasting faew)'\,.
131
132
Precast Balanced Can!ilever Girder Bridges
FIGURE 3.101. Alpine Motor\;'ay, general view of
precast factory and segment storage.
tire process repeated. Figure 3.102 is a view of a
segment in a vertical match-casting position.
Erection procedure for a typical three-span
overpass struclUre was as follows:
I. After the foundations and pier columns had
been constructed, precast concrete slabs were
placed on sand beds adjacent to the piers to form
foundations for the steel falsework towers. The
precast slabs and towers were reusable for sub­
sequent bridges. The erection commenced with
placement of the first segment on top of four par­
tially extended 25-ton jacks, Figure 3.1 03a.
2. The second and third segments were placed
and prestressed to the first segment, Figure
3.J 03h. The joints between the segments were
epoxy coaled as the segments were erected. The
prestressing of the second and third segments to
the first segment consisted of temporary bars
above the top surface of the segments, and other
temporary tendons within the segments near the
bottom of the segments. The four 25-ton hydraulic
jacks under the first segment were then replaced
by four partially extended 100-ton hydraulic jacks
positioned under segments two and three. The
jacks were supported on teAon sliding bearings.
3. The remaining segments were then erected,
forming cantilevers on each side of the falsework
towers, Figure 3. I 03e. The prestressing of the
segments consisted of temporary tendons posi­
tioned above the segments, as indicated in Figure
3.103.
4. The erection of the segments could take
place simultaneously at both piers, or one could
precede the other, Figure 3.103d. Observe that at
this stage of erection each assembly of segments
was independently supported on four large hy­
draulic jacks and hence could be raised, lowered,
-~
FIGURE 3.102. Alpine
casting of segments.
~
:
Motorway.
T.O
- ..
venical
~
match
or rotated if required to adjust its position with re­
spect to its pier or to its counterpart at the opposite
pier. This method eliminated the need for a east­
in-place closure joint at midspan of the central
span. Through the adjustment of the hydraulic
jacks, perfect mating of the two centermost
match-cast segments could be achieved when the
assemblies of segments were slid together as indi­
cated. The time required to erect the superstruc­
ture was significantly reduced by avoiding the use
of a cast-in-place closure joint.
5. At this point in the erection, the first group
of permanent prestressing tendons were inserted
in preformed holes through the segments, after
which they were stressed and grouted, Figure
3.103e.
6. The process proceeded with the erection of
the remaining segments, Figure 3.103f.
7. After installation of precast match-cast
abutments, a second group of permanent tendons
was installed, and finally the temporary falsework
and temporary prestressing was removed, Figure
3.103g.
Alpine Motorway Structures, France
133
(oJ
'b)
(e)
(dJ
(f!
(g)
FIGURE 3.103. Alpine ~!otor\\"ay Bridges, erection
scheme for typical three-span overpasses. (a) Placing the
first and second segments. (b) Transfer to IOO-tonjacks.
(c) First half completed. (d) Joining precast assemblies bv
sliding. (e) Threading and stressing cables. (f) Placing
the end segments. (g) Threading and stressing last ca­
bles.
Overpass structures of two spans could be
erected using the technique illustrated above for
three-span structures, Figure 3.104. As would be
expected, the longer spans required the use of ad­
ditional blsework towers. An overpass bridge,
foundations plus piers and superstructure, could
be co~structed in less than two weeks. Figure 3.105
shows a typical segment being placed in the over­
pass bridge with a mobile crane. Temporary pre­
stress over the deck slab is shown in Figure 3.106.
The viaducts required the manufacture of larger
segments in the same precasting factory used for
the overpass segments, but with casting proceeding
in the usual short-line horizontal fashion. Three
casting machines were used simultaneously to pro­
duce all viaduct segments.
134
Precast Balanced Ca1J,tile7.Jer Girder Bridges
SLIDE.
..
..
5L1DE
!I
,
il
:1,
FIGURE 3.104.
Illidges.
.\lpillc :>.Iotol'\\<!\ Bridges. erectioll
Erccting sCglllcllIs in thc \ <lrious structures re­
quired tile usc or a laullching gal1lr\' of an exccp­
tiollalh light alld elaborate design. all()\\'ing easy
tl;lnsporLllioll ami erection from site to site. Figure
:U ()7 ..\ t\pied 200 It (60 Ill) long calltilever in­
,':
!
/'
,<11('11]('
for two-spall mcrpass
eluding 25 segments. one pier segmcnt weighing
48 t (44 lilt), and 24 tYpicd segments weighing 36 t
(33 nlt) could be accol1lplished ill six to eight
working days, including launching the gantry to
the following pier and achie\'ing continuity wit.h
the precedillg cantileYer. The l1laximum rate of
segment placillg \\'as 12 units in a single day.
This pn~ject is another interestiilg application of
mass-production techniques and the standardiza­
tion or segment a I const ructioll.
3.16
Bridge over the Eastern Scheidt, Holland
The bridge over the Eastern ScheIdt, otherwise
known as the Oosterschelde Bridge, Figure 3.108,
II
FIGURE 3.105. Alpinc Motorway, segment placing in
o\"{'l'pass ",jib crane.
FIGURE 3.106. Alpine
stress o\'cr deck slab.
~otor\\ay,
pro\'isional pre­
Bridge Over the Eastern Scheidt, Holland
FIGURE 3.107. Alpine ",-!otorwav, segment placing ill
viaducts with launching gantry.
135
time restraints for construction, and scarcily of
labor, prefabrication was required to a very high
degree. Since the precast pile elements would be
large and heavy, it was decided that the pier and
superstructure segments should be equally large
and heavy. in the range of 400 to 600 tons.16
A casting yard. Figure 3.110, capable of pro­
ducing all the various precast elements for the
structure was constructed near one end of the
bridge. This facility provided all the advantages of
yard production techniques and the potential for
high quality control.
The 14ft (4.27 m) diameter cylinder piles have
14 in. (0.35 m) thick walls and were cast vertically in
20 It (6 m) lengths. They were then rotated into a
horizontal position where they were aligned. joints
concreted, and the pile post-tensioned. In this
malll1er piles were produced in required lellgths
up to 165 ft (50 m). The assembled pile was then
transported hy barge to the site, where a derrick
picked it up at one end and rotated it into its verti­
190 Ions
39.5fl
60010n5
56ft
8
A
r
~~~~:J
. 410-100 reversed
I/unit
~
FIGURE 3.108. Bridge over the Eastern Scheidt.
overall view or the struclUre.
~~
-ti,.l:::i.
k4..~'.
,,', .
is part of a project known as the Delta Works,
which closed the mouths of many rivers and
streams southwest of Rotterdam to protect the
€oastline from flooding. The bridge consists of
fifty-five :300 It (91.4 Ill) spans, a roadway width of
35 ft (10.7 01), and a vertical navigation clearance
of 50 ft (15,2 m). Parameters considered in the
choice of structural type and span were economics,
foundation restraints, and ice loads,
Substructure consists of three cylinder piles with
a caisson cap and an inverted V pier, Figure 3.109.
The superstructure was assembled from seven
precast elements, one pier segment, and two each
of three progressively smaller segments to produce
one double cantilever span of 300 ft (91.4 m). The
bridge design, therefore. consists of very large pre­
stressed cylinder piles, precast pier elements post­
tensioned together, and precast superstructure
elements erected and post-tensioned together to
form'a double cantilever system with ajoint at each
midspan location. Because of open-sea conditions.
400· Ion caisson
Cylindrical hollow
pries
. ';\ .
~
FIGURE 3.109. Bridge mer the Eastern Scheidt,
schematic of preca~t clements in Ihe .,trllnure (courtew
of Ihe Portland Cement Associatioll).
FIGURE 3.110. Bridge over the Eastern Scheidt, view
of precasting plant (courtesy of the Portland Cement As­
sociation).
Preca.~t
136
Balanced CanJilever Girder Bridges
c<l1 position. CYlinder piles weighted from 300 to
550 tons (270 to 500 mt). The pier cap was also
precast at the same yard, where it was post-ten­
sioned circumferentially and vertically. The in­
verted V portion of the pier was also precast with
provision for on-site post-tensioning to achieve final
assembly.16
Figure 3.111 shows the bridge under construc­
tion. The temporary enclosures between each sec­
tion are to protect tbe cast-in-place joint concrete
against cold weather. Cast-in-place joints 16 in. (0.4
m) wide were used, with faces of the precast ele­
lIIents serraTed to act as shear keys.
The superstrucTure segments were all set from a
traveling steel gamr)" Figure 3.111, that extended
over two and one-half spans at a time. Segments
were barged to their hnallocation, then hoisted in
s\'l11lnetrical order about each pier. The joints were
concreted and the primarY stressing completed be-
FIGURE 3.111. Bridgc mer the Eastern Scheidt, view
of launchillg trus~ alld enclosure for cast-in-place joints
(COUrIesy of the Portland Ccment Association).
..
...
--...I -----_I .....-
L,.U
-- ........
I
11
,1.....
.... I ...
!!
I
___...... -ll.. __....ll
n·
I
.i.
I
-­
... .
...­ •
I
I
I
......... I
•n
-- ....
--............
-- ..........-­ •
I
I
I
I
1:
-- ....•----- ...,--I
I
-- ... ., .. ------_ ... I
...
I
IT
.....
71
3.17
Captain Cook Bridge, Australia
This structure carries a six-lane highway over the
Brisbane River in Brisbane, Australia, as part of
the Riverside Expressway and South-West Freeway
designed to relieve the city'S overloaded traffic
system.
The nm'igatioll requirements were for a 300 ft
(91.4 m) wide horizontal clearance with a venicql
clearance of 4S ft (13.7 m) across 200 fl (61 m) and
40 ft (12 m) at either extremity. However, a 600 ft
(183 m) span became necessary because of the
skew crossing. Adequate bearing rock, at a reason­
able depth, was found at the south bank such that
the pier could be founded on a spread footing. At
the north end, because of the steeply rising bank,
the anchor span was limited to a span of 140 fl
(42.7 m) and the abutment was designed as a
counterweight connected to the superstructure by
a prestressed tie-down wall, Figure 3.114,17
Once the navigation span requirements had
heen met, tile remaining span lengths were se­
lected to meet design requirements, while the
super~tructure depth boundaries had to fall within
a maximum allowahle grade requirement of 3%
and the flood level. The superstructure is a dual
I
­
I
•I
-
-.. .!!
fore the next series of segments were hoisted into
position. Erection sequence is depicted in Figure
3.112. An aerial view of various stages of con.struc­
tion is shown in Figure 3.113. A typical cycle for
two spans of superstructure, not including the pier
segment, involving the raising, concreting, and
stressing of 12 segments, was three weeks.
I
I
rr
..
..
I
FIGURE 3.112. Bridge oyer the Eastern ScheIdt,
schc1llatic of erection sequence (courtesy of the Portland
Cement Association).
FIGURE 3.113. Bridge over the Eastern Scheidt, ae­
rial view of construction showing various phases (cour­
tesy of the Portland Cement Association).
to>:>
-l
-
VIADUCT
APPROACH
I
f
~
BEAR,'NGS
ABUI '"
IIIl:tFoo-..eA'I.·:-"'OO
f
ABUl, ''''
:"RIN:~~~~··
___
·Ii'C~.G
o·
!
110'- 0'
FIGURE 3.114.
~]
~..,..,->B
~~~
~.~~~/
~,,-t.~
/
RY~-i'
TSUOING ·'-Tp;ER 2
I HINGE
ri·~
u~
HINGE
~-"-- J~_~
I
-T~l-TF;;Eo--
lO$~
~,~t~ O"_J:n % GR~_~~ __
9'
EASTSOUND
......",..
...A.
~
.,4'''>
~'"
~.,.
",'"
I
I
/
110'· 0'
r HINGE
'FIXED
"
.
1'$;'-0·
~'
.-r;,;~~.-
-",,-~
J
1
___~L.._ _ _..J.
tr
·-1
---1
__ ~~(f!•.::~.~9 % G~~O(.,
uo'-o"
I
:..~~,~~7"~.':::-::::::
so'-o·
HINGE
'T5~;OING
~-~--.-
1'.s:.:J!..._.
-"-L__.,..:.______________r
~
,-"
~_.
----rPIER___3
1 tAH£S WESTSO
..u_N_o_ _ _ _ _
1 !...AitES
ELEVATION
tojATURAl
_~~o':
_ ! lo~'-9· ¥
Capt. Cook Bridge, plan and cielation, frolll reI. 17.
¢:J
...
I~i! 10'- o~_
EMiJAHM:I1£Hl
TlEWAll
ABUI,'a'
TlEWALL
ABUl ir
..:.I
138
Precast Balanced Cantilever Girder Bridges
structure of prestressed concrete segmental two­
cell boxes, Figures 3.115 and 3.116.17
Steel rocker bearings were llsed to support the
superstructure at piers 1, 3, and 4, and large­
diameter single steel roller bearings were used at
pier 2. Lubricated bronze bearings sliding on
stainless steel were used at the north abutment and
for the movable bearings at the suspended spans.
Steel finger joints, allowing a lOin. (250 mm)
maxirnum movement, were provided at each slid-
FIGURE 3.115. Capt. Cook Bridge, cross section at
pier :~. from ref. J 7.
FIGURE 3.116. Capt. Cook Bridge, two-cell box gir­
der segment being erected (courtesy of G. Bcloff. Main
Roads Department).
ing bearing location and rubber and steel finger
joints at the remaining locations."
The box girder segments have a maximum
depth of 32 ft (9.75 m) and a minimum depth of 6
ft (1.83 111). Segment length is 8 ft 8 in. (2.64 m). A
16 in. (0.4 m) cast-in-place, fully reinforced joint
was used between segments. Maximum segment
weight is 126 tons (114 mt). A total of 364 precast
segments were required in the superstructure with
the two segments over the tie-wall in the south
abutment being cast in place. 17
The contractor chose to locate the precasting
operation on the river bank near the south abut­
ment. This casting yard consisted of a concrete
mixing plant, steam-curing plant, three adjustable
steel forms, segment tilting frame, and a gantry
crane to transport the segments to a storage area
along the river bank. Segments were designed so
that the top flange and upper portion of the webs
had a cOllstant thickness. The depth and lower
portion accolllmodated all variations. allowing the
contractor to cast in two sets of adjustable forms.
Segments were cast with their longitudinal axis in a
vertical position for ease of concrete placement
around the prestressing ducts. Separate interior
forms were constructed for each box to permit
variations in the bottom flange alld web thickness
and size of fillets. Aher casting and curing, seg­
ments were lifted into a tilting frame {() realign the
segment into its normal position ready for han­
dling and storage.];
_A floating crane, designed and built bv the con­
tractor, was used for erection of the segmen ts. I twas
essentially a rectangular pontoon with mounted
A-frame lifting legs rising to 120 ft (36.6 m) with
adequate clearance to service the finished deck
level, while the stability was sufficient to transport
the segments to the erection position, Figure 3.117.
An extended reach was required to position seg­
ments on the first two spans in the shallow water
near the bank. 17
Segments on each side of the pier were sup­
ported on falsework anchored to the pier shafts,
Figure 3.118. From this point additional segments,
as they were erected, were supported on a can­
tilever falsework from the completed portion of
the structure. This falsework was fixed under the
completed girder and supported from deck level,
Figure 3.119. When the capacity of the pier to
carry the segment unbalanced load was reached, a
temporary prop support on driven piles was con­
structed before cantilever erection could continue.
Segment erection then proceeded on each side
until either the joint position of the suspended
Other Notable Structures
139
FIGURE 3.119. Capt. Cook Bridge, cradle support
trusses and temporary support tower (courtesy of G.
Beloff, Main Roads Department).
FIGURE 3.117. Cap. Cook Bridge, ~egment being
transported by barge derrick to 6nal position (courtesy
of G. Beloff, l\Iain Roads Department).
span was attained or the closure gap in span 3 was
reached. The completed st.ructure was opened to
traffic in 1971, Figure 3.120.
3.18
Other Notable Structures
In Sections 3.2 through 3.15 the historical de­
velopment of precast segmental bridges with
match-cast joints has been illustrated by examples,
FIGU~E
3.118. Capt. Cook Bridge, support for seg­
ments on each side of pier (courtesy of G. Beloff, Main
Roads Department).
ranging from the first structure at Choisy-le-Roi to
the largest applications such as the Rio Niteroi and
Saint Cloud bridges. Emphasis has been placed
on North American experience as well as on the
advantages of precast segmental construction for
urban structures (B-3 Viaducts) or repetitive ap­
plications (Alpine Motorways). Two particularly
outstanding structures, deserving special mention
because of their size and characteristics where pre­
cast serrmental was used with conventional joints
(not m~tch-cast) were the Oosterschelde and Cap­
tain Cook Bridges (Sections 3,16 and 3.17). Before
closing this important chapter, let us briefly give
due credit to several other contemporary match­
cast segmental bridges.
3./8.1
CALIX BRIDGE, FRANCE
This Itl-span superstructure has a maximum span
length of 512 ft (156 m) over the maritime
FIGURE 3.120. Capt. Cook Bridge. completed
structure (courtesy of G. Beloff, :vIain Roads Depart­
ment).
.
Precast Balanced Cantilever Girder Bridges
140
......
,
®
,
.
"\
o
®
®
®
Longitudinal closure joint
FIGURE 3.121. Calix Vi,l<!url. Ilcar Cacll, Francc gellcral dilll(·nsiolls.
waterway and typical 230 ft (70111) spalls in the ap­
proaches on both hanks. Dimellsiolls are shown in
Figure 3.121. The deck consists of two parallel box
girders connected by a precast prestressed slab
strip. All segments, \\'ith a maximum weight of 49 t
(43 mt), were cast in a long bench and placed with a
tower crane tra\'eling between the box girders in
the approaches. Segments were barged in for the
main span, and a beam and winch system was used
for hoisting them into place, Figure 3.122.
3.18.2
FIGURE 3.122. Calix Viaduct, placing precast seg­
meIlts ill superstructure.
24'-0"
g'-o"
VAIL PASS BRIDGES, L'.S.A.
These bridges are located on Interstate 1-70 over
Vail Pass near Vail, Colorado, in a beautiful set­
ting at an altitude between 9000 and 10,000 ft
(2700 and 3000 m) above sea level where winter
conditions are critical and the construction period
is very short. Dimensions are shown in Figure
3.123, and a view of one finished bridge appears in
Figure 3.124,
3.183
20'-0"
in
cx:i
Section near midspan
FIGURE 3.123. Vail Pass Bridge, cross-scction gen­
eral dimensions.
TRE,\'T VIADUCT, U.K.
This structure carries the M-180 South Humber­
side motorway over the River Trent and consists of
dual roadways of three lanes each, with a central
median. Precast segmental construction was se­
lected against a steel plate girder design with a
reinforced concrete deck slab. The bridge is sym­
Other Notable Structures
141
FIGURE 3.124. Vail Pass Bridge, a completed precast
segmental structure (courtesy of International En­
gineering Company, Inc.).
metrical with four spans of 159, 279, 279, and 159
ft (48.5, 85, 85, and 48.5 m).
Each roadway is supported by an independent
superstructure of twin concrete box girders vary­
ing in depth from 16 ft (4.9 m) at the piers to 7 ft
(2.1 111) at midspan of the center spans. Principal
dimensions are shown in Figure 3.125. Each box
girder is made up of 91 precast segments 10 ft (3
m) long, varying in weight between 38 t (35 mt) to
82 t (75 mt). All segments were placed in balanced
cantilever with a launching gantry shown in opera­
tion in Figure 3.126, with precast units being deliv­
ered on the finished deck.
3./8.-1
L-n. TiLER.\'.1L'TOB.iH.V BRIDGE, .1L'STRI.l
This structure is located between Salzburg and
Villach, Austria. as part of a new motorwav COI1­
necting Germany and Yugoslavia. The 22-span
twin bridge has a total length of 3820 ft (1167 m)
distributed as follows: 110, twenty at 180, and 110
FIGURE 3.126. Trent
finishing the deck.
Bridge,
3.18.5
KfSHWAUKEE RIVER BRIDGE, U.S.A.
This dual structure carries U.S. Route 51 over tlte
Kishw<lukee River near the city of Rockford, il­
lillois. Dimensions are shown in Figure 3.129. Pre­
stressing is achieved in the transverse and 1011­
gitudinal directions bv bar tendons. All segments
were placed in the structure by a launching gantry.
shown in Figure 3.130, which represents the first
application of this method in the Cnited States.
MOTORWAY
CENTRAL
RESERVE
I
I
•
~~ =======:::::=:::::=====IN=S::!1"U~J~0!i:INr:T:::::~:==:~==::::::::::=::::::;::=r:~
I
__
O
INSITU PARAPET
VARIES APPROX,
a.ooo TO 3.000
I'
4.000
FIGURE 3.125.
gantry
ft (33.5, twenty at 55, and 33.5 m). Box piers have a
maximum height of 330 ft (100 m). The constant­
depth superstructure of 12.5 ft (3.8 111) is made LIp
of 722 segments match-cast in a job-site factory
equipped with four casting machines, Figure
3.127. A launching gantry was used to place all
segments in the two bridges in balanced calltilever,
Figure 3.128.
1""----_ _ _ _ _ _ _ _ _ _ _ _l1_.4_00_ _ _ _ _ _ _ _ _ _ _----+l.1
--,-_ _
launching
0
V ARIES 250 TO
Typical.
400
t
soo
frent Bridge. typical dimensions.
I
Cross
section
Precast Balanced Cantilever Girder Bridges
142
FIGURE 3.127.
L-32 TallernaulObahn Bridge, cast­
FIGURE 3.128.
ing machine.
'J.IH.6
L-32
'rallern<lU tobahn
Bridge,
launching gantrv.
I\.E.\TUCl\.f Rf1!£R [mIDGE, U.S.A.
'.IH.!
This large project represents olle of the m~jor ap­
plications of precast segmental construction in the
United States, The 5770 ft (1759 m) long structure
carries Interstate 1-205 from Vancouver, Wash­
ington, across the :-';orth Channel of the Columbia
River to Government Island near Portland, Ore­
gon. Twin structures carry two 68 ft. (20.7 rn) wide
roadways with span lengths varying between 600 ft
(183 m) and 242 ft (74 m). Typical dimensions of
This structure crossing the Kentucky River is 10­
ciled in Franklin County just south of Frankfort,
Kentucky. It is a three-span structure with a 323 ft
(98.5 111) center span and 228.5 ft (70 m) side spans.
In cross section the superstructure consists or two
rectangular boxes. It is the hrs! precast segmclltal
bridge to he constructed in the United States using
the long-bed casting method, Figure 3.131. A view
during construction is shown in Figure 3.132.
2eiO'-O'
1-205 COLU,\1Bf.4 IUl'EH ImmGE. U.S.A.
170~O'
250'-0' ,
250'-0'
POST-TENS'!?NEO SEGMENTAL CONCRETE 80X GIRDER
EX?
HIGH WATER
[LEV 711,0
AVERAGE WATER
£lEV 694.0
(aJ
. TRANSVERSE
POST - TENSIONING
I
~L_.J9'-1\'j'e·
(b)
(e)
FIGURE 3.129. Kishwaukee River Bridge, superstructure elevation and cross sections.
Elevation. (b) Section at midspan. (c) Section at pier. (From ref. 18.)
(0)
Other Notable Structures
FIGURE 3.131.
cast ing bed.
FIGURE 3.130. Kisim;tukec Ri\er Bridge, \'iew dur­
ing cOllStruction sh()\\ing launching truss.
Kentllcb
Rin'r
Bridge.
long.lillt'
Rin'r Bridge. dll1ing
FIGURE 3.132.
COIl-
stnH tic)!l.
the tllain spam on~r the river are shown ill Figure
:\.13:L Dimensiolls of the cross sectioll. as designed,
are shown in Figure 3.134. However, the contrac­
tor, under a value engineering option in the COll­
tract documents (see Chapter 12), elect.ed to re­
d~sign the cross section to a n\o-cell box sectioll,
Figure 3. US. The colltractor exercised the op-
tion allowed in the bidding docllmellts t.o select
his own c()mtrllUion method and proceeded with
casting in place in cOllventional travelers the two
cantilevers adjacent to the main navigation chan­
nel (piers 12 and I:S). \\'hile all other spans are
or precast seglllental COtlslrll(tiol1. FigtllT :s.1 :\6
shows a rendering or the strncture.
19.(';'rr _ _ _ _ _
FIGVRE 3.133.
1-203 Columbia Rivcr Bridge.
~\
\
\
\
~,
\
cll:\'<ll
ion and plan.
\
...
Precast Balanced Cantilever Girder Bridges
144
11'-10"
67'-10"
t
I
I
I
t
67'-11"
I
'
:=ODDr~
FIGURE 3.134. 1-205 Columbia River Bridge, cross sections.
70'·10'
11J
-ls-'_-9.-I
CROSS SECTION OF PRECAST SEGMENTS
FIGURE 3.135. 1··205 Columbia River Bridge, revised
cross section.
J. J8.8
ZILl1'A U I\.EE BRIDGE, U.S.A,
This bridge is another important example of pre­
cast segmental construction in the lJ nited States.
Located in central Michigan, this 8080 ft (2463 Ill)
long structure carries dual four-lane roadways
over the Saginaw River near Zilwaukee, Michigan.
Principal dimensions are shO\m in Figure 3.137.
FIGURE 3.137. Zil\\'aukce Bridge, typical dimensions.
FIGURE 3.136. 1-205 Columbia River Bridge, ren­
dering of the structure .
The 51 spans vary in length from 155 ft to 392 ft
(47 to 119 m). An additional three-span ramp car­
ries some traffic onto the southbound high-level
bridge, Navigation clearance is 125 ft (38 m) above
the Saginaw River.
For a total deck area of 1, ISO,OOO sq ft (110,000
145
Other Notable Structures
Ii--'iM9.+--.___
429:5
7
!..!.17..!cl.8!!.l.7_ _ _ _•...,1~21Zl~I.
I
I
I
I
I ,.
FIGURE 3.138.
()TT.H,IRSllJ~I,H
BRIDGE, FR.-lNCE
.
This bridge in East France dose to Germany and
the Rhille Ri\'er at the Ottmarsheim hydroelectric
plant is todav the longest clear span of precast
segmental construction and the first major appli­
cation of liglHweight concrete to this type of
structure. Principal dimensions are shown in Fig­
ure 3.138..-\5 shown in the longitudinal section,
lightweight concrete was used only in the center
portion of the two main spans over the navigable
waterway and over the outlet channel of the power
pl~nt. Figure 3.139 is a view of the completed
structure.
3.18.10
~..-~~-J;. ~;-l
I. ~
1
11.70
--I
Ottmarsheim Bridge, general dimensions.
m2 ) there are 1590 large segments varying In
length from 8 to 12 ft (2.4 to 3.65 m) with a
maximum weight of 160 t (144 mt). Segments were
produced in a production-line operation with
short-line casting and placed in the· structure in
balanced cantilever with a large launching gantry
accommodating two slIccessive spans.
3.18.9
·········14197
---...........
weighing a maximum of 50 t (45 mt) are designed
to be placed in balanced cantilever with an aux­
iliary overhead truss (and winch system) in the
approach spans to stabilize the deck over the flexi­
ble piers during construction.
3.18.11
1"·9 FREEIVAr,
.HELBOUR.v/~,
:H/STRAL/.I
This very important project is a recent application
of precast segmental construction to urban ele­
vated structures. The constraints relating to loca­
tion of piers and construction over highway and
railway traffic are comparable to the conditions en­
countered at the B-3 South Viaducts in Paris,
France.
The principal project dimensions are shown in
Figure 3.142. All segments will be placed in the
twin bridge using two launching gantries, which
incorporate the latest technological developments
in safety and eHlciencv.
OVERSTREET BRIDGE, FLORIDA, U.S.A.
This structure crosses the Intracoastal vVaterway
near Panama Cit\' in Western Florida. Dimensions
are shown in Figures 3.140 and 3.141. The main
navigation span is 290 ft (88 mm) long between
piers to avoid anv construction in the water fender
system during operation. Approach spans are 125
ft (38 m) long and rest on I-shaped piers bearing
on precast piles. The main piers consist of twin I
piers of the same design. The total length of
structure is 2650 ft (808 m) divided as follows: 95,
seven at 125,207.5,290, 207.5, seven at 125, and
95ft (29. seven at 38,63,88,63, seven at 38, and
29 m). Precast segments 10ft (3 m) long and
FIGURE 3.139. Ottmarsheim Bridge, view of the
completed structure.
Begin Bridge
Sand Cement
Riprap, (Typ-)
"
'I
-~--t~~-~
11'
a;,
-r­
'I
.1\
.....
II
...
If!
~
~
207'·6"
II
"
II
,
290'-0"
"
(helstrcet
J
I
II
Florida. cross sections.
20'-0"
dn;llitl1l.
~
.,
Hl
~
25'Bnrm
End of
Sla, 320 +
g " ., gag
n~
.,...J..t,...Lot
125'-0" 125'-0" 125'-0" 125'-0" 125'-0" 125-0" 125-0" 95'-0~ 2'-6"
Fi<)rida.
201'-6"
g q g
(herSlrtTI
,..w
2650' -0" Overall Length of Bridge
FIGURE 3.140.
-
FIGURE 3.141.
~
2'-6"195'0"125;-0"125'-0" 125'-0" 125'-0" 125'-0" 125'·0" 125'-0"
Sta, 293 + 59
'La II -", ,-,
I
....
Q'l
I
!
/il!
!
"
<-</..
,
....
'
F';JUR
LANE CROSS 3.ECT:QN
FIGURE 3.142.
F-\1 F
147
References
References
I. Jean :'Iuller, "Ten Years of Experience in Precast
Segll1ental Construction," journal of the Prestressed
Concrete Institllte, Vol. 20,
I, January-February
1975.
"0.
2. C. A. Ballinger, W Podolny, Jr., and M. J. Ab­
rahams, ";\ Report on the Design and Construction
of Segmental Prestressed Concrete Bridges in West­
em Europe-1977," International Road Federa­
tion, Washington, D.C., June 1978. (Also available
from Federal Highwav Administratioll, Office of
Research and Development, Washington, D.C., Re­
port
FH WA-RD-78-44.)
3. Walter PodolllY, Jr., "An Overview of Precast Pre­
stressed Segmemal Bridges,"Jliumal of the Prestressed
CO/l(:rt'le lllsti/ue, Vol. :H,
I, Januarv-February
1979.
"0.
"0.
4.
:.l.
6.
i,
8.
9.
10.
J.
:.tllhiY<lt, "Reconstruction du Pont de Choisy-le­
Roi," Till l'rl wc, Janvier 1966,
372.
Jean Muller, "Long-Span Precast Prestressed Con­
crete Bridges guilt ill Cantilever," Firs/ III/fllla/jullal
SymposiulII, COIINe/1' Bridgl' DI!sign, Paper SP 2,~-40,
ACI PubliGuiotl SP-~3, American Concrete Imli­
wte, Detroit, 1969.
Andre Bouchel, "Les POllts.en Beton Precontraint
de Conrbevoic et de b Grande-Jatte (HaUls-de­
Seine):' La Tn:hlliljul' des Tmvaux, Juillet-Aout
1968,
"Bear River Hridge ," STU P Bulletin of I tlforlllation,
:">iovelllher-Decclllber 197~.
":-Jova Scotia's Bear River Bridge-Precast Seg­
mental Constructiotl Costs Less and the \Ionev
Swvs at Home," BridlV Bllllelill, Third Quarter EJ7:!,
PresllTssed Concrete I nstitule, Chicago.
"John F, Kennedy \lemorial Causeway, Corpus
Christi, Texas," Bridge Report SR 162.0 I E, Port­
land Cement Association, Skokie, III., 19i-1.
G, C. Lace\", and J. E. Breen, "Long Span Pre­
"0.
stressed Concrete Bridges of Segmental Construc­
tion State of the Art," Research Report 1:.1 I I,
Center for Highway Research, The University of'
Texas at Austin, :'1ay 1969.
II. S. Kashima and J. E. Breen, "Epoxy Resins for
Jointing Segmentally Constructed Prestressed Con­
~rete Bridges," Research Report 121-2, Center for
Highway Research, The University of Texas at Aus­
tin, August 1974,
12, G, C. Lacey and J. E. Breen, "The Design and Op­
timization of Segmentally Precast Prestressed Box
Girder Bridges," Research Report 121-3, Center for
Highway Research, The University of Texas at Aus­
tin, August 1975.
13. R. C. Brown, Jr., ". H. Burns, and J. E, Breell,
"Computer Analysis of Segmentallv Erected Precast
Prestressed Box Girder Bridges," Research Report
121-4, Center for Highway Research, The Univer­
sity of Texas at Austin, November 19i4.
14. S, Kashima and.J. E. Breen, "Construction and Load
Tests of a Segmental Precast Box Girder Bridge
:'Iodel," Research Report 121-5, Center for High­
way Research, The Cniversit.y of Texas at Au,lin,
February 1975,
J.
E. Breen, R. L. Cooper, and T. :'1. Gallaway,
":VIinimizing Construction Problems in Segmelllaliv
Precast Hox Girder Bridges," Research Report
121-6F, Center for Highway Research, The Univer­
sitv of Texas at Austin, August 1975.
16, BCll C. Gerwick, Jr., "Bridge over the Eastel"1l
Scheidt," jou1"I1id of the Prestressed Concrete Ins/i/l/fR,
Vol. II,
I, February 1966,
17,":\ Proud Achievement-The Captain Cook
Bridge," Issued bv the Commissioner of \laill
Roads-1972, \1ain Roads Department, Brisbane,
Queensland, Australia.
15.
"0.
18, "Prestressed Concrete Segmental Bridges on FA ·H~
over the Kishwaukee River," Bridge Bulle/in, No. I.
1976, Prestressed Concrete Institute, Chicago,
4
Design
4.1
4.2
4.3
4.4
4.5
4.6
4.7
4.8
if Seg1nental Bridges
INTRODUCTION
liVE LOAD REQUIREME;\;TS
SPAN ARRANGEMEl'.T AND RELATED PRINQPLF..5
OF CONSTRUCTION
DECK EXPANSION, HINGES AND CONTINUITY
4.4.1 Hinges at Midspan
4.4.2 Continuous Superstructures
4.4.3 Expansion of Long Bridges
TYPE, SHAPE AND DIMENSIONS OF THE SUPER­
STRUCTURE
4.5.1 Box Sections
4.5.2 Shape of Superstructure in Elevation
4.5.3 Choice of Typical Cross Section
4.5.4 Dimensions of the Typical Cross Section
TRANSVERSE DISTRIBUTION OF WADS BETWEEN
BOX GIRDERS IN MULTIBOX GIRDERS
EFFECT OF TEMPERATI:RE GRADIENTS IN BRIDGE
SUPERSTRUCT1JRFS
DESIGN OF WNGITUDINAL MEMBERS FOR FLE­
XlJRE AND TENDON PROFILES
4.8.1 Principle of Prestress Layout
4.8.2 Draped Tendons
4.8.3 Straight Tendons
4.8.4 Summary of Tendon ProfIles and Anchor Locations
4.8.5 Special Problems of Continuity Prestress and An­
chorage Thereof
4.8.6 Layout of Prestress in Structures with Hinges and
Expansion Joints
4.8.7 Redistribution of Momellts and Stresses Through
Concrete Creep
4.1
Introduction
Desi~n of concrete hj~hway bridges in the Cllitcd
States conforms to the provisions of The American
Association for Slate Highway and Transportation
Officials (AASHTO) "Standard Specifications
[or Highway Bridges," For railway structures,
specifications or the American Railway Engineers
Association (AREA) should be consulted. For the
148
4.9
4.10
4.11
4.12
4.13
4.14
4.15
4.16
4.17
4.18
4.19
4.8.8
Prediction of Prestress Losses
ULTIMATE BEI\'DING CAPACITY OF LONGITUDI·
NALMEMBERS
SHEAR Al\'D DESIG]\; OF CROSS SECTION
4.10.1 Introduction
4.10.2 Shear Tests of Reinforced Concrete Beams
4.10.3 Difficulties in Actual Structures
4.10.4 Design of Lon"titudinal Members for Shear
JOINTS BETWEEN MATCH·CAST SEGMENTS
DESIGN OF SUPERSTRlJCTURE CROSS SECTION
SPECIAL PROBLEMS IN SUPERSTRUCTURE DESIGN
4.13.1 Diaphragms
4.13.2 Superstructure over Piers
4.13.3 End Abutments
4.13.4 Expansion Joint and Hinge Segment
DEFLECTIONS OF CA;\;lILEVER BRIDGES AND
CAMBER DESIGN ­
FATIGUE IN SEGMENTAL BRIDGES
PROVISIONS FOR FLllJRE PRF..5TRESSING
DESIGN EXAMPLE
4.17.1 Longitudinal Bending
4.17.2 Redistribution of Moments
4.17.3 Stresses at Midspan
4.17.4 Shear
4.17.5 Design of the Cross·Section Frame
QUANTITIES OF MATERIAI..5
POTENTIAL PROBLEM AREAS
REFERENCES
most pan, the proviSIOns in these specifications
were written before segmental construction was
considered feasible or practical in the United
States.
Before discussing design considerations, the
authors wish to emphasize that no preference for
either cast-in-place or precast methods of con­
struction is implied here. The intent is simply to
present conditions that the designer should be
Span Arrangement and Related Principles of Construction
aware of to produce a satisfactory design. Both
concepts are viable ones, and both have been used
to produce successful structures.
In general, the segmental technique is closely
related to the method of construction and the
structural system employed. This is why segmental
construction, either cast in place or precast, has
been often identitied with the cantilever construc­
tion used in so many applications. It is logical to
take bridge structures built in cantilever as a basis
for the design considerations developed in this
chapter. \Vhere other methods, such as incremen­
tal launching or progressive placement, require
special design considerations, such problems are
discussed in the appropriate chapters.
4.2
Live-Load Requirements
In comparing practices ill other countries to those
in the United States. an important parameter to
keep in mind is that of live-load requirements. Fig­
ure 4.1 illustrates the considerable differences
among code requirelllents in variolls countries. l
For a simple span of 164 ft (50 m) and width of
24.6 ft (7.5 m). rhe German specification requires a
live-load design moment 186% greater and the
French requires one 290Sk greater than that of
AASHTO. Some Canadian provinces use the
AASHTO specifications but arbitrarilv increase the
live load bv 25(,}.
149
The depth-to-span and width-to-depth ratios for
segmental construction presently advocated in the
United States have been adopted from European
practice. The lighter live loads used in the United
States should permit further refinements in our
design approach.
4.3
Span Arrangement and Related Principles
of Construction
I n the balanced cantilever type of construction,
segments are placed in a symmetrical fashion about
a pier. The designer must always remember that
construction proceeds with symmetrical cantilever
deck sections centered about the piers and not with
completed spans between successive piers. 2
For a typical three-span structure, the side spans
should preferably be 65 percent of the main center
span instead of 80 percent in conventional east­
in-place structures. This is done to reduce to a
minimum the length of the deck portion next to
the abutment, which cannot be conveniently built
in balanced cantilever, Figure 4.2a.
Where span lengths must varv, as between a
main span and an approach span, it is best to intro­
duce an intermediate span whose length will aver­
age the two flanking spans, Figure 4.2h. In this
manner the cantilever concept is optimized.
Individual cantilever sections are generally made
continuous by insertion of positive-moment ten-
M(tm)
5000
....!'.~
~
'i'::::::::::=2
1~IMax.
,mimi
4000
M
France
CPC
India
~
c:
"0
E
::IE
3000
IRC
Germany DIN 1072
2000
1000
o
10
20
30
40
50
60
70
80
90
100
Q(ml
Span
FIGURE 4.1. Maximum live-load moment (simple span)
(F. Leonhardt. NeU' Practice in ConcrelR Stmctures, IABSE, New
York. 1968).
i
I
Design of Segmental Bridges
150
I '" ~ '" I
~
~
/
.
I
!
i
G.G5-070L·
//$0
.
L
(a)
A
(b)
Section A-A
FIGURE 4.4.
End restraint at abutment.
(c)
FIGURE 4.2.
Call1ilcH.T (On,tluClioll sll(ming choice
oj" ')lan Iellgth" and locatioll
expansion joints.
or
upon closure. I t is preferred not to have any
permanent hinges at midspan. Continuous decks
without joints have been repeatedly constructed to
Icngths in exccss of 2000 ft (600 m) and have
pro\'cd satisfactory from the standpoint of mainte·
!laIJCC and riding quality
For very long viaducHype structures, inter·
mediate expansion joints are inevitable to accom­
llIodate volume changes. 'rhesejoints should be lo­
cated ncar points of contrafiexure, Figure 4.2c. to
avoid objectionable slope changes that occur if the
joint is located at midspan. This consideration will
he discussed in more detail in Scction 4.4.
111 many cases it may not be possible to provide
the desirable optimum span arrangement. Thus,
the end span may be greater or less than the op­
timum span length desired. 2 In the case of a long
cnd span, the superstructure might be extended
over the abutment wall to provide a short addi­
tional span. As shown in Figure 4.3, a conventional
dOllS
FIGURE 4.3.
bearing (I) is prm'ided over the frollt abutment
wall. A rear prestressed tie (2) opposes uplift and
permits cantilever construction to proceed out­
ward from the abutment 10 the joint U1), where a
connection Gill he effectcd with the cantilever from
the first intermediate pier. Figure 4.4 shows an al­
ternative scheme with a constant-depth section. as
opposed to a haunched sectioll. where the deck has
been encased within the abutment \ring walls for
architectural purposes. For the normal end span. a
special segment is temporarily cantile\'cred out so
as to reach the first balanced cantilever constructed
from the next pier, Figure 4.5. Alternatively this
portion could be cast in place 011 falsework, if site
conditions permit.
1n a short-end-span sit uation, cantilever COI1­
struction starts from the first pier and reaches the
abutment on one side well before the midspan sec­
tion of the adjacent span, Figure 4.6. An uplift
reaction must be transferred to the abutment
during construction and in the completed struc­
ture. Consequently, the webs of the main box
girder deck are cantilevered over the expansion
End restraint in abutment.
Deck Expansion, Hinges and Continuity
151
FIGURE 4.5.
Conventional bearing on abutment.
FIGURE 4.6.
,\nchorage
joint into slots provided in the main abutment
wall, Figure 4.7. The neoprene bearings are
placed above the web cantilever rather than below
to transfer the uplift force while allowing the deck
to expand freely.
Interesting examples of sllch concepts are given
in the three following bridges:
GiYors Bridge over the Rhone River, France.
shown in Figure 4.8. The main dimensions are
given with the typical construction stages of the
su perstructu re.
Tricastin Bridge over the Rhone River, France
(Section 2.13.11). :-.Jo river piers were desired for
the structure. which dictated a main span of 467 ft
(142.30 m~, and there was no room on the banks to
increase the side spans so as to avoid the end uplift.
Two very short side spans of onlv 83 fl (23.20 m)
provide the end restraint of the river span. The
uplift is transferred to the abutments, which are
earth filled to provide a counterweight, Figure 4.9.
The magnitude of the uplift force has been re-
ror uplift in abutment.
cluced by the use of lightweight concrete in the
center of the main span.
Puteaux Bridges O\'er the Seine River, near Paris
(Section 2.13.10).
A few bridges have even been built in cantilever
entirely from the abutments. The RealJon Bridge
in France is one such structure, Figure 4.10, where
verv special site conditions with regard to bridge
profile and shape of the valley were best met with
this concept.
Another set of circumstances may be encoull­
tered when it is not possible to select the desired
span lengths to optimize the lise of cantilever con­
struction. Such was the situation of the bridge over
the Seine River for the Paris Ring Road, where a
side span on the left bank could not be less than 88
percent of the main river span over the river, while
very stringent traffic requirements governed the
placement pattern of precast segments on the right
bank, Figure 4.11.
4.4
Deck Expansion, Hinges and Continuity
J
4.4.1
Web cantilever
FIGURE 4.7.
Longitudinal section.
HISGES AT :vIJDSP.·tV
Historically, the first prestressed concrete bridges
built in cantilever were provided with a hinge at
the center of the various spans. Such hinges were
designed to transfer vertical shear between the tips
of two adjacent cantilever arms (which could de­
velop under the live loading applied over one arm
only in half the span length) while enduring a free
expansion of the concrete deck under volume
changes (concrete creep and seasonal variations of
temperature). Continuity of the deflection curve
~=?~:t~Al'~C~-~:
,...
®
RIVE GAUCHE 6
152
",(0)
J.. [~OO)
-
~-_~
.'K""",,_
......
•.
5
FIGURE 4.8. Givors Bridge over the Rhone River, France, span dimensions and typical
construction stages. (I) Construction of left bank river pier segment. The eight segments
either side of the pier are erected, and pier stability is assured by temporary props. (2)
The connection between deck and abutments is made. Temporary props are removed
and the seven remaining segments are placed in cantilever. (3) The above operation is
repeated on the right bank. The central pier segments are poured. Two segments are
erected on either side of each pier, supported by scaffolding. (4) The last segment is
placed in the central span, continuity is achieved between the two cantilevers, and the
~cafTolding is removed. (5) The remaining 16 segments on either side of the central piers
are placed. (6) The 110m spans are completed by pouring the closure segments and
ten~ionillg the continuity prestress. The superstructure is now complete.
~
__________________________
~2~O~J.OO
_________________ __
1:.1~
HMO
10.25
L,ghtweight concrete
~
" 25
Elow,;O"
Section A-A
.-.++-. _ _
!J
Plan
FIGURE 4.9.
Tricastin Bridge over lhc Rhone River. France.
+--­ ------------­ -­
4­
FIGURE 4.10.
I
15.00
!
j3~
Reallon Bridge, France.
153
3
PHASE 1
construction of central cantilever
PHASE 2
construction of right bank cAntilever
1
PHASE 3
closure of central and right bank cantilever
PHASE 4
joining of right bank cantilever with abutment
PHASE 5
construction of left bank cantilever
PHASE 6
closure of left bank and c.:ntral cantilever
PHASE 7
joining of left bank cantilever with abutment
--------- _.-­
:::.
~-:::-::...--:::.::.::.::::::----
~~-'~--~-"".
._C".~----._"., ~8-
_A
....
154
'.v.
(
rr
""~"(
--,.
-.-~-.---~"~---
r
~["~
Deck Expansion, Hinges and Continuity
-~
~
155
--c~-c----,
~
__ ___ , .
I
FIGURE 4.11. Paris Belt (Downslream). (a) Typical
constrllction stages. (Ii) Segment assembly-right bank.
(I) Segment assel1lbly-lert bank.
was thus obtai lied in terms of vertical displacement
but not insofar as rotation at the hinge point was
concerned.
Remember that in this tvpe of structure the deck
is necessarilv fixed at the various piers, which must
be designed to carrv the unbalanced moments due
to unsnlll11etrical li\'c-Ioad patterns over the deck.
On the other hand, these structures are simple to
design because thn are statically determinate for
all dead loads and prestressing, and the effect of
live load is simple to compute. Because there are
no moment reversals in the deck, the prestressing
tendon lavout is simple.
Some disa(l\'antages were accepted as the price
of simplicity of design:
The cleck has a lower ultimate capacity as com­
pared with a continuous structure, because there is
no possible redistribution of moments.
Hinges are difficult to design, install, and operate
satisfactorily.
There are manv expansion joints, and regardless
of precautions taken in design, construction, and
operation they are always a source of difficulty and
high maintenance cost.
The major disad\'antage, revealed only by experi­
ence, related to the exceeding sensitivity of such
structures to steel relaxation and concrete creep.
Because of the various hinges at midpoints of the
spans, there is no restraint to the vertical and an­
gular displacements of the cantilever due to the ef­
fect of creep. Steel relaxation and the corre­
sponding prestress losses tend to make matters
worse, while concrete creep is responsible for a
progressive lowering of the center of each span.
With time, there is an increasing angle break in the
deck profile at the hinge. The magnitude of the
deflection has been reported to be in excess of one
foot (0.03 m).
The difficulties experienced with this type of
construction are such that most governlI1ent offi­
cials in Western Europe will no longer permit its
use.:l
·/.-1.2
CO.VTI.VCOCS SL'PERSTRCCTURES
~.
\.
Further research concerning the exact properties
and behavior of lI1aterials for such structures hav­
ing a midspan hinge would enable more accurate
prediction of the expected deflection and thus
better control. A far more positive approach is to
eliminate the fundamental cause of the phenome­
non by avoiding all permanent hinges and achiev­
ing full continuity whenever possible.
To show the relative behavior of a continuous
structure and one with hinges at midspan, a nu­
merical application was made for the center span
of the Choisy-le-Roi Bridge in two extreme cases:
156
Design of SegtJ;lental Bridges
TABLE 4.1.
Comparison of Crown Deflections (Hinged versus Continuous Structure)
Casl-in-Place
Hinged Structure
v
(in.)
w
E
y
(10 6 psi)
(in. x 103/in.)
(l 0 6 psi)
(in.)
4.3
4.3
4.3
1.80
1.50
0.30
2.4
2.0
0.4
5.1
1.50
0.90
0.60
E
'\0.
Load Stage
Precast
Continuous Structure.
Girder weight
I nitial prestress
3 eu mulati\'e
1 5% Deviation of prestress
[)
Continuity prestress
6 Superimposed load
7 Finished structure (initial)
R Concrete creep and losses
!:J Finished structure (final)~
!O Li\'e loads
2
5.1
5.1
23<;(
6.4
2.1
6.4
w
(in.
X
J0 3/in.)
2.0
1.2
0.8
7(/(
0.30
0.60
1.10
1.70
0.4
0.8
(l.9O
1.1
1.4
6.4
6.4
~().30
2.1
2.2
6.4
0.10
0
0
0.40
OS
~O.IO
O.3()
0
O.R
0.30
()
Explication of symbols:
E = modulus of elasticity for each particular loading stage
l
w
verlieal deflection at crown
allfiulal' hreak at crown (expre,sed in thousandths 01 inch per illch)
= total
Derivation of results:
(I) ... (2)
girder weight and initial prestress
(i) = ('\).,- (5) "- (6) hnished strucrul'e (initial stage)
(9) = (7) ... (HI
fillished 5t ruelme (fillal slagel
n)
Cast-in-place cantilever with a hinge at midspan,
and
Precast segmental continuous construction.
Results comparing the two structures are shown in
Table 4.1 and in Figures 4.12 through 4.14.
The study shows 110 significant difference be­
tween the two tvpes of structures with respect to
tbe theoretical behavior of the cantilever method
under combined dead load and initial prestress,
Figure 4.12. I n fact, the angle change at midspan is
even slightly less for the hinged structure, because
the prestress offsets a greater percentage of
dead-load moments, 83 percent instead of SR per­
cent.
=
'"
RIDged Siruciure
DEAD LOAD
Clnlllmr premUSlng
o
nt, PRESTRESSING
Culilmr Preslressing
:
FIGURE 4.13. Comparison of deflection caused by
creep (hinged versus continuous structure).
CIDtloU!!! PreslresSlng
0.4%0.6%.
.
Caslin Piace
CIDlimus
Hlnaed SlruefUre
precul lliruciure
FIGURE 4.12. Comparison of defieClion under dead
load and prestressing (hinged versus continuous struc­
tUf(~).
Conllnms
PreclIS! SlruC!Ure
!::
CIS! In PlBet
HlnDed S!ruelure
PrlCHS! Stmlure
FIGURE 4.14. Comparison of' deflections caused by
live load (hinged versus continuous structure).
157
Deck Expansion, Hinges and Continuity
When the effect of concrete creep is considered.
however, there is a signiflcant difference between
the two types of structures, Figure 4.13. The
hinged structure has a vertical deflection of I. I in.
(28 mm) and a corresponding total angle break of
0.0028 in./inch. This value is twice that shown in
Table 4.1 and Figure 4.13 for the angle change of
one cantilever, the value of 2.8 being the total angle
break of the two abutting cantilevers. The continue
ous structure indicates a camber of 0.1 in. (3 mm).
and no angle break will ever appear because of full
continuitv.
Further, the effect of deviation of actual pre­
stress load from the design prestress load points
out an important difference in the sensitivity of the
twO systems. Assuming the actual prestress in the
structure to differ from the design assumption by
5%. the corresponding maximum deflection is in­
creased by 2;)o/c in the hinged structure but only
7% in the continuous structure. Therefore, the
continuous structure is three times less sensitive to
possible deviations from the assumed material
properties.
Live-load deflections of the continuous structure
are three times more rigid than the hinged struc­
ture, Figure 4.14. The deflection of a typical span
of the Oleron Viaduct in France is compared with a
continuous span and with a crown hinged ~pan in
Figure 4.15.
From these data it is obvious that the fullest use
of continuity and the elimination of hinges at
midspan whenever possible is beneficial to the
structural behavior of the bridge, to saf<:ty and
comfort of traffic, and to the structure's ac:sthetic
appearance.
I n practice, the continuity of the individual can­
tilever arms at midspan is obtained by another set
of prestressing tendons, usually called continuitv
z
rt
BI
if)
l.JJ
0
et:
W
a...
2:
a...
et:
c
en
~.J
9
~l
~,
l,\
"'.
i
~~:-l
"
.iI~-\t,
25
I·
l-
U
1.>.1
-'
1\\
"­
2
.~
\
\
\
.. r'"
.
4
FIGURE 4.15. Comparisons between live-load deflections for continuous or
hinged structures.
Design oj Segmental Bridges
158
prestressing. which is installed along the span in a
continuous structure. Details of the design aspects
or this prestress will be discussed in Section 4.8.
4.4.3
Maximum deflection under live load is reduced in
the ratio of 2.2 to 1.
Maximum angle break under live load is reduced
in the ratio of 3.0 to 1.
EXPANSiON OF LONG BRIDGES
When the continuity of the superstructure is se~.
lected as optimum for the behavior of the strllC­
Illre. one must keep in mind that proper measures
should be concurrently taken to allow for expan­
sion due either to short-IeI'm and cyclic volume
changes or to long-term concrete creep.
The piers may be made flexible enough to allow
for such expansion or ma\' be provided with elas­
toll1eric bearings to reduce the magnitude of hori­
zontal loads to acceptable levels when applied to
the substructure. This important aspect of the
()\'erall bridge design concept is considered in
Chaptel' 5.
Several structures are currently made continu­
OliS ill lengths of lOOO to 2000 ft (300 to 600 III)
and in exceptional cases even 3000 ft (900 Ill). For
IOllger structures, full continuity between end
aiJutmellts is not possible because of the excessive
magnitude of the horizontal movements between
superstructure and piers and related problems.
Therefore. intermediate expansion joints lIlust be
provided. For long spans they should not be placed
at the center of the span, as in the early cantilever
hridges, but closer to the contraftexure point to
llIillimize the effect of a long-term deflection. Such
a concept was developed initially for the Ole ron
Viaduct and is currently used on large structures
such as the Saint Cloud Bridge in Paris, Sal­
lingsund Bridge in Denmark, and the Columhia
Riyer and Zilwaukee Bridges in the United States.
Detailed computations were made in the case of
the Oleroll Viaduct to optimize the location of the
expansion joint in a typical 260 fl (80 m) span, Fig­
ure 4.15 shows the shape of the deflection curve
for a uniform live loading with the three following
assu m ptions:
For dead-load deflections the difference is even
more significant, such that there is no substantial
difference between the actual structure and a fully
continuous one.
The yariation of the angle break at the hinge
point versus the hinge location along the span
length is shown in Figure 4.16. There seems to be
little doubt that the structure is imprm'ed by selec­
tion of a proper location for the hinge and the ex­
pansion joint.
Theoretically, the ideal hinge position is between
points "1 and B, which are the contraflexure points
for dead and live loads. From a construction
standpoint, such a location for the binge compli­
cates the erection process, for the hinge must be
temporarily blocked and subsequently released
when the span is complete and continuity is
achieved. We will collsider this subject in detail
after examining the layout of longitudinal pre­
stress in cantilever bridges (Section 4.8.6).
It was recently discovered, in the designing of
the Sallingsund Bridge. that the optimum location
::,,;;
<l
Uj
Fully continuous span
Span with a ce11ler hinge
Span with an intermediate hinge located at 29 per­
cent of the span length from the adjacent pier (ac­
tual case)
The advantages of having moved the hinge away
from the center toward the quarter-span point are
obvious:
c:
1 'J.
co
w
-'
"2
'I.
<.5
Z
<l
LOCATIQIL-QLJjlNGE~TWEEN
MID- SPAN-----.!l.t;JD~~
FIGURE 4.16. Variatioll of angle break at the hinge
with hinge location along the span.
Type, Shape, and Dimensions of the Superstructure
of the hinge to control the deflections under
service-load conditions does not simultaneously
permit achievement of the overall maximum
capacity under ultimate conditions. This question
will be discussed later in this chapter.
The preceding discussion of hinge location
applies particularly for very long spans or for slen­
der structures. For moderate spans with sufficient
girder depth it has been found that careftil detail­
ing of the prestress in the hinged span can allow
the hinge to be maintained at the centerpoint for
simplicity (spans less than 200 ft with a depth to
span ratio of approximatelv 20). Such was the case
for the cantilever alternatives of the Long Key and
Seven Mile Bridges in Florida.
4.5
Type, Shape, and Dimensions of
the Superstructure
-1.5.1
BOX SECTlO.\'S
The tvpical section best suited for cantilever con­
struction is the box section. for the following rea­
son s:
I. Because of the consCruction lllethod, dead­
load moments produce compression stresses at the
bottom flher along the entire span length. and
maximull1 nlOTIlents OCCllr near the piers. The
typical section therefore l11ust he provided with a
large bottOlI1 Hange. particularlv near the pIers.
and this is achieved best with a box section.
The efficiencY' of the box section is very good.
and for a given amount or concrete provides the
159
least amount of prestressing steel. The efficiency of
a section is usually measured by the following di­
mensionless coefficient:
with the notations as given in Figures 4.17 and
4.18, where some basic formulas are presented.
The efficiency would be p = I if the concrete
were concentrated in thin flanges with webs of
negligible thickness. On the other hand, a rectan­
gular section has an efficiency of only 1/3. The
usual box section efficiency is p = 0.60, which is
significantly better than that of an [ girder.
2. Another advantage of the large bottom
flange is that the concrete area is sufficiently large
at ultimate load to balance the full capacity of I he
prestressing tendons without loss in the magnitude
of the lever arm.
3. The elastic stabilitv of the structu re is excel­
lent both during construction and llnder service
conditions, becallse the closed box section has a
large torsional rigidity.
4. In wide bridge decks where several girders
must be used side by side, the large torsional still­
ness of the individual box girders allows a very
satisfactory transverse distribution of live loads
without intermediate diaphragms between piers.
5. Because of their torsional rigidity, box
girders lend themselves to the construction of
curved bridge S11 perstruct llres a nd provide
maximum Hexibilitv tor complicated tendon trajec­
tories.
--\-7",.",- . ­
.
, C.G.
--+­
(a)
(b)
Longitudinal section
Typical transverse section
FIGURE 4.17. Typical characteristics of a box section: Total section height: It; cross­
section area: A; mOI\lent of inertia: I; position of centroid; (,. (2; radius of gyration: )"
given hv )"2 = 1/.1; efficiencv ratio: p = r21c ,(2; limits of central core: r21c2 = pc,; r 21(, = p [2;
for the llsllal box girder: p = 0.60.
Design of Segmfntal Bridges
160
n~
d,
<:
F
e = c, - d,
~.
ph
h
I
I
(a)
(c)
FIGURE 4.18. Typical preslress requirements or a
box girder. (0) For maximulll llegatin' mOlllent over the
pier (J)L + LL): tOlallllOlllellt = 1\1; required prcsllTss
F = 1'v11z with:: = (\ - d l + (2; usually o\'er the pierz
0.75 Ii. (h) For maximum positive moment at midspan
(DL + LL): tolalll1olllcnl = M; required prestress = F =
MIz wilh::. (2 - <i2 + ( I ; usually al midspan z. = O.701l. «()
(b)
The optimum selection of the proportions of the
box section is generally a matter of experience. A
careful review of existing bridges provides an ex­
cellent basis for preliminary design. The various
parameters that should be considered at the start
of a design are:
For \'ariable 1ll0lJHcllls (LL): tola) moment \'arialion =
6./\1 (sum of positive and negati\'e LL moments); re­
quired prestress
F
6.M/ph (p
0.60).
All these factors are closely related to each other,
and they also depend largely upon the construc­
tion requirements-for example, the size of the
pr(~ject that will 'require a large investment in
sophisticated casting equipment.
4.5.2
Constant versus variable depth
Span-to-depth ratio
Number of parallel box girders
Shape and dimensions of each box girder, includ­
ing number of webs, vertical or inclined webs,
thickness of webs, top and bottom flanges
SHAPE OF SUPERSTRUCTURE IN
ELEVATION
Constant depth is the easiest choice and affords the
best solution for short and moderate spans, up to
200 ft (60 m). However, constant depths have been
used for aesthetic reasons for spans to 450 ft (140
m), such as the Saint Cloud Bridge in Paris and the
Type, Shape, and Dimensions of the Superstructure
Pine Valley and Columbia River Bridges in the
United States. Figure 4.19a.
When the span increases, the magnitude of
dead-load moments near the piers normaJiy re­
quires a variation of structural height and a curved
intrados. When clearance requirements allow, a
circular intrados is the easier and more aestheti­
cally pleasing choice, although in some cases (such
as the Houston Ship Channel Bridge) a more com­
plex profile must adjust to the critical corners of
the clearance diagram. Between the constant­
depth and the curved-intrados solutions, Figure
4.19, intermediate options may be used, such as:
The semiconstant depth, where the concrete rc­
quired in the bottom flange near the piers is placed
outside the typical section rather than inside thc
box (constant dimension for the interior cell). This
solution has been used on two bridges in France
and is aesthetically satisfactory, Figure 4.19b.
Straight haunches (bridge for the Ring Road in
Paris). In this case caution must be exercised to in­
sure compatibility of the local stresses induced by
the abrupt angle change of the bottom soffit at the
start of the haunch, where a full diaphragm is usu­
ally needed inside the box, Figure 4.19c.
1/15 < h
Increase thickness
at pier
< 1/30
optimum 1/18 to 1/20
L
(a)
Constant inside shape
I
h
1/16 <h,/L
< 1/20
(h)
optimum 1/18
1/22 <haiL
< 1128
optimum ~ 1124
Diaphragm
(e)
< 1/20·
optimum 1/18
1/16 <h, It
1130 <haiL
< 1/50
I
h,
Circular intrados or
third-degree parabola
(d)
FIGURE 4.19 Longitudinal profile for segmental bridges. (a) Constant depth.
Semiconstant depth. (c) Straight haunches. (d) Variable depth.
(b)
161
Design of SegmeJ)tal Bridges
162
4.53
CHOICE OF TYPICAL CROSS SECTJOiV
\Veb spacing is usually selected between 15 and 25
ft (4.5 and 7.5 m) to reduce the number of webs to
a minimum, simplifying construction problems
while keeping transverse bending moment in the
top and bott(;m flanges within reasonable limits.
A superstructure up to 40 ft (12 m) in width is
thus normally made up of a single cell box g.ird~r
with two lateral cantilevers, the span of whICh IS
slightly less than one-fourth the total width (7 to 8
It for a 40 ft width).
For wiele bridges, rnulticell box girders may be
used:
Three webs, two cells: as in the B-3 South Viaduct
and the De\,enter Bridge
Four webs, three cells: as in the Saint Cloud Bridge
and the Columbia River Bridge
Alternatively. large lateral cantilevers and a large
span length hetween webs are accepted with special
pl'Ovisions to carry the cleck live loads transversely:
Transverse flange stiffeners as in the Saint Andre
de Cuhzac, Ve:jle Fjord, and Zilwaukee Bridges
10 in. (250 mm) when small ducts for either verti­
calor longitudinal post-tensioning tendons occur
in the web
12 in. (300 mm) when ducts for tendons \lwelve
in. diameter strands) occur in the web
~
14 in. (350 mm) when an anchor for a tendon
(twelve ~ in. diarneter strands) is anchored in the
web proper
Most codes underestimate the capacity of Iwo­
way slabs. such as the roadway slab or top flange of
a box girder bridge. whether prestressed trans­
versely or mild-steel reinforced. There is a great
reserv'e of strength due to the frame action be­
tween slahs and webs in the transverse direction.
The minimum slab thickness to prevent punch­
ing shear under a concent raled wheel load is ap­
proximately () ill. (150 n1ln). However. it is recom­
mended that a slab thickness of not less than 7 in:
(l75 mm) he L1sed to allow enough flexibility in the
layout of the reinforcing steel and prestressing
ducts and obtain an adequate concrete cover over
the steel and ducts.
Recommended minilllum top flange thickness
versus the actual span length het ween webs should
he:
Side boxes as in the Chillon Viaduct
Alternatively several boxes may be used side by
side to mak'e up the superstructure. Figures 4.20
through 4.24 givc the dimensions of a few struc­
tures selected at random from various countries
throughout the world.
4.5.4
DIM,ENSJONS OF THE TFPICAL
CROSS SECTION
Three conditions must be considered
mining the web thickness:
III
deter­
Shear stresses due to shear load and torsional mo­
ments must be kept within allowable limits
Concrete must be properly placed, particularly
where draped tendons occur in the web
Tendon anchors, when located in the web, must
distribute properly the high prestress load con­
celli rated at the anchorages
Following are some guidelines for minimum web
thicknesses:
8 in. (200 mm) when no prestress ducts are located
in the web
Span less than 10 fl (3 m)
Span between 10 and 15 ft
7 in. (175 riml)
8 in. (200 mm)
(3 \() 4.5 Ill)
Span between 15 and 25 ft
10 ill. (250 mm)
(4.5 to 7.5 m)
n
Over 25 0.5 111), it is usually more ecollomical to
substitute a system 01 ribs o~ a voided slab for a
solid slab.
Early bridges used very thin bottom flanges in
ordcr to reduce critical weight and dead-load mo­
ments. A 5 in. (125 111m) thickness was used in
bridges, such as the Koblenz Bridge in Germany. It
is very difficult to prevent cracking of such thin
slabs due to the combined effect of dead load car­
ried between webs and longitudinal shear between
web and boltom flange. For this reason, it is now
recommended that a minimum thickness of 7 in.
FIGURE 4.20. Typical dimensions of some cast-in­
place segmental cantilever bridges in France. Year of
construction and maximum span length (ft): (a) Moulin
a Poudre (1963), 269. (b) Morlaix (1973), 269. (e) Bor­
deaux Sl. Jean (J965), 253. (d) Givors (J967). 360. (e)
Oissel (1970), 328
(a)
2.60
L:
235
.-.::6:.:.::_0:.::.0_-+.
600
(b)
--'---­
H1GO
I
j
~ID
'"
'00
900._
.. _ _ _ ~_
(<')
liOO
--------
(d)
(e)
163
Design of Segmental Bridges
164
2570
-7--·. .'!i il_"iM'_?'~:JiJ"_iW- -+·"1
--~-~~~~:_,iiiiio
~.,~iIIiiO~
'1'I;iIi'iiiiiiifr'iiiiil'
•.jIIIiiiIi-<t;
,~
I
if)
840-
, , '
.. j -
\:.. E·· 7s:~ -~t
~l
,-­
+1-,.. -1
(g)
1'355
r
--4.­
I
~:
g:
~I
(II)
.'S'I. ~. __
FIGURE 4.20 (Colltinued) (j) Viosne (1972), 197.
Gennevilliers (1976), 564,
(1 i5 mm) be used, regardless of the stress re­
quirements. Where longitudinal ducts for prestress
are distributed in the bottom flange, a minimum
thickness of 8 to lOin. (200 to 250 mm) is usually
necessary, depending on the duct size.
Near the piers, the bottom slab thickness is pro­
gressively increased to resist the compressive
stresses due to longitudinal bending. In the Ben­
dorf Bridge, 680 ft (20i m) span, the bottom
flange thickness is 8 ft (2.4 m) at the main piers
and is heavily reinforced to keep the compressive
stresses within allowable limits.
After this brief review of the various conceptual
choices for dimensioning the deck members, con­
Joirwille (twin deck) (1976), 354. (Ii)
sideration should be given to the design of such
members with particular emphasis on the follow­
ing points:
Distribution of load between box girders in mul­
tibox girder bridges
Effect of temperature gradients in the structure
4.6
Transverse Distribution of Loads Between Box
Girders in Multibox Girders
We noted earlier that wide decks can conveniently
consist of two or even three separate boxes trans­
,
-=-=~~f----==-=---+---=3jW~:s.=66~-+!
i
,,
26
~1
I;
~2~0'7:. . -.!_~3.6~6=- - - 4l~-=-3.:.!. :14:!.-i- - -,3= .:.6~6~-+1 -"'!.41-7 1~20
-""2:",,,074-1
~so t
Jr-m -kT
30
1
3.029 1
< HJ
28.40
I
17.50
17.50
10.50
t
5.$0
.I
10.50
t
14
T& ~. 7 "( Ii
!
P.1·/.
~.
1
-
3.~_.4.U~~5
I 5.458
17.30
P.11­
:
I 3.55
I
4.5°1
1 J30
4.442
J 3.55
~
1
~
l3.029
17.30
1
3~.60
10.92
T96
1
01
1"11
,
--+
i
01
30
~I
!
01
"'<tl
J
-+
,961
9.00
19
9.00
1
10.92
~!
I
30
-
col
....
i
1
s~o
0:
11'\
N
t­
I
5.50
10.60
FIGURE 4.21. Typical dimensions of some precast segmental cantilever bridges in
France. Year of construction and maximum span length (ft): (a) Choisy-le-Roi (1965).
180: (b) Courbevoie (1967), 197; (c) 01eron Viaduct (1966),260; (d) Seudre (1971), 260;
(e) B-3 South Viaduct (1973). 157; if) St. Andre de Cubzac (1974), 312; (g) St. Cloud
(1974:),334; (h) Ottmarsheim (1976), 564.
165
.~__~9=.~~_~
,
!
J
I
i
:
!
(d)
(I' )
if)
_ _~ ~__""!..~ -~--- ~ --~ -­
(g)
,
+--­
1)
on
(h)
166
Figure 4.21 (Continued)
"
--t­
(a)
---r
(e)
-.!
"".
(d)
(e)
FIGURE 4.22. Typical dimensions of some
segmental camilever bridges in Europe.
Year of construction and maximum span length
(ft): (a) Koblenz, Germany (1954), cast in place,
374; (Ii) Bendorf, Germany (1964), cast ill
place, 682; (e) ehillon, Switzerland (1970), pre­
cast, 341; (Ii) Sallingsund, Denmark (1978),
. precast, 305; (e) Vejle Fjord, Denmark (1979),
cast in place, 361.
167
~-
~---~-----
-
>Ii
2.
-------~---~-
..
(!I)
..
~--- .. ~---
(c)
FIGURE 4.23. Typical dimensions of some segmental cantilever bridges in Europe.
Year of construction and maximum span length (ft): (aj Felsenau, Switzerland (1978),
cast in place, 512; (b) Tarento, Italy (1977), cast in place, 500; (c) Kochertal, Germany
(1979), cast in place, 453.
168
Transverse Distribution of Loads Between Box Girders in Multibox Girders
Typical Cross Section
87'-3"
(a)
LJ
0
122'-6~
(h)
122' -6"1
126 '
-cr---'-.
I
1
., .r ­
U
,-_ •• 1
14~
59'
(c)
t
:1]'
t
"\
J
20' -8"
38'-6"
(I' )
\
U)
J
I
39 '
I
(d)
--+-tJ-4'
T
17'-5"
38'-6"
j--
\
t
7
]3' -ll"
I
fiZ'-lO"
(,,0
\I r7
50'-10"
t
(i)
I
1~'-5"
(h)
~
+
'~,
-I
j
36'
59'-3"
I
~
]
38'
FIGURE 4.24. Typical dimensions of some segmental
cantilever bridges in the Americas. Year of construction
and maximum span length (1'1): (a) Rio Niteroi, Brazil
(1971), precast, 262; (h) Pine Valley, U.S.A. (1974), cast
in place, 450: (c) Kipapa. U.S.A. (1977), cast in place,
250; (d) Kishwaukee, U.S.A., precast, 250; (e) Long Key,
U.S.A., precast, 118;(/) Seven ~lile, lJ.S.A., precast, 135;
(g) Columbia River, C.S.A., cast in place and precast,
600;' (h) Zilw<lukee, U.S.A .. precast, 375; (i) Houston
Ship Channel. C.S ..-\., cast in place, 750.
verselv connected by the top flange. A detailed
analysis was made of such decks with regard to the
distribution of live load between the various boxes.
It was. found that in normal structures of this type,
the combined effect of the flexural rigidity of the
roadway slab acting transversely as a rigid frame
with the webs and bottom slab of the various box
169
girders, on one hand, and the torsional rigidity of
such box girders on the other hand, would result in
a very satisfactory transverse distribution of live
loads between box girders. There is no need for
diaphragms between girders as normally provided
for I-girder bridgers.
Comprehensive programs of load testing of sev­
eral bridges, including accurate measurements of
deflections for eccentric loading, fully confirmed
the results of theoretical analysis. This analysis has
been reported in various technical documents, and
only- selected results will be presented in this sec­
tion.
The first bridge analyzed in this respect was the
Choisy-le-Roi Bridge. A knife-edge load P is con­
sidered with a uniform longitudinal distribution
along the span, Figure 4.25. When this load travels
crosswise from curb to curb, each position may be
analyzed with respect to the proportion of vertical
load carried by each box girder, together with the
corresponding torsional moment and transverse
moment in the deck slab. These analyses have
made it possible to draw transverse influence lines
for each effect considered, such as longitudinal
bending moments (over the support or at
midspan), torsional moments, or transverse mo­
ments.
For longitudinal moments it is convenient to use
a dimensionless coefficient, Figure 4.25c, which
represents the increase or decrease of the load car­
ried by one box girder in comparison with the
average load, assuming an even distribution be­
tween both girders. Numerical results show that
the transverse distribution of a knife-edge load
placed on one side (next to the curb) of a twin box
girder produces bending moments in each box that
are 1.4 and 0.6 times the average bending moment.
For the same configuration, a typical deck with [
girders would have an eccentricity coefficient of
approximately 4 compared with 1.4 for the box
girders. There are, however, two side effects to
such an encouraging behavior, which relate to tor­
sion stresses and transverse bending of the deck
slab.
Torsional Moments in the Box Girder An unsym­
metrical distribution of live loads in the transverse
direction tends to warp the box girders and cause
shear stresses. It is their high torsional rigidity
which produces a favorable distribution of loads
between girders. However, the maximum torsional
moments usually occur when only one-half the
structure (in cross section) is loaded, and the re­
sulting stresses do not cumulate with the shear
stresses produced by the full live-load shear force.
170
Design of Segmental Bridges
Span length,
L
1
ct.
[I
ho (at midspan)
Center of span
i
h, (over support)
i
ct.
P
1
l
q
I
(A)
ct.
q
I. ,!i J
2d'
I-
i
"
(aJ
(b)
!.6
I
,
1.
~
:.0
C,6
(e)
~--
----"
(d)
FIGURE 4.25. Principle of transverse distribution of loads bctweell box
girders. (a) Dimensions. (b) Influence line of the shear in the connccting slab.
(c) Transverse illfluence line of longitudinal mOlTlcnt. (d) Trans\ crsc bend­
ing inHuence line at section A.
Transv('r IHornen!s in the Deck Slab The deck slab
cannot be considered as a continuous beam 011
fixed supports because of the relative displace­
ments on the two boxes due to unsymmetrical
loading. Figure 4.25d shows the consequence. If
the slab were resting on fixed supports, the
influence line for the moment in a section such as
(A) would be the typical line (l). Because the box
girders undergo certain deflections and rotations,
the effect is to superimpose the ordinates of an­
other line such as (2).
Numerically, the difference is not as great as
may be expected at first sight, because line (1) per­
tains to the effect of local concentrated truck loads
while line (2), being the result of differential
movements between box girders, pertains to the
effect of uniformly distributed loads. In summary,
deck moments are increased by only 20 to 30%
over their normal values if flexibility of the box
girders is ignored. As a matter of practical interest,
actual numerical values for several bridges in
France with either two or three box girders that
have all shmA'n excellent performance for more
than 10 years are presented in Figures 4.26 and
4.27.
4.7
Effect of Temperature Gradients in
Bridge Superstructures
Experience has shown the sensitivity of long-span
cantilever bridges to concrete creep. This resulted
in the preference for continuous rather than
hinged cantilevers. However, two more problems
arose from this significant change in design ap­
proach, both being the immediate result of con­
tinuity. These problems are (I) effect of tempera­
ture gradient in bridge decks and (2jTectiSiriDUtiOn
Effect of Temperature Gradients in Bridge Superstructures
~
!
I
CD
(?)
2d'
2d
Bridge
Spans
Givars
T
I
Vt
DIS Paris
Ring Park-
1
360'
I
300'
T
-­
29.5
15.7
(110m)P
.---­
i I (92m) +
~
•..
Eccen.
Caeff .
ho/hl
( ft)
-- -.-.-..
(ft)
171
-~--".
.. r " " ­
6.6/18.0
1.14
- ..
13.1
26.2
11.1/18.0
1. 10
15.4
33.9
9.2/15.7
1. 21
14.1
23.3
5.9/14.7
way
CD
I
U/S Paris d
Ring Park-
waY
I
I (79mi!'
Carde
I
®I
Sf
i
i
Juvisy
295'
(90m) ~
~
~
260'
220 '
®
Chai 5y·1 eRai
Q
I
180'
,.
­
I
.....•.
!
1.22
:
I
_._- _.
t
~
+
(66~)
,
f­
\
T
­
­
i
24.9
14.6
I 1. 23
!
:
22.3
11.1
(SSm)
5.2/10.7
8.2
cons tant
I
I
_..
1. 28
I
I
1.4
~~=t~~-T--~~--T--j--I
0~==t=~~~~
2d
T
t
FIGURE 4.26. rransverse distribution of loads between box girders. numerical values
for se\'eral two-box girders.
of internal stresses du.!~()_Long-term effects (steel
relaxation and concrete creep). The importance of
these two new problems was discovered experi­
mentally. All structures are designed, according to
the provisions of the various codes, for changes of
temperature that are assumed to apply to the en·
tire section. Significant bending moments in the
superstructure occur only as a result of the frame
actio;1 with the piers wh'ere a rigid connection is
achieved between sub- and superstructure. Actual
measurements on existing structures confirm this
assumption. The average concrete section under­
goes a progressive shortening due to shrinkage
and concrete creep superimposed naturally with
the usual seasonal temperature variations, Figure
4.28b. The total concrete strain of 120 x 10-6
in./i11. was very moderate for a period of four
years.
Daily readings, on the same bridge, of strains
and magnitude of reactions over the abutment
Design of Segmt:Jlta/ Bridges
172
.t
395 Tim
I
!
~r'Wf
o
I I
2
!
I
1
i
Calculated deflection
,I
I
-- -
3
~
6
7
-'
,....­
!
."..,..­
IE
-:::-­ --2""
-~
I
~~
J"
J
6.4 X 106 psi)
Measured deflection
,
"...,
I
-
Measured deflection
I
....:;.
f::.::::.-­
~--
I
I
r-<
~-
&­
Calculated deflection
(E
6.9 X 10 6 psi)
I
l
I
i
\®r
I
--­
3.90 Tim
I
--......
I
1
FIGURE 4.27.
I
I
...... .L
r­ -
I
I
~
Measured deflection
--­
, -­
----­ .......
------::-
Calculated deflection
IE = 7.4 X 106 psi)
Transverse distribution of loads between box girders.
brought to light a factor that had previously been
ignored. This was the differential exposure of the
bridge deck to the sun on warm summer d;ws. This
·situation is aggravated for bridges crossing a river,
where the bottom flange is kept cool by the water
and the usual black pavement placed over the top
flange concentrates the sun's radiation. Within a
24-hour period the reaction over the abutment
could vary as much as 26%, Figure 4.28c. The
equivalent temperature difference between top
and bottom flanges reached 18°F (lO°C). The
maximum stress at the bottom flange level, due
Design of Longitudinal Members for Flexure and Tendon Profile
---u;
~
115'
J.
11
t
(a)
C"n1t
Iitr;lln J:
10- 6
In
115'
+
a
II
i
33' 6"
LJ
~
.fter adjustment (or seasonal
100
-+---+----=--+-­
liO~--+-----+-~--4--~--,r-~~­
(b)
120
---I---+-I--I\r--+--~-+-+
1 10
--+----1+---+----'I+--\-------\'----t-
10.)
SGM OF
REACJ10NS
T--,---r-+'~--t--f--+--+­
.I",,' 19''' ~ June J. 19,0
::ifti7f(
173
The effect is usually computed by assuming the
gradient to be constant throughout the bridge
superstructure length, which is not necessarily the
case.
Figure 4.29 shows the result for the case of a
typical span built-in at both ends (this is the case of
a long structure with many identical spans). The
stress at the bottom fiber depends only upon the
following two factors:
Variation of height between span center and sup­
port (ratio hJ!h o)
Position of the center of gravity within the section
(ratio c2 !h o)
The lowest stress is obtained for a symmetrical sec­
tion and a constant-depth girder.
The stress increases rapidly when the variation
in depth is more pronounced. For normal propor­
tions the effect of gradient is increased by 50% in
variable-depth girders compared to constant­
depth girders (240 psi versus 160 psi for a 9°F gra­
dient and a modulus of 5 x 10 6 psi).
DIFFERENCE OF
REACTIONS
4.8
Design of Longitudinal Members for Flexure
and Tendon Profile
(e)
FIGURE 4.28. Champigm Bridge. observed values of
concrete sirains and deck reactions. (a) Typical dimen­
sions. (b) Long-IeI'm shortening of bridge deck due to
concrete creep superimposed with temperature varia­
tions. (r) Dailv lemperatLtre variations as exemplified bv
change in rl'aCiions mer al)llt111l'nts.
onlv to this tel1lperature gradient. reached 560 psi
.C3.9 :vIPa), a value completely ignored in the design
assu mptions.
Various countries of vVestern Europe have now
incorporated special provisions on temperature
gradients as a result of this knowledge. In France,
the following assumptions are required:
4.8.1
Toe longitudinal prestress of a cantilever bridge.
whether cast iII place or precast, consists of two
families of tendons:
1.
2.
l.
Add the effect of a 18°F (lO°C) temperature
gradient to the effect of dead loads and normal
volume changes (such as shrinkage, creep. and
maximal temperature differences). The effect
of gradient is computed with an instantaneous
modulus of elasticity (usually 5 million psi).
2.
Add the effect of a 9°F (5°C) temperature gra­
dient to the combined effect of all loads (in­
<;luding live load and impact) and volume
changes. again using an instantaneous mod­
ulus of elasticity.
PRI.VCIPLE OF PRESTRESS LAYOUT
As construction in cantilever proceeds. the in­
creasing dead-load moments are resisted at
each step of construction by tendons located in
the top flange of the girder and symmetrically
placed on either side of the pier. Figures 4.30
and 4.3Ia. These are known as cantilever ten­
dons.
Upon completion of individual cantilevers.
continuity is achieved by a second family of
tendons essentially placed at the center of the
various spans. Figure 4.31 b. Because girder
load moments are small. except through
~ermredlStribution, because of the con­
struction procedure. the continuity prestress is
designed to resist essentially the effect of:
a. Superimposed loads (pavement, curbs,
and the like).
b.
c.
Live loads.
Temperature gradient.
Design of Segmgntai Bridges
174
u,uo!
~
ro ngf
h•
=06')
.2.
=060
h.
~
220-2')0
:-
d'plh
,on,lonl
~nd .ntell.
J2 =
\
ex
/
160 p,i
E,(o.:l:.9)
Ctltfrrcltnt or
Lb.rrmol npons.lon
6& It'rr.prroturr srod;pnl
,on,lonl d'plh
NOiE
I
For olh,"
modul;, or tl01lic;ty
mu!t.ply st rfH
b
E
Y 5pOO.OOO
h,
h.
30
SEeilClN Ai CENifR
ELEVAi lOt; OF ,PAN
FIGURE 4.29.
d.
Effect of thermal gradicnl
Subsequent redistribution of girder load
alld cantilever prestress.
Tensile. stresses are large at the bottom Range
level, but seldom will continuity prestress gain the
full advalJlage of the available eccentricity because
of the stress conditions at the top flange level. Usu­
aIlyihis prestress is divided into tendons, B 1 or B2,
located in the bottom flange, and a few tendons
such as B3 which overlap the longer cantilever
tendons, Figure 4.3Ib.
For the best selection of prestressing methods, it
is essential 1.0 use prestressing units of a capacity
large enough to reduce the number of tendons in
the concrete section, particularly in very long
spans. On the other hand, there must be a
sufficient number of tendons to match with the
number of segments in the cantilever arms. Also,
units with an excessive unit capacity will pose seri­
ous problems for the transfer of concentrated high
loads, particularly for cast-in-place structures,
where concrete strength at the time of prestress is
always a critical factor within the construction
cycle.
In practical terms, prestress bars are as well
adapted to short and medium spans as strand ten­
Oil
box girder decks.
dons (such as twelve i in. diameter strands). For
very long spans (at)(~ve 500 ft) large-capacity ten­
dons (such as nineteen 0.6 in. diameter strands)
with a final prestress force of about 700 kips afford
a very practical solution for cantilever prestress.
For continuity prestress the size of tendons is go\'­
erned by the possibility of locating the tendon an­
chors in such areas and with such provisions as to
allow a proper distribution of the concentrated
load to the surrounding concrete section. Units
such as twelve i in. diameter or twelve 0.6 in.
diameter are usually well adapted with careful de­
tailing for this purpose.
4.8.2
DRAPED TENDONS
I n early applications, both families of prestress
were given a draped profile in the web of the box
section to take advantage of the vertical component
of prestress to reduce the shear stresses. In such a
configuration there is a considerable overlapping
of tendons in the web, because the cantilever pre­
stress is anchored in the lower part of the web and
the continuity prestress is anchored at the top
Range level; see the layout in Figure 4.31c. For a
constant-depth section and for segments of equal
Design of Longitudinal Members for Flexure and Tendon Profile
175
c
~
8..2
0.­
I
I
20,000
I­
rl~
10,000
~ ~t=t
I
I
I
m=~~~
,:J
/
I
'\
I
V /
~ ~
:di
~
I
I.
// /
W~rr
'\ '\
i"\
V
,,;X:
""
V )i( V ~ ~
'­
'"
I
I
.-I ­
PI
I
X /0 ~ V "<
lX.i"'.
["-.. l"'.
II
V/~ ~ ffi V "~
\j..
V v::
:"- l.S7L
VY./§
~ "
:::::::: ~ --:: :::..::: ~ f:=:::: ~ ::--.. ~ :z;,: :;:;::; ~
I
:-..
:::::::
--:: ::--:
~ r'-..
c:
0
;:;
u
~
c:
:;;.
"'
10
:E
Diagrams of moments in a cantilever
l
I I
[I
ITTmr
I I] I I
I
I
I I I I
,
I
I I
I
I
FIGURE 4.30. Typical cantilever moments and pre,tress. When placing
unit H, the increa,e of bending moment is represented by the hatched area
ancl the resultant curve is transferred from position 7 to position 8. Addi­
tional sets of cantilever prestressing tendons are placed each time a pair of
segments is erected. This procedure allows the magnitude of prestress to
follow verv closely the various steps of construction.
length, it is eas\! to completely standardize the lay­
out of prestress in various segments.
:vlechanization of the casting operations is a very
desirable feature. all prefabricated reinforcing
cages being identical. with ducts always at the same
locations. A substantial amount of repetition may
still be obtained in variable-depth members as seen
in Figure 4.32. which represents ~ typical span of
the Oleron Viaduct. The two disadvantages of such
a prestress layout are:
Cantilever tendon anchors are located in the web
and it is difficult to prevent web cracking, particu­
larly in cast-in-place structures, except through the
use of thicker webs and smaller tendons.
Contin'uity tendons extend above deck level at both
ends. The installation of the anchor with the
block-out for stressing is difficult in the casting
form, and good protection against water seepage
to the tendons in the finished structure is a critical
factor.
4.8.3
STRAIGHT TENDONS
Tendons are in tbis configuration located in the
upper and lower flange of the box girder and an­
chored near the web in their respective flanges.
There is no draped profile for the tendons within
the web and consequently no reduction of shear
stresses due to a vertical component of prestress.
This is a disadvantage of this scheme, which may
often require vertical prestress to maintain shear
stresses within allowable limits. On the other hand,
the two advantages are:
Simplicity in both design and construction
Design of Segmental Bridges
176
span
L
Average length of cantilever tendons
0,52
(a)
Avprage Ie!;,L~th of continuity tendons
; 0, 35 ~ 0.50 L
(b)
A : cantilever tendons
D : continui t.y tendons
-­
-­
(c)
FIGURE 4.31. Tvpical layout of longitudinal prestress. (0) Cantilever tendons, (b)
Comlnutty tendons. (r) Standardized layout of tendons for constant-depth segments,
Significant reduction in friction losses of the pre­
stress tendons for both curvature and wobble ef­
fects, and consequent savings on the weight and
cost of the longitudinal prestress of at least 10%, all
else being equal
The Rio Niteroi Bridge (described in Section
3.8) used straight tendons, Figure 4.33. Typical
characteristics of the deck are as follows:
Span length
Width of a box
Two webs at
Longitudinal cantilever
prestress
Longitudinal continuity
prestress
Vertical prestress
262 ft
42 ft
14.2 in. each
42 (12 tin. diam.
strands)
14 (12 tin. diam.
strands)
1 in. diameter bars
-...J
-...J
-
I
I
A
1~"---
I ' ,
10
9'
•
,
"
,,'
$
28
_411
.•
!
I
r--;---]'
Okron Viaduct, longitudillal prestress.
Longitudinal prestress..!
' ....."
"
--?«",-". 'i'
6
7:1
20 16
27
... ,- _ If >
T ra nsverse pre~,t!/es\s
:--"~3-~
"
10 i2 '21 2) 10 1.;
25 17
.. _,.'"'!_ ,,-. ~-.",., ~ _.., ~
"
~
FIGURE 4.32.
Continuity prestress
14-(12 x 112" ¢)
+ 4-(12 x .315" ¢)
J
'..5
19
28
.:--:--:::-~ :!'~-. ~
, .,: -·::'f "--:
-:---
'
16
2~
17
Detail B
U
+ 8-(12 x .315" ¢)
30-(12 xU" ¢)
Cantilever prestress
-,t.;
1J
Zt ,1
Steel distribution
12"
1~
19
19
i
t\
Design of Segmental Bridges
178
V.rtical bars 25 mm ¢ (tyP. )
TOP
PRESTRESS
strand 12.7 mm
tI
cables
BOTTOM PRESTRESS
FIGURE 4.33.
Rio-;\;ircroi Bridge, [\picaJ prestress layout.
Critical stresses near the pier are:
Longitudinal compression
Vertical compression
Maximum shear stress
Diagonal stresses
850 psi
400 psi
580 psi
-110 psi (tensile),
and
1360 psi
(compressive)
Typical details of tendon profiles and anchor­
ages are portrayed for Linn Cove Viaduct in North
Carolina, U.S.A., in Figures 4.34, 4.35, and 4.36.
4.8.4
Su/I1MARY OF TENDON PROFILES A.VD
ANCHOR LOCA71.0l'/S
In the two preceding configurations, tendons were
anchored in the following manner:
I.
2.
For cantilever prestress:
a. On the face of the segment In the fillet
between top flange and web.
b. On the face of the segment along the web.
c. In a block-out near the fillet between top
flange and web, but inside the bo~.
For the continuity prestress:
a. At the top flange level.
b. In a block-out near the fillet between web
and bottom flange.
c.
1n a block-out in the bottom flange proper
away from the webs.
Configurations Ic, 2b, and 2c all permit pre­
stressing operations to be performed safe"" and
efficiently inside the box. Figure 4.37. permitting
such operations to be remo\'ed from the critical
path of actual placement or construction of the
segments. Only those tendons required for
balancing the self-weight of the segments need to
be installed at each step of construction. The bal­
ance of the required prestressing may thus be in­
stalled later, even after continuity is achieved be­
tween several cantilever arms. Tendons for the
additional prestress may then be given a profile
comparable to that used in cast-in-place bridges
with a length extending over several spans. The
practical limit to this procedure is excessive so­
phistication and related high friction losses in the
tendons.
4.8.5 SPECIAL PROBLEMS OF COSTINUITY
PRESTRESS AND ANCHORAGE THEREOF
Tendons for continuity prestress may not, or even
should not, always be located in the fillet between
web and bottom flange. They may be located in the
bottom flange proper. When a variable-depth
member is used, the bottom Aange has a curvature
in the vertical plane, which must be followed by the
prestress tendons. Cnless careful consideration is
i1
!
Design of Longitudinal Members for Flexure and Tendon Profile
179
/1
Ie; '2"
.
J" "
,
$1
FIGURE 4.34.
Linn
C()n~
Viaduct, typical cross section sll<ming prestress
given to that fact at the cOl1cept and detailed design
stages, difficulties are likelv to develop; \\'e mav see
this bv looking at Figures -LHI and 4.39. which
show the free-body diagrams of stresses in the
bottom flange due to the cu]'\'att~re, together with a
f I' numerical example. Curvature of a tendon induces
l..v a di)\\'I1ward radial load. which must be resisted by
transverse bending ()riIlc-bZ)(u)nl flange bet~
tTie\\:ebs,
!'ll Longitudinal compressive stresses in the bottom
\v) flange similad\ induce an upward radial reaction
.in the flange, counteracting at least in part the ef­
fect of the tendons. Unfortunatelv. when the full
live l()ad and variable effects. such as thermal gra­
dients. are applied to the ,superstructure. the lon­
dllelS,
gitudinal stresses vanish and consequently the par­
tial negation of the effect of tendon curvature is
lost. Therefore. the effect of tendon curvature
adds full", to the dead-load stresses of the concrete
Range. '{'he corresponding flexural stresses are
four to five times greater than the effect due to
dead load only. and if sufficient reinforcement is
not provided for this effect, heavv cracking is to be
expected and possibly failure. Practically. the situ­
ation may be aggravated by deviations in the IOGl­
tion of the tendon ducts in the segments compared
to the theoretical profile indicated OIl the drawings .
At the point between segments, ducts are usually
placed at their proper position; but if flexible tub­
ing is used with an insufficient numher of sup­
7
7
I'
I.
7
7
\
9' ..
7
.
!
~i-e
~
I
\..V
I
B
L!'l
I
I
e
7
7
.
I
:,,1
Li:::L
W- \..Y
~.:
I
~'''i-$ ~.
"
.
.
\
,
,
",I
I
-,---'~-~
FOR TEMPORARY PRESTRE SSING
,3{fJ BARS
'\;:6 "
I.
---.----
- - - - .---­
,_'-_--2-J-O~_~__'_·,-·_ _­
ANCHORAGE A
( Along 't
I
const ruclton )
1
1
I
~i
'-:.,
_ _
.1.,.'
I
I
iii'
j'IO\"
I
z' 0"
I
_
I
4"~:
10J.. "
,
I
"i
.;~ ~~I-~I~~~~---t-
~~~~':':::-----==-=--I---~
~~~~.'
7.5~
i '[\.' ~tfll
1\
)
.zd
1
0"
I
___
' :
r
I,:,"
-:..----i=-----.::I
2'
/f2"
'zt":-.::..r
.,
,I
.,
I
. __________ L
I
FIGURE 4.35.
180
Linn Cove Viaduct, top flange prestress details.
.1::"
FIGURE 4.36.
Linn Cove Viaduct, bottom flange prestress details.
181
182
Design of Segmental Bridges
FIGURE 4.37. B-3 South Viaduct. prestressing oper­
ations in box girder.
porting chairs or ties, the duct profile will have an
angle break at each joint. In addition 10 the in­
creased friction losses, t here is a potent ial danger
of local spalling and bursting of the iJJtrados of the
bottom Bange, Figure 4.40, Rigid dUCIS properly
secured to the reinforcement cage and placed at
the proper level over the soffit of the casting
machine or traveler will avoid this danger.
Another item concerning potential difficulties in
continuity prestress relate to the pn~iecti()n of the
anchor block-out in the bottom flange and where
anchor blocks are not close to the fillet bet ween
web and bottom flange, \;\Then this method is used
in conjunction with a ven thin bottom flange (a
UNIT LOA:;
R
R
fREE BODY DiAGRilM
FIGURE 4.38. Secondary
in 1he bOllOll1 11<111gc,
10" Typ.
stn>s~e,
due
flange as thin as 5 or 6 in, has been used in early
bridges), it is almost irnpossible to distribute the
concentrated load of I he anchor block in the slab
without subsequent cracking. For a 7 or 8 in. Bange
il is recommended'that no more than two anchor
1,000'
x 1/2", tendons) Typ,
FIGURE 4.39. Secondary stresses due to cun'ed prestressing tendons, nu­
merical example, Assumed longitudinal radius = 1000 ft. Weight of bottom slab
2000 psi, com­
100 psf. Effect of compressive stresses: unloaded bridge.},
(2000 x 8 x 12)/1000
200psf; loaded bridge, 0
pressive radial Joad:f,.tIR
psi. Effect of prestressing tendons: stranded tendons (twelve! in. dia strands) at
10 in. interval with a 280 kip capacity, mrresponding l-adial load: FIR =
280,000/[(10112) 1000J = 336, say 340 psL Total loads on bottom slab: (1) during
construction, load = 100 psf; (2) unloaded bridge, load = 100 - 200 + 340
240 psi; (3) loaded bridge, load
100 + 340 = 440 psC moment = wet /12 = 9
(9000 x 12)/[( 12 x 64)/6] 840 psi.
kips ftlft, stress in bottom slab:} MIS
/3 :o:()-f{LI)
! ,-.....,',
l -I'
yj
"I f'!l/, / f
or" '.)
""j
-
.:.J":.(;
10 C\ll'ycd 1t'1l­
dOll,
Assumed Longi tudi ria 1 Radi us
1-----1
N
/
QJJ.¥;I vr
I
­
Design of Longitudinal Membr.?rs for Flexure and Tendon Profile
183
tendons may be made continuous through the
expansion joint or equipped with couplers.
d.
e.
Partial elevation
f.
FIGURE 4.40.
1Fcstrcss,
Ellen of
misaligllIllclH 0[' continuity
blocks for (I ~ } ilL diameter strands) tendOllS be
placed ill the sallle transverse sectioll ill conjullc­
tion with additional reinforcing to resist burstillg
stresses. Wherever possible. the anchor blocks for
cOlltinuitv telldollS should f)e placed ill the fillet
between the web alld flallge where the lrallsverse
sect iOll has t he largest rigidity.
LIH)!'T OF PRl;;SrR/~'SS I.V STf?L'CrCR/,'S
JrrJlI 11/\ (;J,'S I.\'/) fY,I'I\',<i/()SJ{)/.\'/S
4.8.6
Sectioll 4.-1:.3 explained how the expallsiolljoints ill
the Sll perstructu re should be located preferablv
ncar the cOlltrallexure poillt of a span rather than
. at midspan as ill previous structures. However.
there is a resultant lOIn plication ill the lOIlSt ru(tion
proless, beclllsc cllltilever erenio" must proceed
through the special hinge segment. A t\pical con­
struction procedure and the related preso'ess Iav­
OUt are presented in Figure 4.-1: I. For the geollletry
of the structure in this figure. the construction
proceeds as follows:
a.
h.
c.
Place the hrst bve segments ill balanced can­
tilever and install cantilever prestress for re­
sistance against dead load.
Place the lower half of the special segment and
the corresponding tendons.
Install the upper half of the special hinge seg­
.ment with permallent. or provisional bearings,
and provisional blocking to permit transfer of
longitudinal compressive stresses. Cantilever
Resume normal cantilever segment placing
and prestressing to the center of the span, with
tendons crossing the joint.
Achieve continuity with previous cantilever by
pouring closure joint and stressing continuity
tendons. Layout of these tendons includes an­
chors in the special hinge segment to transfer
the shear forces in the completed structure.
Remove temporary blocking at hinge. Release
tension in cantilever tendons holding segments
7. 8, and 9 or cut tendons across t he hinge
after grouting.
4.8.7 REIJISTRlBU[/O,v OF .\IO.HENTS lLV/)
STRESSES THROUGH CONCRETE CREEP
In a staticallv indeterminate structure the internal
stresses induced lw the external IO(lds depend
upon the deformation of the structure. In pre­
st res sed COllcrete structures such deformations
IllLlst include not only short-term but also long­
term deformation due to relaxation of prestressing
steel and concrete creep. In conventional struc­
tures sllch as cast-in-place continuous superstruc­
tures, the effect is not signihcallt if all loads and
prestress forces are applied to the statical design of
the completed structure, which is the common case
of construction on sC(lffolding. The behavior of
cantilever bridges, particularlv cast-in-place stnlC­
tures, is <Juite different, because the major part of
the load (the girder load often represents 8W;f, of
the total load in long spans) is applied to a statical
concept that is different from the completed de­
sign. /\s soon as continuity is achieved, the struc­
ture tends to resist the new Situation in which it has
been placed; this is one aspect of a very general law
ill mechal1ics whereby consequences always oppose
their cause.
A very simple example is presented in Figure
4.42, which will provide the basis for a better ap­
preciation of the problem. Assume two identical
adjacent cantilever anns built-in at both ends and
free to deflect at the center. The self-weight pro­
duces a moment:
--8­
at both ends with a corresponding deAection and
rotation at the center of y and w.
Design of Segrr;ental Bridges
184
Cantilever~
tendons
I 11
i:-1
(a)
I
"."'"'~
Temporary-t>
blockmg
I
~
(b)
Iii T
I ' I
-LI-L
I
I
I
Coupler
T'"""~
_
!
!
7~III
L~
(e)
Cantilever tendor1s
I
___,
~__L -__~_ _
L-__~____~__~____~__~__-,~-L,-~__
__
I
(f)
FIGURE 4.41. COllstructioll procniure alld prestress ill a span \\'ith all
expansion joint.
If the load is applied for a short time, the value
of E to take into account is E; (instantaneous mod­
ulus). Assuming that continuity is achieved be­
tween the cantilevers as shown in Figure 4.42c,
there cannot he an angle break at the center, but
only a progressive deformation of the completed
span. After a long time the concrete modulus has
changed from its initial value E; to a final value E f ,
which may be approximately 2.5 times less than E;.
Because the external loads are unchanged and
the structure is symmetrical, the only change in \he
state of the structure is an additional cons.tant mo­
ment M] developing along the entire span and in­
creasing progressively with time until the concrete
creep has stabilized. At all times the magnitude of
this moment acljusts in the structure to maintain
th~__~~~u_me~_~on~~~~.~__at_!~~__~:.n_t.~~
The additional deflection at midspan, ),2' takes
place in a beam with fixed ends under the effect of
ltSO\\'n weight and only because of the progressive
change of the concrete modulus from the value E;
to the value E f .
Considering the concrete strain at any point of
the structure, the total strain Ef is the sum of two
terms:
where
E] =
E2
strain hefore continuity is achieved,
= strain after continuity is achieved.
Hooke's law relating stress and strain at a particu­
lar point in time states:
E
]
=
iL
E·
I
Design of Longitudinal Members for Flexure and Tendon Profile
Er
1=11 E;
185
I
+1:1:\1
In other words. the effect of concrete creep is to
place the final stresses in the structure in an inter­
fiaI"state (either of moments, shear forces, deAec­
tions, or stresses) intermediate between:
-+­
I
Th~~~tialstatical
design with free cantilevers, and
The completed design with continuity.
Assume, for example, EriE;
1
= 0040.
Thus:
004011 + 0.60[2
The relationship is equally true for moments,
shear forces, or deflections.
Moments over the support are:
In the free cantilevers, IV! = Mo
O
M
-Mlt
Mlf
III the continuous structure. i'vl
(d)
~MH
The hnal moment is therefore:
and
?vI I = O.20]W o'
FIGURE 4.42.
crele creep.
RedistrilJlltioll
or stresses through COIl­
At midspan, moments are:
In the free cantilevers. 1W
Similarly there is a relatiollShip between the addi­
tional strain €z and the corresponding stressj~ pro­
duced at the same location bv the same loads
applied in the continuous structure. One mav
.write:
/ ..
€.,=-­
-
E,.
where E( .• the creep modulus. is given by:
or
... (­ 1
./ - E f
Thus:
1 ..
E; )
The corresponding totalslress in the structure then
becomes:
= ()
In the continuous structure, AI
and the actual final momeI1l:
/v1\
= 0.60 A'~H
0.201'.10
The above derivation applies not ollly to exter­
nal loads but also to the effect of prestressing.
Continuity prestress applied to a continuous
structure gives little iI1lernal redistribution of mo­
meI1lS except in multispan structures, where the
spans react with one another according to the ac­
tual construction procedure. Cantilever prestress,
which acts to offset an appreciable part of the
dead-load moments, tends to reduce the distribu­
tion of moments due to external loads, Figure 4.43.
Up to now the concrete modulus has been as­
sumed to take only the two values E i and E f
(short-term and long-term values). In fact, because
construction of a cantilever takes several weeks (or
even several months in the case of cast-in-place
structures), account must be taken of the concrete
strains versus the age and the duration of loading.
186
Design of Segmental Bridges
V1
+'
'"
<11
E
0
::;:
V1
V1
...,'"
\..
V1
(!J
\..
~
""­
'­
0
"''""
0
...J
Span
"0
'"'"
0
a
fa
Mo
LIZ
MGL
Girder Load Cantilever It,oment
Pe
Cantilever Prestress Moment
11 dx
~-
MGL - Pe Moment Inducing Redistribution
fa dx
o I
Moment at ~ under M in continuous beam"
Moment of :nertia (variable)
FIGURE 4.43. Computation of moment redistribution due to' dead load and
cantilever prestress.
Such relationships are presented for normal­
weight prestressed concrete and average climate in
Figure 4.44.
Concrete strains are presented for convenience
as a dimensionless ratio between the actual strain
and the reference strain of a 28-day-old concrete
subjected to a short-term load.
We see that short-term strains vary little with the
age of the concrete at the time of loading except at
a very early age. However, long-term strains are
significantly affected by the age of the concrete.
For example, a three-day-old concrete will show a
final strain 2.5 times greater than a three-month­
old concrete. This is particularly important for
cast-in-place structures with short cycles of con­
struction (two pairs of segments cast and pre­
stressed every week, which has now become com­
mon practice).
Two other factors play an important role in the
redistribution of stresses in continuous cantilever
bridges:
1.
Relaxation of prestressing steel and prestress
losses. Because the stress in the prestressing
steel yaries with time (a part of that yariation
being due precisely to the concrete creep), the
internal moments that produce the deforma­
tion of the structure and therefore originate
the redistribution of stresses "ary continually.
This factor is important because the resultant
moments in the cantilever arms (dead load and
prestress) are given by the difference of two
large numbers, and a variation on one usually
has an important effect upon the result, Figure
4.43.
2.
Change of the mechanical properties of
concrete section. For the sake of simplicity
gross concrete section is usually adopted
computation of bending stresses. In fact,
section to be used should be:
a.
the
the
for
the
The net section (ducts for longitudinal
prestress deducted from the concrete sec­
Design of Longitudinal Members for Flexure and Tendon Profile
I
35
I
~s=~===7~=!=E=E~~
I
I
OAYS
YEARS
MONTflS
187
Because it is difficult for some engineers to de­
pend fully upon computer solutions in approach­
ing a design problem, it is desirable to have orders
of magnitude of the moment redistribution for
preliminary proportioning and dimensioning of
the structure. The following guidelines are based
on experience and judgment.
1. Consider the case of a symmetrical span
made up of two equal cantilevers fixed at the ends
and built symmetrically. Compute girder load
llloments of the typical cantilever and prestress
moments using the final prestress forces and the
tmmformed concrete sections with n
10 (average).
2. Compute the moment at midspan due to the
difference of the above two loading cases (Figurc
4.43). \Iore generally, comput.e in the final stnlC­
ture the moments in the variolls spans due to the
difference between cantilever girder load and
momcnts and final prestress momcms, including
the restraint due to piers if applicable.
:t Reference is made now to the formula given
previously and repeated here for convenience:
FIGURE 4.44. COllcretc strai\ols versus age and dura­
tion of loading. :\otc that stI'ain is gin:n as a dimcnsioll­
less rat.io helll'eell lhe antlal slrain alld t.he refercllce
strain of a 2H-da~'-old connete subjected 10 slron-Iuin
load.
h.
tion) for effect of girder load and prestress
up to lhe lill1e of tendon grouting.
The transformed section (with incorpora­
tion of the prestress steel area with a suit­
able coefficient of transformation) after
grouting, where the coefficient of equiva­
lence iI = EjE,., ratio of the modulus of
steel and concrete, should be taken as a
variable with time, from 5 to 12 or even 15.
The abm'e disclIssion indicates the cOlllplexin' of
the problem with respect to the material properties
and indicates the unreliable results of the earlv de­
Sl"ns.
~
where
I =
final stress (or moment or shear load
in the structure at allY point),
It stress at the same point obtained bv
adding all partial stresses for each
construction step using the corre­
sponding statical scheme of the
structure,
I~ = stress at the same point assuming all
loads and prestress forces to be
applied on the llllal structure with
the final statical scheme,
Ei = initial or intermediate modulus of
elasticity (short-term or for the dura­
tion of loading before continuity),
Er = final modulus (long-term).
.
The onl\' acceptable solution is the global ap­
pro'ach. wherebv a comprehensive electronic com­
pu ter program analyzes step by step the state of
stresses in the structure at different time intervals
alld whenever any significant change occurs, thus
following the complete history of construction.
SlIch programs are lIOW available and have
pro\'t;n invaluable in helping us understand
the behavior of segmental bridges. Thev provide
efficient tools for the final design of the structure.
Using different assumptions on the constructioll
sequence of bridge decks and the corresponding
strains as given by Figure 4.44, we find that the
average value of ErlEi would vary from 0.50 to
O.6i. It is recommended that the conservative
value of 0.67 be used in this approximate method.
Thus the actual moment due to redistribution
should be 0.67, the value computed under para­
graph 2. This moment must be added to the effect
of live load and thermal gradient at midspan.
•
Design of Sel{mentai Bridges
188
tween cantilevers of different ages, and the redis­
tribution of support moment may thus vary in wide
proportions, Figure 4.45. To keep on the safe side,
it is not recommended that the reduction 'in sup­
port moment be taken into account in designing
the prestress forces.
It is interesting at this stage to give some orders
of magnitude of moment redistribution by consid­
ering some fundamental formulas given as refer­
ence in Figure 4.46.
.
It has been assumed:
~ANT
·250
That the secondary moment due to the stressing of
continuity tendons is 6<;;: of the total moment (wer
the support,
YOUNGER
CANTILEVER
OLJER
ILEVER
That the distance, rI, hetween the ccnter of gra\'itv
of the cantilever tendons and the top slab is equal
to 0.0511.
'WMENT 5
DuE TO
.320
RrDlS TRIBUTICN
That the center of gradt~" depending upon the
section dimensions, mil\ van between ((jlli
0.4
alld (21h = O.G) and ((l/h
0.6 and (2111 = 0.4),
ft-kips
+ 1250
(i)
BOTH CANTILEVERS OF SAME AGE
CD
CANT(I) BUILT 0-100 DAYS
CANT(2) BUILT 100-200 DAYS
G)
CANT (2) ONE '(EllR
OLDER
(BUILT
IN
100
From the data indicated above and in Figure
4.46, the percentage of prestressing steel.!), may he
determined as 1'01l0\"s:
THAI-i
4. Correspondingly, the support moment (over
the piers) is decreased bv the same amount. In fact,
the construction of cantilevers in successive stages
is such that continuity is achieved in each span be-
74««<&
.
h
"
•
I
P
= A JCUWg) = 20(JO
1irr,it of the centra 1 core
r2/C2
T(gross
. section)
t
/»»> »9»
inertia
assuming a maximum compressive stress in the
bottom /lange of :WOO psi:
_}:
e.
I
CG
area
assuming a final Sl1'ess in the tendons of J 60 ksi
o
r~ P~=0'05h
A
J
O.GO.
DAYS)
FIGURE 4,45. Variation of redistribution moment in
cantilevcr cOllstructioll with the cOllstruction procedure.
I
That the e/licienn factor is p
efficiency factor
r2/c]
Cl
average stress
~
2000 ~
>; >
,--~------" 2000 ps i
FIGURE 4.46. Approximate moment redistribution (moments over stIppon). Total
moment: M T == M GL + l\1.~L + M UA where l'vl w.
girder load moment, I\1.~I. = superim­
posed load moment, M u == live-load momeTll (including impact). Assumed secondary
moment due to continuity prestress: 0.06 AI T' Final prestress force: P = O.94M r/(e +
(r 2/rl)] = 0.94MT/(e + pcz). Prestress moment (1): Pe = O.94AfT/[1 + (pc2/e)]. Moment­
inducing redistribution: 1\;1(;1, - PI', given by (2): (Mm.
Pe)/Mr M(:fjM r - 0.94/[1 +
(pc)e)] .
Design of Longitudinal Members for Flexure and Tendon Profile
sections is plotted versus the posItion of the cen­
troid with or without transformed area.
It is interesting to study the effect of an acci­
dental variation in the prestress load due to exces­
sive friction in the ducts. Assume, for example, a
reduction of 5% in the prestress load for the case
ci/h
0.5 (symmetrical section over the support)
and lW(lL/M r = 0.80.
The intial values of (MOL - Pel/My are changed
as follows:
For a symmetrical section, C 1 O.5h, and p would,
thus, be equal to 0.63%, a reasonable and common
value. The transformed percentage area of the
steel with n = lOis equal to:
0.125 ~I
np
189
lOOl(
All mechanical properties of the section change
to make the denominator of equation (2) in Figure
4.46 increase and, consequently, the moment­
inducing redistribution increase also. This fact,
which W<:lS completelv overlooked for many years,
is clearly seen in Figure 4.47, where the percentage
of moment-inducing redistribution in the various
Gross area
Transformed
area
Prestress
95%
Prestress
Percent
Variation
0.236
0.265
0.264
0.292
1.10
T'he combined effect of tendon grouting and of
added friction losses increases the redistribution of
moments by 25%.
0.600
Gross Area
- - - - - Transformed Area
0.500
~
0.400
71~
--:~
..,
..:;;',
0.300
0.200
0.100
C,/ h
0.35
0.40
0.45
0.50
0.55
0.60
0.65
c2 1h
0.65
0.60
0.55
0.50
0.45
0.40
0.35
,\.1 (;/. - PI'
,\;IT
Figure 4.47.
Gross
1.12
Transf
Gross
.rransf
0.383
10.500 1
0.474
0.257
0.136
0.165
0.357
0.236
0.265
0.457
0.336
0.365
Moment redistribution, numerical values over support.
Design of Segmental Bridges
190
-I.B.8
PREDICTION OF PRESTRESS LOSSES
The prediction of losses in prestressed concrete
has always been subject to uncertainty. This is due
to the high stress levels used for the prestressing
slee!, the variable nature of concrete, and its pro­
pensity to creep and shrink. As recently as 1975,
AASHTO made a major revision to its code to pro­
vide improved methods for predicting prestress
losses. The Structural Engineers Association of
California has an excellent report on creep and
shrinkage control for concrete in general. The re­
port concludes thaI special attention should be
given to material selection and proportioning. For
creep and shrinkage calculations many European
engineers recommend the guidelines of the Feder­
ation 111lernationale de la Precontrainte, Comite
Europeen du Beton (FIP-CEB).
The design computations for segmental pre­
stressed concrete bridges are very involved for the
construction phase. Every time a segment is added
or a tendon is tensioned, the structure changes,
and it must be reanalyzed. As the segment ages, the
concrete and prestressing steel creep, shrink, and
relax. Thus, each segment has its own life history
and an elastic modulus that depends upon the age
and composition. To accurately compute all of
these effects hv hand, throughout the life of the
structure, would be very difficult, part.icularly
during the constrllction phase. Comprehensive
computer programs such as "BC" (Bridge Con­
struction) and others have been recently developed
and are now available to aid the design engineer.
In addition to construction analysis, these pro­
grams will check the completed bridge in accor­
dance with AASHTO specifications. I t is possible
to revise them to satisfy other codes or loadings,
such as AREA.
:\ot only are all prestress losses properly evalu­
ated and taken into account, hut redistributions of
moments due to concrete creep and steel relaxa­
tion are automatically incorporated in the design
analysis.
4.9
Ultimate Bending Capacity of
Longitudinal Members
Basically, the design approach of segmental
bridges is one of service load. I t is important, how­
ever, not to lose sight of the ultimate behavior of
the structure to ensure that safety is obtained
throughout.
In simply supported structures, the ultimate
capacity is very simply analyzed by comparing in
the section of maximum moment:
The total design load moment including girder
load and superimposed load (DL) and live load
(LL)
The ultimate bending moment of the prestressed
section AI"
Depending on the governing codes and the usual
practice in various 'countries, this comparison may
be done in various ways:
Apply a load factor on DL and LL and a reduction
factor for materials 011 Ivl"
Applv a single factor K on (DL + LL) and com pare
with M"
Applya single factor K on LL only and compare DL'
+ KLL \\'ith M Ii
I n all cases, the designer must first compute the
ultimate capacity of the section considering the
concrete dimellsions alld characteristics of pre­
stressing tendons (and possible conventional rein­
fOI'Cement). From previous studies it may be shown
that the ultimate moment of a prestressed section is
cornputed very simph' bv considering a dimen­
sionless factor called the weight percentage of pre­
stressing steel, q (see Figure 4.48).
To accoullt for the fact that the concrete char­
acteristics are less reliable than those of the pre­
stressing steel, which are well known and very con­
stant,'/; is usually taken equal to the guaranteed
minimum tensile strength, whereasj;. is assumed to
be only SOCX of the 28-day cylinder strength.
Considering now the case of segmental super­
stl'uctures, which are most generally continuous
structures, one Illay take the conventional ap­
proach of considering the various sections of the
member (for example, support section and
midspan sections in the various spans) as inde­
pendent from one another in much the same wav
as for simple members. Such simplification over­
looks the capacity of the redundant structure to
redistribute, internally, the applied loads, which
seems to be a conservative assumption.
In fact, it is not always as conservative and safe as
it looks, as will be shown by an example computed
numerically for a typical span of the Rio Niteroi
Bridge. For such a span the design moments are as
follows (in foot-kips X 1000):
Ultimate Bending Capacity of Longitudinal Members
191
3.6
b
t
1000
d
...J,..
strain
diagram
L­_ _ _
T
FIGURE 4.48.
Cltimate moment of a prestressed section. (1) Dimensionless coefficient,
area of prestressing steel, b = width of section, d = effective
depth of section (distance between centroid of prestress and extreme compression fiber),
I; ultimate tensile strength of prestressing steel,f;. = ultimate compressive strength of
concrete. (2) Value of ultimate moment: for q' < 0.07,lVI u 0.96AJ:d; for 0.07 < q' <
0.50, AJ u
(1 - 0.6q')AJ'/d.
q' = (A j bd) (f~Ij:.), whereA,
Girder load
Superimposed load
Support
Midspan
116
to
5
0
l26
29
Total dead load (DL)
Total live load (LL)
5
2~
Total (DL + LLl
l55
Live-load moment in simple span: :37
27
The ultimate moments have been computed for all
sections for both positive and negative bending.
The envelopes of ultimate moments are shown in
Figure 4.49.
, Neglecting any moment redistribution, the situ­
ation would be the following over the support and
at midspan:
Section
Moment
Support
y[idspan
,¥Ill
256
126
79
Dl.
LL
;¥Iu
or:I-[" =
29
L6:5(DL + LL)
DL + 4.5 LL
:5
22
2.93(DL + LL)
DL + 3.4LL
The picture is substantially different when looking
at redistribution due to plastic hinges. Assuming
an overall increase of both dead and live load
simultaneously (loading arrangement A), we ob­
tain the overall safetv factor by comparing the sum
of ultimate moments over the support and at
midspan:
256
+ 79
=
335
and the sum of simple span moment due
LL:
DL: 126
LL
+5
to
DL and
= 131
37
168
Total
The overall safety factor is thus:
K
= 335
168
20
.
approximately 20% higher than for the support
section considered alone. In fact. it is more impor­
tant and more realistic to consider only an increase
of the live load, which is the only variable factor in
the structure. Proceeding as before, the safety
factor On LL only would be:
K = _3_3_5=_1_3_1
= 5.5
However, this is not the actual safety factor of the
structure, because there exists a more aggressive
loading arrangement than that where all spans are
live loaded. In the case where the live load is
applied to only every second span [arrangement
Design of Segmental Bridges
192
I
1
T I.
~.1.
260'
i
.
I
I
260'
Elevation
FIGURE 4.49.
.
1
.
Support
L'ltimale bending capacity of a continuous deck.
L'Itimate negative moment at midspan:
131
I n such structures a \'ery important characteristic
must be emphasized. At the time of ultimate load
failure, due either to negative moment in the un­
loaded spans or positive moments in the loaded
spans, the maximum moment over the support has
only slightly increased above the value at design
load (169 against 155) and is far below the ultimate
moment of the section (256). Three interesting
consequences may be derived from this fact:
169
I.
38
Actual dead-load moment in simple span:
126+5
This value of 169 is substantially lower than the ul­
timate moment at that support section considered
by itself (Mu = 256).
The failure appears when the second plastic
hinge appears at the center of the loaded span
under positive moment (tension at the bottom
fiber). The limiting value of the safety factor K is
such that:
and
.~II
i
(b) in Figure 4.49], the first plastic hinge will ap­
pear at the center of the unloaded spans with a
negative moment (tension at the top fiber) and the
su pport moment reaches the following limiting
value:
131 + K . 37
260'
ILive-load arrangement (A)I
Support
=
~,I.
i
LL.
LL
169 + 79
I
K
= 3.2
2.
Because the overall safety of the structure is
not dependent upon the ultimate moment
near the su pports, it is not necessary to dimen­
sion the bottom flange of the concrete section
in this area to balance the ultimate capacity of
the prestressing tendons.
The global safety factor of the structure de­
pends directly on the capacity of the sections
near midspan for both positive and negative
moments. The capacity for positive moments is
given by the continuity tendons placed in the
Shear and Design of Cross Section
bottom flange for service-load conditions. The
capacity for negative moments depends upon
the tendons placed at the top flange level to
overlap the cantilever tendons of the two indi­
vidual cantilever arms. The magnitude of this
overlap prestress does not appear as a critical
factor when designing the structure for service
loads, yet it plays an important role in the ulti­
mate behavior of the structure.
3. At ultimate load, it was shown that the areas of
the members close to the supports are sub­
jected to moments only slightly in excess of de­
sign load moments and in most cases below
cracking moments. No early failure due to
combined shear and bending is anticipated.
In long structures where hinges and expansion
joints are provided in certain spans, the same de­
sign principles may be applied to analyze the ulti­
mate capacity. Hinges represent singular points
through which the moment diagrams must go re­
gardless of the loading arrangement under consid­
eration. It was found that the optimum location of
the hinge with regard to ultimate safety is some­
what different from the location allowing the best
control of long-term deflections. It may be of
interest therefore to move the hinge slightly to­
ward the center of the span, which has a further
advantage of simplifying construction.
4.10
Shear and Design of Cross Section
-1.10,1
I,VTRODUCTION
Designing prestressed concrete members for shear
represents a challenging task for the engineer, be­
cause there are many differences of opinion and
large variations in the requirements of the various
codes. In particular the ACI code and the
AASHTO specifications differ in several ways
from the FIP-CEB and other European codes.
It is common practice in many countries to de­
sI(Tn
reinforced concrete and prestressed
concrete
/')
.
members for shear by allowing the concrete to
carry a proportion of the shear loads while stirrups
(formerly in conjunction with inclined bars) carry
the rest. A complete agreement has not yet been
reached on this aspect of design for shear:
The French ('odes (CCBA, for example) allow
nothing to be taken by the concrete and the total
shear to be carried by the transverse steel, which is
certainly an overconservative approach. Obviously,
193
the beneficial effect of longitudinal compression
(either in columns subject to axial load or in pre­
stressed members) is taken into account.
The recent FIP-CEB code allows some proportion
of the shear to be carried by the concrete.
ACI code allows a larger proportion of shear to
be carried by the concrete with a consequent sav­
ings in stirrup requirements.
4.10.2
SHEAR TESTS OF REINFORCED
CONCRETE BEAMS
Tests were recently carried out in France in order
to increase the knowledge of this phenomenon,
both on simply reinforced concrete and on pre­
stressed members. 4 Static tests on reinforced con­
crete I beams showed that the steel stress in stir­
rups increases linearly with the load and is three
times smaller than it would be if the concrete car­
ried no shear, Figure 4.50. In this respect, all codes
are fully justified in taking the concrete into ac­
count as a shear-carrying component.
However, dynamic testing on the same beams
showed a very different behavior. A cyclic load was
applied between one-third and two-thirds of the
ultimate static load for one million cycles, where­
upon the beam was statically tested to failure, Fig­
ure 4.51. Before cracking, the elastic behavior of
the homogeneous member kept the steel stress in
the stirrups very low. However, before 10,000 cy­
cles, a crack pattern had appeared that remained
to the end of the test and became more and more
pronounced with a continuous increase of the in­
clined crack width. Crack opening reached
in.
(1.5 mm) at the end of the dynamic test. l\lost
probably stirrup rupture took place about 600,000
cycles, although the ultimate static capacity of the
n-
Ii. P (tonn!;oS)
J
I
20 1
10
o
FIGURE 4.50. Stade test of reinforced concrete I­
beam steel stress in stirrups.
194
Design of Segmental Bridges
.\
FIGURE 4.51. Dynamic test of reinforced concrete
I-beam web cracking and yariation of steel stress in stir­
rups.
beam after dynamic testing was substantially the
same as for the other beams, which were tested
only under static loads. Such tests show that the
conventional approach of designing web rein­
forcement for static loading with a large part of the
shear carried by the concrete may not provide ade­
guate safety in the actual structures as soon as web
cracking is allowed to develop.
4.10.3
DIFFICUL71ES IN ACTUAL STRUCTURES
Another source of information is afforded by the
behavior of existing structures. Fortunately,
examples of difficulties imputable to shear in can­
tilever box girder bridges are scarce. The authors
are aware of only two such contemporary exam­
ples, which are summarized here for the benefit of
the design engineer.
The first example relates to a box girder bridge
dcck constructed by incremental launching and
shown in Figure 4.52. Permanent prestress was
achieved by straight tendons placed in the top and
boltom flanges, as required by the distribution of
moments. During launching an additional uniform
prestress was applied to the constant-depth single
box section, which produced an average compres­
sive stress of 520 psi (3.60 MPa). l'\ear each pier
there was a vertical prestress designed to reduce
web diagonal stresses to allowable values.
During launching a diagonal crack appeared
through both webs between the blisters provided in
the box for anchorage of top and bottom prestress.
The corresponding shear stress was 380 psi (2.67
:\1Pa), and there was no vertical prestress in that
zone. The principal tensile stress at the centroid of
the section was 200 psi (1.40 MPa), which is far
below the cracking strength of plain concrete. In
fact, the webs of the box section were subjected to
additional tensile stresses due to the distribution of
the large concentrated forces of the top and bot:
tom prestress. Tbe truss analogy shown in Figure
4.52 indicates clearly that such tensile stresses are
superimposed on the normal shear and diagonal
stresses due to the applied dead load and may
therefore produce cracking. This could have been
prevented by extending the vertical prestress in the
webs further out toward midspan.
The second example concerns a cast-in-place
variable-depth double box girder bridge with
maximum span lengths of 400 1'1. Because the
bridge was subsequently intended to carry
monorail pylons, two intermediate diaphragms
were provided at the one-third and two-thirds
points of each span, as shown in Figure 4.53. Pre­
stress was applied by straight tendons in the top
and bottom Hanges and vertical prestress in the
webs to control shear stresses. Diagonal cracking
was observed in the center web only near the in­
termediate diaphragms with a maximum crack
opening of 0.02 in. (0.6 mm). Repair was easily ac­
complished by adding vertical prestress after
grouting the cracks.
A complete investigation of the problems en­
countered revealed that cracking was the result of
the superposition of several adverse effects, any
one of which was almost harmless if considered
separately: (1) The computation of shear stresses
failed to take into account the adverse effect (usu­
ally neglected) of the vertical component of con­
tinuity prestress in the bottom flange of a girder
with variable height. (2) The distribution of shear
stresses between the center and side webs was
made under the assumption that shear stresses
were equal in all three webs. In fact the center web
Shear and Design of Cross Section
l~ll,.t LOAD
lSO'.,..
I....
"n'on \' A
NO
VERTICAL
AVERAGE
COMPRESS:ON . .
520 p.l1
PRESTRESS
1 HROUliH
,.
B01H
195
IN THAT ZONE
CRACK
WEBS
PARIIAL
LOMGITUDIMAL
SEOIOM
OIAGONAl
TEHSIOH
OUE 10 PRES I RESS
(OISIRIBU1l0" '" WEB
TRUSS
TYPiCAl
FIGURE 4.52.
~ALf
(ROSS
SECTIOM
ANALOGY
A- A
Example of web cracking under application of high prestress forces.
( ct)
( .6)
FIGURE 4.53. Example of web cracking in a 400 ft span. (a) Typical cross
section. (b) Partial longitudinal section.
carries a larger proportion of the load, and shear
stresses were underestimated for this web. (3) The
vertical web prestress was partially lost into the in­
tenllediate diaphragms, and the actual vertical
compressive stress was lower than assumed. (4)
Present design codes do not provide a consistent
margin of safety against web cracking when verti­
cal prestress is used. This margin decreases
significantly when the amount of vertical prestress
increases. In the present French code, the safety
Design of Segmental Bridges
196
factor against web cracking is 2 when no vertical
prestress is used and only 1.3 for a vertical pre­
stress of 400 psi. (5) At present. vertical prestress is
usually applied with short threaded bars, and even
when equipped with a fine thread they are not
completely reliable unless· special precautions are
taken under close supervision. Even a small anchor
sel significantlv reduces the prestress load, and il is
nOI unlikely that the actual prestress load is only
three-fourths or even two-thirds of the theoretical
prestress.
It should, however, be emphasized that the
difficulties mentioned above have led to progress
in this field, and the increase ill knowledge has en­
sured that these examples remain rare exceptions.
Practically all existing box girder bridges have per­
formed exceptionally well under the effects of
shear loads and torsional moments.
4.10.4
DESIGN OF LONGITUDINAL MEMBERS
FOR SHEAR
Tlte essential aspects of this important prohlem
are:
Dimensioning of the concrete section particulady
in terms of web thickness
Design of transverse and/or vertical prestress <llId
of conventional reinforcement
The two
m,~jor
considerations are:
(s)
Lt1HfIT/J.oINAl
Jr/ussu
~
I"
___ ...._~B
(.6)
FIGURE 4.54. Computation of nel applied shear
(a) \'enical component of prestre~s. (Ii) Effect or
inclined hOllom flange (Resal effect). (r) !'\et she"r f01C(,.
She"r force due to applied loads
/': deduct vcrtic:!I
compollent of draped tendolls =
~ P sin 0'1: add yeni·
cal compollent of cOlltinuity tendons
+ 1 P sin 0: 2 : de­
duel Resal effeci =
·B tan f3; total is net applied
shear force = V,..
load.
are obtained by cOllsidering stresses on sections
perpendicular 10 the top flange (which is usually
the orientation of joints between segments) and
projecting the loads 011 the section for determining
shear stresses. The total net shear force is the sum
of the following terms:
Shear force due to applied loads.
At the design stage (or, in modern code language,
serviceability limit state) prevent or control crack­
ing so as to avoid corrosion and fatigue of rein­
forcement.
Reduction due to \'enical component of draped
tendons where used.
At the ultimate stage (or load factor design concept
state or ultimate limit state) provide adequate
safety.
Reduction due to the inclined principal compres­
sive stresses in the bottom flange (usually called the
Resal effect after the engineer who first studied
members of variable depth). Because the direction
of the principal stresses in the web is not fully de­
termined, it is usual to neglect the added reduction
of shear force derived from web stresses.
For the box sections used in cantilever bridges the
behavior under shear must be investigated:
Increase due to indination ofcolltinuity tendons in
the bottom flange for variable-depth girders.
In the webs.
At the connections between web and top flange (in­
cluding the outside cantilevers) and web and bot­
tom flange. Figures 4.54 and 4.55 show a suggested
method to compute shear loads and shear stresses.
Modern computer programs analyze the box
girder cross sections perpendicular to the neutral
axis and take into account all loads projected on
the neutral axis and the section. Equivalent results
Shear stresses may further be computed' from
shear force and torsion moment using the conven­
tional elastic methoas.
Tests have shown that the presence of draped
tendon ducts in the webs, even if grouted after ten­
sioning, changes the distribution of shear stresses.
To take this effect into account, it is suggested to
compute all shear stresses using a net web thickness
that is the actual thickness minus one-half the duct
Shear and Design of Cross Section
197
b'
b' Gross web thickness
d diameter of duct
(a)
FIGURE 4.55. Computation of shear stress. Typical box section:
net web thickness b = &' - ~d; shear stress due to shear force Va net
applied ,hear load = v
V" . Qi[(Il;) 'f], where Q = statical moment at
centroid, b = net web thickness, f = gross moment of inertia, V"
net
applied shear load; shear stress due to the LOrsion moment = v
C/(2·b·5), where C = torsion moment, & = net web thickness, 5 = area
of the middle closed box. Note: check the shear stress at centroid level.
diameter. Ducts for vertical prestress need not be
taken into account because they are smaller and
parallel to the vertical stirrups, which compensates
for the possible small effect of the prestress ducts.
Web-thickness dimensioning depends upon the
magnitude of shear stress in relation to the state of
compressive stress. In the case of monoaxial com­
pression (only longitudinal prestress and no verti­
cal prestress) the diagonal principal tensile stress
must be below a certain limit to insure a proper
and homogeneous margin of safety against web
cracking with its resulting long-term damaging ef­
fects. Figure 4..56 suggests numerical values based
'0£1 the latest state of the art that are believed to be
realistic and safe. Numerical values for allowable
shear stresses under design loads are given in Fig­
ures 4.57 and 4.58 for 5000 and 6000 psi concrete.
Web thickness must therefore be selected in the
various sections along the span to keep shear
stresses within such allowable values. It may be
that construction requirements or other factors
make it desirable to accept higher shear stresses.
It is necessary in this case to use vertical prestress
to create a state of biaxial compression. Figure
4.56h indicates the corresponding procedure.
The vertical compressive stress must be at least 2.5
times the excess of shear stress above the value
for monoaxial compression.
When vertical prestress is used, the beneficial ef­
fect of increasing the length of the horizontal com­
ponent of the potential crack in the web created by
the horizontal compression due to prestress is par­
tially lost. In fact, if both horizontal and vertical
compressive stresses are equal,j~ j~, the direc­
tion of the principal stress is given by (3 = 45 0 as in
(a)
(b)
FIGURE 4.56. Allowable shear stress for mono- and
biaxial compression in box girders. (0) Monoaxial com­
pression: allowable shear stress v = 0.05J;. + 0.20/~:
corresponding diagonal tension = Jp given by v 2 = Jp(f,r +
Jp). (&) Biaxial compression: allowable shear stress = v =
0.05 J:. + 0.20J,r + OAOJu; corresponding diagonal ten­
VI + Jp) (jIJ + Jp).
sion = j~ given by v:!
Design of Segmental Bridges
198
,r,:;
I~yf&,
l------1,--­
~~~~~~~~~~~9f~~~(l~O~'l)
~~---+--
V/ndX
k'O/,?I1!<7A'TAL
In monoaxial state wilblr
C17/fI"/'?ESSIY£ STrlESS
/" if"')
FIGURE 4.57.
IN.
AII()wable shear stresses
f()}
,j;
stresses higher than a limiting \'alue of 1OV'];, be
accepted prior to careful investigation based Oil
'
I researc h ,
speC!'fi c expenmenta
In this respect, a very interesting case arose for
the construction of the Brotonne Viaduct in
France (described in Chapter 9), where an excep­
tionally long span called for minimum weight and
consequently high concrete stresses. The most
critical condition for shear stresses developed in
the 8 in. (0.20 m) webs near the piers of the ap­
proach spans, where a maximum shear stress of
640 psi (4.5 MPa)'was accepted together with an
unusuall\' low longitudinal compression stress of
500 psi (3.45 J\.lPa). Vertical prestress was used in
this case. The chan for a 6000 psi concrete, Figure
4.58, would give:
= :)000
500 psi, V
=
400 psi.
In biaxial state with./ u = 550 psi, V 620 psi, \\'bich
is suhstantially equal to the actual shear stress of'
640 psi.
A test was conducted to stud"; the behavior of the
precast prestressed web panels in the normal de­
~;ign load stage and up to failure, Fi~ure 4.59. Re·
suits are shown in Figure 4.60. The ultimate
capacity of the web was very large and probably far
in excess of the needs. I t is believed that web
FIGURE 4.58.
psi.
AlIO\\'ablc shear stresses forr:
6000
ordinary reinforced concrete. If a higher vertical
stress is used, a crack with f3 > 45° could develop,
with a consequent reduction of the horizontal
length over which concrete and reinforcement
must carry the total shear. To prevent such a situa­
tion, it is deemed preferable to use a vertical com­
pressive stress not greater than the longitudinal
compressive stress,I!J < Ix.
Finally, considering present knowledge on the
behavior of prestressed concrete beams under high
shear stresses, it is not recommended that shear
PLAN
VIEW
lRANSVERSE 5EClION
FIGURE 4.59. Brotonne Viaduct, test set-up for pre­
cast web panels.
Joints Between Match-Cast Segments
Slr!',\SfS al dPlign Ilage (approach viaducl):
500 psi
550 psi
640 psi
Horizontal compressive stress
Vertical compressive stress
Shear stress
RfSlI/l.\
or
lell
at rupturi':
\iormal Load
630 I
H4:0 I
Clrimale ,hear
Horizontal compressive stress
Vertical compressive Slrcss
Shear sln~ss (elastic theorv)
uniform
840
1.3
1650 p,i
. 580 psi
,33()O psi
2200 psi
JOilll dC'ilron:d and multiple kc\'s shcarcd
011. Panels illlaCI.
FIGURE 4.60.
web
Brotolll1e Viaduct, results of precast
P;lIlCI test~.
cracking control can be obtained on Iv bv proper
stress limits at the design load level.
Whcn designing longitudinal bridge members
for shear. another important factor remains to be
considered, which has sometimes heen meriooked
by inexperienced designers. It concerllS longitudi­
llal shear stresses developillg between the webs and
the top and bottom flanges as. shown in Figure
4.61. When web stress<.:s ha\'e been verified at the
level of the celltroid, it is not necessan to make a
detailed stud\' at other points of the web lsuch as
levels (d) and (e)l, although the principal tensile
stress Ilear the pier may be slightly higher at point
(d) than at the cel1ler of gravity. 011 the other
hand. to keep the integrity of the box girder, it is
very important to \'erifv that shear and diagonal
stresses ill sections (a), (b), and (c) are within the
/"
FIGURE 4.61.
(bnges.
/"
L[)ngitudinal silear between web and
199
same allowable values as set forth previously for
the webs and that a proper amount of reinforcing
steel crosses each section.
This leads to the design of transverse reinforce­
ment ill the cross section to resist shear stresses.
According to the provisions of the ACI Code and
the AASHTO specifications, the web shear steel
requirements are controlled by the ultimate stage.
The net ultimate shear force is given by the fol­
lowing formula, based on the current partial load
factors:
where
= net
shear force at ultimate stage,
actual shear force due to the effect
of all dead loads, including the re­
duction due to \'ariable depth where
applicable,
V u , = shear force due to live loads in­
cluding impact.
V f> = unfactored vertical component o!
prestress where applicable.
Vu
V D/,
Effects of temperature gradients' and volume
changes are usually small ill terms of shear load
and may be neglected except in rigid frames. On
the contrary, shear due to moment redistribution
and secondary effects of continuity prestress must
be illcluded. A partial safety factor on material
properties is applied to the ultimate load state.
4.11 Joints Between Match-Cast Segments
Joints between match-cast segments are usually
tilled with a thin la\er of epoxy to carry normal
and shear stresses across the joint. In the earlv
strllcwres, a single key was provided in each web of
the box girder to obtain the same relative positioll
between segments in the casting yard and in the
structure after transportation and placing. This
kev was also used to transfer the shear stresses
across the joint before polvmerization of the
epoxy, which has substantially no shear strength
before hardening. Figure 4.62 summarizes rhe
force system in relation to a typical segment both
Juring erection and in the completed structure.
Provisional assemblv of a new segment to the
previously completed part of the structure is usu­
ally achieved by stressing top (and sometimes bot­
tom) longitudinal tendons, which inducc forces FI
(and F2)' The resultant F of FI + F2 resolves with
the segment weight W into a resultant R. The verti­
cal component ofR can be balanced only by a reac­
Design of Segm~ental Bridges
200
F1
Fl
I
~
p
2
,w
(a)
D
lAIL
\
.
(b)
FIGURE 4.62. Typical scgment in relation to the forcc system.
of segment(s). (iJ) Segmcllt(s) ill the fini~hed structure.
tion such as R I given by the inclined face of the key,
while the balance of the normal force is R z which
produces a distribution of longitudinal compres­
sive stresses. In the finished structure, all normal
and. shear stresses are naturally carried through
the joints by the epoxy material, which has com­
pressive and shear strengths in excess of the seg­
melll concrete.
A series of interesting tests were performed for
the construction of the Rio- Niteroi Bridge in Brazil
to verify the structural behavior of epoxy joints
bet ween match-cast segments. A I -to-6 scale model
was built and tested to represent a typical deck
span near the support and the corresponding
seven segments as shown in Figure 4.63.
ELEVATION
(0)
Provisional assembly
A crack pattern developed in the web when the
test load was increased above design load, as shown
in Figure 4.64. The epoxy joints had no influence
on the continuity of- the web cracks, and the be­
havior of the segmental structure up to ultimate
was exactly the same as that of a monolithic struc­
ture. Failure occurred for concrete web crushing
when the steel stress in the stirrups reached the
yield point. The corresponding shear stress was
970 psi (6.8 MPa) for a mean concrete cylinder
strength of 4200 psi (29.5 MPa).
The first bending crack had previously occurred
for a load equal to 93 percent of the computed
cracking load, assuming a tensile bending strength
of 550 psi (3.9 MPa). Otber tests \vere performed
DETAIL
or
JOINT
f - - - ­ .... 40.00
~4,1lQj
FIGURE 4.63.
Rio-Niteroi Bridge, partial e1evatioll and joint detail.
Joints Between Match-Cast Segments
201
!, .
r-
I
i'
"
, \'~
.. ,' .
....
-
.........
-...
.
s:}J}:'~~~Y2if~:~:;· •. :'"
'
..
-~ ~
~'~:'
":-:-:
-0
FIGURE 4.64. Rio-Niteroi Bridge, web crack pattern at ultimate in model test.
in order to study the transfer of diagonal principal
compressive stresses across tpe segment joints as
shown in Figure 4,65, Prismatic test specimens
/
or
/3
Efficiency
(,,)
PRISMATIC
were prepared, some with and some without shear
keys across the joint, and tested for variolls values
of/3. the angle between the principal stress and the
neutral axis
the girder. In the case of the Rio
~iteroi Bridge the value of /3 is between 30 and
35°, For a reinforced concrete structure /3 = 45°.
A preliminary test showed that the epoxy joint
had an efficiency of 0.92 as compared to a
IIlonolithic specimen with no joint (ratio between
the ultimate load P on the prismatic specimen with
an epoxv joint and with a monolith specimen). For
various directions of the joint the results are as
follows:
PRISMATIC
WITH KEYS
(b)
FIGURE 4.65. Rio-Niteroi Bridge. test specimens for
web, (a) Crack panel'll in web and related test specimen.
(b) Actual test specimens.
0°
30"
60°
0.94
0.98
0.70
It can be seen that for values of /3 smaller than 45°
(which covers the entire field of prestressed con­
crete members) the compressive strength is hardly
affected by the presence of the inclined joint. All
these tests confirmed earlier experimental studies
to show that epoxy joints are safe provided that
proper material quality together with proper mix­
ing and application procedures are constantly ob­
tained.
Several early incidents in France, and some more
recently in the United States, have shown that
these conditions are not always achieved. The logi­
cal step in the development and improvement of
epoxy joints was therefore to relieve the epoxv of
Design of Segmental Bridges
202
any structural function. The multiple-key (or
castellated-joint) design embodies this concept and
provides for simplicity, safety, and cost savings.
Webs and flanges of the box section are provided
with a large number of small interlocking keys de­
signed to carryall stresses across the joint with no
structural assistance from the resin. Figure 4.66
shows the comparison between the structural be­
havior of an early joint with a single web key and a
joint with multiple keys, assuming that the epoxy
resin has improperly set and hardened. It is nmN
recommended that multiple keys be used in all pre­
cast segmental projects, as shown in Figure 4.67.
\Vith the current dimensions used for depth and
height of multiple keys, the overall capacity of the
joint is far in excess of the required minimum to
transfer diagonal stresses safely up to the ultimate
load state.
i
Potential
~
fajlure~,plane,
I
J
It=
'- / Fo
I
'­
4.12
Design of Superstructure Cross Section
The typical cross section of a box girder deck is a
closed frame subjected to the following loads; Fig­
ure 4.68:
Girder weight of the various components (top and
bottom flanges, webs)
Superimposed loads essentially applied to the top
flange (barrier, curbs and pavement) and some­
times to the bottom flange, as when utilities are in­
stalled in the box girder
Live loads applied on the deck slab
A tvpical box girder element limited by two parallel
cross sections, Figure 4.68b, is in equilibrium be­
cause the applied loads are balanced by the dif­
ference between shear stresses at the two limiting
sections. To design the typical cross section the as-.
sumption is usually made t.hat the shape of tbe sec­
tion remains unchanged and that the closed frame
may be designed as resting on immovable supports
such as A and B. Bending moments are created in
the various sections of the frame due to the applied
loads. Maximum moments occur in the deck slab
due to live loads in sections such as (a), (1)), and (0.
,,(/)
" '-
:
(aJ
(b)
FIGURE 4.66. Joint between match-cast segments,
comparison between single- and multiple-key concepts.
(d)
(.6)
FIGURE 4.67.
Precast segment \"ith multiple keys.
FIGURE 4.68. Design of deck cross section. (a) Typi­
cal loading on cross section. (b) Free-body diagram.
Special Problems in Superstructure Design
Because the wehs are usually· much stiffer than the
flanges and the side-deck slab cantilevers and the
center-deck slab between wehs are huilt into the
webs, most of the deck-slah moments are trans­
ferred to the weh, with a maximum value in section
(d) at the connection between web and top flange.
In bridges where transverse or vertical prestress or
both are used, the design of the deck cross section
is not greatlv affected by the f~lct that moments and
normal forces computed in the frame superimpose
their effects on the shear stresses due to longitudi­
nal bending mentioned in Section 4.lO.
The case is more critical when only conventional
transverse reinforcing steel is used in both flanges
and webs. A common method, based on experi­
ence, is to compute the steel area required on
either face at critical sections such as (a) through
(e), showl! in Figure 4.68, for the following:
1.
2.
Shear stresses ill the longitudinal members.
TLlllsverse bending of the frame.
The minilllulll amollnt of steel should Ilot be less
thall the larger of the followiilg:
item I pillS olle-hal r of Item 2,
item 2 plus one-hair of item 1, or
0.7 limes the slim of item I and item 2.
4.13
Special Problems in Superstructure Design
All design aspects covered ill the preceding sec­
tions pertain to the design of deck members for
bending and shear regardless of the local problems
encountered O\·er the piers or abutments and at
intermediate expansion joints when required. This
section will now deal with such local problems,
which are of great practical importance.
.f./3./
DI'IPHR.-JGMS
It \V,IS mentioned in Section 4.6 that the combined
capacities of the deck slab in bending and the box
girder in torsion allow a verv satisfactory trans­
verse distribution of live loads between girders in
the case of multiple box girder decks. It has there­
fore been common practice to eliminate all trans­
vel'se diaphragms between box girders except over
the ab'ulments. Diaphragms inside the box section
are slill required over the intermediate piers in
most projects.
4.132
203
SUPERSTRUCTURE OVER PIERS
The simplest case is exemplified in Figure 4.69,
where a deck of constant depth rests upon the pier
cap with bearings located under the web of the box
girder. The reaction is transferred directly from
the web to the bearings, and there is need only for
a simple inside diaphragm designed to transfer the
shear stresses, due to possible torsion moments, to
the substructure. A more complicated situation
arises when the bearings are offset with regard to
the webs, Figure 4.70. Reinforcing and possibly
prestressing must be provided ill the cross section
immediately above the pier to fullfill the following
I'll nctions:
Suspend all sheal' stresses carried by the web under
point A, where a 45° line starting at the bearing
edge illtersects the web centerline (hatched area in
the shear diagralll).
Balance the moment (R . d) induced by the bear­
ing offset.
Looking at other schemes, we find that decks of
variable depth pose several challenging prohlems.
Figure 4.71 shows an elevation of a box girder
resting on twin bearings designed to improve the
rigidity of the pier-to-deck connection and con­
sequently reduce the bending llloments in the
deck, which will be described in greater detail in
Chapter 5.
When the loading arrangement is symmetrical in
the two <1(~jacent spans, the transfer of the deck
reaction into the piers through the four bearings is
just as simple as for the case shown in Figure 4.69.
:\[atters look very difficult for an unsymmetrical
loading condition either in the completed struc­
ture, Figure 4.71. or during construction, Figure
4.72. Let us assume that the total deck reaction is
transferred to the pier through one line of bearings
only (for example, HI in Figure 4.7 I, for an excess
of load in the left span). The compression C2 car­
ried by the bottom flange at the right is no longer
balanced by the corresponding reaction R 2 , and an
abrupt change in the system of internal forces re­
sults in a large vertical tensile force T 2 , which has to
be suspended on the total width of the box section
by special reinforcement or prestress. In long-span
structures, these local effects are of no small mag­
nitude. Taking the example of a 40 ft (12 m) wide
box with a 20 ft (6 m) wide hottom flange and a
span of 300 ft (90 Ill), the load carried by the bot­
tom flange will probably be around 3000 t (2720
mt) and the angle change above the right bearing
Design of SegmeJ}tal Bridges
204
t
4,65 ________.. _'_.'_
j.
o
o
'"
---i­
ben rlngs
~j.4],-_+-,,"-7=-8
-+-___---..:3:..:.,00
2.25
SECTlO.'\
FIGURE 4.69.
A-A
SECTION
Picr segment for deck of constant ckpt h and simple
.JJISTA/EtlTJIJN OF ,fNEAP.
J"TAESSES IN WELlS
FIGURE 4.70.
_*'e
Deck over piers \\'ith offset bearings.
ahout 10 percent. The corresponding unbalanced
load is therefore 300 t (272 mt), and this is more
than enough to split the pier segment along the
section between the web and the bottom flange if
proper consideration has not been given to the
problem with respect to design and detailing.
Tbe situation may be even more critical during
cOllstruction, Figure 4.72, if the unbalanced mo­
C -C
SllppOlI.
ment induces uplift in one of the two bearings. The
load of the anchor rods (2) has to be added 10 the
unbalanced load resulting from the angle change
of tbe bottom Hange.
The diaphragm systems shown in Figures 4.71
and 4.72 are of the fl type where botb inclined
diapbragm walls intersect at the top flange level.
Any unsymmetrical moment that produces a ten­
sion force in the top Hange T and a compressioll
force in the bottom flange may tbus he balanced by
l1ormalloads sucb as F) and C j , Figure 4.71, witb
no secondary bending. In tbis respect, tben, it is a
satisfactory scheme. Detailing may, however, be
difficult because of the concentration of rein­
forcement or prestress tendon ancbors in the top
flange area, whicb usually is already overcrowded
witb longitudinal tendon ducts. A simple and more
practical design, although less satisfactory from a
tbeoretical point of view, is to provide vertical
diaphragms above tbe bearings. This is the logical
choice wben the deck is rigidly connected with a
Deflections of Cantilever Bridges and Camber Design
4.13.4
205
EXPANSION 10l,VT AND fllNGE Sr:GMHNT
The expansion joints required at intermediate
points in very long structures need a special se~­
ment to transfer the reaction between the two sides
of the deck, When the expansion joint is located
close to the point of contraflexure there is no pro­
vision for any uplift force, even with a load factor
on the live loading.
The hinge segment is therefore made up of two
half-segments, as shown in Figure 4.75:
The bearing half (reference A), which is connected
by prestress to the shorter part of the span
The carried half (reference B), connected by pre­
stress to the longer part of the span
Measures are taken to continue cantilever con­
struction through the hinge segment until closure
is achieved at midspan: see Section 4.S.6.
Inclined diaphragms provide an efficient way to
suspend or transfer the reaction through the
bearings into the flanges and webs on both sides 0\
the box section, Figure 4.75.
One of the largest structures incorporating a hinge
segment of this type is the Saint Cloud Bridge, de­
scribed in Section 3.12. A typical detail of this seg­
ment is shown in Figure 4.76.
Neoprene bearings
FIGURE 4.71. Deck of variable (/t:pth, permanent
deck-to-pier bearing arrangemenl.
box pier and where the pier walls are continued in
the deck, as showll in Figure 4.7:~. Here again the
transfer of all svmmetricalloads hetween deck and
pier is simple, and design difficulties arise for un­
symmetrical loading. At the connecting points :l
and 8, Figure -1.73. between the top flange and the
vertical diaphragms, the part of the top flange ten­
sion load T such as Tl induces into the diaphragm
another tension load T~, and both loads result in an
unbalanced diagonal component T: l , which must be
resisted both bv the webs and bv special provisions
such· as stiffening beams.
C/.1 J.3
EXD (1BLTJIE.VTS
A special segment will be provided at both ends of
the bridge deck with a solid diaphragm to transfer
torsional stresses to the bearings. as shown in Fig­
ure 4.74. The expansion joint is, therefore. ade­
quately supported by the end diaphragm on one
side and the abutment wall on the other side.
4.14
Deflections of Cantilever Bridges and
Camber Design
Each cantilever arm consists of several segments.
fabricated, installed. and loaded at differem poims
in time. It is important therefore to predict accll­
ratelv the deflection curves of the val'iolls cantile­
vers so as to provide adequate camber either in the·
fabrication plant for precast segmcmal construc­
tion or for a<ie(lu<lte adjustment of the form travel­
ers for cast-in-place construction.
When the structure is staticallv determinate, the
cantilever arm deflections are due to:
The concrete girder weight
The weight of the travelers or the segmel1l placing
equipment
The cantilever prestress
After continuity between individual cantilevers is
achieved, the structure becomes statically indeter­
minate and continues to undergo additional
deflections for the following reasons:
206
Design Qf Seg11Jental Bridges
2r--+--~.
@
I
~olo~
\_ _
...
'-.
FIGURE 4.72.
..
_-­
Tcmporan' pier and deck conllection.
Continuity prestress
Removal of travelers or segment placing eqUIp­
ment
Removal of provisional supports and release of
deck to pier connections
Placing of superimposed loads
Subsequent long-term deflections due to con­
crete creep and prestress losses will also take place.
Compensation for the following three types of
deflections must be provided for by adequate
camber or adjustment:
I.
2.
3.
Cantilever arms.
Short-term continuous deck.
Long-term continuous deck.
It has already been mentioned that the concrete
modulus of elasticity varies both with [he age at the
time of first loading and with the duration of the
load (see Section 4.8.7). Deflections of types 2 and
3 above are easily accommodated by chant,ring the
theoretical longitudinal profile by the corre­
sponding amount in each section to offset exactly
all future deflections. A more delicate problem is to
Deflections of Cantilever Bridges and Camber Design
207
accurately predict and adequatelv follow the
deHections of the individual cantilever arms durin~
construction. It is necessary to analyze each con­
struction stage and to determine the deflection
curve of the successive cantilever arms as construc­
tion proceeds, step by step. A simple case with a
five-segment cantilever is shown in Fi~ure 4.77.
The broken line represents the envelope of the
various cleHection curves or the space trajectory
followed by the cantilever tip at each construction
~tage.
FIGURE 4.73.
By changing the relative angular positions of the
various segments bv small angles, such as
0'"
-0'2, and so on, the cantilever should be assembled
to its final length with a satisfactorv longitudinal
profile as shown in Figure 4.78, for the simple case
considered. The practicalities of this important
problem are covered in Sections IIA and 11.6.
Pier sl')-\"Illl'111 I"il h \lTtical diaphragms.
~ 2.00
A
~----.:=-=---_Lf
2.25
~
T
Sl::CTlO\"
A-A
SECTlONC-C
O!
."
N!
i
I
--t
SECTION
B-B
FIGURE 4.74.
ment.
Outline of end segment over abut­
208
Design of Segmental Bridges
1.50
A-A
SECTlO:-<
S.ECTIOl'
C-C
B- 8
S,~CTI(l0:
FIGURE 4.75.
1-1 illge segml'llt wilh l'xpansiolljoilli.
COUPE
B.B
COUPE
A.A
ELEVATION
4.oof
.~
_
r- ..
r-
. \ibussoir porleu r
r'
~0
F
Ii _
~~
FIGURE 4.76.
,..;
'"
..
2.55
'-r
Saint Cloud Bridge, hinge segment with expansion joint.
It is interesting to compare the relative impor­
tance of deflections and camber for cast-in-place
and precast construction. Figure 4.79 shows values
for an actual structure, where computations have
been made for the two different methods. The cal-
culational assumptions given in Figure 4.79 indi­
cate that in most cases the difference would be
even more significant if a cast-in-place cycle of less
than one week were employed and if precast seg­
ments wel'e stored for more than two weeks. How­
5EGMENTS
Segments N"
N"
4
....
tr
21
g
4
3
2
---
'"
4.4
'\,
ENVELOPE OF
3
"-
::>
S
CURVES.
""
\
'"
\
(5
a.
a.
\
\
::>
V>
,
\
\
,­,
,
FIGURE 4.78. Choice and control of camber.
\
\
\
\
\
\!
\
I
FIGURE 4.77.
Deflections of a typical cantilever.
CROWN
1.1.1
....
«
o
LI
d
~r
d ..10
d ... 26
d+6
d+24
d -2
d -22
d+11
d .. 27
d+ 12
id+27
~1·r-~--~---+--~----~--+---~---+----~--+---4-------~
"-I
01
STRUCTURE
1.1.11
«
...
1
01
A SSUJI,IPTIO::-;S
PRECAST
Casting
one segment per day
Placing
two segments par day
Segments at least 2 weeks old for placing
<::'-_~'E:~~:~~~E
:
, one segment per week
Prestressing: 30 days after casting
FIGURE 4.79.
-+---1--------=--d----,---1-4-
Comparison of deAections between precast and cast in place structures.
209
Design of Segmental Bridges
210
ever, one would normally expect a cast-in-place
cantilever arm to resist deflections two or three
times greater than the precast equivalent.
4.15
Fatigue in Segmental Bridges
Basically, prestressed concrete resists dvnamic and
cyclic loadings very well. Eugene Frevssinet dem­
onstrated this fact tift" years ago. He tested two
identical telegraph poles under dynamic loading.
Olle was of reinforced concrete and the other of
prestressed concrete; both were designed for the
same loading conditions. The reinforced concrete
member failed after a few thousand cycles. while
the prest ressed concrete memher sllstained the
d\'l1<llllic load indefinitely (sc\'eral million cycles).
Fatigue in concrete itself has never been a prob­
lem in ;111\ known structure. hecause a variation of
compressive stress in concrete may be supported
indefinitel\'. When reference is made to fatigue in
prestressed concrete, it is alwa\'s inferred that
f~lIiglle problel11s arise in t he prest ressing steel or
convelltional reinforcing steel as a result of crack­
ing due either to bending or to shear. If cracking
could be avoicled in prestressed concrete struc­
tures. the fatigue problem would he completely
eliminated.
Figure 4.80 shows the resistance to fatigue of
prestressing strands currently used in prestressed
concrete structures. The diagram shows tl}e limit
of stress variation causing fatigue failure versus the
mean stress in the prestressing steel. For come­
nience. both values are expressed as a ratio with
respect to the ultimate tensile strength. For a steel
stress of 60% of the ultimate the acceptable range
of variation is :±:8~ of the ultimate for a number of
ncles between 1()6 and 107 • Lsing. for example,
270 ksi qualit\' ~trand. this variation is therefore
22,000 psi or a total range of 44.000 psi.
Because dvo<ul.lic loading on a bridge is of a
short-term nat ure, the concrete lI10dulus is high
and the ratio hetweell steel and concrete moduli is
of the order of 5. Consequentlv, the maximum
concrete stress ill an lIncnlcked section that would
cause a fatigue failure would he 44,000/5
1-\1-\00
psi, a \'alue which is probablv tell tillles the stress
\'arialion under design live loads in highway box
girder hridges, All uncrackcd prestressed concrete
strucillre is therefore cOl11pletcl\ safe \\ith respect
to Llligue, regardless of the magnitude of li\T
loads. A limited allloullt of cracking, although (011­
sidered unadvisahle frolll a corrosioll poilll of
view, is 110t critical if kept under control.
Tests and experience show that a grouted pre­
stressing tendoll can transfer hOlld st I'esses lip to
b1
2' 0.4
Stress variation
causing failure
fs
Afs
0.20
FIGURE 4.80.
Resistance to fatigue of prestressing strands.
Fatigue in Segmental Bridges
5'00 psi to the surrounding concrete. Taking the
example of a typical (twelve ~ in. diameter strand)
tendon with an outside diameter of 2.5 in. (64
mm), a stress variation of 40,000 psi in the steel
produces a tendon force variation of 73,000 lb (33
mt), and the bond development length across a
crack is then 73,000/(500 x 2.5 x 7T) = 18 in. (0046
m), see Figure 4.81. The corresponding crack
width € is equal to the elongation of the pre­
stressing steel between points A and B with the
triangular stress diagram-that is, 40 ksi over an
average length of 18 in., or
€
=
E~ = ~06.000
x 18
=
0.028 in. (0.7 mm)
A safe crack width limit of 0.015 in. (0.4 mm) can
be accepted to eliminate the danger of fatigue in
the prestressing steel. In fact, instances of fatigue
in segmental structures are extremely few and far
between.
An isolated case has been reported of a bridge in
Dusseldorf, Germany, where failure occurred as a
result of fatigue of prestressing bars. The cast-in­
place structure was prestressed with high-strength
bars coupled at every construftion joint. After ten
years of service, ajoint opened up to ~ in. (10 mm)
and caused bar failures at the couplers. All investi­
gation revealed that a bearing had frozen and pre­
vented the structure from following the longitudi­
nal movements due to thermdl variations. This
accidental restraint induced high tensile stresses in
the concrete and caused cracking, which first ap­
peared in the construction joints precisely where
bar couplers were located. The live-load stress level
in the prestressing steel increased from 850 psi (6
eFlAe",.
1!ucr
FIGURE 4.81.
cracked section.
Fatigue in prestressing steel across a
211
MPa) for the previously uncracked section to
14,000 psi (96 MPa) for the cracked section and
induced failure in the bars. A recommendation was
made as a result of this fatigue problem that coup·
lers should be moved at least 16 in. (0040 m) away
from the construction joints and that reinforcing
steel should be provided through the joints if
practical. Another sensitive factor relating to
fatigue in web reinforcing steel was mentioned in
Section 4.10.2 for reinforced concrete test beams.
No such danger would exist in prestressed con­
crete if shear and diagonal stresses were kept
within the limits that control web cracking.
In conclusion, fatigue in prestressed concrete is
not a potential danger if design and practical con­
struction take into account a few simple rules:
1.
Avoid bending cracks in girders by allowing no
tension or only a limited amount at either top
or bottom fibers for normal maximum loads,
such as the combination of dead loads, pre­
stressing, and design live loads including mo­
ment redistribution and half the temperature
gradient.
2.
Avoid web cracking by keeping diagonal ten­
sile stresses within allowable limits by proper
web thickness and possibly vertical prestress.
3.
Design and maintain bearings and expansion
joints that allow free volume changes in decks.
Temperature stresses that cannot be COIl­
trolled can give rise to enormous forces that
may either tear the deck apart or destroy the
piers and abutments. 111 this respect, elas­
tomeric bearings, which work by distortion and
cannot freeze, are safer than friction bearings.
which are more easily affected by dust and
weathering of the contact surfaces.
Insofar as crack control in segmel1lal structures
is concerned. it is usually felt in Europe that exces­
sive concrete cover over the reinforcing steel and
prestress tendons does not prevent corrosion but
merely increases the crack width.3 For example.
the typical 2 in. (50 mm) cover commonly used in
bridge decks in the United States is considered ex­
treme in Europe. The 4 in. (100 mm) cover for
concrete exposed to sea water would be a complete
surprise to European engineers.
Several examples of common practice in seg­
mental bridges are given as a simple comparative
reference in Table 4.2.
Design of Segmental Bridges
212
TABLE 4.2. Concrete Cover to Reinforcing Steel
and Prestress Tendons in Europe
Concrete cover
(in.)
Germa.n,'"
H to 2
H
H
~
Descri ption
Reinforcing steel
Outside exposure, tendons
Inside exposure, tendons
France
Transverse reinforcing steel
Longitudinal reinforcing
steel or tendons
(normal atmosphere)
Corrosive atmosphere
(salt water)
2
IVetherlands
H
H
2
to
2~
Reinforcing steel and tendons
(normal exposure)
Lightweight concrete
Salt water exposure
4.16 Provisions for Future Prestressing
For larger segmental bridges, it may be necessary
to modify the prestress forces after construction.
An example would be a bridge built using can­
tilever construction where positive-moment (con­
tinuity) tendons are added after erection. Or, as
discussed in Section 4.8.6, some tendons may be
released to articulate a joint. In addition to these
adjustments immediately after construction, addi-.
tional prestressing may be required at a later date
to correct for unanticipated creep deflection or for
additional loads such as for a new wearing surface.
In Europe on some bridges spare tendon ducts are
provided for this reason. A reasonable assumption
would be to provide for 5 to 10% of the total pre·
stress force for possible future addition.
Since the tendon anchorages for the spare ducts
are inside the box girder and generally located at
the web-flange fillet, they are readily accessible. If
future prestressing is needed, it is only necessary to
insert the required tendon in the duct,jack it to its
designed load, anchor and grout it. Since all this
work can be done inside a box girder, it is not nec­
essary to interrupt traffic, and the workmen are
fully protected.3
4.17
Design Example
The Houston Ship Channel Bridge now under
construction in Texas, U.S.A., is an outstanding
example of segmental construction and represents
the longest box girder bridge in the Americas as of
this writing. Typical dimensions were given in Sec­
tion 2.14. This section will deal with some design
aspects of this prestressed concrete s~gmental
bridge.
4.17.1
LONGITUDINAL BESDING
Each of the four identical cantilever arms is made
up of:
Ten segments 8 ft long (maximum weight 415
kips)
Six segments 12 ft long (maximum weight 464
kips)
Thirteen segments 15 ft long (maximum weight
457 kips)
Longitudinal tendons are as follows:
Cantilever tendons: 42 (nineteen 0.6 in. dia
strands) + 50 (twelve 0.6 in. dial. Twelve addi­
tional bars used during construction are incorpo­
rated in the permanent prestress system.
Continuity tendons in side sfmns: 20 (twelve 0.6 in.
dial.
Continuity tendons in crnter span: 40 (twelve 0.6 in.
dial.
A typical layout of the cross section was given in
Figure 2.82.
_
The main loading combinations considered in
the design are summarized in Table 4.3. The lonTABLE 4.3. Houston Ship Channel Bridge, Main
Design Load Combinations
Load­
ing Case
(1)
(2)
(3)
(4)
(5)
Description
Allowable
Tension on
Extreme
Fiber, Top
or Bottom
(ks!)
+ (P) + (E)
+ (P) + (L + 1)
(D) + (P) + (L + 1) + HC!.T) + (T)
(D) + (P) + !(L + 1) + (C!.T) + (T)
(D) + (P) + (W)
(G)
0
(D)
0
25
25
25
Notations: (C) girder load, (D) total dead load including
superimposed dead load, (L + I) live load plus impact, (P) pre­
stress, (E) construction equipment, (tlT) temperature gradient
of 18"F between {Op and bottom fiber, (Tl temperature and vol­
ume changes, (W) wind load on structure.
Concrete strength and stresses: f~
6000 psi
864 ksf (42.1
MPa).
Basic allowable compressive stress: O.4f~ = 346 ksf (l6.8MPa).
Design Example
gitudinal bending of the box girder has been
analyzed using the Be program, which considers
the effects of the creep, shrinkage, and relaxation
at each construction phase. Figure 4.82 shows the
diagram of prestress forces due to cantilever and
continuity tendons at two different dates:
After completion of the structure and opening to
traffic (780 days after start of deck casting)
After relaxation and creep have taken place (4000
days)
Significant values of the prestress forces are given
in Table 4.4. The variation of stresses in the center
and side spans is shown in the following diagrams
for the corresponding loading cases:
Figures 4.83 and 4.84, all dead loads and prestress
at top and bottom fibers
Figures 4.85 and 4.86, live load and temperature
gradient at top and bottom fibers
It is easily shown from these diagrams that all
stresses in the various sectipns are kept within
the allowable values mentioned in Table 4.3. The
!..ONGITUD!p..j.AL PRf5TRE"5SING: A;&:IAl FORCE
(KIP)
GOODO
\(;1>
C"''''TIL[VtR PAESiRES!oIIolG(TlHf 7eo D"Y5)
r."NlllEIt~IL~R!~_FtE~J..!!!i
[TIME -4000 OAY!»
~--------,'-JL---f-"'lML-"'"
I~
195 '
375 FT
""X1t~·U'"
WEIG~l
SEGHENT
WEIG~lS
Of ONE" TRA.lJtI..[,R :
II
mt)
(B'):;
415 K. (ISEI
(I~'):
4b4 K. (~IDm\)
l''') ,
457 K. ('1.07 mt)
'2.~O K. (1.04
mk)
FIGURE 4.82. Houston Ship Channel Bridge, typical
segment layout and longitudinal prestress.
213
TABLE 4.4. Houston Ship Channel Bridge,
Significant Values of Prestress Forces
Prestress Force (kips)
Maximum cantilever
prestress in side
span
Maximum cantilever
prestress in center
span
:Ylaxirnum continuity
prestress in side
span
:'vlaxirnum continuitv
prestress in center
span
Day
780
Day
4000
Percent
Loss
54,710
51,310
6.2
54,390
49,280
9.4
9,540
8,760
8.2
18,130
16,780
7.5
maximum compressive stress at the bottom fiber
level appears in the section located 124 ft from the
pier and is equal to 335 ksf under the combined
effect of all dead and live loads and prestress.
4.17.2
REDISTRIBUTION OF l'vlOMENTS
The exceptional size of the structure gives rise to a
moment redistribution of particular importance.
The Be program allows a complete analysis of the
behavior of the structure under the separate and
combined effects of loads and prestress; also the
effect of concrete creep and steel relaxation can be
considered separately.
Figure 4.87 shows the variation of stresses at top
and bottom fibers along the center span between
days 780 and 4000, which correspond to bridge
opening date and the time when materials will have
stabilized (concrete creep and shrinkage having
taken place and prestress having reached its final
value). The magnitude of the variation is remark­
able, particularly at bottom flange level where it
exceeds 100 k..\[ (700 psi or 4.90 ~fPa).
To isolate the effect of concrete creep on mo­
ment and stress redistribution, a section near
midspan may be analyzed where cantilever pre­
stress is neglibile. Results for the section located at
a distance of 352 ft from the pier are summarized
in Figure 4.88. The redistribution moment is equal
to 52,000 ft-kips.
It is interesting to compare this result, obtained
through the elaborate analysis of the Be program,
with the result of the approximate method out­
lined in Section 4.8.7. Figure 4.89 shows the mo­
ments in a typical cantilever under girder load and
final prestress. The prestress moment has been
computed using a reduced eccentricity obtained by
Design of Segmental Bridges
214
.3QQ i<SF
I
/
/
/
I
o
f
/"\
\
\
\
\\
kSF
179
". .... "',
I
I
I
I
I
~TIME 4000
,,~
\
\
\
\
108
\
20'
FIGURE 4.83. HOUSIOIl Ship Channel Bridge. lOp filler preslres~ IOI~ (DL) + (p) at tillle'
7S0 days and 4000 davs. Stresses at top fihel of the deck, Dead load at lime 7HO da\~ \"hell
lhe bridge is ,illst opened to traffic alld at lim(' 4000 ([a\'s.
transforming the steel area in the concrete section.
Therefore, the prestress moment is equal to:
Pe(l - np)
where e
geometric eccentricity,
10, transformed coefficient,
p = percentage of prestress steel in the sec­
tion (varying between 0.5 and 0.7%).
n
The total midspan moment produced in the con­
tinuous span with fixed ends under the combined
effect of girder load and final prestress is equal to
84,000 ft-kips. Therefore, the actual redistribution
moment obtained by the Be program is equal to:
52,000 _
84,000 ­
of the total moment
The recommendation given in Section 4.8.7 to take
a ratio of 2/3 gives a satisfactory approximation.
4.17.'3
STRESSES AT ,HIf)SP.1.Y
Because of the moment redistribution the bottom
fiber near midspan is subjected to increasing ten­
sile stresses while the top fiber is always under
compression. 1t is therefore sufficient to consider
the state of stresses at the bottom fiber after creep
and relaxation.
The results are shown in Table 4.5. It is instruc­
tive to compare the relative magnitude of the vari­
ous factors influencing the stresses at midspan
(stresses in ksf at bottom fiber):
1.
2.
Live load
Moment redistribution
(difference between 250 for
GL and 159 for prestress) .
3. Temperature gradient
4. Temperature fall
44
91
48
18
Design Example
TABLE 4.5.
Houston Ship Channel Bridge, Stresses
at Midspan
Bottolll Fiher
Stresses (ksO
Panial
CUTllulative
are light in comparison with those used in other
coulltries, particularh' in France and Great Britain.
These two factors tend to increase the importance
of moment redistribution in relation to the effect
of loads computed in the conventional manner,
+250
\foment redistribution due
(() GL
\[oll1ent red isrribut ion d tie
to prestress
.\!oment redistributioll due
to (GL) + (P)
All dead loads and all final
prestress (lhHll Be pl'O~
gram illcluding Illomellt
redist ributioIl)
4.17.4
159
+ 91
-66
Live load + impact
Temperature gradient,
44
-lH
I.
IO;l!lin~
combinations in
Fi~UI'l;
18
+22
(25)
·Ul5,
"Comhination or \Iaximulll ::'1' + T (maximum temperature
differential is improhable in winter),
2.
3.
Vertical dead-load shear force: 4:350 kips.
Resal effect: the compressive stress at the cen­
terline of the bottom slab is 192 ksf and the
angle with the horizontal is 0.055 radians,
Bottom slab area: 53.5 sq it.
Resal effect: 192 x 53,5 x n.055
570 kips.
i\et dead-load shear: 3780
----'-­
Live-load shear force: 430 kips.
Corresponding shear stresses in this section:
IIQ
b
The influence of the temperature fall (effect 4) is
imputable to the frame action between deck and
piers and would not appear in a conventional deck
resting on its piers with flexible bearings. Consid­
ering only the other three factors combined, as in
loading combination (4) of Table 4.3, the
m<lXimUlll tensile stress at the bottom fiber of the
'midspan section is:
91+44+
48
=1
2
ksf
The live-load stress is onl", 44 ksf or 44i 159 = 28
percent of tbe total.
In all good faith, a design engineer would have
com pletely O\'erlooked effects 2 and 3 only a few
vea.rs ago and consequently underdesigned con­
siderably the continuity prestress. The situation
has now completely changed, and the knowledge
of materials together with the powerful tool of the
computer allows segmental structures to be de­
signed safely and realistically.
It is as well to remember that the Houston Ship
ChaLll1el Bridge is of exceptional size (which tends
to increase the im portance of dead load and mo­
ment redistribution) and that American live loads
SHEAR
The variation of shear stresses along the centel­
span under design loads is given in Figure 4,90 to­
gether with the corresponding longitudinal com­
pressive stress at the centroid.
The most critical section is located 187 ft from
the pier centerline, The numerical values in this
section are as follows:
J"T = 18°[­
Temperature fall,
T
-40°F
Loadillg combillation (:!)."
(D) + (P) + (I~ + I)
Loading c01llbillation (4),"
(I) + (P) + ~(L + I) + J.T + T
"See
215
14
rr
web thickness
4 ft
Total shear stress under design load (no load
factor) :
v
3780 + 430
4210 kips
Shear stress:
v= 4210
x
4,
5.
6.
= 75.2
ks!"
Longitudinal compressive stress:j.r
160 ksf
Vertical prestress. The contract specifications
called for a vertical prestress for the entire
deck giving a minimum compressive stress of:
3VJ;. = 232 psi = 33.S ks!"
Verification of allowable shear stress.
Using the formula proposed in Section 4.10.4:
v
= 0.05j~
+ 0,20j.r + 0.40jy
the allowable shear stress is:
V max
= 0.05 x 864 + 0.20 x
160 + 0.40 x 33.5
= 88.6 ksf
while the actual shear stress is onlv 75.2 ksf
Design of Segmental Bridges
216
r~onOH
BOTTOM FleER
C (KSF)
300 KSF
MIOSPAN
-~
.,/"
"
,,......-­
-­ "
'..
... ,
r­
t
'
____~--~/----__-----------------'~'~~~K~~F------------~----------~_+\
/~TIHE 4000
\\
,­
,­
\
r--"
\
I
TIME dOOO---l.
I
\
I
\
I
\.. ..... ,---,
I
I
lOa KsF
r
I
I
I
I
FIGURE 4.84. Houston Ship Channel Bridge, bottom fiber Slresse~ jilr (DL) + (P) at
time 780 days and 4000 days. Stresses at bottom hber of the deck. Dead load at time 780
days when the bridge is opened to traffic and at time 400n days.
7.
Principal stresses at design loads for the slate
of stress:
v == 75.2,
Ix = 160,
and 111
33.5 ksf
The two principal stresses are.=..! (tension) and
195 (compression).
The angle of the principal stress with the hori­
zontal is given by:
tan f3
=
=
Vu
Principal stress:
pression).
102 ksf
23 (tension) and 217 (com­
Direction of the principal stress given by:
tan f3
0.56
0.466
I f vertical prestresses were not used, the prin­
cipal stresses would become:
(tension) and 190 (compression)
8.
Corresponding shear stress:
Principal stresses at ultimate stage.
For the load factors l.3D + 2.17L, including
the effect of prestress, the ultimate shear force
IS:
v u = 5710
kips
Web shear cracking at this level of stress would
be unlikely. Assuming that the concrete carried
none of the ultimate shear across the potential
crack shown in Figure 4.91, the total shear load
should be resisted by the vertical tendons and the
conventional stirrups acting on a length equal to:
~x_l_=~
Q
tan f3
0.56
25ft
The unit force per foot of girder is therefore:
Design Example
" , . . - - .........
/
"
217
LOAD {MAXI
MINI
TOP FIBER
/
/
/
/
LIVE LOAD MAXI
LIVE LOAD MINI
LIVE LOAD MINI
375fT
FIGURE 4.85.
------_·+I··-----------=3~7~.~F~T----------~.1
Houston Ship Channel Bridge.
lOp
fiber stresses for (L
-i-
J) and (fl.T =
18°F),
57 10 =.::;~
"')8 k''lpSI'I"mea I t' t
The ultimate capacity of tendons and stirrups is:
Tendons in three webs
Stirrups-0.88 in. 2/1ineal ft
per web at 60 ksi
220 kips/lineal ft
158 kips/lineal ft
278 kipsllineal ft
shear force per unit length of girder to be carried
across the crack is:
1
0.85
x 5710
0.14 x 0 ,,:)~ = 240 k'IpS II'mea I t"t
The corresponding amount of steel (grade 60)
would be for each web:
1
G.~~
= 268
< 378 kipsllineal ft
and is easily met.
If no vertical prestress had been used. the slope
of the shear crack would be:
tan f3
0.487
Using the limiting value tan f3 = 0.5 instead of the
actual value (as explained in Section 4,10.4), the
240
3 x 60
The condition V"Ifj> < Vs becomes:
= 1.33 in.2flineal ft
This amount of steel would still be reasonable
(0.7%).
4,17.5
DESIGN OF THE CROSS-SECTION FRAME
Owing to the magnitude of the project, particular
attention was given to this problem. Five finite
element analyses were performed to analyze:
The local effects in the transverse frame,
Design of Segmer:tal Bridges
218
tfcBoTTOM
LIVE LOAD
{~t·~"
. 40l<SF
,I
liVE LOAD MAXI •
LIVE LOAD MA:<.j
~ MID5PAN
LIVE LOAD MINI
/
/
I
/
/
/
'20
z
o
/
\
\
\
\
\
\
/
TE"MPERAT RE GRADIENI
/
\
\
I
IS·F
\
\
\
"I
I.
(T
\~-/:75 '..,1______..
j' 40
\
+....______ 3=-7.:.-5::......:F_T'--_\._-::_'_-_-_-_-_-_----1
FIGURE 4.86.
= IWF).
Houston Ship Channel Bridge, hottom fiher stresses for (L + J) and (!::.T
The possible differential deHections between the
three webs of the box section,
The relative hehavior of sections close
or al midspan,
10
the piers
The effeci of diaphragm restraint near the pier.
The dimensions of the cross section at midspan are
given in Figure 4.92 with the nine critical sections
where moments and axial loads were computed for
as many as fourteen loading combinations.
A typical set of results is shown in Figure 4.93 for
the midspan section. For the section located 187 ft
from the pier centerline (already considered for
maximum shear stresses), the moments and axial
loads are substantially the same as for the midspan
section. Excluding the vertical prestress, the most
critical loading arrangement gives the following
values at the upper section of the outside web (sec­
tion e of Figure 4.92).
Moment 11.9 kip-ft/rl
Axial load 5.4 kip/ft
The steel section required at design stage for grade
60 steel stirrups is 0.34 in. 2 /lineal ft. Applying the
recommendations of Section 4. 10.4 for the simple
case of a section without web prestress, the re­
quirements for steel on both faces of the web
would be:
For shear of the longitudinal member:
t x 1.33
= 0.67 in. 2 llineal ft
For bending of the transverse member:
0.34 in. 2 /lineal ft
Quantities of Materials
219
~
l:::. f TOP GIRDER LOAD
2001-------=~::::t:::===+_
,111'''-''
z
o
<fl
<fl
w
~
100
KSf
I:
o
<.)
STRE55 VARIATION
AT TOP FIBER
Z
<I
a.
<Jl
o
----­ ______ rl:::.f
....
"'"-- ­
..... _
STRESS VARIATION
.""':."
....
...
Z
1:
BOTTOM PRESTRESS
""
AT BOTTOM FIBER
~
100
o
!Il
Z
l:::. f BOTTOM
Lu
I-
GIRDER LOAD
700+-____________..._________________~._---~~~----~~--_+_
FIGURE 4.87.
rel;Lxat ion.
Hou~toll
Ship Channel Bridge, variation of :;!J'esses due to creep and
The rwmmlllll area should thus be the higher of
the following values:
0.67 + ! x 0.34
.1
x 0.67 + 0.34
0.7(0.67 + 0.34)
0.84
in. 2 /lineaJ
ft
With vertical prestress: 378/3
Without vertical prestress: 2
kipsllineal ft
126 kips/lineal ft
X
0.84 x 60 = 101
= 0.67 in. /1ineal ft
2
=
0.71 in. 2 /1ineaJ ft
I t1 the actual structure, the stirrups in this section
are #6 bars at 12 in. centers, giving on each face a
steel area of 0,44 in.2 together with the rllinimum
vertical prestress of 44.2 kips/lineal ft (average
com.pressive stress of 230 psi).
The ultimate capacity of the section reinforce­
ment is therefore:
4.18
Quantities of Materials
Before closing this chapter, it is interesting to give
some statistical results concerning the quantities of
materials required in segmental box girder
bridges. Unit quantities have been computed by
dividing the total quantities for the bridge
superstructure by the deck area, using the total
width of the prestressed concrete structure. The
220
Design of Segmen!al Bridges
Stresses, Top Fiber (kst)
780
Loadillg Case
Cantilever Prestress
Girder + superimposed
dead load
Total
Variatioll from
780 days 10 4000 days
SOil'
Stresses, Bottom Fiher (ksl)
Dr/i'.1
4000 Dr!)'s
- 6.36
-56.93
63.29
136. J 8
780 Dms
4 ()()O Da)'\
13(U~2
-20.20
-16J.OH
-266.50
(j l.H9
293.50
41.69
132.42
72.89
+90.73
1: Tensile stresses are positive.
Soil' 2: This l110melll
is the difference between girder load, 142,000 It-kips, alld cantile\er prestress, gO,nOn ft· kips.
11
= -
72.89
Corresponding moment variatioll:
1
.:Hi
(11 +/2) II
+ 90.73) 4774
15
AM = 52.000 It-kips
N
'<t
0::)
II
...c::
II
N
U
12= + 90.73
FIGURE 4.88. Houston Ship Channel Bridge. analy­
sis or section at ;152 ft froJn pier.
/TOh~NT
IAI'.lJUt:INt;
fl£IJISTRllJt.lTI/)N
average concrete quantity per span foot varies with
the span length. For each struct ure considered, the
span length used is the average span of the various
two-ann cantilevers. The longitudinal prestressing
steel is given in pounds per cubic yard of deck con­
crete versus the same span length. It is assumed
that prestressing tendons are made up of strands
with 270 ksi guaranteed ultimate strength. From
the charts given in Figures 4.94 and 4.95, it may be
seen that the average quantities of materials may
be represented by the following approximate for­
mulae:
Concrete (ft 3/ft 2)
= 1.0 +
(L1250)
Longitudinal prestress (lb/ft2)
spans up to 750 ft)
4.19
= 1.0 +
(L160) (for
Potential Problem Areas
As with any type of construction with any material,
problems arise that require the attention of not
only the designers, but contractors and subcon­
tractors as well. No matter how good the design, if
FIGURE 4.89. Houston Ship Channel Bridge, rapid
computation of moment redistribution.
(11)
80
i
COMPRESSIVE
5TRE55
If,,)
IBO
;,"
IGO
----
221
Potential Problem Areas
~~
--
~ ... '"
.... -------:}"
.......
EFfECT OF
'\
TOTAL PRESTRESS \
\
\
'\
'\
140
60
\
'\
,
120
WEB SHEAR 5iRE5
11 (KSI')
100
40
l.
I
80
60
40
20
20
52
1'24
172
202
232
292
352
375
i
FIGURE 4.90. Houston Ship Channel Bridge, variation of web shear stress and aver­
age compressive stress in center span under design load,
7AN
~ ~ 0.455
TAN ~', 0.3%
the structure is not properly constructed, there will
be problems. Conversely, no matter how diligent
the contractor, if the design details are poor,
problems will result, Obviously, if the design and
the construction are poor, problems are com­
pounded.
/f
i----,--'-i
L"'OI-lR CIRCLE FOR MQNO-A:r,lIU, CCMPRESSION
TRAr..SVERSC TENDONS
(4X,6"01. STRANO)
SPACING
J
FT
In
1"
l..­
FIG\JRE 4.91. Houston Ship Channel Bridge, shear
and principal web stresses in section 187 ft from Pier
(under design loads),
9
In
I
..ili
FIGURE 4.92. Houston Ship Channel Bridge, design
of transverse frame at midspan.
Design of Segmental Bridges
222
:\1,
Prestressing
~1.
DL + PIT
16,59
10.92
-5.24
13,22
6.93
-6.68
-0.92
1.45
5.03
8.01
1.96
-8.82
3.01
4.23
5.88
0.22
-2.93
-1.25
0.08
2.88
-1.25
0
2.14
0.35
(l.O6
-'-5.23
-0.78
4.11
1.75
7,98
-9,51
]] ,87
-4.55
-4.50
2.59
-6,25
;..;, dead load
:\, transverse
prestressing
0.06
50,75
-(),53
51.06
-0,65
51.26
-0.59
51.35
4.24
-0.31
6.08
0.31
0,55
-0,29
0.66
-0,29
0,53
-0.29
:\.DL+PIT
',;. live load
:\. DL - PIT -'- LL
+1
50.8]
50,53
50,61
50.76
5.77
(),26
0.37
0,24
50,81
50.53
50,{) I
50.76
3,93
1.1 ()
5,36
5.77
0.26
0.37
0,24
1\1, Jive load
with IMi 111aXI
1\1. DL + PIT + LL
+1
SO/I':
Web vertical preslress is nOI included.
3.
Compressive axial forces arc
positive. Positive bending mo·
ments caw,e tension at the
broken linc face,
SIGN CONVENTION
FIGURE 4.93. HOUSIOIl Ship Channel Bridge, 1110­
<lnd axial forccs in transverse frame at midspan.
1IH'IIlS
Problems are generally associated with quality
control. poor design details, or a lack of under­
standing as to how the structure will behave, either
through ignorance or because a particular phe­
nomenon is ullknown to the current state of the
art, or a combination of all these factors. The fol­
lowing list of problem areas, as they are known to
the authors, is presented so that those involved in
designing and building segmental bridges may
take adequate measures and precautions to avoid
these problems.
1.
Improper performance of epoxy due to mis­
handling of mixing and application procedure,
particularly in rain and cold weather. The con­
sequences are largely reduced by the use of
adequate shear keys in webs and in both top
and bottom flanges of the box section.
2. Grout leakage between adjoining ducts at
joints between segments, particularly in pre­
cast segmental construction. Conformity of the
ducts at the joints is a desirable feature if prac­
tical. The use of tendons outside the concrete
eliminates this problem.
Tensile cracks behind tendon anchorages,
particularly for high-capacity continuity ten­
dons in the bottom flange of box sections.
.
4, Transverse cracking or opening of joints, or
adjacent thereto, due to the combination of
several factors such as:
a, Underestimation of moment redistribution
due to concrete creep,
b. Thermal gradients in the box senion,
c. Warping of segments due to improper
curing procedures.
Several such points have been already ad­
dressed in this chapter; others are discussed in
Chapter 1 L ShtlUld the recommendations
given be followed both in design and construc­
tion methods and in supervision, no more
difficulties of this nature are to be expected.
5, Laminar cracking in deck slab or in bottom
flange due to wobble and improper alignment
of duns at the joints between adjacent seg­
ments. Such incidents have been experienced
more often in cast-In-place construction than
in precast construction. However, care should
always be taken insofar as deck alignment is
concerned in all segmental projects.
6. Freezing of water in ducts during construction,
especially those anchored in the deck slab
(vertical prestressing tendons or draped con­
tinuity tendons).
7. Excessive friction in ducts due to wobble.
Proper alignment will reduce friction factors in
segmental construction to tbose currently ob­
served in conventional cast-in-place post­
tensioned construction.
S. Improper survey control in segment man­
ufacture for precast segments as well as in the
field for cast-in-place segments.
I
s.o...
,-...
u.
"'.
'u.
..::!.t
>­
':
...z
"a"
...'"
'"'"
:z
0
,.j
/.<=
~al
J
0
0
x
u
'"Cl
FIGURE 4.94.
Fherage quantities of deck
COllnetl'.
15 -:­
14 (
!~
!
12
T
II
~
I
...
-....
'"
i
10';'
~
...w
'"
s
1
:)
6
f
5
•r
3 i
2
!
100
200
300
.loa
500
sao
AVERAGIi ,PAN
FIGURE 4.95.
aoo
700
L
Cft)
Average quantides of longitudinal prestressing steel.
223
Design of Segmental Bridges
224
References
I. F. Leonhardt, "!\'ew Trends in Design and Construc­
tion of Long Span Bridges and Viaducts (Skew,
Flat Slabs, Torsion Box)," International Asso­
CIation for Bridge and Structural Engineering,
Eighth Congress, New York, September 9-14,
1968.
2. Jean Mnller, "Ten Years of Experience in Precast
Segmental Construction," Journal of the Prestre.lsed
I. January-February
Concrete Instituli', Vol. 20,
1975.
"0.
3. C. A. Ballinger, W. Podolny,jr., and :VLJ. Abrahams,
"A Report on the Design and Construction of.Seg­
mental Prestressed Concrete Bridges in Western
Europe-1977," International Road Federation,
Washington, D.C., June 1978. (Also available from
Federal Highway Administration, Offices of Re­
search and Development, Washington, D.C., Report
No. FHWA-RD-78-44.)
4. '"Effets de l'effort tranchant," Federation Inter­
nationale de la Precontrainte, London, 1978.
5
Foundations, Piers, and Abutments
5.1
5.2
5.6.2
River Piers and Foundations for Choisy.le-Roi,
Coumevoie, and Juvisy Bridges, France
5.6.3 Piers and Foundations of Chillon Viaducts, Switzer·
land
5.6.4 Main Piers and Foundations of the Magnan Viaduct,
France
5.6.5 Main Piers and Foundations for the Dauphin Island
Bridge, U.S.A.
5.6.6 Deformation and Properties of Piers with Flexible
Legs
5.6.7 Elastic Stability of Piers with Flexible Legs
INTRODUCTION
LOADS APPLIED TO THE PIERS
5.2.1 Loads Applied to the Finished Structure
5.2.2 Loads Applied During Construction
5.3 SUGGESTIONS ON AESTHETICS OF PIERS AND
ABUTMENTS
5.3.1 Structure Layout
5.3.2 Aesthetics of Piers
5.3.3 Aesthetics of Abutments
5.4 MOMENT RESISTING PIERS AND THEIR FOUNDA·
TIONS
5.4.1 Main Piers for the Brotonne Viaduct, France
5.4.2 Piers and Foundations for the Sallingsund Bridge,
Denmark
5.4.3 Concept of Precast Bell Pier Foundation for the
1·205 Columbia River Bridge, U.S.A.
5.4.4 Main Piers for the Houston Ship Channel Bridge,
U.S.A.
5.5 PIERS WITH DOUBLE ELASTOMERIC BEARINGS
5.5.1
5.5.2
5.6
Scope and General Considerations
Description of Structures
Oleron Viaduct, France
Blois Bridge, France
l:pstream Paris Belt Bridge, France
5.5.3 Properties of Neoprene Bearings
Notations
Deformations of Neoprene Bearings
5.5.4 Deformation of Piers with a Double Row of Neop·
rene Bearings
5.5.5 Properties of Piers with a Double Row of Neoprene
Bearings
5.5.6 Influence of Thickness and Arrangement of Neo·
prene Bearings on the Variation of Force in a
Three-Span Structure
PIERS WITH TWIN FLEXIBLE LEGS
5.6.1 Introduction
5.1
Introduction
Probably the area most challenging to the civil en­
gineer is that of foundation design and construc­
tion, presenting the largest potential dangers but
5.7
FLEXIBLE PIERS AND THEIR STABILITY DURING
CONSTRUCTION
5.7.1
5.7.2
Scope
Description of Representative Structures with Tem­
porary Supports
Downstream Paris Belt Bridge, France
Saint Jean Bridge In Bordeaux, France
5.7.3 Review of the Various Methods of Providing Stabil·
ity During Cantilever Construction
5.8
ABUTMENTS
5.8.1 Scope
5.8.2 Combined Abutment/Retaining Wall
5.8.3 Separate End Support and Retaining Wall
5.8.4 Through FiU Abutment
5.8.5 Hollow Box Abutment
5.8.6 Abutments Designed for Uplift
5.8.7 Mini-Abutment
5.9
EFFECT OF DIFFERENTIAL SETTLEMENTS ON CON­
TINUOlJS DECKS
5.9.1
5.9.2
Effect of an Assumed Pier Settlement on the
Stresses in the Superstructure
Practical Measures for Counteracting Differential
Settlements
REFERENCES
also yielding the most significant savings to proper
design concepts or refll1ecl construction methods.
The first industrial application of prestressed con·
crete was related to solving an insurmountable
problem of foundation underpinning.
225
Foundations, Piers, and Abutments
226
The transatlantic terminal built in Le Hane
Harbor in France on the English Channel was
opened for operation in 1934 to receive the new
generation of fast passenger ships between Europe
and America. Improper foundation of the rear
bays of the new building caused immediate con­
stant settlements at the rate of! in. (12.7 mm) per
momh with no foreseeable limit, except the total
ruin of the f~lCilit\·, Figure 5.1. Eugene Freyssinet
proposed a unique system of underpinning, which
was immediately accepted and implemented,
whereby prestressed concrete piles were man­
ufactured in the basement of the existing building
in successive increments and progressively driven
1)\ hydraulic jacks to reach the stable lower soil
strata. found at a depth of more than 100 ft (30.5
Ill), Figure 5.2. This example should certainly
make olle cautious against excessive optimism in
foundation design; at t he same time it exemplifies
the remarkable potential of prestressed concrete in
solving unusual problems.
In concrete bridges. often greater savings may
be expected from optimization of foundation and
pier design than fmlll the superstructure itself.
This chapter will deal with certaill specific aspects
of piers, abutments. and foundations for bridges
built in balanced cantilever. Similar concepts may
be extended to cover other construction methods
(span-by-sp<ln, inuemental launching. and so 011).
Piers with many different shapes have been used
in conjunction with cantilever construction. For
example, single piers, double piers, and moment­
resistant piers have all been used. The cantilever
segmental construction method has an important
influence and bearing on the design concept of the
structure. Resistance and elastic stability of piers
during construction require careful investigation.
Temporary piers or temporary strengthening of
permanent piers or a combination of both have
been used. However, the choice of piers that have
adequate stability without temporary aids is highly
desirable. Piers of a box section. or twin flexible
legs. either vertical or inclined, are equally satis­
facton-o
The use of full continuity in the superstructure
implies that proper steps have been taken to allow
for volume changes (shrinkage, creep and thermal
expansion) at the supports. Bridges such as the
Choisy-Ie-Roi (Section 3.2), Courbevoie (Section'
3.2), and the Chillon Viaduct (Section 3.6) show
how the use of piers with flexible legs makes it pos­
sible to achieve full deck continuity and to build
frame action between deck and piers without im­
pairing the free expallsion of the structure. The
com'el'ging pier legs used at Choisy-Ie-Roi reduce
and even cancel the amount of bending trans­
ferred to the pier foundations. Vertical parallel
legs such as t hose in the Courbevoie and Chillon
5ofLSl f d(a
-/6.00to -ZI)OO
FIGURE 5.1.
Le Ha\Te transatlantic lerminal, typical section.
6
Progressive and Span-by-Span
Construction 0.[ Segmental Bridges
6.1
INTRODt:cnON
6.1.1 Progressive Placement Method
6.1.2 Span.by.Span Method
6.2 PROGRESSIVE CAST·IN·PLACE BRIDGES
6.2.1 Approach Spans to the Bendorf Bridge, Germany
6.2.2 Ounasjoki Bridge, Finland
6.2.3 Vail Pass Bridges, U.S.A.
6.3 PROGRESSIVE PRECAST BRIDGES
6.3.1 Rombas Viaduct. France
6.3.2 Linn Cove Viaduct, U.S.A.
6.4 SPAN·BY·SPAN CAST·IN·PLACE BRIDGES
6.4.1 Kettiger Hang, Gennany
6.4.2 Krahnenberg Bridge. Germany
6.4.3 Pleichach Viaduct, Germany
6.4.4 Elztalbrucke, Germany
6.1
Introduction
Thc concepts or the progressive placel1lellt and
span·h\<·spall methods of segment;d cOllstructioll
were introduced in SectiollS l.YA <lnd \.9.3, re­
spectiw:h. rItis chapter will explore these concepts
ill grcater detail. rhcse two ll1ethods have not
lllade the cOll\entiollal cast-ill-place 011 ralsc\\ork
ll1ethod obsolete: the cOllventional method is still
applicable ami economical where site, environ­
mental, ecological, and economic considerations
permit. \Vhat these two methods do is to open up a
field where prestressed concrete structures were
hitherto !lot practical and where they now can eco­
nomicalh compete with structural steeL
The progressive placement and span-bv-span
methods are simiia'r in that construction of the
superstructure st:Jrts al onc clld and proceeds con­
tinllouslv to the other, as opposed to the balanced
cantilever mel hod where superstructure is con­
structed as counterbalancing half-span cantilevers
6.4.5 Guadiana Viaduct, Portugal
6.4.6 Loisach Bridge. Germany
6.4.7 Rheinbriicke Dusseldorf.Flehe. Germany
6.4.8 Denny Creek Bridge. U.S.A.
6.5 SPAN-BY-SPAN PRECAST BRIDGES
6.5.1 Long Key Bridge, U.S.A.
6.5.2 Seven Mile Bridge. U.S.A.
6.6 DESIGN ASPECTS OF SEGMENTAL PROGRESSIVE
CONSTRUCTION
6.6.1
6.6.2
6.6.3
General
Reactions on Piers During Construction
Tensions in Stays and DeHection Control During
Construction
6.6.4 Layout of Tendons for Progressive Construction
REFERENCES
all each side of the various piers. Also, both
methods are adaptable to either cast-in-place or
precast construction.
6.1.1
PIWGRESSIVE PLACE,HEST ;HETHOD
This method was developed to obviate the con­
struction interruption manifested in the balanced
cantilever method, where construction must pro­
ceed symmetrically on each side of the various
piers. In progressive placement. the construction
proceeds from one end of the project in continu­
ous increments to the other end; segments are
placed in successive cantilevers from the same side
of the various piers. When the superstructure
reaches a pier. permanent bearings are placed and
the superstructure is continued in the direction of
construction.
The first implementation of this method, which
used cast·in-place segments, was on the Ounasjoki
Bridge near the Arctic Circle in Finland. It was
281
282
Progressil'e and Span-by-Span Construction of Segmental Bridges
later extended to the first lise of preca:;t segments
in the ROlllbas \'iaduct in eastern France,
rhe essential ;)(h'antages of this method are as
follows:
I,
~.
:L
The operatiolls are continuolls alld are carried
oUl from that part of the structure already
constructed, Access for personnel ami mate­
riab is cOll\'ellienth' accomplished over the sur­
face of the structure alI-cad\ cOlllpleted (free
of the existing terrain). This lIla\' be of impor­
tance with regard to urban \'iaducts cantile­
\'ering o\'(~r Ilumerous obstacles,
ReactiOlls to tlIe piers are \"crlieal and 110t sub­
ject to am ullsYlIlmetrical bellding mOlllents,
Ihus ;I\'oiding the llced for telllporan bracing
during COllstruction,
Thc lIlethod is adaptable to curved stl'u('\ure
geol1lctn,
rhe following are tile disadvantages:
L
~,
~~,
it is difficult. il nOI impossihle, to utilize tillS
Illet hod ill 1 he COllst ruction of the lirst spalL
Usually the lirst span must be erected on
falsework. In sOll1e rare instances it may he
po~sible to cantilever the first span from the
ahut lIIent,
Forces imposed upon the ;;uperstructure. de­
pending 011 the method of umstruction. are
cOIllpletcly dilferent (in sign and order of
magnitude) frolll tlIose present in the struc­
ture under senice load, COllsequellth', a telll­
porary exterIJal support s\'stem is required
during ('ollstructiol1 ill order to maintain the
stresses within reasonable limits and minimize
the cost of' unprodunive temporary pre­
stressing. Faisework bents may be used (as in
tile LinIl Cove Viaduct), but the more usual
solution is that of a mobile temporary mast
and cable-stay system (Figure 1.57,). For the
progressive placement method the mast and
cable-stay system is relocated progressively
over the piers as construction advances,
In t his system the piers are subjected to a reac­
tion from the self-weight of the superstructure
approximately twice that in the final stalic ar­
rangemem of the structure. Hmvever, this is
gellerally lIot critical to the design of the piers
and foundations, as the effect of the dead load
is rarely larger than half the total load includ­
ing horizontal forces.
\Vhen cast-in-place segments are used in COIl­
jUllctioll with the progressive placemellt method,
the rate of construction is le'is than that for the bal­
anced cantilever method. in that t here is 0111", olle
locatioll of construction actiyity, That is, onl~' one
segmellt can be cast (at the en'd of the cOIllI;leted
portioll of the structure) rather than two (one at
each end of the balanced cantilevers), This slow­
ness may he minimized by the use of longer seg­
ments, hut this solution is limited b, the low resis~
I<Illce 01 the \'Ollllg concrete, On the other hand.
the lISe 01 epoxv:.-joined precast segments may
perl1lit an average rapidity of construction comp,;­
rable to that of balanced cantilner with a launch­
ing girder.
Ii.! ,2
S/JA.\'-/ll'-SP.4S ,HFIHO/)
As indicated ill Chapter I, the span-In-span.
met hod was developed to meet the need for COlI­
SI ruet ing long viaducts wit h relat jyeh short spans
such as to incorporate the advantages 01 halanced
ca lIt ile\'er COllst run iOll,
Frolll a cOlllpetiti\e ]loillt of \'jew, the capital in­
vestlllellt ill the equiplllent lor this type of (Oll­
st run ion is considerahle. I t has heen suggested I
titat olle-third of t he cost of the equiplllent be de­
pl'eciated lor a gi\'en site alld that at least four uses
would be required to achieve lull depreciation, ill­
cludillg illterest 011 the capital illvestment. H (}\\'­
ever, costly lIlodiliGitions tltat lllay be required
hecause 01 changes ill bridge widths or span limi­
tatiollS are not considered in tlte above write-oil
polin'. It would, therefore, be ad\lsahle for a COII­
tractor ilJ\'estillg ill tltis t\'pe of eqlliplllellt to con­
sider sOllie type of lIIodular plalllling so that
lIlodificatioll for future projects might be kept 10 a
lIlillinlllm, It might he possible to ha\'e a basic piece
01 equipment with illterchangeable clements.
There is. of cour,e, the potelltial of leasing this
equiplllent to others as a means of' l'etirillg the
ca pi tal illYest men!.
Wiufoh t l. 2 has categorized stepping segmel1tal
construction into four subgroups:
I,
2.
3.
4.
With-on-the ground nontravelillg formwork.
With traveling fonnwork or on-the-ground
stepping formwork.
With off-the-ground stepping formwork.
In opposite directions starting from a pier.
The first category is generally used where there
are a large number of approximately equal spans
Progressive Cast-in-Place Bridges
of a low height above existing terrain. It is gener­
allv limited to structure lengths of approximately
1000 ft (300 111) and to nonuniform span lengths
that prohibit a forming system of uniform size.
Normally in span-br-span construction the
superstructure is of constant cross section (at least
insofar as external dimensions are concerned), and
the work proceeds from one abutment to the
other. I f a large center span exists, it will be formed
first, possibly to an inflection point in the adjacent
spans. The fonmvork is allocated such that it is
used to cast the spans in the approaches proceed­
ing from the center, in both dil'ectiolls, toward the
abutments. Forms and scaffolding are disassem­
bled and reerected in an alternating sequence and
in elements that Gill be conveniently handled by a
crane.
In the second category of span-by-span con­
struction. for economical justification of equip­
ment. the total length of structure must be at least
lOOO ft (300 111), the overall cross senion constant,
the structure of low height, and the terrain
along the longitudinal axis approximately level.
\Iaximuill spall for this category is approximately
165 it (50 Ill). and a large n~u111ber of equal SIXll1S
are required to achieve repetitiveness and thus
eCOIlO1ll"':'
The falsework and for1l1s are general\v a span
length (either I he dimensioll fr0111 pier to pier or
from inflectiol1 poinl to illilection point), Figure
6.1 a The fOrInwork is hxed to the scaffolding and
travels will1 it. The bottom of the formwork is de­
signed with a hinge or cOlltinuOlls trap-door device
such that the scaffolding and forms can travel past
and dear the piers. The scaffolding is moved for­
wal d on r~llis. If a found,lIiol1 for the scaffolding,
forms, and weight of superstructure is found to be
too costlv or unsafe. a scheme may be used where
tbe rails GllT\' onlv the load of the scaffolding and
fonmvork. Once in position, the scaffolding is
supported at the piers, or at the forward pier, and
the completed structure at the rear by auxiliary
brackets: thus construction loads are transmitted to
the pier foundations.
Where conditions exist as in the previous cate­
gorv. but the structure is high with reference to the
terrain or crosses over difficult terrain or water,
the third category may be used, whereby during
the stepping and casting operations the equipment
is supported bv the piers or bv a pier and the pre­
viollsly completed portion of the structure.
Where conseclltive spans in the range of 160 to
500 ft (50 to 150 m) are contemplated and the fac­
tors mentioned above prevail, the type of con­
283
r2
i
rl
I
~~~~,
L2
Form
LI
Scaffolding at concreting position
Construction direction
, Under-carriage
Advancement of Scaffolding
3;JO
;- --17.00·
'":
Section 1-1
9,20
7,80
9,20 3,30
Hinged bottom plate
Section 2-2
FIGURE 6.1. Schemalic of procedure for movable
scaffolding, from reCerence 3 (courtesy of Zement und
Beton),
struction indicated bv the fourth category may be
considered. This system uses a gantry rig that has a
length one and one-half rimes that of the span. In
this method segments are cast ill each direction
from a pier, as ill the balanced cantilever method,
except that the form traveler and segment being
cast are supported bv the gantry. This method is
actuallv a balanced cantilever method and not a
span-by-span method of COllst ruction as defined
here.
The advantages of the span-by-span method of
construction, besides those associated with seg­
mental construction in general, pertain to the pre­
stressing steel requirements. Since the segments
are supported bv the form travelers, there are no
cantilever stresses during construction, and pre­
stress requirements are akin to those of conven<
tional construction on falsework or those for the
final condition of the structure,
62
6.2.1
Progressive Cast-in-Place Bridges
APPROACH SPANS TO THE BENDORF
BRIDGE, GERM.-1NY
As discussed in Section 2.2, the Bendorf Bridge
was constructed in two parts. The western portion
Progressive and Span-by-Span Construction of Segmental Bridges
284
Flood
o
0
166.45
44.55
-------1-­
Construction in
free cantilever
216.50
m
Construction
c
,
,
,
'\
Construction
~Phase
~,-~-,,--j sequence
I
57.50
,
m
'Phase 5 by progressive placing, segment length 4.00 m.
FIGURE 6.2. Bendorf Bridge, Part Two (East), construClion procedure, from refer­
ence 1 (courtesy of Beton- and Stahlbelonbau). Phase 5 b~ progressive placing, segment
length 4.00 m.
.
(pan one), Figure 2.9, consists of a snnmelrical
seven-span continuous girder constructed by the
cast-in-place balanced cantilever method. The
eastern portion (pan two), Figure 2.10, consists of
a lline-span continuous approach struclUre h;'l\'ing
an overall length of 1657 ft (505 111) with spans
ranging from 134.5 ft (41 m) to 308 ft (94 111).
III t he construction of the a pproach spans, Fig­
ure 6.2, the hve spans from the east abutment were
built in a rOlltine manner with the assistance of
falsework bents. The four spans over water were
C(~nstrllcted by the progressive placement method,
using cast-in-place segments and a temporary
cahle-stay arrangement to reduce the cantilever
stresses. The temporary stay system consisted of a
structural steel pylon approximately 65 ft (20 111)
high and stays composed of Dywidag bars.
6.2.2
OUXA~JOKI
BRIDGE, F!.,\'LASD
This structure is near the cit\' of Rovaniemi, Fin­
land, and crosses the Ounas River jusl above its
junction with the River Kemi near the Arctic Cir­
cle. The structural arrangement consists of two 230
ft (i0 Ill) interior spans and end spans of 164 fl (50
m), prestressed longitudinally and transversely.
The first end span and 75 ft (22.75 111) of the
second span were cast-in-place in a conventional
manner on lalsework inside a temporary wind­
shielded protective cover, Figure 6.3. Outside
temperature cluring this operation ranged from
-20 10 30°C. Subsequent progressive cantilever
constructioll was performed ,,'jth the aid of a tem­
porar\' pdon alld stan, Figure 6.4. The same'
stages were repeated in the remaining spans. The
su perstruct 11 re was cast-in-place with the assis­
tance of one form traveler, Figure 6.5. During
these stages 01 construction, for protection against
low temperatures, form traveler and form were
fully enclosed, Figure 6.5. This enclosure was insu­
lated with 4 in. (l00 mm) of fiberglass.
Hardening of the concrete took an average of 76
. hours. Temperature of the concrete was main­
tained between 35 and 45°C at mixing and between
20 and 25°C during casting, Curing inside the
form traveler enclosure was assisted bv warm-air
blowers. Concrete strength was 5000 psi (34.5
MPa). Segment length was 11.5 It (3.5 111), and it
was possible to reach a casting rate of two segments
a week.
Construction slarted in ]966 and was completed
in 1967. Table 6.1 lists the temperatures recorded
during seven months of tbe construction period.
The progressive placement method proved effec­
tive and work progressed throughout the year
even during arctic conditions.
FIGURE 6.3. Ounasjoki Bridge, temporary protective
structure (courtesy of Dyckerhoff & Widmann).
Progressive Cast-in-Place Bridges
TABLE 6.1.
285
Ounasjoki Bridge, Temperature Variations
Month
'remperature
A\eragc 0(:
.\Iaximlllll °C
.\linimul11 0(:
.\!arch
-
April
9
_.:)
0.4
+5.8
-2!1.4
+9,9
-16.8
:>Vlav
June
Julv
August
September
+5.6
+24.6
-12.2
+ 11.7
+24.9
+ 14.:)
+25.7
+3.0
+ 14.8
+28.5
+5.8
-'-8.7
-'-19.3
-4.7
-'-0.1
6.2.3
VAlL PASS BR[f)CES, C.S.A.
The Vail Pass structures are part of Interstate 1-70
ne;u' Vail, Colorado, in an environmentally sensi·
tive area. Of the 21 bridge structures in this pn~j.
ect, seventeen were designed and bid on the basis
of alternate designs (Chapter 12). In the segmental
alternative the contractor was allowed the option
to construct as cast-in.place segmental. A group of
four bridges approximately 7 miles (11.3 km)
southeast of Vail were successfully bid as cast-in·
place segmental and used the concept of progres­
sive placement.
I\\'o of these structures are contained ill a four·
span dual structure over Black Gore Creek, Figure
G.t>. The other two structures are a three-spall
FIGURE 6.4. Ounasjoki Bridge, winterprool' travel­
ing form (nmnes\ of Dn;kerholT & Widmann).
T
~,
n
-----.~~~----------------~-~-----------
FIGURE 6.5.
Ounasjoki Bridge. progressive placing scheme.
Progressive and Span-by-Span Construction of Segmental Bridges
286
747'-10·
-+--___-..:2::.:2:~S:...·-_0=-'_'----,'t
I
ft.
11....._---'-14.::6,_·-....:3=-·_'_ _
+ __.!:.'1'1~::," __ ..
, _ _ _ _-..:2::.:2"'5:...·-_0=-·_ ___
l ...
Pier 3
'I'
ft.
Pier ..
·6
(. Bridge abut. 2
II
.
TYPICAL ELEVATION
42'-0'
Ii
Bridge
Symm. obout ~
excepf os noled
2" ASvhalt (future)
"-8"
9'-6"
MID-SPAN
NEAR
TYPICAL
FIGURE 6.6.
ft.
PIER
SECTION
Vail Pass Bridges. Black Gore Creek Bridge. typical ele\·,nioll alld sectioll.
eastbound bridge and a four-span westbound
bridge. both crossing Miller Creek, Figure 6.7.
Became the structures are relatively short and
the spans small, they were constructed by the
progressive placement method with' temporary
falsework bents. The work and time required to
transport and reassemble the form travelers (as in
the balanced cantilever method) was thereby
minimized. Construction started from both abut­
ments and proceeded progressively toward the
center of each bridge. 4
For each of the two structures in the Miller
Creek Bridge, form travelers were assembled atop
30 ft (9. I m) long segments at the abutments. As
segment casting began, the side spans were sup­
ported at every second segment by a temporary
hent. Arter reaching the first pier, segment con­
strllction proceeded in normal fashion to midspan
of the easthound structure. In tbe westhound
st ruct ure, when midspan of bot h in terior spans was
reached, temporary bents were again used to com­
plete the remaining half-spans to the center pier.
After reaching the cellter of the bridge, one form
traveler of each bridge was dismantled, and the
remaining form traveler was used to cast the clo­
sure pour. In this manner the form travelers for
each bridge were assembled and dismantled only
once, as opposed to the method of assembling two
forms at each pier and dismantling upon comple­
tion of two half-span cantilevers about each pier.
For the Black Gore creek structures, to save criti­
cal construction time, both end spans of one
struclure and one end span of the other structure
were built on falsework, while the form travelers
Progressive Cast· in·Place Bridges
287
abut. 2
.J
~=-
E. B. ELEVATION
It.
It Pier
Pier 2
'3
GrO!.W1d line
W, B, ELEVATION
42'-0"
~
Bridge
I..
Symm, about
2" A~pholl
,
It.
except as noled
\'-6"
(future)
8'-0·
i'
TYPICAL
FIGURE 6.7.
Vail Pass Bridges.
~Iiller
were occupied at the Miller Creek Bridges. Upon
conlpletion of their work at :\liller Creek, the form
travelers were transported o\'er the completed end
spans of the Black Gore Creek Bridges and con-
10'-0·
9' - '3 ~/9·
SECTION
Creek Bridge. typical eb'ation and section.
struction continued in the progressive placement
manner, Figure 6.8.
Because of the limited construction time a
three-day cycle was required for segment casting.
288
Progressive and Span-by-Span Co!,struction of Segmental Bridges
Construction specifications required a concrete
strength of 3500 psi (24 MPa) at the time of post­
tensioning and 5500 psi (38 .MPa) at 28 days. Since
the time required for forming and placing ofrebar
and tendons is somewhat fixed, the only operation
that could be acljusted was the concrete curing
time. This was accomplished b,' using a special
water-reducing agent that allowed the develop­
ment of 3500 psi (24 MPa) concrete in 18 hours,
Because of lack of experience with the specific
water reducer, honeycombing was experienced in
the early stages of construction. Eventually a 2~ day
cvde was achieved.
FIGURE 6.8. Yail Pass Bridges. Black Gore Creek
Bridge, under construction (courtesy of Dr. Man-Chung
Tallg, DRC Consultants, Inc.).
ROM8A5
PLAN VIE \.1­
(0)
FIGURE 6.9.
Rombas Viaduct, plan and sections. (a) Plan. (b) Typical bridge sections.
(e) Typical segment section.
289
Progressive Precast Bridges
Coupe C
Coupe A
\___ I_IJl
"'
2.501
5.50.~
Coupe D
Coupe 8
I
I Variable
r~-
~T:""'I
.i_
_\-_--0
-3:00
I"
-----i-I-'-'
1
'I'
5.50
.,.j
- - - - - - - - I,
11
.~-.t-:-i--l-I-
LT
]
5.50
I
Var
'I'
I
Var 680 760
1~~~1
V_.!]l
12.751
1"0"" "I
:
~
8
(b)
(c)
Figure 6.9.
6.3
6.3.1
(Colltinued)
Progressive Precl1:st Bridges
ROAcfBAS VhWUCT. FRA.SCE
The Rombas Viaduct is a constant-depth super­
structure, supported on neoprene bearings, with
nine continuous spans ranginj5 from 75 ft (23
111) to 148 ft (45 111). This structure is curved in plan
witq a minimum radius of 900 ft (275 111) and of a
variable width, owing to the presence of an exit
ramp, Figure 6.9. Total length is 1073 ft (327 m),
and the viaduct has two parallel single-cell boxes.
In cross section each single-cell box is 8.2 ft (2.5 m)
deep and has a width of 36 fr (11.0 m). A <:onstruc­
tion view of the end of a segment is presented in
Figure 6.10.
Construction of this structure employed the
progressive placing of the precast segments. Tem­
porary stability was provided by a cable-stay sys­
tem, Figures 1.57 and 6.11, which advanced from
pier to pier as the construction progressed. Seg­
ments were progressively placed, starting from one
Progressive and Span-by-Span Construction of Segmental Bridges
290
FIGURE 6.10. Rombas Viaduct, end \jew of segment.
FIGURE 6.12.
Romba, Viaduct, \'jew of swhel crane.
FIGURE 6.13.
Lilln Cove Viaduct, photomolltage.
_ ...
FIGURE 6.11.
a nd mast.
Romba s Viaduct, \'leW of cable stays
abutment, by means of a swiveling hoist, Figure
6.12, advancing along the deck.
6.3.2
Lll\'l',' COVE
VIADUC1~
U.S.A.
A progressive placement scheme is being used for
the Linn Cove Viaduct on the Blue Ridge Parkway
in North Carolina, Figures 6.13 and 6.14. It is a
FIGURE 6.14.
Linn Cove Viaduct, artist's rendering.
Progressive Precast Bridges
1243 ft (378.84 Ill) eight-span continuous structure
with spans of 98.5, 163,4 at 180, 163, and 98.5 ft
(30.02,49.68, four at 54.86,49.68, and 30.02 111)
and sharp-radius curves, Figure 6.15. In cross sec­
tion it is a single-cell box ginler with the dimen­
sions indicated in Figure 6.16.
Because of the environmental sensitivity of the
area, access to some of the piers is not available.
Therefore, the piers will be constructed from the
tip of a cantilever spall, with men and equipment
291
being lowered down to construct the foundation
and piers. The piers are precast segments stacked
vertically and post-tensioned to the foundation,
Figure 6.17.
The extreme curvature of the alignment makes
the use of temporary cable stays impractical. Tem­
porary bents at midspan will be used to reduce
cantilever and torsional stresses during construc­
tion to acceptable levels. The temporary bents are
erected in the same manner as the permanent
~Pier 1
I,
o
00
-~
_ P1er 3
o
OJ
Pier 4
Pier 5
Pier 7
/
Brg. Abut. 2
FIGURE 6.15.
Linn Cove Viaduct, plan.
N)
Ie
N)
31('
-'---~---'
J
'
I.'
[1
I
"H_,i(
I
I
I
L.
(2'
¥tr7l
(­
).t;
HALF SECTION AT POST - TENSIONING BLOCK
FIGURE 6.16.
TYPICAL HALF SECTION THRU SEGMENT
Linll Con; Viaduct, typical seglllC'llt cross sectioll.
5a IXloJ! ~.
Span-by-Span Cast-in-Place Bridges
6.4
Span-by-Span Cast-in-Place Bridges
6.4.1
KETrFCER HANC, CEIV,,1ANY
The first application of the off-ground methodol­
ogy (category 3). Section 6.1.2. was in 1955 on the
Kettiger Hang structure near Andernach (Federal
Highway 9), Figure 6.19. 3 This system cOllsists of
four scaffolding trusses of slightly more than a
span length and two cantilever girders of about a
two-span length. The scaffolding trusses support
the entire concrete weight during casting. The
cantilever girders serve to transfer or advance the
scaffolding trusses to the next span to be cast. The
concrete form or mold rides with the scaffolding
trusses and is thus repeatedly reused.
Construction
bar tendons
through
segments
not shown
6.4.2
FIGURE 6.17.
293
Linfl CO\'e Viaducr, segmental pier.
piers, llsillt-i a still-leg derrick at the end of the
com pletcd Gltltilc\'ered poni4)11s of t he structure,
Figure 6.18. When the temporary bents are no
longer required, they arc dismantled and removed
bv eqllipment located Oil the cOlTlpleted portio II of
t he bridge deck.
KRAHNENBERG BRIDGE, GER1lv1ANY
A variation of the off-the-ground system was used
on the Krahnenbergbrlicke near Andernach COIl­
structed from 1961 to 1964, Figure 6.20. 1 .:1 This
structure has a length of 3609 ft (1100 111), a COll­
stant depth of 6,56 ft (2.D m), a width of 60.7 ft
(18.5), and spans of 105 ft (3~ m). The site is on a
slide-susceptible hillside, requiring difficult foun­
dations, and its cun'ed alignment follows the to­
f)()t-iraphy, all of which economically £~Ivored the
span-by-span technique.
STIFF LEG DERRICK
. PLACING PRECAST SEGMENTS
---.l_'--.l..-..I.-...i--,i.<;-..I.-..I.-..I.-.....L-.I..---L--i---J. ____ .1 _ _
:+---90'
-------~·1~~------9d=-------~
..... COMPLETED
PRECAST BOX PIER
..... FUTURE
: TEMPORARY SUPPORT
1
.'"
~~ ... f.O
FUTURE PERMANENT
' :
PRECAST BOX PIER ... !~J
,
"
,
_L
____ ...l
FIGURE 6.18.
Linn Cove Viaduct, erection scheme for progressive placement.
Cantilever
beam
Roller
bracket
Scaffolding
truss with
steel forms
I!
1~
II il
~
---~~
---.
~~~~~--~----~--~l---------~~~~~~~~~~----~~~--~~----t-----~------
L.1
I
1..---1
351,20 ........,-.---39'20----.~·--351,20~---'----39.20--------- 351,20--'-~'--351,20
!I. 00
Scaffolding truss at concreting position
~
'
.. r
2
Section 1-1
:§:
I'
~
!i,
:
~
I
~
L2
..625
/ ..,
.£:
i
~~
-
y
Transverse
adjustment
Travel
direction
"
.,
"
','
~"
-.;
Cantilever
beam
1V1
('. r"
R oller
b racket
/
•
/."
351.20-''-----351.20---~..;_~--39,20---...l.'- . - - - 3 9 , 2 0 - - - - -......~---351,20----..;,·.>--
,I'
,i
,I
Forward
l'
\------.1
39,20
51,00
Advancement of the Scaffolding truss including forms
3% slope
,I
1,aO{1 '7;20 ~,80
Section 2-2
Rear
~/ crane truck
6,125
I crane truck
i"'" -....,..
Travel
direction
;,'
Advancement of the cantilever beams
FIGURE 6.19. Kettiger Hang. schematic of the constructioll procedure,
ellce ;) (('(Junes;, or Zemell{ lIml Beton),
tWill
refer­
Exterior
scaffold
girder
Interior
scaffold
girder
(11)
m
JY
+
+
3t-3E' j:
~
J1.7S
(b)
294
IUQ
-...j.. .-- ~o.QIl
- -(c)
--J1.7S
,-...... 7ZSQ ..j
-1--- J1,7J
.
Span-by-Span Cast-in-Place Bridges
In this project four formwork supporting gird­
ers were used. Two interior girders were rigidly
connected together by transverse horizontal brac­
ing. The formwork was arranged so that the forms
hinged at the bottom and folded down to allow
passage, during advancement, past the piers, Fig­
lire 6.20a. The fOllr girders were supported on the
hexagonal piers by transverse support beams at­
tached to the pier. I n this manner the four lon­
gitudinal formwork support girders were sup­
ported on two piers, while an additional set of
transverse support beams were attached to the
forward pier. Figure 6.20b.
Latticework cantilever extensions at both ends of
the longitudinal formwork support girders ex­
tended their length to twice the span length, so that
a stable support was provided by the tral1S\erSe
StlppOri girders during advancement. The outside
girders had joints or links at the connectioll with
the cantilever latticework so that the curvature of
the strllcture could be ,lCcOlllmodated during their
adv,lt\cement. The elevatioll of the outside girders
was adjusted bv hnlralllic jacks to accommodate
superclevatioll. During the advanceillent opera­
tioll IlIe outside girders were advanced first and
then the center two girders:Figure 6.20c. When
the forward elld of the interior girders reached the
transverse supporting beams, the rear transverse
beams of Ihe previollsiv cast span were no longer
required. Thev were dismantled 1'1'0111 the pier.
These transverse beams were erected on the next
forward pier bv a crane, Figure 6.20b.
The exteriOl' formwork of the two-cell box gird­
el' was attached to the longitudinal support gird­
el's and only required adjustment for curvature.
The illterior forms of the cells wCI'e dismantled
~lI1d reasselllbled on the !Iext span after reinforce­
ment was placed in the bottom flange and webs.
FIGURE 6.20. (OPpOIile). KI'ahnenherg Bridge. sche­
matic of construction, from reference I (courtesv of lhe
American Concrete Institute), (a) Cross section. (b)
Formwork equipment in working position. (c) I: Work­
ing position: l'einforcing, and concreting on formwork
equipment: installing the supporting constl'Uction on the
next following pier bv means of derrick and straight-line
trolley. II: After concreting and prestressing: lowering
of equipment; opening of formwork Haps; shifting for­
ward of outer girders; dismantling of the first rear sup­
porting girder by straight-line trolley; intermediate stor­
age at center pier. Ill: Partial pony-roughing of center
girder; dismantling and placing in intermediate for stor­
age of second rear girder. IV: Final shifting forward of
cetHer girders: jacking up of equipment; closing of
formwork Haps; new working position.
295
Average casting rate was 706 ft:l per hr (20 m:l).
FOllrteen days was required for conslruction
a
span.
or
6.4.3
PLEICHACH VIADUCT, GER,HANY
1n 1963 construction started on the 1148 ft (350 m)
long Pleichach Viaduct 1.3 carrying a federal high­
way between Wurzburg and Fulda; it was the first
use of the span-by-span technique for a dual
structure, Figure 6.21. Span length is 11 9 ft (36.25
Rear crane truck
Forward crane truck
Scaffolding girder at concreting position
Advancement of the scaffolding girder including forms
Construction joint
Advancement of the scaffolding and cantilever girders
R-Scaffolding
girder and forms
RV-Scaffolding
and
can tilever girder
'''.50~
Cross section
FIGURE 6.21. Pleichach Viaduct, schematic of the
construction procedure, from reference 3 (courtesy of
Zement und Beton).
296
PrQgressitle and Span-by-Span CQ7].structiQn Qf Segmental Bridges
m), with each two-cell box girder having a width of
47.2 ft (14.4 m) and a depth of 7.2 ft (2.2 m). The
superstructure construction equipment was
erected behind an abutment in a position to con­
struct one superstructure. Upon reaching the op­
posite abutment, the equipment was shifted later­
alh' for the return trip to construct the other
superstructure. Because of the narrowness, only
one longitudinal support girder was required, as
opposed to the two girders required for the
Krahnenberg Bridge. This girder is slightly longer
than twice the span length. The two outside girders
are approximately one span length.
The outside girders were advanced simultane­
ously by a carrier mweling at the front of the cen­
tral girder and at the rear by carriers running on
the deck of the previously completed section.
Durillg concreling, the two outside girders are
supported Oil brackets at the forward pier and sus­
pended from the completed portion of the
superstructure. The center girder, relieved of the
load of the two outside girders, is then advanced
one span and again connected to the outside gird­
ers by the hinged bottom formwork, thus func­
tioning as an auxiliary support girder. This se­
quence of operations is commonly referred to as
the "slide-rule principle."
The piers have a width of 16.4 ft (5 m) and have
an opening at the top to allow passage of the cen­
tral support girder, Figure 6.21. The width of the
pier is determined by the need for sufficient bear­
ing area lor the bearings and clearance for the
central support girder. \Vhether the central open­
ing at the top of the pier should be concreted in is
one of aesthetics.
0.4.4
ELZTALBRUCKE, GERMANY
The EI7_talbrucke,5.6 Figure 6.22, was constructed
in 1965 at Eifel, West Germany, approximatelv
18.6 miles (30 km) west of Koblenz. I ~ crosses the
deep valley of the Elz River with a total structure
length of 1244 ft (379.3 m), Figure 6.23. The
superstructure has a width of 98.4 ft (30 m) and is
supported on a single row of octagonal piers up to
328 ft (l00 m) in height, Figure 6.24. Owing to the
height of the valley, conventional construction on
falsework would have been economically prohibi­
tive. Therefore, a span-by-span system of self­
supporting traveling scaffolding was used, Figure
1.53.
The Autobahn between Montabauer and Trier,
which had been in planning before World War II,
FIGURE 6.22. Elztalbriicke, view of completed
structure (courtesy of Dip!. lng. Manfred Bockel).
had to cross two large natural obstacles, the Rhine
River north of Koblenz (see the Bendorf Bridge,
Section 2.2) and the Elz Valle\'. In 1962 tenders
were called for on the Ell, Valley structure. Bidders
were provided with the grade requirements, di­
mensions for a single or a dual structure, the loca­
tion of the abutments, and the foundation condi­
tions.
A consortium of Dyckerhoff & Widmann AG,
Wayss & Freytag KG, and Siemens-Bauunion
GmbH investigated four possible prestressed con­
crete construction possibilities 5 :
1.
A three-span variable depth structUre similar
to the Bendorf Bridge
2.
3.
4.
A six-span constant-depth structure
A frame bridge
A nine-span "mushroom" construction with a
center row of piers
These four schemes were proposed, as were a large
number of different ones in both steel and con­
crete by other firms. The successful low bid was for
scheme 4 above. The nine-span "mushroom" con­
struction was approximately 4'7( less costly than an
orthotropic-deck, three-span continuous steel
girder and 7% less costly than a prestressed con­
crete girder bridge of six spans. 6
The Elztalbrucke, extending the methodology
used earlier for primarily low-level urban viaducts,
was the first application of the "mushroom" cross
section for a high-level structure crossing a deep
valley. Previously, this type of construction, be­
cause of its short, stiff piers, required a number of
expansion joints in the deck to accommodate
thermal forces, elastic shortening, creep, and
shrinkage. In this structure, owing to the flexibility
of the tall piers, only one expansion joint was used,
Koblenz
east abutment
JI8,65f A
318,910
r:
B
E
0
f
Jcl,m
JIS,.07
I!!!I
..w~ '~ W
II
7,00
... ' "
Iii
lii!1
IIl,i
,,[
Trier
west abutment
32],969
ji'
;11
III
I
Ii
I
/Ii
II
/11
'~~
illJ) -
ro
~
en
1M,"
7,00
~5IJ
7,5IJ
III
"
Ii
E
MO -SL,85,.0
Iii
1
ZJ!J,8J
7,00
m,m
I
'I
Ii!
D&W rock anchors
Jc2,',7f)
Iii
III
__
m,zo v
H
Ii
,I
'" ,j~1/)
II
Ii
~ Ii
5,50
7,00
i
.,,5LC'~91
7,50
i,5{i
Longitudinal cross section
(11)
30 cm stone
facing
B
c
o
F
[
fl
H
Plan
(b)
FIGURE 6.23. Elztalbriicke,
(courtesy of Der Hauingenieur).
N)
<.0
..:r
cross seCIlOll a nd plan, frolll Ie ference 5
Longitudinal cros~ section. (b) Plan.
I
K
298
Progressive and Span-by-Span Construction of Segmental Bridges
in the center spall. This joint is located 38 ft (l1.6
111) from pier E. The superstructure is l11onolithi­
calh' connected at all piers and the ahutments.
At the center of each span is a 43 It (13d 111)
long, lIl<lssi\e fiat plate, which in cross section has a
thickness \'arying from the centerline (crown oj
road\\';}\) of
in. (650 mm) to 17~ in. (450111111) at
the outside edges. The "mushroom" ponion or the
span \'aries in thickness, trans\-ersely and lon­
gitudinally, to 8 It· (2.45 m) at the pier. The
superstruclllre is prestressed longitudinally ·and
transversely.
The octagonal piers ha\'{~. ill cross senion, exter­
nal dimensiolls of 15.75 by 19 It (4.R bY 5.H 111) witii
a wall thickness of I H to I in. (300 to 350 111m).
An)' gi\'en pier has a constallt cross section lor its
entire height. The percentage of' \'(Ttical reill­
lorcel11elll. with a cOllcrete cover on the outel' aJl(1
interior faces of' 1.5 ill. (40 Illlll). \aries froJll O.H to
1.2 tlc or the gross cOllcrete area. Piers were (,011'­
strllcted by slip-forming. The eight pier shafts
were COllst ructcd in Se\'ell months. The tallest pier,
;) 11.6 rt (95 Ill) ill height. was slip-forllled and cast
at a rate of ahout 2G It (1'1 1lI) per day and thus J'C­
quired 12 days to constmcl. The top 4 n (1.2 III)
portioJl of the pier was cast with the superstructure
by the trawling scallolding. On the top or the slip­
formed pier lour 7.2 h (2.2 m) high pedestals were
cast to pro\'ide tlte support for the caJltile\'er gir­
der i'rom the traveling scaffolding, Figure 6.25:"
The tr,ivelillg sc:tlfolding was asselllhled at
abutment A alter c01Jlpletion of the ai>U1l11CJlt and
the hall-mushroolJl pndectil1g therefrom. This
101'111 traveler, Figure 6.26, aCCOIl1IJ1O(\ales a lull­
widt h span-lengt h segment of 12:i It (:i7.5 Ill).
Alter the hrst span. two weeks were required to
complete <t superstructure spall. Tbe first opera-
FIGURE 6.24. Elztalbrucke, cross section at pier E,
from reference 5 (courtesy of Der Bauingenieur).
FIGURE 6.25. ElztalbrLicke, construction \'iew (cour­
tesy of Dip!. lng. Manfred Bockel).
Side longitudinal girder
Center longitudinal
girder
Side
support
bearing
Upper catwalk
Pier
Lower auxiliary
scaffold
Travel direction
J75oo-+----------J7500
---------+4o'-~+-------J7500
----
Longitudinal cross section
(a)
Center longitudinal
girder
Side longitudinal
girder
Plan
(b)
Concreting sequence
!II
011
---- 8Z50
(II)
'5::00
Hanger
-- IOOIJI)
,Formwork at
concreting position
~
T /
~~~zt~~~==~~~~~
\>!I---
Formwork at
concreting position
traveling position
Section A-B
position
Scaffolding after
advancement
Section C{)
(d)
(c)
FIGURE 6.26. Elltalbrucke, form traveler, from reference 5 (courtesy of Der
Bauingenieur), (a) Longitudinal cross section. (b) Plan. (e) Section A-B. (Ii) Section C-D.
299
300
Progressive and Span-by.Span C-vnstruction of Segmental Bridges
tion was to cast a 42.65 ft (13 Ill) wide center por­
tion of the bridge. After hardening and initial
stressing, the two outside edges, each 27 ft (8.25 m)
wiele, were cast. Subsequently the form traveler
was advanced to cast the next span. 5
As mentioned previously, an expansion joint is
located in the center span. During construction this
joint was "locked" until construction reached pier
G; then the joint was released. 5
During concreting the forms are suspended by
steel bars, and during advancement the forms are
carried by the bottom arm of the transverse can­
tilevered steel members. The form traveler, Figure
6.26, essentially consists of two approximately] 41
ft (43 m) long longitudinal girders and eight trans­
verse frames in a "e" configuration which sur­
rounds the deck construction. The tTansverse
frames may be prm'ided with a covering to protect
the workmen and the construction from the
weather. At the forward end an approximately 72
ft (22 m) long cantilever beam, located on the cen­
tcrline. is projected to the next pier for support.
6.4.5
GUADIASA VIADUCT, PORTUGAL
This structure is located on national route 260
crossing the Guadiana River between Beja and
Serpa, Portugal. The \'iaduct has a total length of
1115 ft (340 111) and consists of 197 ft (60 m) spans
except for the river spans, which are] 64 ft (50 m).
Trans\'ersely, the superstructure is 53.8 ft (16.4 m)
in width composed of two single-cell box girders.
Each box girder is 19.35 ft (5.9 m) wide, with the
depth varying from 6.5 ft (2.0 m) at midspan to 9.8
ft (3.0 m) at t.he piers. After construction of the box
girders. a longitudinal centerline closure is poured
and cantilevered sidewalks are constructed.
The superstructure is constructed by the span­
by-span method. from inflection point to inflection
point, by an overhead self.launching form carrier,
Figure 6.27. The form carrier consists of 279 ft (85
m) long trusses of a depth varying from 9.8 It (;3.0
m) to 16.4 ft (5.0 m). Forms for concreting the
superstructure are supported by two series of sus­
penders. One set pierces the concrete flanges and
r End traveler support
Forward support --;
..r:----.c--~--:if\:'---:7K-J'l\Tif -_-7K-I'r':---/,,"-7K"'--.....j,~
/
Rear support
I
3rd Phase
52.00
60.00
~,-+
Elevation
(a)
Typical cross section
(e)
Section at forward support-forms open
(b)
FIGURE 6,27. Guadiana Viaduct, elevation and sections of form carrier. (a) Elevation.
(b) Section at forward support-forms open. (e) Typical cross section.
Span-by-Span Cast-in-Place Bridges
is 'Iocated inside t he box cell. The other set is ar­
ranged outside the box and supports the forms
when stripped and traveling past the piers in an
open position, Figure 6.27.
During concreting of the superstructure the
form carrier is supported on the forward pier by
an arrangement of a telescoping tubular cross
frame, at the rear; it is supported on the
superstructure at a location 26 ft (8.0 m) forward
of the rear pier. When the form carrier is being
launched forward, it moves over a support at the
tip of the completed superstructure cantilever
(near the inflection point), and its rear support
rides on the surface of the completed superstruc­
ture. The form carrier (including all equipment)
weighs 209 tons (190 mt).
301
Box girder
T-beam
):).50
:2i_2,5C-;
::
Loisachbrucke, cross sections, from
(courtesy of Dyckerhoff & \Vidrnann).
FIGURE 6.29.
6.·/,()
LO/S.1ClI BRIDGE. GERMA,VY
The federal autobahn between Munich and Lin­
dau has an alignment that transverses the Mur­
nauer swamp area near Ohlstadt and thus crosses
the Loisach River and the old federal highway B-2
(Olvmpiastrasse). Figure 6.28. Because of flooding
and poor soil conditions an embankment was not
possible, alld a decision was lllade requiring a dual
viaduct bridge st ructu re wit h a IOtallength of 4314
It (1315 Ill).'
The 2:~2.H ft (70.96 111) lIlaill span crossing Ihe
Loisach River is a variable-depth single-cell box
girder constructed by the free cantilever method.
Depl h or the box ),{irder varies from 9.84 ft (:>.0 111)
to 5.58 ft (1.7 m), Figure 6.29. '['he approach spalls
are of a T-beam cross senion, Figure 6.29, COIl­
structed by the span-by-span method with the forlll
carriers rUllllillg below the superstructure. Figure
6.~30 is a longitudinal section of the bridge within
the area of the approach spans. showillg the form
carrier running below the level of the top slab..
ure 6.31 shows the form traveler in action.
reference
1:1
The dual structure has a total width of 100 ft
(30.5 1l1). Figure 6.29, and each half is supported
Oil two circular piers, excepting the Loisach spall
which is supported Oil wall piers. In the total
lellgth, the dual structures are subdivided illto
three sections by two transverse joints, Figure 6.28.
III plan the structure has a radius of 4265 h (1300
m) at the .vlunich end, allli the curvature reverses
at the Loisach with a radius of 6562 ft (2000 m).H
The completed structure is showll in Figure 6.32.
The circular piers arc 4 ft (1.2 III) ill diameter
and arc supported 011 20 in. (500 mm) driven piles
with an allowable load capacity of 176 tons (160
lIlt). Pile depThs van' frolIl 42 to 72 ft (1:3 to 22 Ill).
A total of 1182 piles were driven for a total length
of piling of 63,650 ft (19.400 m), with an average
length of pile of 53.8 h (16.4 m). Load capacity of
the piles was deterIIlined from eleven load tests
taken to 265 tons (240 mt).
Because of the poor soil conditions ami
gnmlld-water pressure, the substructure was COIl-
Box
FIGURE 6.28. Loisachbriicke, layout and undersiele view of bridge. from reference 1:1
(COllrtesy of Dyckerhoff & Widmann).
302
Progressive and Span-b),-Span
Co~struction
of Segmental Bridges
FIGURE 6.30. Loi~achbrucke, longitudinal and cross section showing form tr;l\-eler
(couneS\' of Dip!. lng. Manfred Bockel).
-
FIGURE 6.31.
l.oisachbriicke, \'iew of form traveler
ill aClioll (courtes\ of Dip!. lllg. Manfred Bockel).
quired at midspan. The radius and superelevation
in a support length were held constant. Superele­
\'ation varies from·+5.5 to -4%. For a normal span
88:i0 ft3 (250 m 3) of concrete were placed in nine
hours.R
Becallse of the tight time schedule, work was
continued through the winter months in defiance
of the extreme harsh weather conditions in the
Loisach Valle\'. A weather enclosure was mounted
OIl the form traveler and heated b\' warlll-air blow­
ers. In t his enclosure t he reinforcement and pre'­
heated concrete was placed. In addition, the fresh
concrete was protected by heal mats. In this man­
lier the work could proceed up to an outside tem­
peratllre of 5°F ( 15°C). Construction cycle per
span was gradually reduced, after f~lllJiliarization,
from all original 14 days to se\'en days. Following
completioll of the western roadway up to the
Loisach the form traveler was transfened to the
eastern roadway for the return trip to the Munich
abutmellt. All 38 spans on the :'vlunich side were
completed hy the elld of February 1972, saving
lline weeks in the construction schedule.
On the Garmisch side of the Loisach the movable
scaffold s\'stem cOllsisted of four principal girders
292 ft (89 111) in length and 9.8 ft (3.0 111) deep,
Figure 6.:i3. Superelev<ition varies from +4 to
-5.5% .
FIGURE 6.32. Loisachbrucke, view of completed
structure (courtesy or Dip!. lng. ,Manfred Bockel).
stnKted in pits enclosed by sheet piling. The round
piers \',II'Y in height from 9.8 to 23 ft (3 to 7 m).
Because of the delay in pile driving, resulting from
the soil conditions, the foundation completion was
delayed jmll1 October 1970 to April 1971.
The 73 T-heam spans were constructed with two
span-by-span form travelers whose operations
were synchronized. On the :'vfunich side of the
Loisach four 223 ft (68 m) long and 4.26 ft (1.30 m)
high principal form support girders are supported
in the 100 ft (31 m) spans on cross beams at each
pier, which in turn are supported off the pile caps.
For the longer spans an auxiliary support was re­
Because of the dela\' ill the pile driving, the first
span was started in Decem her 1970 with a 12-week
delav. The last approach span on the left of the
Garmisch side was completed in A ugust of 1971.
The traveler was then transferred to the other
roadway for the return trip and all 35 bridge spans
were completed b\' March 1972. By a gradual re­
duction of the work cycle from ]4 days to seven
days, nine weeks were saved in the construction
schedule. Not only was the loss of time resulting
from the foundation work made up, but a time ad­
vantage was attained.
The four box girder spans (two in each dual
structure) on either side of the principal span over
the Loisach were cast on stationary falsework. Aux­
iliary cross beams to support the falsework girder
were supported on driven piles. The two main
1
Span-by-Span Cast-in-Place Bridges
303
ers were transferred to the opposite ()Ier for the
remaining seven segments. H
After a construction time o/" approximately :W
months the bridge was completed in 1972, shortly
before beginning of the Olympic Games.
6.4.7
FIGURE 6.33. Loisachbl'licke, cross section of mo\'­
ahlc scaffold svstCll1. from reference H (courtesy of
J)vckerllOll& Widlll<lnn).
spalls of ~:~~.H ft (70.96 ttl) were collstructed by the
free cantilen~r method. Thirteen segments of 16.4
ft (5 ttl) were required: six segments \vere cast
from one pier and then the cantilever form travel­
RHEISBRt'CKf; f)L'SSEU)ORF·HEHE,
GER:"U,Vr
This is an asymmetric cable-staved bridge with an
inverted concrete Y-pvlon, Figures 6.34 through
6.37. The overall length from abutment to abut­
ment is 3764 ft (1147.25 m). The Rhine River span
is 1205 ft (367.25 111) long and is a rectangular
three-cell steel box girder with outriggers to sup­
port a 135 ft (41 111) wide orthotropic deck, Figures
6.36 and 6.37. At the pylon there is a tramition
from the steel box girder to prestressed concrete
box girders, which are used for the thirteen 197ft
(GO til) spans in the approach viaduct. The struc­
ture is continuous throughout ils entire length,
having expansioll joints on I: at the abutments.
The approach viaduct has from pier 9 up to pier
U, Figure 6.37, a five-cell box girder cross section
with a width of 96.8 It (29.5 m) and a depth of 12.5
ft (3.8 m). This heavy cross section, Figure 6.36,
resists the anchorage forces from the cable stays.
For the balance of the viaduct length from abut­
ment to pier 9 the cross section consists of two
single-cell boxes, a continuation of the exterior
cells of the five-cell box girder cross section. How­
ever, the interior webs of each box are of less
FIGURE 6.34. Rheinbriicke Dusseldorf-FIche, artist's rendering (courtesy of Dyck­
erhoff & Widmann).
Progressive and Span-by-Span Cgnstruction of Segmental Bridges
304
\
.
-1.
::::::
a.
.
FIGURE 6.35.
_-~_
\>.
-=
Rheinbrucke Dusseldorf-Flehe, VIew
from construction end of approach viaduct looking to­
ward the pylon under cOllstruction.
thickness than that of the five-cell cross section.
The width of each box then becomes a constant 23
ft (7.0 m) outside-to-outside of webs. A diaphragm
occurs at each pier.
'rhe approach spans were constructed segmen­
tally by the span-by-span method with construction
joints at approximately the one-fifth point of the
span. As described in Section 6.1.2, the method
used here employed movable falsework, Figures
1.54 and 6.38: supported from the ground. The
197 rt (60 m) spans were poured in place in one
unit from construction joint to construction joint.
This required continuous placement of as much as
3200 cubic yards (2500 m 3 ) of concrete. After each
section was cast in place and reached sufficient
strength, the prestress tendons were stressed and
the falsework was moved forward to repeat the
cycle.
6.4.8
DENNY CREEK BRIDGE, U.S.A.
The Denny Creek Bridge is the first implementa­
tion of the span-by-span method of constr'uction in
the United States. It is located a few miles west of
Snoqualmie Pass in the state of Washington and
will carry the 1-90 westbound traffic down off the
pass. It is a three-lane, 20-span, prestressed con­
crete box girder design with a total length of 3620
ft (1103 m) on a 6% grade, Figure 6.39. 'rhe con­
tractor. Hensel Phelps Construction Company,
elected a construction method similar to those used
in many German and Swiss designs where the area
is environmentallv sensitive.
Because of th~ ecological and environmental
sensitivity of the' project site, construction of the
piers was carried out under extreme space restric­
tions. The contractor was allowed a narrow access
road for the full length 01 the project and addi­
tional work and storage area at each pieL 9
The 19 pier shal'ts have a hollow rectangular
cross section with exterior dimensions of 16 by 1()
it (4.R8 [)\ 3.05 Ill), a wall thickness of 2 it (0.61 m),
and heiRhts rarq.~inR from 35 to 160 ft (10.7 to 48.8
m), Figure 6.40. Twelve piers are supported on rec­
tangular footings. The other seven piers are sup·
ported on pier shafts sun k through talus and till
and kned illto solid bed rock, Figure 6.41. Pier­
shaft diameter is 12 it (3.66 m) with a maximum
depth of shaft below the terrain of 80 ft (24.38 m).
The superstructure was constructed in three
stages, Figure 6.42. In the fil-st stage, bottom flange
and webs were constructed from a 330 it (100 m)
long movable launc,hing truss, Figure 6.43. The
twO trusses used for constructing the "U" portion
of the box section rested on landing wings at the
piers, Figures 6.44 and 6.45, as the launching truss
moved up the valley, sliding from pier top 10 pier
top. The construction schedule called for one span
every two weeks. The entire scaffold system was
supported on six jacks to adjust for proper align­
ment, two jacks at the rear of the span or initial
pier and four jacks at the advance section or next
pier.
The launching truss was designed to support the
outside steel forms of the box section, Figure 6.46,
and to facilitate removal of the inside forms,9 Fig­
ure 6.42. Track-mounted cranes installed at the
top of t.he truss frame lifted and moved the inside
forms from the web, hanging them on the truss so
that they were moved forward with the advance­
ment of the launching truss. Figure 6.47 is an
interior view of the working area between trusses.
Visible are the overhead track for the 15 ton (13.6
mt) cranes located near each web. Also visible are
the cable hangars from the roof frame for the
bottom slab support during casting.
The steel trapezoidal box form used for con·
J~
17U\t'lh,J"
Steel Superstructure
i
~.;::::::::E~----_________ __ __ __ __ __ _
: ~1ICll mo
~
~
~
•
P)-Ion
~
41"'"
"-.,,.,:::::_-------:-:::~~ --". ..
! m.o~~-r--~-~~."!'~""'ICIf~
,,,
"
I
mo
" :t' ':
--if
,~;::"""'- ~ I
-~
1I.1SO
pso
I
"")
lOt) ,
-
~SIl'~:
m
iT7~aDl~r
T:lOoo
I
~
-
-'
~
-
~
I
I
Reinforced Concrete Superstructure
Heavy Section
.".
~
It. "" .k'...,
llhC!J
0
·
11<>;1
'lj
s"a
°0
[8..1.
~:I ~i
.."" :,,,,,,,.~!.Co-
L
IJ!JI t!
I r;ao I
"""
pax!
'l7'5
~
.~ ~ 4
-
11*
'""
I PSO
Reinforced Concrete Supeniitructure
Normal Section
.0
[OD~r
.., :
..... !
l!!9''It)Q
dt!ll
I ,..
I
j
mo
MiG
mo
"lQQ
FIGURE 6.36.
<.>0
o
Vl
Rheinbriicke
Dl!ssddorl~Flchc,
de\atioll of
and cross sections.
'"OS I
D°
.100!!!
I.
w
o
O"J
Eleval i ""
lrhWl
10
"
12
13
rrhWl
13.60.0, '80.0
367.25
151!
110.25
Plan
\
\'"1;
\
~
Bearing Condilions
1+1
+
+
+
+
+
+
+
+
FIGURE 6.37.
+
+
+
+
+ Unrestrained
:: Wind bearing
+
+
~
Rhei1lhriid.e Dusseldorf-Fiche, plall and eie\";\tion.
+ Unrestrained
Span-by-Span Cast-in-Place Bridges
FIGURE 6.38.
view 0[' girder.
Rheinbrucke
Dusseldorf-Fiehe,
end
~truC!ion was insulated with styrofoam, Figure
G.48, and had heat cables installed (<Inuated if
need be) to help llIailltain the temperature and
rate of cure. Also, heat blankets were available to
go ()\er the senion to reduce heat loss and main­
tain a COllstant temperature ill cold weather.
COllcrete was hatched hOJll a plant erected near
the west alHltl1lellt lIslng the highway rig·ht-or-wav.
The cOl1traC1or lIsed three H C.lI \<1 (Ii. I Ill;]) ready-
307
mix trucks for mixing the concrete, which was then
pumped to the proper location. Superstructure
pours were about 300 cu yd (229.4 ma) and took
about nine hours, using two concrete pumps and
the track-mounted cranes installed in the truss
frame. Concrete strength required was 5000 psi
(34.47 YfPa). The contractor obtained 3500 psi
(24.13 :\IPa) in three days using tin. (19 mill)
aggregate. The 28-day strength ranged from 6100
to 6600 psi (42.06 to 45.5l MPa).
In stage two the top Hange between the webs was
placed. \-1etal forms, Figure 6.49, were supported
from the bortom flange and webs, Figure 6.42.9
In stage three the two top flange cantilevers were
placed, Figure 6.42, bv a movable GIITiage that
rode on top of the box cast ill stage two, Figure
6.42. Upon completion of stage three, the trans­
verse prestressing of the top (lange was accolll­
plished. The completed section is 52 ft (15.08 Ill)
wide, providing three traffic lanes.
The Washingtoll DOT sponsored the design.
Three alternatives were prepared for bidding
purposes. One was an in-house state design; tile
ot ber two were prepared bv olltside consultants.
The Dyckerhofl & Widmanll design proved to be
;.1,1
-,,
\. ..t ' :"~ ~ .. rl\.,.,.t-""­
, '",,~ ,~~1.1-: to
.•
l
.,
I
,
1,­
""
"l.
~\,
"·,11­
'.
~l,
' ......."
'-I
5'
tlJL
FIGURE 6.39.
Denny
Creek
Bridge,
perspecri\e sketch.
Progressive and Span-by-Span
308
~onstruction
FIGURE 6.40. Denny Creek BI-irige, new of piers
under construction (courtesy of J. L Vatshell, Wash­
ington DOT).
the most economical. VSL Corporation was the
subcontl-actor proyiding the prestressing expertise.
6.5
Span-by-Span Precast Bridges
0.5.1
LOSG KEY BRIDGE, U ..S.A.
Long Key Bridge in the Florida Keys carries U.S.
Highway I across Long Key south to Conch Key.
The existing bridge consists of 215 reinforced con­
crete arch spans, ranging in length from 43 to 59 ft
(\3.1 10 18 m) for a total bridge length of 11,960 ft
(3645 Ill).
The new bridge, presently under construction, is
50 ft (15.2 111) between centerlines and just north
and parallel to the existing structure. It is a precast
segmental box girder constructed by the span-by­
span method and consisting of 101 spans of 118 ft
(36 m) and end spans of 113 ft (34.4 m'} for a total
length of 12,144 ft (3701 m). The roadway width
between barrier curbs is 36 ft (11 m), Figure 6.50,
to accommodate a 12 ft (3.66 m) roadway and a 6 ft
(1.83 Ill) ~houlder in each direction. Figure 6.51 is
of Segmental Bridges
FIGURE 6.41.
types.
Delli1\" Creek Bridge, substructure
an artist's rendering showing the precast V -piers
with the 7 ft (2m) deep box girder segments.
In the preliminary design stage three methods of
segmelltal construction were considered: balanced
cantilever, span-by-span, and progressive place­
ment. The progressive placement method was dis­
carded because it was felt (at the time) to be too
new {or acceptance in U.S. practice. It was later
introduced on the Linn Cove Viaduct in :\orth
Carolina (see Section 6.3.2).
This is the first use of a precast span-by-span
method in the United States. The segments are
transported from the casting yard to their location
in the structure by barge. The segments are then
placed with a barge crane on an erection truss,
which is supported by a steel grillage at the V-piers.
Each span has a 6 in. closure pour after all the
segments have been placed on the erection truss
and properly aligned. The essential operations are
indicated in Figure 6.52.
Segment weight is approximately 65 tons (59
mt). Each segment is placed on the erection truss
on a three-point support and brought into its final
position. It takes approximately four to six hours
Schematic of movable scaffolding
Stripped position ..,
I
I
Overhead
dollies
Stage two
o...
70'
Jacks for grade,
Truss jacks
superelevation and camber
'. ---Jacks
Rollers and jacks
Stage one
Stage three
FIGURE 6.42. Denm Creek Bridge. schematic of construction stages. from reference 9
(counes\ of the Portland Cement Association).
FIGURE 6.43.
ing truss.
Dennv Creek Bridge, view of launch­
FIGURE 6.44. Denny Creek Bridge, view of landing
wings at piers (courtesv of J. L Vatshell, Washington
DOT).
309
310
Pro.gressive and Span-by-Span Co.nstructio.n o.f Segmental Bridges
FIGURE 6.46. Denn\ Cn'ck Bridg-e. \ in,' of' outside
steel fonm (courtesy of J. L Yatshell. Washington
DOn.
FIGURE 6.45. Denny Creek Bridge, close-up vic\\' of
landing wing (counes\, of J. L. Vatshe11. Washingto1l
DOT).
to place the seglllents required for one spall. The
contractor has placed as malJl' as three spans per
week for a t(>lal or :154 ft (lOS Ill) of completed
superstructure per week and has <l\'eraged 2.25
spalls per week.
Allother major deviation from United States
practice ill this pn~ect was the use of external pre­
stressing tendons (located inside the box girder
cell). This requires that the tendons be considered
as ullbonded for ultimate-strength analysis. Plac­
ing the tendons inside the box girder void allows
the web thickness to be minimized. Tendon
geometry is controlled by deviation blocks cast
mOllolithically with the segments at the proper lo­
cation in the span, Figure 6.53. These blocks per­
form the same function as hold-down devices in a
pretensioning bed. The tendon ducts between de­
viation blocks or anchorage locations or both are
composed of polyethylene pipe, which is then
grout-injected upon completion of stressing
operations-a corrosion protection system similar
to that used for the cable stays on some cable-stay
bridges. HI.11
FIGURE 6.47. Denll\ Creek Bridge, \'iew of interior
working area between trusses (courtes\ of Herb Schell.
FH\\,A Region 10).
"-'-- 1:11·;4.
FIGURE 6.48. Denny Creek Bridge, insulation on
exterior steel forms with installed heat cables (courtesy
of Herb Schell, FH\\,A Region 10).
Span.by-SpGn Precast Bridges
.
311
-,;.
FIGURE 6.51.
FIGURE 6.49. Denl1v Creek Bridge, \"in\ of l11l'\al
form wied /()I' stage-two construnion (courtes\ or J L.
Valshell, Washington DOT),
Section at pier
FIGURE 6.50.
Long Kev Bridge. artist".; rendering,
The external tendollS overlap at the pier seg­
ment to develop continuity, The bridge is cotltitlll­
OllS betweetl expansion joims for eight spans, 94-l
t't (2HH \11). After the closure pOllr reaches the re­
quired strength, the post-tensioning is accol1l­
plished and the span is complete. A :30 in. (7liO
mIll) diameter waterline is installed inside the void
of the box girder. The erection tl'llSS is then low­
ered and llloved awa\, from the completed span,
l'he erection truss is handled at a one-point
pick-up location bv a C>shaped lifting hook, Figure
6.5~, The truss is sllpported against the barge
crane and lIloved pamllel to the Ilew bridge ulltil it
Section at midspan
Long Ke\' Bridge, typical cross section of superstructure,
312
Progressive and Span-by-Span c..onstruction of Segmental Bridges
The span by span erection concept utilizes a temporary steel assembly truss
in conjunction with a barge mounted crane as shown. The steel truss
spanning between the piers is equipped with post-tensioning tendons along
the bottom chord to facilitate adjustments for deflectiOns and lowering the
truss upon completion of the span.
Iii
I
FIGURE 6.52.
Long Key Bridge, span-by-span erection scheme.
reaches the position for a new span, and the cycle is
repealed.
6.5.2
SEVEN AlILE BRIDGE, U.S.A.
The Seven Mile Bridge, Figure 6.54, in the Florida
Keys carries U.S. Highway 1 across Seven Mile
Channel and Moser Channel from Knights Key
west and southwest across Pigeon Key to Little
Duck Key.
The existing structure consists of 209 masonry
arch spans, 300 spans of steel girders resting on
masonry piers, and a swing span over Moser
Channel. The spans range in length from 42 ft
in. (I3 m) to 47 ft 4t in. (14.4 m) for the masonry
arches and from 59 ft 9 in. (18.2 m) to 80 ft (24.4
m) for the steel girders resting on masonry piers,
which along with the 256 ft 10 in. (78.3 m) swing
span, produce a total bridge length of 35,716 ft 3
in. (10,886 m).
Span-by-Span Precast Bridges
313
DETAIL 1
$CoiJlr'
PERSPEC TlVE
I·"/~O"
VIEw
DETAIL
SuII!"
2
'''-I~lr
ELEVATION
FIGURE 6.53.
out. ­
Long Key Bridge, typical tendon lay­
'.
FIGURE 6.54.
Seven Mile Bridge, anist's rendering.
The new bridge, presently under construction, is
located to the south of the existing bridge. It is a
precast segmental box girder constructed by the
span-by-span method with 264 spans at 135 ft
(41.15 m), a west-end span of 81 ft
in. (24.88 m),
and an east-end span of 141 ft 9 in. (43.2 m) for a
in. (l0,931 m). The
total length of 35,863 ft
roadway requirements are the same as for the
Long Key Bridge and the cross section is almost
identical, Figure 6.50. Seven Mile Bridge crosses
the Intracoastal Waterwav with 65 ft (19.8 m) verti­
cal clearance, and its alignment has both vertical
and horizontal curvature.
The consultants, Figg and \Iuller Engineers,
I nc., used the same concepts as had been used for
the Long Key Bridge. except they omitted the
V-pier alternative in favor of a rectangular hollow
box-pier scheme that is precast in segments and
post-tensioned vertically to the foundation system.
As mentioned in Section 1.9.3, the contractor
elecred to alter the constru<:tion scheme ill this
bridge from that of the Long Kev Bridge bv sus­
pending the segments from an overhead truss
rather than placing them on an underslung truss.
The essential operations for construction of a typi­
cal span are as follows:
1.
2.
3.
4.
Transportation of all segments by barge to the
erection site.
Assembly of all segments in a span (with the
exception of the pier segment) on a structural
steel frame supported by a barge.
Placing the pier segment on the pier adjacent
to the previously completed portion of tbe
deck with the overhead truss working in can­
tilever.
Launching the overhead truss onto this newly
placed pier segment.
Progressive and Span-by-Span Construction oj Segmental Bridges
314
5.
6.
7.
Lifting in place the entire assembl\' of tvpical
segments with four winches supported bv the
truss.
Post-tensioning the entire span after the clo­
sure joiIll has been poured between the
finished span and the new span.
Launching the overhead truss to repeat a new
cycle of operations.
Arter a period of adjustment, the method has
allowed a speed 01 construction equal to that for
the assembly truss scheme used for the Long Key
Bridge. One complete span rna\ be constructed in
olle da\", and as Ill;\m' as six 135 ft spans have been
placed ill a single week. Figure 6.55 shows the as­
semhl\" of segments being erected in a "'pical span.
6.6
Design Aspects of Segmental Progressive
Construction
6.6. J
(; J;;,\'EIU L
The use of temporary sta\'~ to earn the weight of
segmellts during construction induces onlj' a nor­
tllal compression load ill the deck ami a very lim­
ited <t11l0UIJl of bending. COllsequclllh', the static
scheme of t he st ruct u re during const ruction is very
close 10 that of the finished struClUl·e. This is a
si~nificallt advantage OH~r the conventional can­
tilen:'r construction scheme, where continuity of
the sliccessive cantilc\er arms results ill two static
schelllcs significantly different het ween const ruc­
tion and sen'ice.
Because of this similarit\ of static scheme
throughout erection and service, it is expected that
I he lanllI1 of prestress tendons fOllnd in cast-in­
place strtlctures or in span-In-spall construction
FIGURE 6.55.
span.
Sc\'C1l
Mile
Brid~e,
erection of a typical
-should be applicable to progressive construction,
with the added advantage that the tendons can be
regularly stressed and anchored at the successive
joints between segments in a simple manner. .
On the other hand, progressive construction dif­
fers in several aspects such. as pier design and
deflection control during construction, calling for a
more detailed examination.
6.6.2
REACT/aSS as PIERS DCRISC
CO.\'STRllCT/OS
Construction of a tvpical span proceeds in two
stages, as shown in Figure 6.56: (I) pure cantilever
erection, of a length (l from the pier, and (2) con­
struction with temporan staYs on the remaining
length (L - (f). Length (f should be selected (within
the nearest number of segments being placed) such
as 10 keep t he girder load moments O\'er the pier
within allowable limits.
Assuming that this moment is of exactly the
same magnit ude as t he fixed end moment of a
t\'pical span tInder the same unit load W, OIle may
write:
H'(l2
WL2
~
12
-==~~
J
_pH
1­
FIGURE 6.56.
tions on piers.
Progressiye construction, deck reac­
Design Aspects of Segmental Progressive Construction
for a constant-depth girder, which is the general
case for progressive construction. Thus:
a
= 0.408L
l2.5 ks!"
The difference is small and usually more than
offset bv the fact that horizontal loads during con­
struction are smaller than during service.
6.6.3
= O.4()WL + 1.268 x O.08WL = O.50WL
During the second construction stage the weight
of the remaining part of the span is supported bv
the tempOl'arv stavs, which are anchored in the
rear span as close as possible to the previous pier so
as not to induce undesirable variations of moments
in the lasl completed span. Consequentlv, the
weight of that part of the span induces in the pier a
react.ioll eq lIal to:
O.hWL
+ l.!O
l. U()
1.02/;VL
The total reaction <lUI'ing construction applied to
the pier is thus:
R = O.30WL + 1.02WL
as opposed to R = WL for cast-in-place or span­
In.·-span cOl1struction. This temporary increase of
girder load re,lCtioll of 62% will evelltuallv vanish
whell construction proceeds. It is importallt to
verify how critical this pier temporan overload
may he lor the design of the substructure. Taking
the example of a 130 to 200 It span, the average
loads ~lre as follows for a 40 ft wide bridge de­
·signed for three 1~lIIes of traffic:
Girder load
Superimposed load
Equivalent live load including impact
8.0 ksf
1.3 ksf
2.6 ksf
The maximum reaction during construction COIIl­
pares with that after completion as tollows (values
gl',:en are the ratio between reaction and span
length):
l.
2.
over the support
(15%),2.6 x l.lS
0.40 L
Fora = 0.40L the moment over the piel' is equal to
AI = 0.08WL2. The moment over the preceding
pier, for a structure with a large number of identi­
cal spans, is equal to O.268AJ. Therefore, the reac­
tion over the pier at the end of this first stage of
cOllstruction can be easily computed as:
R
315
During construction, l.62 x 8.0 =
Compkredsrruaure:
<).
Girder load
8.0
,b. Superimposed load
1.5
c. Live load, including
provision for continuity
1:3 ksf
TENSIO,vS IN STAYS AN/) /)EFLlc'CT/O,v
CONTROL DL'RI.\'C COXSTRL'CTION
As shown previously, progressive construction of a
tvpical span entails two successive stages:
Cantilever construction on a !engt h
1/
Temporarv sllspension by
part of the span (L
a)
the relllalllll1g
Slays 011
This second stage induces small deflectiolls and
rotation, provided that the vertical cOll1ponent of
the slav loads balances t he total deck weight. On
the other hand, the ti rst-stage cons! rtlction not
only creates slIbstantial deflections but also changes
the geometric position of the entire spall, as lI1av be
seen in Figure 6.57.
The weight (Wa) of the deck section produces:
A rotation of the previous span, w,, which will
pn~ject at the following pier and create a vertical
deflection, Y I
a deflection of the cantilever proper, Y2
a rotation at the end of the cantilever, W2, which
will project again at the following pier imo a
deflectioll W~ (L
(/)
Altogether the total dellection is:
H!
'.
~ ('>L2 ' 17;
24EI-
v,}
+
,I
~([
L
")
W
If we let Il = af L. the del1ection can then be written
as:
vVL I "(2' 1--;:;
24EI uv· J
With II
lion is:
+ 4. II
0.4 as assumed before, the total deHec­
Y = 0 .032
. -I WL4
where
W
unit deck load,
L = span length,
316
Progressive and Span-by-Span
C~nstruction
of Segmental Bridges
}:' = concrete modullls,
I
section inertia.
A simple parallletric analysis will reveal the im­
pOrlance of this problem. If tV is the specific gravity
of concrete and A the cross-sectional area, then ~v
= ,vA. It was shown in Chapter 4 that the efficiencv
factor of a box section is:
t:,
p =
=
--=-L----t-! _~.L...
0.60 to 0.63
If the section is symmetricaL {, = (2
0.5 h (II =
section depth). and I = 0.157 Ah2 max. If (;1 =
0.33 Ii and (2
0.6711, which is the practical dis­
sym melr), of a box seelion. I = 0.133,411 2 111i n. For
all practical purposes, assume I = O.14Ah2. The de­
flection then becomes:
Because the construction proceeds rapidly, E
shollld be taken lor short-duratioll loading: that is,
E = 800.000 ksf; t.he specific gravity of concrete is w
= 0.15 kef. The slcndcmess ratio Llh varies be­
tW('CI1 18 and 22. Results are shown in Figure 6.58.
Constructioll of a 200 ft span, for exalllple, with
a slenderness ratio 0120 wiI1 he accompanied h~' a
deflection under girder load (without prestress) at
the next pier of 8.3 inches. The construction
method is therefore ven sensitive \() concrete
dc!lcCliolls. which are lI1a~llified b\' the great lever
arm of the first-stage construction of the spall
projecting its intrinsic deformation to the follow­
lIlg lHer.
Fortunately, prestress will give a helping hand
and contribute to substantially decreasing the
girder load deflection. The minimum prestress re­
quired at this stage is to balance the tensile stresses
induced by the girder load moments. "Vith the
same notations as above, one may compute the
prestress force and the corresponding moment for
three positions of the neutral axis:
(lilt
0.5
(2/11 = O.S
Efficiency factor
Distance from
centroid or prestress
Eccentricity of prestress
Lower central core
p = 0.60
to
d
O.OSh
e
r 2 1c 1
= 0.30h
!
y TI1TAL
I
01/15
"
,
'y/ I.'
I
lUI I
FIGURE 6.57.
Pmgrcssiv{'
(()llSlrunioll.
def(Jrlll<l­
lIons,
For an efliciency factor p = 0.65 thc corresponding
\,tlues would be:
0.58
0.47
0.39
The prestress will therefore reduce the deflections
by the same amoulll-that is, approximately half
the total girder loud deflections. The resultant
deflection (girder load + prestress) still remains
very sigIlificant as SOOI1 as the span length is above
J 50 /'t. These deflections must be taken into full
account to compute the camber diagram (for seg­
ment precasting).
The next important point to consider here is the
second-stage construction of a tvpical span when
the remaining part of the girder is suspended from
the temporary sla\,s. The concrete girder and the
group of stays form an elastic svstem that supports
the applied loads: girder load for the segments al­
ready in place, swivel crane and new segment
0.4
(21h = 0.6
(11h = 0.33
czlh = 0.67
= 0.60
p = 0.60
(lilt
p
d
0.05h
d
O.OSh
top fiber
Lever arm 01 prestress
Prestress moment
(ratio of girder load moment)
= 0.45h
e
r 2 1c 1
0.75h
~~
0.75
= 0.60
__
0.3~
0.71
= 0.3Sh
0.36h
e = 0.28h
r21c I = 0.40h
0.7 J h
0.68h
= 0,49
=
0.28
0.68
= 0.41
=
Design Aspects of Segmental Progressive Construction
o
:sp.. .., (flJ
so
FIGURE 6.58.
100
ISD
100
Progressive c(ll1strllctioll, deflenions.
traveling o\'(~r the bridge with the trailer and trac­
tor. Two examples ha\'e been considered to show
the relative response
the variolls componellts of
this elastic s,"stem toward the application of' a load.
or
l. f08 /1 (33m) sjJan This was one tvpicd span
of the Rombas Viaduct. The spall has heell as­
sumed to be completed except for the pier segment
over the next pier. For this construction stage, the
swivel crane and the new segment applv to the
staved cantilever a load of 88 tons (80 mt). In view
of the great stiffness of the concrete girder com­
pared to the group of stavs, the total moment in­
duced bv the load remains alinost entirely in the
coilcrete girder and there is only a small spontane­
ous increase of the stay loads, as shown in Figure
6.59. The magnitude of temporary prestress in the
deck must be designed accordingly to keep all
joints under compression for all intermediate
loading cases.
where progressive construction was cOlltelllpblcd
for a viaduct with a large number of identkal 260
ft (80 m) spans all made up of 26 segments lOft C)
m) long. Figures 6.60 and 6.61 show the distribu­
tion of moments between concrete girder and
temporary stays at three successive stages of seg­
ment placing: segments IS, 20, and 25, respec­
tively. The first nine segments are placed ill can­
tilever; the following 15 segments are suspellded
from temporary stays, while the last typical seg­
ment and the acUacent pier segment are placed
without stavs.
The proportion of the load (alld corresponding
moment) (aken by the stavs increases as the can­
tilever length increases ancl, when the last segment
is placed, more than half the load is supported b\'
the stavs. For very-long-spa n stayed bridges, this
distrihution of load between stavs and concrete
girder reaches the situation where the load is al­
most entirely supported by the stays and the COll­
crete girder is subjected onlv to an axial force, ex­
cept in the area of the longest st~n's.
The consideration of' distributioll of loads and
mOll1ents between stays and concrete girder has an
important aspect during construction-that is, the
accuracv of the tension in the stays ami cOl1Se­
quences of an accidental deviaLion between com­
puted values of stressing loads in the stavs and
their actual values in the held. For example, take
the simple case of a span L with 4O<Ic huilt in pure
cantilever and the remaining 60o/c suspended bv
stays (see Figure 6.56). The moment over the pier
due to the second-stage construction load is .'1.1
0.4~WL2. Assume that an accidental deviation took
place of 5% between the design loads for the Slavs
and the actual values obtained in the field (owing to
friction in the jacks, illaccurac~' in the pressme
gauges, and so on), As a result, an additional mo­
ment will appear over the pier of LlM .fo 0.42 WL 2
=. 0.021 WU. The corresponding tensile stress ~tt
the top fiber (assuming the error in stay loads was
to reduce the theoretical values by 5%) can be eas­
ily computed b\':
0.02liiJAUc j
ApCIC2
0.02IwP
With IV
2: 260 ji (80 m) span This example is taken
from a recent design for a large project in Europe
317
0.15 kef, p = 0.60, and
2
tlf = 0.0088 Lh
C2
0.6011:
Progressive and Span-by-Span Construction of Segmentai Bridges
318
FIGURE 6.59.
I'rogressi\'l' constructioll. illcrease of st<l\ loading,
The stress ill ksl 1'01' 1~/"
20 (slcndcrIlcss ratio) is
tht' following lor s(,\'eraJ span lengths:
::00
Assu me I hat the ill<lCClI ran' of the sla\ loads leaves
ill the concrcte girder 5~i 01 its own weight to be
carried \)\ bending: the resulting deflection over
the pier would he:
WL4
O,OllH E1
This stress is !lot critical for short spans but 111<1\'
becolll(' significant for Jong ones. The simple deri­
\,;ttiolJ gi\'Cll abO\e shows that control of the st<l\'­
l<:nsiolling operatiolls ;11 the site should always he
Oil the safe side with due allowance fOT inaccuracy.
A de\'iatioll ill the tension of the sta\'s will also
affee! t he deflect ions during const ruction. Without
t he presence of the stays the total deflection ()\'er
the next pier due to the load on the length (L - a)
would be:
y
=
which gives for u
)
0.4 as before:
, = 0 <)'166 ~t'L 4
,~"
"
This value should be compared to the effect or the
hrst-sta~e constmctiol1, which \\"as previously given
as:
y
0.0327
1~~1
In summary, a SO/C deviar.ion of the stay tension
loads will increase the call1ilever deflection due to
girder load by 36%. Considering the benefJcial ef­
fect of prestressing for the latter, we see that ap­
proximately 7% deviation of the stay load produces
the same deflection as the first-stage construction
loads including prestressing. This shows that the
deflections are important, particularly for long
spans built in progressive construction, but that
proper deHection control is an excellent tool to
319
References
rOTAl
(usr.)
/'!Q/,!E~T
!1Ol!fllT CARRlfD
illY CONCRETE QlltDER
t5!J()(J '.
IS SUlfurs
Iii CANTrU:lItll
no F1
51'A1t
6MQ'1
~
.
tT
(43.1
r.)
/
r
TOTAL I!O/'llJiT
IwfOI'fEltT
CAMICD &)f
CONC1tI'l'l GrrtDcJt
tl5lXJ'A ....---;---;~_~__
; - - 'TJTAl 110/'1tNT
I
110"un
C~RIID
BY CO/ol,MU ilRIIDl
FIGURE 6.61.
or 1ll0lllCI1I
FIGURE 6.60. I'roglc\~i\e uH1~lrl1(li()ll.
0111101111'111 b('II\'(,CI1 ~ral's al1d 14irder.
di~lrihllli()11
I'erih I hal slresses ill rile COllcrele girder are alw;t\s
kepi within allowable limits,
()JLI
Pro14re;.siH' CO IlS I ruct iOll, disl riblll ion
bCIIH'l'1l ;.1;l\S
and
deL
Possihh a third familv of' tendons made of internal
SI<lVS with a draped profile and anchored over the
pi~rs ill the diaphragm. Ihe purpose of which is 10
supplelllelli hoth olher families vdlile reducing Ihc
net shear stresses ill the webs hecause of the \'erti­
ed componcllt of prest ress,
I..llf}{F OF //:',\/)()SS F()!{ J>/wr;I?ESSIlE
(;()SSIRL'CTI()X
References
or
Beculse the sialic scheme al the end
each COll­
.SIl'lIC1ioll slep is identical to Ihat of a cast-in-place
structure, Ihe permanent tendons Gill he installed
in the strtlctllre immediately, without the transi­
tion situations required by other construction
methodologies such ,IS incremental laullching.
.\ tvpical prestress lavow for progressiv'e COIl­
structioll \\ill rhus include:
,\ hrst family of tendons located in the top Hange
()\er the v;lriolls piers, with anchors symmetricallv
locHed ill blisters, the purpose of which is to resist
negative lllornelltS over r he supports.
A second f;lll1iiv of tendons located along the span
ill the bottom Hallgeand also anchored in blisters
inside the box section. LJsually the top and bottom
blisters are joined to a web rib, allowing temporary
preslress hal'S 10 he anchored during segment
placing.
I. H, Willfoill. "PH'st rcssed Concrete l)ridg-e Con­
strunioll lI'ith Sleppill~ Forllll\'ork EquiIIIl1CI1I,"
First IlIIcrn;tlional SnnposiulIl COII{TCtC Bridge De­
sign, Papcr SP ~:1-2H, AU Publication Sl'-:!:l,
American Concrete Institllte, DCTroit, 19!JY.
,) H. Win!()ill, "Die Vel"\\TIHlullg­ \'on Vorschllriis·
Iungell biem Briickellbau" (The l'se of (,ravcling­
Formwork ill Bridge Construction), Intcrnalional
Associatioll Brid~c and Structural En~ineerin~,
"inlh COllgress. ;\lI1sterdal1l. :'>!av H-13. 197:.!,
:1, H. rilul, "Spannbelon iIll Briickenbau,"
Edoll. Heft 4::, Dezelllber 1962'1.
Zi'II/fIIllIl/d
4. :-.rall-Chung Tang, "Recent De\·eloplllent of Con­
strunioll Techniques in Concrete Bridges," Trans­
portation Research Record 665, Bridge Engineer­
ing'. Vol. 2, Proceniill{!,s of the Transportatioll Resl'flrc/t
Board COlljt'fl'lIl'1'. September 2.')-27. 1978,51. Louis,
:'>10.• "alional .\eadem\" of Sciences, \VashinglOn,
D,C.
Progressive and Span-by-Span Construction of Segmental Bridges
320
:), l', FillSterw<\lder <lnd H. Sch<lll1heck, "Die EI/.lal­
hriicke," DI'I' BrIll/l/grllll'ln, Heft (i, JlIIle J96(i, and
Heft 1, Jallllan 1967.
Ii. 1-1. Thill. "Brilckenbau," Betoll­ und Stahlbl'lOllbau,
I left
;1,
\1a\ 19G6.
"Ball del' Loisachbriicke bei Ohlstadt,"
DYil'idag-Brrirh/1' 1971-3, Dn:kerholl & Widmann,
AG. \lunith.
H. :\l]on.. "Bau<lllshihrullg der Autobahnbriicke tiber
die Loisach hei Ohlstadt." Dnl·idllg-Berichtt 1972-5,
IhckerhofT 8.: Widmann, AG. \1ullich.
I.
:\11011.,
, 9, Allon" "Denny Creek-Franklin Fans Viaduct,
'''''ashingtoll,'' Bridge Repon SR 202.01 E, Portland
Cement Association, Skokie, 111., 1978.
10. Anoll" "Florida's Long Key Bridge to Utilize Pl:ecast
Segillental Box Girder Span-hy-Span Construction,"
Bridge Repon, Post Tensioning Institute, Phoenix,
Arizona, January 1979.
Jr., "An Overview or Precast Ple­
stressed Segmental Bridges,"Journal oflhl' Pres/res.lN/
COII(1('/1' Jl1slilulr, Vol. 24, :'\0. I, January-February
1979.
11. ';"alter Podolny.
7
Incrementally Launched Bridges
7.1
7.2
7.3
7.4
7.5
7.6
INTRODUCTION
RIO CARONI, VENEZUELA
VAL RESTEL VIADUCT, ITALY
RA VENSBOSCH VALLEY BRIDGE, HOLLAND
OUFANT'S RIVER BRIDGE. SOUTH AFRICA
VARIOUS BRIDGES IN FRANCE
7.6.1 Luc Viaduct
7.6.2 Creil Viaduct
7.6.3 Oli Viaduct
7.7 WABASH RIVER BRIDGE, U ...S.A.
7.8 OTHER NOTABLE STRUCTURES
7.8.1 Muhlbachtalbrucke, Gennany
7.8.2 Shepherds House Bridge. England
7.1
Introduction
The cOllcept of incrementallv launched segmental
prestressed concrete bridges was described in Sec­
tioll 1.9.5. This chapter will describe the im­
plementation of this innovative concept in several
'representative projects.
Since the implementation of the incremelltal
launching technique on the Rio Caroni Bridge,
some eightv bridge superstructures have been con­
structed bv this method through 1976. with
gradual refinements and improvements in the
method. l Bv concentrating the casting of segments
behind an abutment with a tel'}1porary shelter, if
required, this method can provide the sallie qualitv
control procedures and quality of concrete that can
be achieved in a concrete precasting plant. It
minimizes temporary falsework, extensive form­
ing, and other temporary expedients required
during construction bv the conventional cast-in­
place on falsework method. Basically the method
enta~ls incremental fabrication of the superstruc­
ture at a stationary location, longitudinal move­
ment of the fabricated segment an incremental
7.9
DESIGN OF INCREMENTALLY LAUNCHED BRIDGES
7.9.1 Bridge Alignment Requirements
7.9.2 Type, Shape. and Dimensions of Superstructure
7.9.3 Span Arrangement and Related Principle of Con­
struction
7.9.4 Design of Longitudinal Members for Flexure and
Tendon Profile
7.9.5 Casting Area and Launching Methods
7.9.6 Launching Nose and Temporary Stays
7.9.7 Piers and Foundations
7.10 DEMOUTION OF A STRUCTURE BY INCREMEN­
T AL LAUNCHING
REFERENCES
length, and casting of a new segment onto the one
previoush cast. In other words. the procedllre call
be considered as a horizontal slip-form technique,
except that the fabrication and casting occur at a
stationan' location, Stringent dimensional control,
however, is an absolute necessitv at the stationan'
casting site, since errors are verv difficult to correct
and result in additional costs in launching. I
Straight superstructures are the easiest to ac­
commodate; however, curvature (either vertical or
horizontal) can be accomplished if a constant rate
of curvature is maintained. If the grade of the
structure is 011 an incline, it is preferred to launch
the structure, wherever possible, downward.
Where the fall is 2%, the superstructure has to be
pushed or held back, depending upon the
coefficient of friction. Where the fall is in excess of
4%, special provisions are required to prevent a
"runawav" superstructure during launching. I To
the authors' knowledge, this situation has never oc­
curred. Piers, either temporary or permanent,
should be designed to resist the lateral force pro­
duced by the launching operation. A friction force
varying from 4 to 7% has been considered for de­
321
322
Incrementally Launched Bridges
sign purposes, although values of only 2 to 3~o/c
have been observed in the field.
At presellt, it is felt that this system can be used
lor superstructures up to 2000 ft (610 m) in length;
for longer structures incremental launching is ac­
complished from both abutmelHs toward the
center of the structure. The technique has been
applied for spans up 10 200 It (60 m) without the
use of temporary supporting bents and for spans
lip to 330 ft (100 111) with such bents. Girders usu­
ally have a depth-to-span ratio ranging from
one-twelfth to one-sixteenth of the longest span
a1Jd are of a constant depth. The launching nose
has a length of appnlximately 60% of the longest
span.
The principal ad\'antages of the incremental
bunching Illcthod are the ro\lO\.... ing~:
I.
2.
3.
4.
5.
6.
\:0 Ldsc\\'ork is required for the construction
of the superstruct ure ut her than possibly
falsework bems to reduce span length during
cOllstructioll. 111 this mallner camilever stresses
dUI'ing launching can be mainrained wilhin
allowable lilllits. If falsework bents should
pro\'(' to he impractical. then a system of tempo­
raJ'\' slaVs can be used as indicated ill Figure
] .6:t Obviously, depending on site conditions,
any or all comhinations of temporary bents,
'Iauncbing nose, and temporary stays may be
used, the point being Ihat conventional use of
falsework is greatly minimized. Tbis is par­
ticularly interesting for projects in urban areas
or spanning over water, bighways, or railnmds.
Depending on the size of the project there can
be a substalltial reduction in form investment.
Because casting of tbe segments is centralized
at a location behind the abutment, tbe eco­
nomic advantages of mass production and a
precasting plant operation can be duplicated.
The method eliminates transportation costs of
segments cast at a fixed plant and transported
to the site.
It eliminates heavy cranes or launching trusses
and associated erection costs.
It eliminates epoxy joints. Since epoxy is not
involved, construction can continue at lower
temperatures.
Camber control and other geometry controls
are easily obtained.
Disadvantages are as follows:
1.
As mentioned in Section 1.9.5, bridge align­
ment for this type of construction must be
2.
3.
4.
either straight or curved; however, curvature,
either vertical or horizontal, must be of a con­
stant radius.
As mentioned above, strict dimensional control
during casting is required. Any mistakes in
casting are difficult and expensive to correct,
especially if they are not discovered until after
some length of bridge has been launched.
The superstructure must be of a constant sec­
tion and depth. This is a disadvantage in long
spans, where a val-iable-depth section would
provide a better economy of materials_
Considerable area is required behind the
abutment(s) for casting the segments. In sOllie
project sites this lllay llot be feasible.
In the present state of the art of illcreme11lalh
launched hridges there appear to he basically two
llJcthods of cOllstructioll, which we shall call roll:
lirwou.s {(lsling and balalLled wslillg. They are dif·
ferent in mode of execution and in their areas
of lltilizatiOlL The cOlllinuous casting mcthod is
sOJl1ewhat analogous ro the span-by-span methud,
and balallced casting is similar to the cantilever
method.
The cOlltinuous casting method is generally used
for long viaduct-t\pe structures with numerous
equal (or nearly equal) spans. Its principal charac­
teristics are the following:
I.
Entil-e spans, or portions of spans, are COll­
ere ted ill fixed forms. The forms are reused, as
in the span-by-span llIethod, except that the
forms are fixed instead of mobile and are
moved from span to span. Subsequent spans
(or portions of a span) are cast and joined to
the one previousl\' cast, and the superstructure
is progressive I\' launched.
2_ Csually the casting area behind the abutment
is long enough to accommodate either a span
length plus launching-nose length or some
multiple of span segment length plus launch­
ing-nose length.
3. Operations involve successive concreting and
launching. The principal phases are: forming;
placing of reinforcing and tendons; concreting
and curing; tensioning and launching.
4. The two types of superstructure cross section
used have been box girder and double T.
5. Longitudinal prestressing consists of two
tendons concentricallv
families of tendons:
.
placed and tensioned before launching, and
tendons placed and tensioned after launch­
.
323
Rio Caroni, Venezuela
ing-that is, negative-moment tendons over
the supports and positive-moment tendons
in the bottom of the section in the central por­
tion of the span.
The balanced casting method is used for smaller
projects up to a total length of 650 ft (200 m). It is
used for symmetric three-span structures where
the central span is twice the end span. Its principal
characteristics are:
1.
')
3.
4.
Concreting of segments is accomplished sym­
metrically with respect to a temporary support
located in the embankment behind the abut­
ments. This method is similar to the balanced
cantilever except that the forms are supported
on the embankment fill.
Two areas of casting are required, one behind
each abutment. The half-superstructures are
constructed at opposite ends of the project.
The distance between the abutment and the
axis of the temporary massive support is gen­
erally slightly less than one-fourth tbe length
of the project.
Al'ter the two half-supt;rstructures have been
cOllcreted on the access fill, the two halves are
lallllched over the piers andjoined at midspan
of the central span bv a closure pour, which
usuallv has a length of 3 ft (1 111).
Longitudinal prestressing consists of three
families: cantilever tendons for each segment,
located ill the upper portion of the cross sec­
tion and stressed before launching; continuitv
tendolls, tensioned after closure and situated
in {he lower flange; and provisiollal tendons,
located ill the lower flange, tensioned before
launching, and opposing (he calHilever ten­
dOllS.
There are two methods of launching. The
method used on the Rio Caroni Bridge, Figure
1.67, has the jacks bearing on an abutment face
and pulling on a steel rod, which is attached by
launching shoes to the last segment cast. The sec­
ond, and more Cll rrent, method is essentially a
lift-and-push operation using a combination of
horizontal and vertical jacks, Figure 7.1. The verti­
cal jacks slide 011 teHon and stainless steel plates.
Friction elements at the top of the jacks engage
the superstructure. The vertical jacks lift the
superstructure approximately
in. (5 mm) for
1au!lching. The horizontal jacks then move the
superstructure longitudinally. After the super­
structure has been pushed the length of the hor-
FIGURE 7.1. Incremental launching-jacking mech­
anism (courtesy of Prof. Fritz Leonhardt).
izontal jack stroke, the vertical jacks are low­
ered and the horizontal jacks retracted to restart
the cycle. l Figure 7.2 is a schematic depiction of
this cycle.
To allow the superstructure to move forward,
special temporary sliding bearings of reinforced
rubber pads coated with teHon, which slide on
chrome-nickel steel plates, are provided at the
permanent piers and temporary bents, Figures 7.3
and 7.4. A sequence of operations showing the
bearing-pad movement 011 the temporary bearil1~
is depicted in Figure 7.5. A temporary bearing with
a lateral guide bearing is shown ill Figure 7.6.
7.2
Rio Caroni, Venezuela
The design for this structure was proposed by con­
sulting engineers Dr. Fritz Leonhardt and Willi
Ballr or the firm Leonhardt and Andra, Stuttgart,
West Germanv, ill an international competition.
Design and plannitlg occurred in 1961 and con­
struction in 1962 and 1963. This structure, Figme
7.7, consists of a two-lane bridge with end spans of
157.5 ft (48 m) and four in terior spans of 315 ft (96
m), for a total length of 1575 ft (480 m).1 The site
provided some formidable construction problems.
The Rio Caroni River during Hoocl stage reaches a
depth of 40 ft (l~ m) with velocities of 13 to 16
fUsec (4 to 5 Ill/sec), thus eliminating the consider­
ation of a cast-in-place concrete superstructure on
falsework. Balanced cantilever segmental con­
struction was considered; however, the interrup­
tions during high-water periods would require an
extensive construction period with attendant high
costS.3
The proposed method consisted of assembling
and prestressing the entire length of bridge on
324
Incrementally Lflunched Bridges
(a)
FIGURE 7.3. I ncrclI1ental
launching-longitudinal
section of launching bearing. from reference 3 (courtesy
of the American Concrete Institute).
(bi
--.--­
FIGURE 7.4. Laullching
Bridge. Il!diana.
FIGURE 7.2. Schematic of launching jack operation.
lafLift. (b) Push. (r) Lowcr. (iI) Rctract.
land adjaccllt to thc bridge sile, using precast seg­
ments, and launching ill a longitudinal direction,
mer the piers. into final position. Temporary piers
were used al midspan of each interior span to pro­
duce ten equal spans of 157.5 ft (48 m) during the
launching of the superstructure. Accommodation
of on-site assembly of the total superstructure re­
quired a 1600 f't (500 m) long fabrication bed to the
rear of one abulment, which was partly excavated
ill rock and had to be backfilled and compacted
UpOll completion of the project. At the far end of
..
h<:arillg.
Wabash
Riyer
this f'abrication beel stationary steel forms were in­
stalled to cast the precast box segments, which were
18 It 4 in. (5.6 lll) high and cast in 30 ft (9.2 m)
lengths.
After the precast segments attained suf'ficient
strength they were stripped from the form and po­
:-.itioned in the fahdcation bed to correspond with
their locatiolJ ill the final structure. The segments
were mm·ed from t he form 011 wooden rails accu­
rately positioned in the assembly bed, employing
formica sheets and a petroleum-base lubricant
between the hOUOlll or the segment and the top of
the wood rails, Figure 7.8. A space of I ft 4 in. (40
cm) was left between tbe precast segments for an in
situ joint. Accurate positioning of the segments in
the assemblv bed was required before casting of
Lhe joints. To avoid shrinkage damage, the joints
wel-e cast dUl'ing the second half of the night so
that the temperature expansion of the precast
segments during the heat of the day would com­
pensate for the shrinkage in the cast-in-placejoint. 3
After the joints were cast, concentric prestress­
ing located inside the box and passing through
openings in the web stiffening ribs, Figure 7.9, was
prestressed with a force of' 5000 tons in one opera­
Rio Caroni, Venezuela
325
II
u
-
FIGURE 7'.7. Completed Rio Caroni Bridge. from
reference 3 (courtesy of the American Concrete Insti­
tute).
-FIGURE 7.8. Precast segments
(courtesv of Arvid Grant).
FIGURE 7.5.
Telllporan ,liding be<]ring. sequence of
operations.
FIGURE 7.6. Incremental
launching-temporary
bearing and lateral guide bearing (courtesy of Prof. Fritz
Leonhardt).
In
assembly
bed
tion. The prestress tendons were continuous
around a large half-round concrete block at one
end of the structure, Figure 7.10.' This block
reacted against a number ofjacks and a 10ft (3 m)
thick concrete bulkhead wall. By activating the
jacks between the block and the bulkhead and
causing a movement of 9 ft (2.8 m) in the stress
block, the initial prestress force was induced into
the tendons. The prestressing tendons were not
attached to the webs. To reduce the hazard of any
accidental elastic instabilitv condition, temporary
steel bracing frames were installed at 60 ft (20 m)
intervals.:! The 3:3 ft 10 in. (10.3 m) top flange of
the box girder section was transversely prestressed,
Figure 7.9.
Upon completion of the prestressing operations
the superstructure was readv for launching over
the temporary and permanent piers to its final po­
sition. To maintain acceptable levels of concrete
stresses, as the girder was launched over the 157.5
ft (48 m) spans, a 56 ft (17111) tapered structural
steel launching nose was attached to the leading
326
Incrementally Launched Bridges
10"··----·------····---_
.. -------i_----13'-II"---.'2'.rI', 1'-0"
! v'l
/
~
Stress steel
:
'""
l!II§-71--Longitudinol
stress steel
"','"
·--16'- 5 " - - - - -......,.·..----16'- 5"---·-~"",,
FIGURE 7.9. Rio Caroni. girder (l()S~ sectioll. fmlll rcic)'cll(c :\ (oUrl('s\
or the Amcricall COllcrele IIl,tituIC).
,;
,
\
lesY
FIGURE 7.10. Rio Caroni. prestressing block (cour­
or ..\)'yid Cralll),
FIGURE 7.11. Rio Camlli, launching nose, from ref­
erence :) (courteS\' of the Aillerican Concrete Institute).
elld of the superstructure, Figure 7.1 1. Two dou­
hlejacks with a tOlal capacil\' of ROO tons, Illoullleci
against the bridge abutment and pulling on steel
rods fastened to t he girder, proyided the horizon­
tal force required for the longitudinal launching
mOYCmClll. To accommodate movement o\,er the
piers, two sliding bearings were pl'Ovided at each
temporary and permanent pier LOp. These bear·
ings collSisted oj chrome, polished steel plates
which supported teflon covered bridge bearings
which were placed ill all illverted position such that
they bore agailIst the underside of the girder and
slid OIl the stcel plates. After a launching move­
lllCllt of ;) It (96 CIll) ill the longitudinal direction
the operation was halted to allow the entire
superstructure to be jacked \'erticall\', simultane­
ously al all piers. The teflon plates were then
moved back to their original position (the one they
occupied whell the launching operation started)
and rotated 180 degrees, with respect to a vertical
axis, to compensate for anyone-directional mo\'e­
ment of the teHon coating. Longitudinal launching
11100'emenl OCCUlTed at a rate of 2~ in.!min (6 COl!
min); thus, olle 3 ft (6 cm) increment of movement
took 16 minutes. A total cycle of operation, after
subsequenl synchronization, which included the
simultaneous jacking at 22 locations and reposi­
tioning of 22 tefloll bearings, required 30 minutes
Val Restel Viaduct, Italy
for each 3 ft (96 cm) of movement. In this manner,
a daily movement of 63 ft (19.2 m) could be ac­
complished. The required initial jacking force for
launching was 220 tons; this gradually increased to
400 tons for the total girder weight of 10,000 tons,
which indicates a friction of 2 to 4%.3
After the launching operation was completed,
the initial concentric prestressing tendon profile
was changed to accommodate the loading condi­
tion in the superstructure after temporary piers
were removed. To accomplish the change in ten­
don profile, special V-shaped rods were installed
so that they projected upward through the top
flange or downward through the bottom flange,
the tendons being cradled in the V rods. The rods
were then jacked simultaneously at 24 points up­
ward or downward, depending on their location.
During this operation the half-round stress block,
Figure 7.10, was gradually released such that upon
final positioning of the tendons it had retracted 8 ft
6 in. (2.6 m). After the tendons had been relocated,
thev were attached to the web and concreted for
corrosion protection.:;
The procedure used for the construction of the
Rio Caron! Bridge, although technically adequate,
is prohibitively expensive. The methodology has
since been refined such that segments are cast di­
rectly behind the abutment in lengths of 33 to 100
ft (10 to 30 111) and incrememally launchecl after
curing of the last segment cast. l
7.3
Val Restel Viaduct, Italy
Because of rugged mountain terrain the alignment
of a 1050 ft (320 m) portion of this viaduct re-
327
quired a sharp horizontal curvature of 492 ft (150
m) radius, and a vertical curvature of approxi­
mately 8860 ft (2700 m) radius, Figure 7.12.
Maximum pier height is 212 ft (64.61 m). Site con­
ditions and alignment precluded construction by
the balanced cantilever method or conventional
cast-in-place on falsework, leading to the decision
to construct by the incremental launching method.
The curved 1050 ft (320 m) length of this via­
duct consists of 52.5 ft (16 m) long segments, which
were fabricated in an enclosed shed behind an
abutment. The bottom flange and bottom stubs of
the webs of the first segments were cast first, Figure
7.13a, b, in·a 52.5 ft (16 m) length, and approxi­
mately 118 ft (36 m) behind the first abutment.
After curing and stressing of the partial segment it
was jacked forward an increment of 52.5 ft (16 Ill)
toward the abutment, where the balance at" the
section was cast, Figure 7.13a, c. At the same time
the [arm work vacated by the first-segment bottom
flange was reused for the castiug of the bottom
flange of the second segment, monolithically with
the previous segment. After launching another
52.5 ft (16 m) increment the cycle was repeated
until the superstructure was completed. 4
Placement of the bottom flange mild steel rein­
forcement is shown in Figure 7.14, with the web
forms in the background. The side forms for the
webs and underside of the top flange cantilever,
and the hydraulic jacking arrangement for strip­
ping, are illustrated in Figure 7.15. Reinforcement
in the top flange is shown in Figure 7.16 and the
completed top flange with the following segment ill
the background in Figure 7.17. The completed
segment with rails in place as it emerges from the
casting shed is shown in Figure 1.61.
Elevation
(b)
Plan
(a)
.FIGURE 7.12. Plan (a) and longitudinal profile (b) of the Val Reslel Viaduct, showing:
A. shed for the construction of the deck segmems; B. hydraulic equipment used for
launching. From reference 4.
(a)
E
g
N
(b)
(c)
FIGURE 7.13.
(d)
Construction stages Val Resiel Viaducl. from referellce 4.
Val Rcstel. placement ofbollOIll flange
)einfill'CCIllCtll. rrom reference 4.
FIGURE 7.16. Val Reslel, lOp flange reinforcement,
from reference 4.
FIGURE 7.15. Val Restel, side form stripping mecha­
ni~Jl), from ref'crence 4,
FIGURE 7.]7. Val Resrel, completed top flange, with
reinforcement for next segment in background, from
reference 4.
FIGURE 7.14.
328
329
Ravensbosch Valley Bridge, Holland
The superstructure cross section is shown in
Figure 7 .18a. Widt h of the segment is 29.5 ft (9.0
m). Total depth of segment is 8.13 ft (2.48 m), for a
depth-to-span ratio of 1113. The top nange has a
thi<.:kness of 9.8 in. (250 mm) and the bottom
flange a thickness of 5.9 in. (I50 mm). Figure 7.ISb
is a longitudinal section of the superstructure
showing a lavoUl of the second-stage prestressing
tendons required after launching to accommodate
loads 011 the final structure. Figures 7.19 and 7.20
show the interior anchorage blocks for the
second-stage prestressing before and after con­
creting, respectively .
.-\ complete ode of fabricating and launching a
5:2.5 ft (16 m) segment was ~lCcomplished in four
nine-hour working da\'s. Actuailaullching time for
one segment was {)O to 65 minutes. l Figures 7.21
and 7.22 show the laull<.:hing nose approaching
and landing on a pier. Views of the <.:ompleted
structure are ShOWIl in Figul'cs 7.23 and 7.24. COIl­
struction of this bridge was accomplished ill ten
months. frolll JanuaI'\' 1972 through October'
1972.
7.4
of6 it (1.8111) bv 19 ft (5.8111) with wall thickness 01
1.3 ft (0.4 m). Figure 7.26.
The superstructure consists of two single-cell
trapezoidal box girders connected at the i11lerior
upper flange tips bv a 8.3 ft (2.3 Ill) slab and pre­
stressed transversely, Figures 7.26 and 7.27. Ea<.:h
box has a width of 56.S ft (17.32 m) and a constant
depth of 10.8 ft (3.3 111) for a depth-to-span rat io of
1/17. The top flange has a thickness of9.8 in. (250
mm) and the bottom flange a thickness of 7.9 ill.
(200 mm). Top flange cantilever is 13 ft (4.01 m).
Each dual structure consists of 22 segments ap­
proximately 62 ft 4 in. (19 111) in length. The C011­
-'1
--'" - ,--,::.,
''',:'
if',
---
,
e
,
Ravensbosch Valley' Bridge, Holland
The 1378 ft (4:?O Ill) long Ravensbosch Valley
Bridge ncar Valkcnburg represents the first bridge
in Holland built by ;he incremental launching
method of segmental construction. Figure 7.25.
This dual structure has end spans of 1~~7.8 ft (42
111) ;ll1d six interior spans of 183.73 ft (36 111). Hol­
low rectangular piers van' in height from 21 ft (6.5
111) to 77 ft (23.5 Ill) and have exterior ciimensions
.~~~~~~~.~--~~-~~~~--.-~_~~~~~~
FIGURE 7.19. Val Restel. second-stage prestressin~
anchorage block hefore ~()ncretillg, from ref'crence 4.
n
~
FIGURE 7.20. Val Restel. second-stage prestressing
anchorage block after concreting. from reference -I:.
ia)
~!> ~7mm -
Ca/JleltU 7mm
(h)
FIGURE 7.18. Val Restel.
From reference 4.
(a)
,I
I'
Cross section of deck. (b) Longitudinal section of deck.
330
Incrementally Launched Bridges
FIGURE 7.21. Val Restel, launching nose approach­
ing pier, from reference 4.
FIGURE 7.24.
refercllce 4.
Val Restel, completed Viaduct. from
FIGURE 7.22. Val Restcl. launching nose landing on
pier. from referellce 4.
FIGURE 7.25. Ravembosch Valley Bridge, general
\iew (courtesy of Brice Bender, BV:\/STS).
FIGURE 7.23. Val Restel, \"iew of incrementally
launched cUl'ved viaduct after launching, from refer­
ence 4.
struction of the superstructure was based upon a
cycle of one segment per week.
To accommodate bending mornents during
launching operations a 52.5 ft (16 m) long launch­
ing nose was used, Figure 7.28, in conjunction with
a concentric first-stage prestressing consisting of26
It in. (32 mm) diameter Dywidag bars per box
girder. In addition, temporary piers were used at
midspan, Figure 7.28. During launching, friction
amounted to 2 to 4%, equivalent to a maximum
pushing force of 430 tons for a completed box
girder.
1'1
iii
Olifant's River Bridge, South Africa
331
FIGURE i.26. Ravell~bosch Valley Bridge. dual structure cross section (courtesy of
Brice Bender. BV:\!STS).
After completion of the launching, second-stage
prestressing following a parabolic profile and COI1­
sisting of 12-0.62 in. (16 mm) diameter strands was
installed and stressed. This structure was com­
pleted in 1975.
7.5
FIGURE i.27. Ra\cllsl)()sch Vallcy Brid).\c. girder
cross section (courtcsv of Brice Bender. BV:-;!STS).
FIGURE 7.28. Ravensbosch Valley Bridge. view of
launching nose (courtesy of Brice Bender. BV:\/STS).
Olifant's River Bridge, South Africa
This railroad structure, upon completion, held the
world's record for t.he longest bridge accomplished
by incremental launching. It has a total length of
3395 ft (1035 m), consisting of 23 equal spans of
147.6 ft (45 m). The final structural arrangement
consists of 11 continuous spans on each side fixed
at the abutment and one simply supported center
span-that is, an expansion joint on either side of
the center span. With this structural arrangement
the braking force of the trains (transporting iron
ore) is transmitted to the abutments (10% of live
load). In this manner the flexible piers can be lIsed,
resulting in an economy in the foundations by
comparison with the classical solution, where the
longitudinal force is transmitted through the piers
to the foundations.
All 23 spans were incrementally launched as 23
continuous spans from one abutment, Figure 7.29.
During launching the two expansion joints were
made temporarily continuous by temporary pre­
stressing. The joints were released after the struc­
ture was in place and before it was rested on its
permanent bearings. A launching nose, 59 ft (i8
m) long, was prestressed to the first segment to
maintain the cantilever stresses, during launching,
in the concrete within allowable limits. The tip or
332
Incrementally l;aunched Bridges
END
BENT
P1
~'te!i:\Q;;JI "'"'~
,
2~nJi:t~
3~'i~!'lii'19!\b~
1<­
Construction of the superstructure was accom­
plished in nine 1110mhs. Segments were span
length, with the theoretical cvcle per span of ten
hours attained in the tenth operation and 'gradu­
ally reduced to seven hours at the conclusion of
casting operations. Reinforcing cages were prefab­
ricated in templates at the side of the forms. A
cycle of operations consisted of the following:
Cleaning and adjustment of forms
Placemel1l of r.einforcing and tendons for the
lower flange and webs
Concreting of this first phase
Placelllent of reinforcing and tendons for the
upper Bange
Concreting of this phase
FIGURE 7.29. Olifant's Rin'f Bridge. increlllelltal
1""llchillg arrallgement.
the laulJching 110se had a jacking arrallgement to
acc(lIIl1llodate denection of the nose as it ap­
proached lite pier.
III cross section, Figure 730, the superstructure
is a cOllstant-depth rectangular single-cell box
girder. Depth is 12.5 It (3.BO 111); the top flange
is IH I't (5.50111) wide and the bottom flange 10 h
(3, I 0 Ill) wiele. The webs and Itll1ges are of a con­
stant thickness throughout the structure. Web
thickness is 13.75 in. (0.35 111) and contains verti­
cal iJ;lr prestressing tendons to carry shear. Longi­
tudinal prestressing is straight and contained in
the flanges. Anchorage blocks for the longitudinal
tcndons arc continuolls across the width of both
flanges (interior buttresses) to asslIre a 1I10re favor­
able distribution throughout the section. There
arc no diaphragms at the piers; the interior cor­
ner fillets are such as to permit the effect of tOl'­
sion to be accommodated by a transverse box
frame.
I.
FIGURE 7.30.
3.10
./
Olifalll's Rh'cr Bridge, cross section.
Tensioning of tendons in second phase of previous
span cast
Tensioning of tendons in first phase of span in
forms
Stripping of forllls
Launching
After launching, and before placing the structure
on its final bearings. it was necessary to adjust the
joints wit bin ~ in. (10 ml1l). The principal difficul­
ties in accomplishing this operation were:
Temperature differential between night and day,
which produced a variation in length of the
superstructure of 9.8 in. (250 mm)
Age of concrete at time of adjustment, which var­
ied from !line months to ten hours
Jacking operations, which could not retract the
structure in case of an error in pushing forward
The solution of the temperature problem was to
quickly accomplish the adjustment early in the
mornillg. Because of the constant temperature
during the night the temperature of the super­
structure was known, and its length was deter­
minable in spite of the thermal inertia of the
concrete.
The superstructure was then jacked into its
theoretical position on the abutment and firmly
maintained by a system of blockage. The temporary
tendons that had fixed the first joint were released
and jacks were placed into the joint to push the
remaining 12 spans and place the central simple
span in its exact position. The second joint was
then opened, and jacks at the other abutment po­
I,
! '
Various Bridges in France
sitioned the last II-span portion of the super­
structu re.
When the superstructure had thus been placed
in position, it was jacked lip 011 the piers, and the
temporary sliding bearings were replaced by the
permanent bearings.
7.6
Various Bridges in France
7.6.1
UiC VIADL'CT
This is a dual structure 912 ft (278 m) long on a
curve of a 3280 ft (1000 m) radius. The super­
structure was constructed by incremental launch­
ing of complete spans on sliding bearings. Resis­
tance of the structure to its dead load during
launching was accommodated by a temporary
cable-stay system in which the tension was acuusted
as construction proceeded, Figure 7 .31. ~o
supplementary prestressing was provided during
t he launching phases. A 26 ft
111) launching nose
was provided at the leading end in order to reduce
the weight of the cantilevered structure.
It is a continuous strllctlll'e supported on neo­
prene bearings and has a double-T cross section,
as indicated in Figure 732. Roadway width is 46 It
(14.0 m), and depth of superstructure is a constant
10.3 ft (3.15 111). Spans are 1:33.5 ft (40.7 111).
7.6.2
CRElL VL1lJCCT
This structure consists of eight continuous spans
having a total length of 1102 ft (336 m), crossing a
railroad and the Oise River. The project is of inter­
est in that it was launched from both abutments
without the use of a launching nose or a temporary
cable-stay svstem. However, temporary bents were
used to control the cantilever stresses. In cross sec­
tion the superstructure is a single-cell box, Figure
7.33.
Segments for each of the two half-super
structures were from 65.6 to 98.4 ft (20 to 30 m)
in length. A launching was effected upon com­
pletion of each segment. After the t\1!0 half­
superstructures had been launched to their final
position, a closure pour of 3.3 ft (1 m) in length was
consummated to provide continuity.
333
Concentric tendons from one end to the of her of
each half-superstructure, coupled together at each
phase of concreting of segments
Straight, short tendons in the top flange over the
piers and in the bottom flange, centered in thc
span and tensioned after launching
Continuity tendons, tensioned after laullchillg,
situated in webs and anchoring at the upper flange
Short parabolic tendons, located in the webs and
anchoring in the top Range, tensioned after
launching
Temporarv tendons in the upper Hange, having
the same effect as the cantilever tcndolls
7.6.3
OLl Vl.-lDL'CT
This viaduct spans the vallev of Oli ill 15 spalls of
l34.5 it (41111) for a totallellgth 01'2017 ft (GIS Ill)
at a height of 197 ft (60 m). The structure has
a grade of 5.355% and a horizontal cun'C \\ilh a
radius of 6700 ft (2046 m). Total weight of the
superstructure is IG,500 tons (I5,nOO I11t).
Incremental launching in this structure, rather
than pushing the superstructure out mer t he piers,
was accomplished b\' a restrained lowering down
the grade. The force required in braking the
structure was approximately 660 tons (tWO IIlf) as
compared to the estimated force of 1540 10m
(1400 mt) to push the structure uphill.
In its hnal configuration, because it was difficult
to accommodate horizontal forces due to braking
and seismic effects in the tall flexible piers, the
superstructure is anchored in the terrain in the
area of the abutments by a tie of a large stiffncss.
All of this longitudinal global force is aCCOIll1110­
dated in the large stiff tie. the abutments, and the
relatively short stiff piers in each bank. <c\ central
joint divicles the structure into two independcllI
structures.
Cpon completion of launching and before plac­
ing the superstructure on its permanent bearings.
it was necessary to "unlock" the joint that held the
two half-superstructures together during COIl­
struction and to adjust its position within approxi­
mately ~ in. (10 mm). This operation was COIl­
d ucted as follows:
Longitudinal prestress consists of six sets:
Cantilever tendons, tensioned before launching,
located in the top flange and anchored in fillets at
the intersection with the web
The superstructure was restrained at the upper
abutment until the distance between its theoretical
position and the end of the lower abutment was
approximately 8 in. (200 mm).
334
Incrementally L:.aunched Bridges
PHASE 1
I"~,
(~)
placing of the launching nose
concreting and prestressing of the first span
launching of the first span
e:
PHASE 2
concreting and prestressing of the second
erecting the cable-stay system
launching of the first two spans
s~an
PHASE 3
concreting and prestressing of the third span
launching of the first three spans
PHASE t.,
Ti-:.~-
concreting and prestr~ssing of the fourth span
launching of the first four spans
PHASE 7
.---P_5~_~ __ ~~.,'fL~_"2.-'D
__ " _~t,I"~ _ _ _ _ j9_!2.... ~_~~~ ___',oo:~,.oo.1\IX".nl!l).'ur;:._
~
;-
m~I'
1.------ •"---.
••••••
I,
,!,
:
,.
=.'i
'"
.
====,Ir=i.~===:::Z;.CC~~=',~:
,. ;;>-"
.1
,;----~
.. ~, ......!-, .........
-;-.
completion of launching operations
disassembling of the launching nose and
cable-sLay
<;,y';,Lt::1ll
placing on permenant bearings
placing and tensioning of phase 2 prestressing
FIGURE 7.31. Luc Viaduct. incrememallaunching phases. (0) Placing of the launching
nme. concreting and prestressing of the first span, launching of the first span. (h) COIl­
creting and prestressing of the second span, erecting of the cabk~-stay system, launching
of the first t\,'O spans. (c) Concreting and prestressing of the third span, launching of the
fIrst three spans. (d) Concreting and Prestressing of the fourth span, launching of the first
four spans. (e) Completion of launching operations, disassembling of the launching no.'>e
and cable-stay system, placing on permanent bearings, placing and tensioning of
phase-two prestressing.
The temporary tendons connecting the two half­
superstructures were successively detensioned.
However, two temporary tendons restrained the
lower half-superstructure. The upper half-super­
structure was fixed to the upper abutment by a
system of prestress bars and complementary
reinforcement installed in the upper abutment.
The t\\'o temporary tendons restraining the lower
half-superstructure were detensioned in incre­
ments, allowing the lower half-superstructure to
Wabash River Bridge, U.S.A.
FIGURE 7.32.
Luc Viaduct, cross section.
11.00
.. --. --_. - - - - - - j
5.50_----"
!
23%
I.
0
I;:::
I~
'
50
2.75
FIGURE 7.33.
Creil Viaducl. cross sectioll.
descelld to a blockillg svstelll in,the lower abutment.
Fixillg of t he lower hal f-su perst ructll re to the
lower abulillellt was thell accolllplished.
The superstrllcture
bearings.
7.7
W;IS
positioned Oll its filIal
Wabash River Bridge, U.S.A.
This structlIre. the hl'st ilIcreIllelltally launched
seglllental bridge constructed in the Ullited States,
carries two lanes of C.S. 136 over the Wabash
Rjver Ilear Covington, Indiana. It is a six-span
structure with end 'pans of 93ft 6 in. (28.5 Ill) and
four interior spans of 187ft (57 m), Figure 7.34.
Roadway width is 44 ft (13.4 m). Pier heights are
approximateh' 40 ft (12 111): average river depth is
11ft (3.35 Ill) with low water at 8 ft CZ.4 Ill) and
high water at ~4 ft (7.3 nl). The superstructure is a
two-cell hox girder with a constant depth of 8 h
(~.4 111). The project was awarded in September of
197t)· with a completion date of October 1978. The
entire superstructure was completed in ","ovel11ber
of 1977.
Original design plans prepared by American
Consulting Engineers, Inc., of Indianapolis for the
State Highway Commission called for a precast
segmental balanced GlI1tilever design: however,
the bid documents permitted alternative methods
of constructing the superstructure. The successful
contractor, a joint venture of Weddle Bros. Con­
335
struction Co., Inc., and the Ralph Rodgers Con­
struction Co., both of Bloomington, Indiana, in­
vestigated three alternatives for thc superstructure
construction. These alternates included cast-in­
place segments supported on falsework, incre­
mental launching, and the cast-in-place segmental
balanced cantilever method. Incremental launch­
ing was the successful method and reportedly
saved $100,000 over the other precast segmental
method:-' The V.S.L. Corporation of Las Gatos,
California, was the subcontractor for prestressing
and launching.
A 140 ft (42.7 rn) casting beel was located behind
the west abutment of the bridge alld could accolll­
Illodate three 46 ft 9 in. (14.25 m) segll1ents. The
forms for casting were supported on I beall1s .
which were supported on steel piling to provide a
solid foundation and prevent any settlell1ent of the
casting bed, Figure 7.35. The bottol11 third of the
two-cell box superstructure was cast at the 1l10st
westerlv end of the casti ng bed, Figu re 7.35. I twas
thell advanced 46 ft 9 in. (14.25 111), where forIlls
for the balallce of the sectioll were positioned, Illild
steel reinforcelnellt and prestressing tendons
placed, and the babnce of the seglnent cast. Figure
7.36. After the segIllent had been poured alld
cured, the 20-ton j;lcks that held the forll1s in posi­
tion, Figure 7.37. were released to break the bond
and rcmove the forl1ls. The large ll1etal fOrIm
stayed in place and were simplv swung in and out
as needed. The segl1lellt was thell advanced to the
forward third of the castillg bed for slIrLIce
fillishing by a collvelltional Bidwell screed. Figure
7.:~H, before Iaunchillg over the abutment. In this
mannel' a production-lille ll1ethodologv was
l1laintained. Three segIllents were always in vari­
ous st;lges of fabricarioll, with reinforceIllent and
prestressing telldolls continuous between seg­
ments.
The first-stage pour required approxill1ateh' s:~
vd: l (40.5 m:J) alld the second pour required frolll
101 to 130 vel:J (77.2 to 99.4 m:l). It took approxi­
mately four hours for each pour. Twenty-eight-day
design strength was 4800 psi (3.37 kg/mm~). and
6000 to 7000 psi concrete strengths were actually
attained (4.2 to 4.9 kg/mm2). A 3500 psi (2.46 kg/
mm 2 ) strength was required before stressing, and
this was normally achieved in 24 to 30 hours. As
segments were com pleted, each was stressed to its
predecessor by first-stage prestressing consisting of
eight tendons of tweh'e ~ in. (12.7 mm) diameter 27
ksi (190 kg/mm2) strands, Figure 7.39. Initially the
contractor was able to complete one cycle of seg­
ment fabrication and launching in two weeks:
336
Incrementally Launched Bridges
AT
M::::>SPAN
A"f PIERS
8-0
ELEVATION
.Q1K~ ..Of
MOVEMfNJ )100­
CONSTRUCTION ELEVATION
CONSTRUCTION PLAN
FIGURE 7.34. Wabash River Bridge: cross section of girder, from reference 6;
~trllClioll
COJ1­
details, from reference 2,
however, as experience was gained, two cycles per
week were attained.
To accommodate the launching stresses a 56 ft
(17 111) launching nose was attached to the lead
segment, Figures 7,34 and 7.40. In addition, the
four interior spans had temporary steel bents at
midspan, Figures 7.34 and 7.41. In this manner
the total structure length was divided into ten
equal spans of 93 ft 6 in, (28.5 m) during the
launching procedure.
Because of the longitudinal force on the piers
during launching, the permanent piers were tied
back to tbe abutment with four prestressing
strands each, These strands were stressed to 96
kips (43,545 kg) before launching commenced.
Each temporary pier was tied back to the preced­
FIGURE 7.35.
support.
Wabash
FIGURE 7.36.
Wabash Ri\'er Bridge, casting bed.
FIGURE 7.39.
stressing.
Wabash Ri\er Bridge, first-stage pre­
Rh'er
Bridge,
casting-bed
FIGURE 7.37.
Wabash River Bridge, side form jacks,
FIGURE 7.38.
top flange.
""'abash Ri\er BI'idge, surface finishing
337
Incrementally Launched Bridges
338
FIGURE 7040.
Wabash Ri\'er Bridge, launching nose.
J
~4,itlf'i1ffitt~~
horizontal jacks an 18 in. (457 mm) stroke. The
vertical jacks lifted the superstructure ahout .~ in.
( 13 mm) and the horizolltaljack pushed it forward
17 in. (432 mm). Each jacking o'cle required'about
fJ\e minutes, and the entire launching of a 46 rt 9
in. (14.25 m) segment required about three hours.
Temporan' bearings. Figure 7.4, were located at
each temporary bent and permanent pier. During
the launching operation workmen were stationed
at each bearing location to insert the teflon pads as
the superstructure slid over the bearings: To
maintain lateral alignment or the superstructure,
lateral guide bearing~. Figure 7.43, were also 10­
clIed at each temporary bearing and also used
teflon pads. Workmen would tighten bolts on one
side of the superstructure and loosen them on the
opposite side to push the superstructure lateralh.
Fillal positioning of the superstructure on the east
abutment was withinh in. (0.8 111m) or its pre­
~Clil>ed location.
.
7.8
Other Notable Structures
illg permanent pier bv two stavs or lOin. hy lOin.
(~S4 IIlIll hy ~54 111m) stl'llctllral sleel tubing. Fig'­
ures 7.:14 and 7.42.
The jackillg procedure during launching used
t ht' two-jack S\'stelll (one \'ertical and one horizon­
Ld) and teflon pads, as described in Figure 7.2. The
vCltical jack~ had a 2 in. (50 llllll) stroke and the
Allot her example of this I\Ve of constructioll is the
\1iihlbachtalbnkke ahout 30 llliles (50 km) south­
west or Stuttgart, West Germany, Figure 7.44. This
structure has an overall length of 1903 it (580111)
with 141 It (43 111) spallS. The far-side trapezoidal
box girder is shown in Figure 7.44 cOlllpleted from
abutment 10 abutment: the near-side trapezoidal
box girder has heen launched frolll the lefl abut­
ment and the launching nose has reached the first
pier. A general view or the SI ruct ure is presented ill
Figu re 7.45.
FIGURE 7042.
tuhing lie.
FIGURE 7.43.
bearing.
FIGURE 7041.
Wabash Ri\cr Bridge, temporary steel
bellI.
Wabash Rh'cr Bridge, structural steel
Wabash River Bridge, lateral guide
l
339
Other Notable Structures
FIGURE 7.47. \Ilihlhachtalhrticke,
stressing tendoll anchorage.
FIGURE 7.44.
\llihlbachtalhrllCke, aerial \'iew.
FIGURE 7.45.
\fiihlbachtalbriicke, general \'iew.
111
pre­
!
FIGURE 7.48. \fiihlbachtalhriicke, second-stage pre­
~tressillg ;mchorage block.
7.8.2
\liihlbachtalbrucke, segment
first-stage
.(
Some ide;1 of the size of the box girder IlW\ be
obtained frol1l Figure 7.46, showing the intel·ior of'
the fornnvork at the rear of the abutment. First­
stage prestressing telldon anchorage at the lOp or
lhe web I1l<lV be seen in Figllre 7,47. The ;lIlchor­
age block for the second-stage prest ressing is lo­
cated inside the completed box, Figure 7..tH.
FIGURE 7.46.
tiollarv forms.
!
sta­
SHEPflJ:'IWS HOlJSE BRIf)(;E, F.S(;LA.Yf)
The Shepherds House Bridge is the hI'S! illcn~­
mentalh' launched bridge constructed in Englalld.
This highway structure crosses four railroad tracks
at. Sonning Cutting, Ileal' Reading, about 30 ll1ile~
(48 km) west of London. The new structure COII­
trasts sharply with an existing brick arch srrUC[Ul'C
huilt in 1838 bv Brunei, a famolls English en­
gineer. The existing structure consists of three cir­
cular brick arches supported on tall brick piers
with the abutments founded in the sides of the
cutting.' A general plan showing the existing
bridge, railroad tracks, and alignment of the new
structure is presented in Figure 7.49. H
340
Incrementally
La~unched
Bridges
FIGURE 7.49. Shepherds House Bridge. general plan, from reference 8 (courtesv of
JnstilUtion or Civil Engineers).
III 1971 the north abutment settled and the
bridge was temporarily closed for repairs.
III \larch of ]972, hecause the life expectancy of
tile existing structure was in question and because
it did not comply with current highway standards,
the !l.finistry of Transport instructed consulting
engineers, Bullen and Partners, to prepare a study
to determine the type and method of construction
lor a new structure. The new bridge provides a
dllalillg of the existing road, and in the future the
existing bridge will be replaced by a parallel struc­
tllre.
exi~ting
Because British Rail was engaged in extensive
lIlaintenance and upgrading of the tracks prior to
introduction of high-speed trains, there would be
se\'(~re limitations on track possession. Further, it
was dictated that piers between tracks were to be
avoided and that fOllndations on the north slope of
the ctltting were not to disturb the foundations of
the existing bridge abutment. Construction work­
ing area was restricted because traffic was to be
maintained on a residential street at one end and a
trunk road at the other end. Soil conditions re­
quired that any temporary conditions that would
load or disturb the slopes was to be avoided, thus
requiring pile foundations with the pile caps at the
surface to avoid extensive excavation in the slopes. s
The consultants initially studied five possible
schemes for construction of a bridge. Schemes
using cast-in-place construction on falsework had
earlier been rejected.
An incremental launching scheme was recom­
mended, even though there were no accurate cost
data for construction in the C.K. The consultants
concluded that this scheme, although of shorter
lengt h than customary for this type of construc­
tion, would solve the problems of restricted work­
ing space and interference with residential streets
and would require the least track downtime.
The west elevation of the bridge is shown in Fig­
ure 7.50. Span lengths, determined by track loca­
tion, are 75.5 ft (23 m), 121.4 ft (37 m), and 82 ft
(25 m), The bridge is fixed at the south abutment
with an expansion joint at the north abutment. The
casting hed for the production of 31.5 ft (9.6 m)
segments was located to the rear of the south
abutment. The south abutment was located to pro­
vide maximum work space for the casting bed and
lO clear a large number of Post Office communica­
tion cables. Interior piers band c were designed to
withstand the friction forces exerted during
launching operations. In addition, pier c, located
close to the railroad tracks, was subject to damage
or complete demolishment in the event of a de­
railment. Therefore, the superstructure was de­
signed lO withstand the removal of pier c by an ac­
cident. Six untensioned but anchored Macalloy
tendons in certain segments were added so as to
preclude ultimate collapse with no live load on the
bridge and pier c removed. 7 •s
Normally, in this type of construction, the cast­
ing bed is of sufficient length to accommodate at
least two and sometimes three segment lengths,
such that the bottom flange may be cast separately
in advance of the webs and top flange. In this proj­
ect, with restricted space for the casting bed, it was
decided to cast one complete segment in one pour.
II
Other Notable Structures
_______
3'.~OO~O
____________________
341
~2~.OOO~
____
~
levels in molre& 00.
Dtm.naiQnlI in miUuneltU
FIGURE 7.50. Shepherds House Bridge, we!it elevation, from reference 7 (courtesy of
The Concrete Society, London).
A maXl!l1UI11 of three weeks was allowed for con­
struction and launching of a segment. This time
was later reduced to two weeks except for those
segments with a diaphraglll. 7 A typical cross section
of the box girder segment is shown in Figure 7.51.
The launching sequence is shown in Figure 7.52.
The steel launching truss nose was first erected
using a temporarv intermediate support. The first
segment was cast against the launching nose and
post-tensioned bv Macalloy bars, some of which
were llsed to COllnect the launching nose to the first
segment. The launching nose, in position, before
the launching of the first segment is shown in Fig­
ure 7.53. After the first segment had been
laullched forward, the next segment was cast and
post-tensioned to the previous one. This proce­
dure was repeated until the completed bridge was
I'
launched to the north abutment. The launching
nose passing over pier c is shown in Figure 7.54.
Arrival of the launching nose at pier b is shown in
Figure 7.55. The launching nose was removed
after the concrete superstructure arrived at pier b,
Figure 7.56.
The superstructure was launched over tempo­
rary bearings, which consisted of high-grade con­
crete pads with a
in. (1 mm) thick stainless steel
plate damped and tensioned across the top sur­
face. Lateral guide bearings were also provided to
keep the superstructure on line. Cpon completion
of launching the superstructure was jacked in a
predetermined sequence and the temporar\,
bearings were replaced with permanent bearings. H
The jacking force for launching was provided by
two jacks pulling on a set of nine 0.6 in. (I5 mm)
*
IOlOOmm
E
E
~
lOOO mm
.1
FIGURE 7.51. Shepherds House Bridge, girder cross section, from refer­
ence 8 (courtesy of The Institution of Civil Engineers).
342
Incrementally L!,lunched Bridges
Stage 1; Cast first unit and
connect to launching nose
Stage 2. Launch to piet C
Stages 3-5: Launch over tracks
FIGURE 7.54. Shepheld~ HOllse Bridge, launching
nose passing O\'er pier c, from reference 7 (courtesy of
The Concrete Sociel\, London).
Stage 6· Launch to pier B
Stage 7 Continue launch
Stage 8: Reach pier B and remove nose
Slage, 9 and 10: Complete launch
FIGURE 7.52. Shepherds HOllse Bridge, ~equence of
increlllcntal launching. 1'1'0111 reference 8 (collrle~y of
'"he InSI illli ion 01" Ci\"il Engineers).
FIGURE 7.55. Shepherds House Bridge, launching
nose at pier b, from reference 7 (courtesy of 'rhe Con­
crete Societv, London).
FIGURE 7.53. Shepherds House Bridge, launching
110;,(' ill position before launching, fron; reference 7
(collrlesy oj The Concrete Societ\', London).
di<lnleter cables passing under the casting bed and
anchored to I he front of the abutment. The load
was applied to a fabt'icated bracket secured to the
rear of the se"ment bv bolts coupling with the
projecting ends of the MacalJoy bar tendons in
tlte top and hottom Ranges of the segment, Fig­
ure 7.57. The two jacks were operated in tandem
by a single pUlllp. This system required 30 seconds
for jackillg and 30 seconds for retracting for each
10 in. (254 mIll) stroke. H
~,
L
FIGURE 7.56. Shepherds House Bridge, superstruc­
ture launched to pier b and launching nose removed,
from reference 7 (courtesy of The lA.lnCrete Society,
London).
Design of Incrementally Launched Bridges
343
The dimensiolls for typical cross sections pre­
sented in Section 4.5.4 remain valid for the web
I hickness, but the top flange and bottom /lange
thickness may ha\'e to be increased, depending on
the l\-pe or prestressing iayou t adopted (see Sect ion
7.9.4).
7.9.3
FIGURE 7.57. Shepherds House Bridge, segment
being bU!lched from fOl!l1work, frolll reference 7
(courles\ of lhe CO!lcrete Sociel;-, LO!ldon),
7.9
Design of Incrementally Launched Bridges
The desi),!;ller must ;Llw;L\'s remeillher th~u ill order
to cOllStrllct increlllelltalh I:lllllched I)ridges, the
horizontal alld \'e!lical aliglllllent must he either
straight or consLmt h cllned or twisted. This is
gelleralh Ilot the case, a~ road pl~lllllers ~Ire not
bridge builders..\s a l1l~llIer or fact, it is the SOn]! of
the bridge deck that has to be desiglled with a COII­
stan! radius or curvature: the traIlS\'el'se canlilc\er
of the deck Ibllge Clli be \';tried to accoIlllllodate
possible small de\·i~ltiolls.
/,9.2
SP/L\' ARR,/X(;E.HEST AX/) RI:LITEI)
PRIXClPU:' Of" COXS1RL'CT/OS
The constant-depth requirement limits the eco­
nomical lise or this const ruction Illet hod 10 spans
not longer than 150 to 200 ft (50 to 50 Ill). II is
advanlage()lIs if all the spans are equal ill length.
However, much 101l(!;er spans have been built 1)\
utilizint; special techniques ill conjullction with the
basic principle of incremelltal laullching-.
A three-span const ruct lOll ll1av be lallllched
from both sides. In this way the center Sp~1l1 can be
twice I he lel1~t h of t he edge spans wit hou t increase
of the stresses in the deck. TiIe span configuration
then becomes: L-'.!.L-L (see Figure 7,5H),
Champig-Il\ Bridge ne;lr Paris was the fil'st stnlc­
Ilire of this t\pe. Longer bridges are often
launched from one side onh (Ihe record leng-tlt is
Ihat of Olilant's Ri\er Bridge ill South Africa, ill
excess of 3:H)() ft), A.llxiiiarv temporan' devices are
llsed to reduce the hending tllotnellls in the trollt
portion of the deck (launching Ilose or lower stars)
ITPI:', .111.11'[<; .IS/) f)f.H/:',\Sf(),\S OF
SL P F. H.SrraCfL 'N,I:'
This method of construction requires a cross sec­
tion with a constant depth, since the designer has
to insure the resistance of the superstructure,
under its 0\\,11 weight, at all sections as the launch­
ing proceeds. Economic cOllsiderations dictate a
constant IllOll1ent of inertia.
Two tv pes of cross section have been lIsed to
date: the box girder and the double T. The box
girder prm'ides a better stillness and resistance to
torsion and at the same time <In easier placement of
the prestressing tendons in the cross section. The
depth of the box is llslIallv one-twelfth to one­
sixteenth of the longest span, the first value ap­
plving to larger and the second to smaller spans.
Table 7.1 su I1ll11arizes the characteristics of several
incremenralh' launched bridges.
FIGURE 7.58. Three-span sYmmetrical incremelllaliv
laullched bridge.
TABLE 7.1.
:\alllc
:\uel Viaduct,
France
BOlTigliolle
Viaduct,
France
Kimonkro
Bridge,
Year
Characteristics of IncrementaIly Launched Bridges
C ross Sect ion
41'
1976
"I
IE
13
1976
~
1978
IE
31.3'
I
39'
Tet Viaduct,
Ft'<I 11 ce
IE:
"I
~
~I
:vla rolles
Bridge,
France
Crcil Bridge,
France
344
135
807
135
Launched
Weight (t)
Vertical
Curve
Horizolltal
Curve
6,000
Slope 6%
R = 2,460 ft
807
6,000
Slope 5.5o/c
R
lIS
709
3,600
141
()60
1%
915
(It)
2,460 ft
Straight
13
Lue Viaduct,
Franfe
Oli Viaduct,
France
rotal
Length
y
I \'01'\' Coast
l'aillon
Bridge,
France
I\pical
Sp<m
(It)
34'
1976
!'
f---......
40,5'
1976
'I
~1
13
1972
I"
197H
I'
29.5'
'I
I~
36'
'I
7,900
l.l51
135
2.018
131
345
194
1,102
15,000
Slope 3.Ho/c,
Straight
Slope 1.3Vc
Curve
Slope 5.85o/c
R
= 6,712
it
345
Design of Incrementally Launched Bridges
TABLE 7.1.
(Continued)
Launched
Weight (t)
VenicaJ
Curve
(It )
.rotal
Length
(It)
262
1,732
13,000
Slope 0.7%
138
1,10,7
9,700
335
1,476
169
1.562
138
1.398
108
469
Tvpical
:\ame
Gronachtal
Bridge.
Germany
Year
1978
46.3'
I'
1
~
I
\
I~ 175' .1
Val' Viaduct.
France
1976
Inn Bridge.
Kufstein,
Germanv
1965
Sp~1I1
C ross Sect iOIl
32'
I'
I
\
'1
~r
Koehes Vallev
Hridge,
Germanv
Querlin Guen
Bridge.
Germany
'LJ
I
Ahcou
Aqueduct,
France
Ingolstadt
Bridge.
Danube
Bridge.
;;J
1967
.
19'
Hori/.ontai
Curve
R
7,217 ft
Straight
~t
'I
OJ
..... 1
---L
1978
""._M_
I
62'
0
JOt
I
,--:r:::
=t 8
6 spans
197 to
2 x
1.246
377
as. previously indicated in some of the examples de­
scribed in this chapter.
When the spans become too large, intermediate
temporary bents are used. This was done for the
first bridge over the Caroni River in Venezuela,
The record span length for incrementally
launched bridges was obtained by a structure over
the. Danube River designed by Prof. Leonhardt,
the originator of the method, Figure 7.59. The cost
of the temporary bents depends greatly ort the
foundation conditions; it may be prohibitive if the
bent height is greater than 100 ft (30 01) and soil
conditions require deep piling.
For very long bridges, intermediate expansion
joints are needed, much the same as for cantilever
bridges. The expansion joints are temporarily
fixed by prestressing during launching and are re­
leased at the end of construction to allow for ther­
mal expansion iIi the structure during service. A
very ingenious variation of this principle was de­
346
Incrementally Launched Bridges
FIGURE 7.59.
Danllile RiH'1 Bridge, :\lIst ria.
\'(,Ioped for the Basra Bridge in haq, where a COIl­
nete swillg spall was laullched IOgether with the
approach spans as a single unit alld later arr;lllged
to SCI'\(' its purpose as a lllo\'able hridge mer the
11;[\ Igation channel, Figllre 7.()O.
;. (j./
f)j'-'S!(;.\' OF !.o.\'G!Tl '/)/.\..11.. \IF.\1!1FRS FOR
nISl'ln ..IX/) 'IF.\'f)()X j'IWFlLI:'
During laullchillg-. the SIlperstructure is subjected
to cOlltinllalh ailcrnalillg bcnding IllOlllellts, so
t ha t a 11\' OIlC sect iOll is SII hjected to a conlin ual
\';ll'iatioll 01 bellding mOlllellts, hoth positi\e and
FIGURE 7.60.
neg-alive, as shown in Figures 7.61 and 7.62. These
hendillg moments are balanced by internal uni­
form axial prestressing.
In the final stage, additional tendons are re­
(juired to supplelllent the uniform axial prestress­
ing- in order to carry the service loads. Conven­
tiollal solutions are applied \0 this problem, and in
t he pre~ent discllssion we need ollly enlarg-e UpOIl
the specific problem of the axial prestressing. For
t his prestressing-, tendons are ~o arranged that the
cOlllpressi\e stresses are the sallle over the entire
cross-section;ll area. The required telldons are
placed in the top and bOIlOl1l flang-es of the box
section. The\ an' usualh' straig-ht. tClISioned be/ore
launching-, so couplers are needed at each joint
between slIccessive seglllents.
Seg-II 1<:'11 t lengt h Illa\ \,ar\, f'rolll 50 1t (15 Ill) to
/()() It (;)() Ill). As Ilotecl ill ollr discllssioll of the
progressive constnlCtioll Illethod, then' an~ lilllita­
tiolls to IIIe deck's ctpacitv 10 carr~ its own weight'
dlllillg bunchillg when the Irollt part is in can­
tilever hnolld a t\picaJ pier. To keep hending
mOIlK'llts and stresses withill allowahle values, it i~
IIsllally nccessan to lise a \;lIlllching nose, a light
steel IlH':lllher placed ill frollt of the cOllcrete
structure to allow Sllpport frolll the Ilext pier,
rather thall launching the cOllcrete deck allthe wa\,
with no support. \:lIllHTical values are given ill
Figures 7.61 and 7.62 for the critical maximum
positi\'{:, and negative Illoments during Iaullching.
AssUllling the unit \\'eig-III of the launching lIose
10 he I WI( of t he weight of I hc connete deck (a
vallie sOlllewhat lower than ;l\'crage), the critical
Basra Bridge, Iraq.
I
FIGCRE 7.61.
OFL~1l2)[6a" -i-
Critical negati\'c moments during launching with !lose,
6')1(i
0: 2 )]. '\Iultiplier: WL2/12. For ')I = 0,10:
a
/3
)d o
0,20
0,30
OAO
0.50
0.80
0.70
0,60
0.50
0,82
1.09
1.46
1.95
1.00
0.00
6.00
;VI"
o
L·
FIGURE 7.62.
(WC'1l2)(0.933
-!sp-'I> ",.>1,""'/
. in fJ'l"c./ S'j>Jh • ~
Critical positive moment during launching with nose. Ml
2.96')1/3 2 ). '\Iultiplier
WC'1l2. For ')I
0.10:
/3
,\'1,
0.20
0.30 .
0.40
0.50
0.80
0.70
0.60
0.50
0.74
0.79
0.83
0.86
1.00
0.00
0.93
a
347
348
Incrementally La,;nched Bridges
ll10ments are as follows for \'arious lengths of the
launching nose:
:'\ose Length,
I'erccnt or
hpi"ll Spall
:'faximulIl l'.foIl1ellts
Support (lHo)
Span (M ,)
iHo/Jl,
1.95
1.46
1.09
0.82
0.86
0.83
0.79
0.74
')
')­
_._1
50
60
7ll
~()
1.76
1.38
l.J1
:\!olllent factor is J-FL 2/l2
(W
wC'ight of concrete per unit length and L =
span length)
FIGURE i .65.
Technologically, the uniform axial prestress may
be illStalled in the superstructure in several differ­
above the concrete deck with steel deviation sad­
dles at intermediate joints.
The three solutions above h:l\c their relative
merits and disadvantages:
(,Il!
ways:
I.
Straight tendons rUllning through the top and
bottolll flange of each segment, joined by
couplers at the joillls between segments.
Straight tendons running through the top and
hOIlOlll flanges. anchored ill hlod.-outs inside
the box girder. Figure 7.63.
TCIIl))()ran' curved tendons may be used to
b;dance the final continuity tendons during
construction. These tendons are outside the
concrete sectioll between supports. Figure
7.64. This met hod has been used for several
large pndects.
<)
Figure 7.65 sho\\'s the Sat horn Bridge in Bangkok.
Thailand. with the temporary tendons illstalled
FIGURE 7.63.
FIGURE 7.64.
tem.
Lapped prestressing tendons.
Temporary external prestressing sys­
Sathorn Bridge, Thailand.
1. The first solution lIlay require local thick­
elling of the concrete flanges for placemenl of
the couplers. However, it is often preferred to in­
crease the thickness 01 the flanges over the entire
bridge length lO simplifv casting of the segments.
Axial prestressing tendons are permanent and
cannot he removed. They must he incorporated in
the hnal prestressing layout. The joints between
segments have to be carefully designed. owing to
the presence of couplers and concrete voids that
may significantly we<.tken the section.
2. The main ach'<lntage of the second solution
pertains to the removal and reuse of those tendons
not required in the final prestressing layout. How­
ever, the cost and difficulty of pnl"iding a large
number of block-outs offsets a significant pan of
the advantage of removing the temporary tendons.
1n order to obtain a satisfactory shear resistance
from the webs, particularly during launching with
alternating shear and bending stresses, the
configuration of the box section and location of the
upper and lower blisters must be carefully consid­
ered. This problem was mentioned in Chapter 4 as
presenting potential difficulties. A satisfactory so­
lution is shown in Figure 7.66. where upper and
lower blisters are not in the same vertical plane. A
sufficient amount of vertical prestress will insure
the resistance of webs against shear during all con­
struction stages.
3. The third solution is theoretically a satisfac­
tory one, allowing the permanent prestress to be
installed during construction and the temporary
prestress to be designed only to counteract the un­
Design of Incrementally Launched Bridges
349
reinforcement must be made
densely prestressed.
FIGURE 7.66.
Offset lapped prestressing tendons.
desired efFects of the former during moment re­
versals created bv the successive launching stages.
In practice, inst'allation of the tendons passing
from the inside to the outside of the box section is
not particularh simple. An attempt should be
made to reuse these temporary tendons to reduce
the investment in nonproductive materials.
A comparati\'e analysis between the first two
methods of temporarv prestressing has been made
for a typical railway bridge, Solution 2 requires
19% more conventional reinforcement than solu­
tioll 1 because of the many blisters and more elabo­
rate tendon layout. The total cost of materials
(concrete prestress and reinforcement) is 9%
higher for solution 2 than for solution I, These re­
SUIIS Illay be signifkantlv different for highway
bridges, where the ratio between girder load and
superimposed dead and live loads is ven different.
1.9,) ClSTlXG .1REA ,1ND
LI exCi II.\'G .\.1ETHODS
The precasting area is located behind one abut­
ment and has a length usually equal to that of two
or three segments. There are two different
launching methods:
L
The bunching force is transmitted Froll1 the
jacks bearing against the abutment face to the
bridge by pulling tendons or steel rods an­
chored in the bridge soffit.
2. A launching device consisting of horizontal
ancl vertical jacks is placed over the abutment.
The vertical jack rests on a sliding surface and
has a special friction gripping element at the
top. The vertical jack lifts the superstructure
for launching, and the horizontal jack pushes it
horizontally.
The designer should be concerned with the fol­
lowing items:
The first launching method applies high local
forces to the concrete soffit where the pulling de­
vice is anchored. Careful design of the passive
Ifl
an area already
The second launching method requires sufficient
vertical reaction on the vertical jack. This could be
critical at the end of launching, when the required
launchinD'
o force reaches its maximum with a corre­
sponding small vertical reaction.
A very precise geometry control is required during
launching. The possibility of foundation settle­
ment must be considereel in the design. Whichever
launching method is used, after completion of the
launching· procedure the deck must be raised suc­
cessively at each pier so that the permanent bear­
inD's
o may, be installed. This phase also calls for careful analysis.
1.9,6
L1USCHING NOSE /l1','D
TE.HPORARY STAfS
The large cantilever moments occurring in the
front part of the superstructure that is being
launched from pier to pier inevitably call for spe­
cial provisions to keep the bending stresses and the
temporary prestress within allowable and eco­
nomically acceptable limits. Two methods have
been used together and separately, as previously
mentioned:
:\ steel member made either of
plate girders or of t.russes is temporarily pre­
stressed into the end diaphragm of the concrete
bridge, which is the front section of the deck dur­
ing launching.
Tower and sta}'s: This method was described ill
Chapter 6 for progressive construction, Its appli­
cation to incremental launching, however, needs a
special approach, because the relative position of
the tower and the Slavs changes constantly with re­
gard to the permanent piers.
Launching nose:
The advantage of the launching nose to reduce
cantilever momems in t.he concrete superstructure
was discussed in Section 7.9.4. It is important not
onlv to select the proper dimensions of the
launching nose but also to take into proper account
the actual Aexibilitv of the steel nose in comparison
to that of the concrete span. This relative Aexibilitv
may be characterized by the following dimension­
less coefficie 11 t:
K
=
£..1.,
£,./"
350
Incrementally Launched Bridges
where E, and Ec refer to steel and concrete moduli,
and fs and f" are the moments of inertia of the steel
nose and concrete superstructure. Figure 7.67 pre­
sents the results of a study analyzing the variation
of the maximum support moment in the concrete
deck for different launching stages with the rela­
tive stiffness K. This chart conf1rms the obvious
fact that a flexible nose has only a limited efficiency
in reducing the moments in the concrete deck. The
following table gives the characteristics of several
structures using a launching nose and serves as a
reference for preliminary investigations of the op­
timum launching method.
Brid),('
Wabash Ri\'(T
Oil Rin-r
Sao lit'
Roche
Launching
\\'('i),(l1! of'
:\os(' Lenglh
Launclling
lit
:\os(' (!ons)
(111)]
Slavs
iifi
:10
:\0
!1~)
:-16
Yes
()!1
:\0
:\0
( 17)
(I X)
93,5 (2X.:i )
12-l.!'l (:~H)
90
To allow the method to be effective in all
launching stages, it is necessary to constantly coJ)­
trol the reaction of the tower applied to the con­
crete deck. When the tower is above one pier; it is
totally efficient. When launching has proceeded
for another half-span length, the tower and stays
produce additional positive moments at midspan,
exactly contrary to the desired effect. For this rea­
son the tower may be equipped with jacks between
the concrete deck and the tower legs, and the tower
reaction may be constantly adjusted to optimize the
stresses in the concrete superstructure. Figure 7.68
shows a device being successfully used for the first
time in the construction of the Boin'e Viaduct,
near Poitiers, France,
/,9,/
PIERS ASD FOUSDATIOXS
The loads applied to Ihe piers and foundatiom
during the incremental launching procedure are'
\'er\' difIerelll from those appearing during ser­
vice, The static configuratioll of the piers is also
For longer spans the launchillg nose is not neces­
sarily the optimum solution, while Icmporan bellts
lll<l\' also he expensive, A tower-and-stay sYstem
has been successfully used either alone or in COIl­
jUIl('(ion with a laullching nose to reduce the call­
tilc\'er mOlllents ill the front part of the super­
structure,
~,-+
~
t..
1
...
/./
",$
FIGURE 7.67.
lllOlllClll ,
".8
(),'
Variation of the maximum support
FIGURE 7.68.
Boivre Viaduct, near Poitiers, France,
351
Design of Incrementally Launched Bridges
different. During construction, the bridge slides
over the pier tops and the buckling length of the
piel- is larger than that during service. The hori­
zontal force applied to the pier top is also higher
than during service, thus requiring a close study of
this construction phase.
Load, Acting on the Piers The various systems of
horizontal forces that may act on the piers depend
on the followillg:
Longitudinal profile of the superstructure
Direction of launching
______i'Eiction coefficient of sliding bearings
Notation:
()
angle of hridge superstructure with respect to
the horizontal; tall I:J
r
¢ = angle of friction of sliding bearings: tan <p p
R = total reaction of the superstructure on the
pier: vertical and horizontal components V
and H, normal and tangential components N
and T
(h)
FIGURE 7.69. Reactions on piers during launching.
upward launching. (b) downward launching.
(a)
The following rom cases will be considered (see
Figure 7.69):
I.
8 > 4>, upward lalillching: Sliding starts on the
bearings when the inclinar.ion of the reaction R
with respect to the vertical is:
F = N(tan ()
3.
a II <p,
H
//tan(II+4»
For smail values of I} and <1>:
H
2.
(r
+
p)V
<p, downward launching: Sliding starts
when a
I:J - (p. The horizontal force on the
pier acts in the direction opposite to that of
movement with a value:
II
H
Vtan(e~cf»
. For small values of the angles:
H=(r
p)V
Because p varies with environmental condi­
tions (cleanness of the plates in particular), the
launching equipment and the pier will be de­
sjgned for H = rV. The downward movement
of the bridge is controlled by a restraining
jacking force:
tan 4»
N(r - p)
For the same reasons as above. the safe value
of F is equal to Sr.
I} < 4>, upward launching:
As above, the hori­
zontalload applied to the pier is:
I-I
4.
or F
(r
+
p)V
8 < 4>, downward launchiug: In this case the
horizontal load on the pier is applied in the di­
rection of the movement with a value of:
H=(r-p)V
Because of the possible variation in the angle
of friction, it is safer to provide a braking sys­
tem to control the movement of the bridge.
Pier Cap Detailing The pier caps must be care­
fully detailed in order to provide room for the fol­
lowing devices:
Temporary sliding bearings
Vertical jacks to lift the bridge after launching to
install the permanent bearings
Horizontal guiding devices during launching
352
Incrementally Launched Bridges
Adjusting jacks for correction of the relative dis­
placements bel\~) piers and deck
/
Moreover, to {educe the pier bending moments
induced by launching, the sliding bearings are
often eccentric. However, it is possible to reduce or
balance this horizontal force b\ installing ties an­
chored in the ground. If the piers are verv high,
the horizontal force can be eliminated bv using
jacking equipment directh' installed on the piers.
Demolition of a Structure by
Incremental Launching
7.10
\\'e close this chapter with an unusual application
showing the interesting potential of incremental
lallnching. An overpass structure over the A-I
!l1otorwa\' non h o/' Paris needed to he demolished
{()I' replacement by another structure as part of a
highway relocation program. The limited head­
room hetween the existing bridge soffit and the
clearance diagram. IOget her with the considerable
Iraflic on 1he major I1lOlOrw<\v providing pcrrna­
nenl access from Paris to Charles de Gaulle Air­
port, made all conventional methods of demolition
extremely diITicult and unadapted.
A very simple scheme was devised whereby the
deck was launched awa\, from the traffic onto the
approach embankment to be conventionallv de­
molished at leisure. The dimensions of the bridge
-
LAUHQlING
--
and the principle of the method are shown in Fig­
ure 7.70. The 900-ton st.ruct.ure had a width of 26
ft and the following spans: 46,
46 ft.
The existing reinforcing did not provide th'e nec­
essary strength to resist superstructure dead load
during launching. Therefore, a rear launching-out
tail 26 ft long was installed at the end opposite the
direction of launching, while exterior post-ten­
sioning tendons were placed above the deck \0
strengthen the structure.
The bridge was lifted off its hearings 7 in. to in­
stall sliding bearings and lateral guiding devices in
preparation for the operation. The whole opera­
tion was performed in
weeks as fol\ows:
Design and preparation of the contract
Mobilization and purchase of equipment
Launching
References
I. \",'illi Baur, "Bridge Erection b\ Launching b Fast,
Safe, and Efhcienr," Cillit ElIgilll'l'1'illg-ASCE, Vol.
47, :\0. 3, ;"1arch 19i7
REAR NOSE {TAil
--- --
II
_-+ . . . . . -'4'-"6~'_ _+-
LATERAl.
;UIDE5
900 t
TOTAL W£lGIlT
PROCEDURE
2}
lI!'T
TOTAL BRIO(O[
PLACE ROLL~RS
SCHEDULE
7~
0\1"'1 PIERS
_ DESIGN
_ Moe.
3)
IN$,ALL
APPROACI4
CONCRE,E
4)
!'ILL AND
8,
TOTAL
51('2 WEEKS
CONTRACT:
'2
2
PURCHASES
_ LAUNCHING
BEAM~
PLACt[ PROVI510.. Al..
A REAR .. ost:
'26
FT.
PIT
,RAFFIC IN,f:RRUP'TlOH :
AND
(10
P.M. TO
LONQ
FIGURE 7.70,
g
Traffic was interrupted for onl\' fOllr nights be­
tween 101'.\1. and 6 ."o.:V1. The operation turned out
to he a complete success in ~pitc of its originality.
+-----'4""b"-'---+-t _ _"",55"-'_ _-+__-""5,,,,,5_'
1/
2
2
Bridge over A-I, launching out.
6
,...M.)
4
1,i!(OI-!.'T!I
353
References
2. Anon., "First I ncrementally Launched Post-Ten­
sioned Box Girder Bridge to Be Built in the enited
States," Bridge Report, ifec;;mb~r 1976, Post-Ten­
sioning Illstitute, Phoenix, Ariz.
3. Arvid Grant, "Incremental Launching of Concrete
Structures," Journal oj thl' A //Iaican COllcrl'te Institute,
Vol. 72, :'\0.8, August 1975.
.t. Anon., "Val Restel Viaduct for the Provincial Road
:'\0. 89 :-.lear Rovereto, Trenro," Pre.I'/rl'ssf'd Concrele
Structures ill Italy 1970/197.J., ;\ssociazione Italian<l
Ct'lllento Armato E PrecornplTS~() (.\\CAP) and
Associaziollt' I wli,m<l Ecollonica Del Cemento
(AITEC), Rome 1974.
5. Anoll., "Segmental Box Girder Bridges \fake the Hig
Time in C.S.," Engiuntiflg Sl'w\-Rurml, \larch 2,
197H.
6. Anon., "Wabash River Bridge, Covington, Indiana,"
Portland Cement Association, Bridge Report,
SR201.01E, 1978, Skokie, Ill.
7. M. Maddison, "Crossing the Cutting willl Segmenrs ar
Sonning," Concrele, The Journal of Ihe Comrl'te S()cil'ly
(London), Vol. 12, :'\0. 2, Februarv 197H.
8. K. H. Best, R. H. Kingston, and \1. J. Whatley, "lll­
cremental Launching at Shepherds House Bridge,"
Proceeding-r, Insiliululli oj Civil Ellg/llnn, Vol. ()4, Part
I, February 1978.
8
ConcTete Segmental Arches,
Rigid FTatnes, and l~russ BTidges
8.1
8 ')
8.3
8.4
8.5
INTRODUCTION
SEGMENTAL PRECAST BRIDGES OVER THE
MARNE RIVER, FRANCE
CARACAS VIADUCTS, VENEZUELA
GLADESVILLE BRIDGE, AUSTRALIA
ARCHES BUILT IN CANTILEVER
8.6
RIGID·FRAME BRIDGES
8.7
8.6.1 Saint Michel Bridge in Toulouse. France
8.6.2 Briesle Maas Bridge. Netherlands
8.6.3 Bonhomme Bridge, France
8.6.4 Motorway Overpasses in the Middle East
TRuSS BRIDGES
8.7.1
8.5.1
8.5.2
8.5.3
8.5.4
Review of Concept~ Summary of Structures with
Temporary Stays
Neckarburg Bridge, Germany
Niesenbach Bridge, Austria
Kirk Bridges, Yugoslavia
8.1
Introduction
All arch hridge, in a pnlpcr setting, is an eleganl
and graccful structurc with acsthetic appcal. IIl­
... tiJl(tin.-h', a lannan relales to all arch hridge as a
forlll Ihat follows ils function. Long before pre­
sl ressed concrete was devcloped as a tech Ilolog\',
COlHTcte arches were lIsed for long spans, taking
advantage of the compressivc stress induced bv
gravitatiollal forces into a ctIned member Illuch as
earlicr gClJcrations of huilders had done with
Ill;tSOlJn' arches.
Three bridges designed and built ·bv Eugene
Fre\'ssinel het ween 1907 aml 19 lOin central
Frallce were 10 become a major landmark in the
dc\'cloplllcI1I of concrele struci ures. I n the Veur­
<Ire lhidge, Figure H. I, the three hinged rein­
forced concrete arches had a dear span of 238 ft
(72.50 m) alld an unusual rise-to-span ratio of] 115
diclated by the topography of the site and the sud­
den floods of' Ihe Allier River. The \'enture was an
unqualifled success both during load testing and
aher opellillg 10 traffle. As Freyssinet wrote in his
memoirs:
354
Retrospect on Concepts for Concrete Truss
Bridges
8.7.2 MangfalJ Bridge, Austria
8.7.3 Rip Bridge, Australia
8.7.4 Concept for a Cro~sing of the English Channel
REFERENCES
,JI(I,I a Iriu'lIIjlh. Oil Ihl' riKlil b(III1i, (I hill
{)lwrlou/iIlIK lli(' hridK(' ,lilt was ottlljlir't/ liv Sf'l'f·ral
Load If,llillK
Ihow(JJu/ stH·r/alon 11,110 had lalil'lI (ht'lr plate alrNu'.)' al
dawlI 10 11'{1Ith llif' failurl' o/the liridW' !,ret/ictcd Ii) (J
lowl //f'Uls/m/H" ,101d 10 sOllie /II/haN))' (olll/H·lilor. Thesl'
hopI'S WIT!' d(,(l'iZ'nl, (!lui wc Iwd a COli Ii IIUOU5 Iml!' of
/iNn'v ,,[mill rolln,l tra;'diIlK till' bridK(' bark and Jorth
quilf ullabl!' 10 prodllte (/l)vlhillK //lure tho II Ilu· rompuled
{'{wi" rlff/I'(lio/l.1.
Belweell 1907 and 1911, howe\'er. fears de­
veloped in Frevssinel's mind. II seemed thai the
hand rails, which had been properly aligned al the
lime of Ihe load lest, were showing some convexity
IOwaI'd Ihe sky £II the Ilodes of Ihe crown hinges. By
the spring of 1911 the crown had moved down­
ward as much as 5 in. (0.13 m), and corre­
spondingly the springings had raised appreciably.
Without telling an~'one, Freyssinet mobilized a
team of four devoted men and placed hydraulic
rams at the arch crowllS to raise the bridge spans to
their original profile; he then replaced the hinge
by a rigid concrete connection between the two
abutting half-arches. This near-disaster was the
Introduction
- -
--- - FIGURE 8.1.
first consefluence seen in a 'itructure of a phenom­
enon t heretofore com pletel v ignored: long-term
concrete creep.
Other beautiful concrete arches were also con­
structed in the same period. The Villeneuve
Bridge over the Lot River in southwestern France,
Figure H.2, is an interesting example. The twin
arch ribs are of plain concrete with a clear span of
316 ft (96 m) and a rise of 47 ft 4 in. (14.5 Ill). Each
rib has a solid sectioll 10ft
m) wide ~Ind 4 ft 9 ill.
(1.45 m) deep built in at both ellds illto the con­
crete abutments. The reinforced concrete deck
rests upon the arch ribs through a series of thin
spalldrel columns, faced with red brick.
Construction began shortlv before World War I
and was interrupted for four year'i, fortunately not
before the concrete arch ribs could be GIst on a
wooden falsework, Figure H.3. Inllllediateh' upon
completion, hydraulic rams were used at the
midspan section to lift the concrete arches off the
Ldsework and acti\'ely create the compressive stress
in them, a techniqlle from Fre\ssillet's fertile mind
that already contained the germ of the idea of pre­
stressing.
ct
FIGURE 8.2.
355
Villeneuve Bridge m'er the Lot River.
\'curdlc Bridgc.
The bridge was completed in 1919 and kept the
world's record for long-span concrete .'itructllre.'i
for several years. The photograph appearing in
Figure 8.2 was taken bv olle of the authors in the
summer of 1980; it shows that beautiful structure
in a rell1arkable state after sixty vears of contillu­
ous operation under constallt urban traffic.
Another Freyssinet design, the TOlllleills Bridge
over the Garonne Ri\'er, was built at the sallle time,
~\I1d he considered it to be one of his nicest bridge
structures, Figure 8.4.
The Plougastel Bridge in Brittal1\, Figure I.:~8,
reached for longer spans with concrete arches. For
t he first time a box section was emploved, calling
on an ingenious method of construction in which ,I
wooden falsework was floated into position and re­
used se\Tral tillles for the \'arious arch ribs. Di­
mensions of the structure and t\'pical details of the
arches are shown in Figure 8.5, which is a bcsilllile
of a document published in 1930.
The three arches ha\'e a span length 01611 ft
(186.40 m) and GIlTV a single-track railroad ;lI1d a
two-lane highwa\'. The reinforced concrete trussed
double deck ,ICcoIllIllodates the train track Oil its
lower level and the highway on the upper. ;\Tear
the arch crown in each span, the train passes
through the arch rib.
The arch ribs were onlv slightlv reinforced and
the quantity of steel was 39 Ib/\'d:l (2:~ kg/Ill:I), in
spite of the relati\'ely thin walls used for the box
section.
The three arch ribs were constructed one after
the other on a temporary wooden arch built on
shore and Aoated into position for each of the
three concrete arches, Figures 8.6 and 8.7. This
wooden arch was 490 ft (ISO \11) long and weighed
550 tons (500 mtl, including the two reinforced
concrete end sections, which allowed the thrust
created by the concrete arch ribs to be transferred
1.>0
c.n
O'l
LE
GENIE
CIVIL
~--~~~~~~~~~.-
i"
,
---
-
'.
Fin,1
Fin'.! 11;)
1) I'~l
ail::;
Fin·:\
Fill, 2.
Dem.] cli:val.Jon
. \ Il
ell
flfj
Filr·~j
rhl
.1.
Fi(I·8
!'iff·l>- Dcml-coope du tabhm', a
clef
FIGURE 8.3.
ViIlCIlClI\'L'
Tdrtiel1p
rill
tablw['
Segmental Precast Bridges Over the Marne River, France
FIGURE 8.4. Tonneins Bridge over the Garonne
River, France.
to the arch spnl1gll1gs completed earlier on the
foundation caissons.
Two barges and a temporarv steel tie slightlv
above the water level, with the help of the large
tidal range, allowed the tral!sfer of this faisework
from the construction area to the three positions of
use and its final return after completion of the con­
crete structure.
As this outstanding ulldertaking neared COIII­
pletion in 1930 after live veal'S of uninterrupted
effort, Frevssinet expressed his thoughts as fol­
lows:
In B riitan.v light is lihe a fail)' who cunsta Iltf.y plays at
cOl'aillg nature with [many! changing coats, now of
Ifad, nuw ofsifl'l'T or o//Jear/s, or of something immllte­
. rial and radiant.
Toward the fe'ming 0/ the load testing of lhe bridge. she
had spread her most sumptuous treasures on the roadstead
and each line 11' lhe work, changl'd into a lung rosary
unreal light, added another tOl/ch of beaut)' to till' mar­
vellous whole, proving in this way tltat the Fair.v of the
Roadstead had already adopted the child that men had
im/J()sed Oil her and had known how to weave for him
garments magnijiant enough to hide all the imperji'ctiolls
of the worh.
8.2
Segmental Precast Bridges over the
Marne River, France
Located some 30 miles (50 km) east of Paris, the
Luzancy Bridge represents probably the first ap­
plication of truly segmental construction as we
357
know it today. It incorporated so many innovations
in a single structure that it would not be out of
place in today's modern bridge technology.
The single-span structure, Figure 8.8, is a
double-hinged arch with a distance between hinges
of 180 ft (55 m) and a very tight clearance diagram
for river navigation that allowed only 4 ft 3 in.
(1.30 m) below the finished grade of the roadway.
Consequently, not only is the bridge structure very
shallow, 4.16 ft (1.27 m), at midspan, but the rise­
to-span ratio of the arch is unusual: 1123. The
bridge consists of three parallel box sections made
up of pre~ast segments 8 ft (2.44 m) long, con­
nected after placement in the structure by precast
slab sections at both top and bottom Hanges, Figure
8.9.
The bridge is prestressed in three directions:
The 4 in. (0.10 m) webs are vertically prestressed
resist shear.
to
The longitudinal box girders are then prestressed
to connect the precast segments and resist bending.
The negative-moment prestressing tendons at the
top flange level over the arch springings are lo­
cated in grooves provided at the top surface of the
precast segment upper flange and are ultimateh
embedded in a 2 in. (50 mm) concrete topping.
This dense, high-quality concrete pavement pro­
vides the sole protection for the high-tensile steel
wires and also sen'es as the sole roadway wearing
course. In spite of the excellent behavior of this
structure after more than 34 years of operation, it
would probably be difficult to envisage duplicating
it todav.
Transverse cOllllection between the box girders
and the connecting slabs is achieved by prestress­
Ing.
There was no cOllventional reinforcing steel in
the bridge superstructure except in local areas.
such as the Freyssinet concrete hinges at the arch
springings. The erection was just as remarkable as
the conception of the bridge. Each box girder con­
sisted of 22 segments, which were cast in a central
yard at the rate of one a dav (little progress has
been achieved after thirty years). Afterward thev
were carefully aligned on concrete blocks to take
the profile of the finished structure with proper
provision for camber. The tin. (20 mm) wide joints
were dry packed to allow segment assembly by pre­
stressing. In fact, the 22 segments of each box
girder were assembled at this stage in three units:
two side units made up of three segments each. and
the center unit incorporating the remaining 16
<:;0
CJl
00
LE GENIE CIVIL
ONT
,EN
ETO
AETvlE, SUR
EL ORN, PRES DE PL 0
GAS
'ad.. tUl M¥I
"'I'r'M,/In"IN/iV!
~;(T.,t:"--
.FIGURE 8.5. Plougastcl Bridge. dimensiolls of the st rurt II Ie alld details or the arches. a
facsilllile of a docllmcllt puhli~h('d ill I!1:30.
L (
NIS
)
Segmental Precast Bridges Over the Marne River, France
FIGURE 8.7.
FIGURE 8.6.
359
Plougastel Bridge, wooden falsework.
Plougastel Bridge, wooden falsework.
segments with a length of 170 it (52 rn) and a
maximum weight of 134 tons (122 mt). All three
units were assembled on the bridge centerline im­
mediately behind one abutment, while the delta­
shaped sections representing the arch springings
were GIst ill place over the abutment in their final
location in the structure.
A special aerial cableway made up of two steel
towers resting on both batiks and properly an­
chored to the rear, a svstem of suspended winches,
ane! a unique elliptical drum aHowed the transfer
of the precast girder units from their assembly po-
.j
,
~.:1,~.j".J
,
FIGURE 8.8.
LuzaIlCV Bridge.
foulre median/] - Dem! coupe dans (axe
Oemt· coupe
a /a
FIGURE 8.9.
eM
Dem!· coupe
a 211 "'00
de la eli
Luzancy Bridge, concrete dimensions.
360
Concrete Segmental Arches, Rigid Frames, and Truss Bridges
51110n on the banks to their final location in ~<
structure. In spite of a seemingly involved concept,
the operations were carried out safely and rapidly;
a center beam was placed in only eight hours and a
complete arch including all preparatory and
finishing operations was assembled in 120 hours,
Figure 8.] O.
Another interesting feature of this structure was
the incorporation at both arch springings of Freys­
sinet fiat jacks and reinforced concrete wedges
between the arch inclined legs and the abutment
sills, to adjust and control the arch thrust and the
bending moments at midspan.
FIGURE 8.12. One of the five Marne River Bridges:
'The bridge was opened to traffic in May 1946
Esbly, Anet, Changis. Trilbardou, and lJssv.
after successfullY proving its structural adequacy
Figure 8.12, at the following locations: Esblv, Anet,
through a comprehensive series of static and
Changis,
Trilbardou, and Ussy. All five bridges
d\namic load tests, following a custom still in use
have
the
geometric dimensions shown in Figure
today in several European countries. Figure 8.11
8.13:
gives a view of the finished structure.
This first precast segmental arch bridge was fol­
Distance between hinges: 243 it (74 m)
lowed a few years later bv a series of five other
Rise of the central axis at the crown over the abut­
structures, all of the same type and in the same
ment hinge: 16.3 ft (4.96 m)
geographical area, the valley of the Yfarne River,
Depth at crown: 2.82 ft (0.86 111)
Deck width: 27.5 ft (8.40 m)
The deck structure is made up of six precast gir­
ders, each consisting of:
Two precast
spnngmgs
delta-shaped
sections
at
the
Thirty-two precast' segments 6.8 ft (2.07 111) long
and weighing from 2 to 4.2 tom (1,8 to 3.8 mI).
FIGURE 8.10.
Luzanc" Bridge, erection of central
section.
FIGURE 8.ll.
rise.
Luzaney Bridge, view showing flat arch
The same design and construction principles
used at the Luzancy Bridge were repeated for this
series of five bridges, except for some improve­
ments commensurate to the experience gained
from the first structure and taking into account the
importance of the project. Precasting of the 960
segments was achieved in a factory completely en­
closed and using the most modern concrete man­
ufacturing techniques of that period.
Each segment was fabricated in two stages in
heavy steel forms. Top and bottom flanges were
cast first, with high-strength steel stirrups em­
bedded in both units. After strength was achieved,
a set of steel forms equipped with jacks was placed
between the flanges, which were jacked apart to
stress the web pretensioned stirrups. Then the web
was cast between the flanges. There was no need
for any conventional reinforcing steel in the pre­
cast segments.
The concrete was vibrated with high-frequency
external vibrators, then compressed for maximum
t::!
:
~4
ti-;-~
,
>}.
",
,.~.
"
;
,
~
~
riii~
It
.­
~
~
or,
or.
~
~
;..
C'll
:..,
~
.,
-
t
~
j
§
"
f
]
::!\
~
~
.e
,.;
~
8'
S
:it
]
~~
~
361
362
Concrete Segmental Arches, Rigid Frames, and Truss Bridges
compaction and steam cured for a fast reuse of the
forms. The equivalent 28-day cylinder strength
was in excess of 6500 psi.
l\:ear the precast factory, an assembly yard al­
lowed the segments to be carefully aligned and as­
sembled by temporary prestressing into sections,
which were transferred into barges to be floated to
the various bridge sites. Each longitudinal girder
was thus made up of six sections:
The two delta springing sections
Two illtermediate five-segment sections
Two center ten-segment senions
Halldling or these various sections was perforl1led
In the Llizalln cahle-way properl\' rearranged for
the purpose.
The stahility oj the side scctiol!s, at both ends,
was ohtaillcd 1)\ temporan' calltilcHT cables <lll­
rlwred ill the ahUltllents, while the two cenler sec­
liolls wcre sllspellded to Ihe cableway uIHil casting
01 tlte wet joinls was completed and longitudinal
prestressillg illslalled to allow the an:hes to support
their OWlI weight. Figures I:U4 through 8.16 show
Ihe various sequellces of the an'l1 cOllstructioll,
while Olle 01 the finished hridges is shown ill Figure
H.li,
The qu,llltities of malerials for the superslI'uc­
ture were ven low, considering the span length
alld the slenderlless or the stnlcture:
FIGURE 8.15.
Marne River Bridges. ereclioll of cell­
tral se('lioll.
Precast ronCl-ete: :lS:I y<1'I (2iO m:')
Reinforcillg' steel: 13.2 tOllS (12 ml)
Prestressing steel: 13.2 tOllS (12 mt)
For a deck area of 6540 it 2, the quantities per
square foot were:
FIGURE 8.16.
t ral sen ion .
\larne Ri\'er Bridges, erection of C(,I1­
Precast concrete: 1.46 ft 31ft 2
Reinforcing steel: 4.0 Ib/ft 2
Prestressing steel: 4.0 Ib/ft 2
FIGURE 8.14.
Ii 011.
1\larne River Bridges, erened end sec­
As in the Luzancy Bridge, the high-density con­
crete placed over the exposed longitudinal pre­
stressing tendons was also used for the roadway
Caracas Viaducts, Venezuela
\larne Ri\'er Bridges, cOllJpleted struc­
FIGURE 8.17.
ture.
we;lrillg course. The behavior of these bridges has
been excellent for thirty years,
8.3
Caracas Viaducts, Venezuela
In Venezuela in 1952 a highway was being con­
structed between Caracas and La GlIaira airport.
Alignmem of' this highwav necessitated crossing a
gorge at thrt'e locatiolls :vith relativel\ large
bridges. These structures were designed and con­
structed LInder the direction or Eugene Frevssinet. I
,·\lthollgh the three bridges aI'e similar in ap­
pearance, Figures 8.18 and 8,19, thev vary In
FIGURE 8.18.
Caracas Viadtlcts, Bridge I.
TABLE 8.1.
Bridge
363
Caracas Viaducts. Bridg('s '2 and :1.
length as shown in Table 8.1. ~ Preliminary investi­
gations indicated that adequate soillllaterial would
probably be found irregularly at great depths.
Construction of abutments to resist large bending
moments under these conditiolls would be difficult
if not impossible. The decision was therefore lIlade
that the abutments would resist olllv the centered
thrust or the arches alld that the hending moments
applied to the abutment would be reduced, as far
as practical, to zero. This required that hinges be
located as Ileal' as possible to the points of origin of
the ;ll\:hes. Because of consideration of long-term
creep deformation Oil bllckling of tlte arch and
possible conscq lIences of abut llIent displacemcnt
as might be caused bv an earthquake, the decision
was made to eliminate a crown hinge, thlls result­
ing ill t\,'O hinged arches,'
Although rhe bridges v<lr~' consider;lbl; in di­
l1lensions. thev are quite similar ill appearance, Be­
calise of lhe vallev prohle, it was possible to use the
same basic desigll for all three structures. All were
designed for A:\SHO H20-44 loading. Wherever
possible, the elements were standardized ill order to
minimize design and maximize precasting and pre­
fabI-icat ion.
Pilasters were placed at each end or the arch in
Bridge 1 so as to avoid an unpleasant appearance
of a change without transition from the main
structllre 1.0 the approach viaducts.
Caracas Viaduct Arches
Total Length
Hciuht lrom
Bed "of Gorge
10 U It C)08.0 111)
IBO It (25:~ m)
700 ft (2I3 ...t m)
230 It (70.1 Ill)
2..t0 It (73.2 lll)
170 It (51.0 tIl)
\lain Span
190 It (151.H Ill)
4:70 ft (14:5.7 111)
4;"):3 It (131:\.1 Ill)
364
Concrete Segmental Arches, Rigid Frames, and Truss Bridges
",
I ,
Piers of the access \ltaduct.
hIOged a! the h:(l!
Caracas S.1e
FIGURE 8.20. Caracas Viaducts, cleYUlioll of Bridge 1, from reference 1 (courtesv of
Ciyil Enginecring-ASCE).
An elevation of Bridge 1, Figure 8,20, shows the
principal dimensions and foundations of the arch.
The three hridges have identical cross sections,
Figure 8.2l. The poured-in-place concrete deck
topping varies in thickness from 2 in. (50 mm) at
the edges to
in. (190 mm) at the center to pro­
\'ide a trallsverse slope of l.57c for drainage. Each
deck span, except at the crown, consists of eight
precast prestressed I girders. Variations in span
lengt h of the deck girders are accommodated by
adding or rcmoving standard form units. 1dentical
transvcrsely prestressed precast stay-in-place deck
slahs span transversely between the deck girders.
Continuity of the deck girders is accomplished by
longitudinal tendons placed in a groove in the top
of the top flange of the girders. 2
Approach piers alld spandrel columns over the
arches consist of three I-shaped columns of a
standard cross section shown in Figure 8.21. A
five-segment precast cap beam on the columIls re­
ceives the eight deck I girders. A perspective of the
deck over the piers is shown in Figure 8,22. The
precast deck girders, cap beams, and slab are sup­
ported on the cast-in-place piers, and the whole as­
sembly is prestressed vertically, transversely, aI1d
longitudinally.
The center span consists of three parallel
double-hinged arch ribs 27 ft 6 in, (8,4 m) on
center, Figure 8,21. Each arch rib is a box with a
width of 10 ft 6 in. (3.2 m) and a slightly varying
depth fmm 9 ft 6 in, (2,9 m) to lOft (3,05 m) at the
supporting points of the deck. To provide in­
creased capacity to resist end moments developed
by horizontal loads, the width of the ribs is in­
creased to 17 ft (5.18 m) at the spring lines. The 5
in. by 5 in. (127 mn) x 127 mm) fillets provided at
each inside corner of the box are to reduce the
concentration of torsion stresses. Thickness of the
bottom flange of the box rib was kept to a
minimum to reduce weight on the falsework. The
~ standard cross section through arch
:"1",
"'
~>o'~ i I ~"t,~
* - - 1 0 ' 6 11 - - ­
,
Cross section of pier A-A
FIGURE 8.21. Caracas Viaducts, typical cross section, from reference 1 (courtesy
of Civil Engineering-ASCE).
Caracas Viaducts, Venezuela
365
FIGURE 8.22. Caracas Viaducts. perspective of deck over piers, from reference
1 (courtesy of Civil Engineering-ASCE).
thicker top flange provides the box rib with the re­
quired area and moment of inertia for resisting
t hrllst and live-load llIoments.
Design of these structures considered a design
wind pressure of 50 psf (2.4 k~/m~). The arch ribs
carry part of the wind pressure to which they are
directly subjected: the remainder is transmitted to
the deck structure bv bending of the spandrel col­
umns and the connection of the arch rib to the
deck at the crown. The arches were assumed to be
transverselv fixed in the foundations, the end mo­
ment developed in the springings resulting in a
slight transverse displacement of the pressure
line.~
Thus, the deck structure was chosen as the prin­
cipal member to resist wind loads, requiring the
exclusion of all Joints in the deck from abutment to
abutment. The condition of deck continuitv leel to
the attachment of the deck to the arch on both
sides of the arch crown. This was aCCO!1l plished by
prestressing the continuous cables provided over
the top flange of the girders and anchoring them
into the arch. Six girders were connected to the
arch in this manner; the two intermediate girders
that 'do not rest directly on the arch were
lengthened to the crown, Figure 8.21. 2
During construction, an open joint was provided
at the crown. In this joint Freyssinet Hat jacks
staggered with concrete wedges were inserted,
acting as a hinge for the arches to adjust the pres­
sure line during different phases of construction.
Expansion and contraction of the deck due to
temperature, creep. and shrinkage take place over
an approximate length of IDOO ft (305 m), de~
veloping approximatelv symmetrically on both
sides of the arch crown. Free movement 0[' the
deck structure over the pilasters was accommo­
dated bv providing two concrete rockers over each
transverse wall of a pilaster. The rockers consisted
of a 3 ft 6 in. (1.07 m) high continuous wall
throughout the width or the bridge with a continu­
ous Frf'vssinet-tvpe concrete hinge at both the top
and bottom. Approach piers were fixed in the deck
at the top and hinged at their footings. Because of
their height, these piers have sufficient flexibility to
allow movement of the deck without developing
appreciable bending moments, the exception being
the short stiff piers next to the abutment, which
were hingetl both top and bottom. 2
We shall describe the construction procedure for
the superstructure of Bridge I, which was also
used for the other two bridges. Because the cable­
way did not have the capacity to transport the deck
girders across the canvon, precasting operations
were established at both ends of the bridge. During
construction of the foundations, precasting opera­
tions were started at both sites at either end of the
bridge.
When the foundations for the approach piers
were completed, the cableway transported and po­
sitioned the precast Fre\'ssinet pier hinges to their
respective locations, where they were grouted to
their respective foundations. Pouring of the piers
then commenced, lIsing special steel forms at­
tached to the hinge blocks. Two sets of forms were
used in leap-frog fashion to maintain a pouring
366
Concrete SegmentalArches, /ligtdFrames, ano Truss Bridges
rate of 5 ft (1.52 m) per cia\. Because olthe hinge
al I he base of each pier column, Ihe piers required
Icmporarv support unlillhe deck girders could he
placed. The firsl 25 ft (7.62 Ill) lift of each column
in each pier was supported bv a light sleel scar
folding Ihal surmunded each colul11 n; the scaf­
foldings, in \Urn, were braced logel her. Succeed­
ing 25 ft (7.62 111) lifts were braced 10 the previous
lift hy light timher trusses. :\s t lie colul11ns in the
piers rose, steel reinforcement was placed; at the
sallie tiI1le, holes for vertical prestressing tendons
were cast in the concrete by the insertion of H in.
t:1H III 111) steel tuhes, which were withdrawn H
hours after concrete placemellt.
L' pon completion of t he three colu m ns of an ap­
proach pier, precast segments of the cap beam
were placed atop the columns and prestressed
HTticallv to them ,IS indicated ill Figure 8.22. The
\1\0 intermediate cap beam seglllents were placed
1)\ the cablcw,1\ and lemporarily held ill position
hI' steel brackets. Four prestressing tendolls were
then placed through t he cap beaJll segmcnts and
the fOllr \crtical I i ill. (:~H llllll) joillls between the
segmcnts wcre packed with a rich mortar. At'ter
eight to ten hOlils the longitudillal tendom in the
cap healll \\'('re strcssed and allchored to cOlllplete
a pier bent. which was then reach \0 receive the
deck girders and slabs. The 1:17 It (41.75 111) high
pilasters at each end or the arch are four-celled
hollow boxes 20 b\' HO ft (6.1 x 24.4 111) in plan with
all walls 41 in. (120.65 111111) thick. They were ("011­
stmeted in lifts with special steel forl11s that were
Icap-frogged. Ten \'Crtical prestressing tendons
<lllchored into t he foundation provided stability
against wind forces.:l
Upon completion of the abutments and the first
approach piers, erection of the bridge deck girders
and slabs cOlllmenced. It was accomplished with a
126 ft (3H.4 m) long structural steel lattice girder
galltr\', 60 It (IH.3 m) of which extended as a can­
t ilever. One 4 H It (14.6 111) span, COil sisting of eight
precast beams alld 112 precast slabs, required nine
working days ami a crew of 16 l11el1. When the ap­
proach yiaduct c1ecks werc in place, they were pre­
stressed longitudinally b\ prcstressing tendons
placed ill the grooves of the top flange of the deck
girdns, which wel'e anchored at one end il1lo the
abutmellt ami at the other end o\'er the arch pilas­
ters.
The three arch ribs of the main span were cast in
place on a light wooden falscwork, which was re­
used almost in its entiret\' for the two other
bridges. Basically, the system adopted was to erect
the timber lormwork for casting the arch ribs by
the cantile\'er method, this formwork being placed
by the merhead cablew;n alld held in place b\ a
system of cable stalS.-;Phus, the arch rib was essen­
tially constructed to the quarter-point s. The -center
half-span formwork was constructed as a light
wooden trussed arch assembled at the bottom of
the camOI1 and winched into position from the
ends of the quarter-span cantileyers. The timber
falsework t russ was wedged against the concrete
arch ribs already erected. It acted as an arch under
the weight of the bottom flange concrete, t1'an5­
mitt ing it s t hrust.to the cantile\'cred arch sections
pre\iously erected. Later the timber falsework
acted compositeh \"it h t he hardened bottom flange
concrete to support the webs and top flange of the
hollow box arch rihs when t hey were placed.'
The following discussion describes the erection
sequellce or the cellter-spall arch ribs.:! The fIrst
falscwork unit ill the quarter-span (or each arch
rih consisted of a tilllber platforlll ;) I ft (9.45 Ill) ill
length with" width of 27 f't Hill. (H.43 Ill) at the
spring lille and a widt h of 17 It 2 in. (5.23 m) at the
opposite end, Figure H.~g (Phase I). This platform
was C0I1S\J1IC\cd of g x lOin. (76.2 x 254 111m) tim­
hers 011 edge at 10~ in. (267 mill) centers covered
OIl Ihe uppel' face with tin. (12.7 III Ill) thick
plywood. It provided the form for the bO\lolTt of
the arch rib. For the first section or the quarter­
span, three of these units (one for each rib) were
placed In the cablewa\', supported by cable staYs A
and B. and their position adjusted by hydraulic
jacks at Ihe ends of the anchor cable stays. ~ext
tOllr precast Freyssinet hinge blocks were posi­
tiolled ,It the spring line and assembled into one
hinge block hy prestressing thelll together. Forms
were then erected 011 the ralsework for the webs of
t he arch rib, ami placement of concrete com­
menced, Figure 8.23 (Phase
As the weight of
each increment of concrete came onto t he forms,
the cable stays elongated and the geometry of the
arch-rib soffit had to be carefully adjusted bv the
hydraulic jacks.
C pOll completion of the cOllcreting for the first
section of the quarter-span, falsework section 2 was
attached to it and supported by two more cable
stavs, C amI D. After geometry adjustment, con­
creting continued, Figures 8.23 (Phase 3) and 8.24.
As a result of the position of the cable stays and the
concreting sequence, angular deformations were
possible between falsework sections I and 2.
Thereforc, a temporary concrete hinge was placed
in the lower flange of the arch rib, which would
allow angular deformation but transmit the thrust
to maintain equilibrium. When the concreting of
/
/
/
/
/
/
FIGURE 8.23. Caracas Viaducts, erection and construction sequcnce. from reference
Ci\'il Engineering-A5CE).
~~
((DUnCS\ of
367
368
Concrete Segmental Arches, Rigid Frames, and Truss Bridges
.~
• .'f
1
.;
FIGURE 8.24.
sprillgillgs
()ll
Caracas Viaducts. constructioll of arch
suspellded scdloldillg,
the second portion of arch rib was completed and
adjustment made, the temporary hinge
was blocked and the two sections were prestressed
t()~etl!eL In the same manner. temporan' hin~es
were lIsed lor the remaining sectiolls of the
quaner-span arch rib am! at each end of the cen­
Iral half-span arch sectioll,
The firsl Iwo secliollS of arch rib thus became a
COI1liIlUOUS member supporled at the ouler end by
cable SlaYS, and during conslruction of the resl of
the arch its ~eo!l!etric posilion was adjusted by
cable slay l),
The next operalion was Ihe erection of the third
lalsework ullit consisting of a Irusswork. Its weight
was slIch that it could not be accommodated by the
cahleway. Therefore, it was assembled al the bot­
tom of the canyon below its position in the arch.
The OllIeI' end was lifted by the cab!ewa\' and the
inner end by a winch located at the end of the pre­
viollsly concreled section of the al·ch. Stay cables E
passing over Ihe pilaster were attached, and the
bottom flange of the new arch rib section was cast,
Figures 8.23 (Phase 4) and 8.25.
In like manner the next section of trussed
falsework was positioned and supported by cable
stav F. l\"ext, concrete lor the bottom flange of the
rib was placed, including small concrete brackets
which protruded below the bottom flange totake
the Ihrust of the 267 fl (81.4 m) central falsework
after its positioning, Figure 8.23 (Phase 5).
In Ihe last phase of the quarter-span concreting,
the vertical webs were fOnlled and concreted, as
well as a few narrow strips across the top to provide
stiffness to the arch-rib members, which at this
slage had a C-shaped cross section, Figure 8.23
(Phase 6). The anchor stay cables were again ad­
justed 10 bring the 125 ft (38 m) quarter-span into
its proper position.
The central 267 ft (81.4 m) falsework span had
been assembled at the bottom of the canvon below
its final position in the arch, Figure 8.26. The ends
of the timber falsework arches were lied logether
by sleel cables acting as lies to keep the arch
falsework rigid. The whole central falsework was
hoisted inlo positioll by winches localed at the ends
of Ihe cll1tile\'erecl quarter-span unils, Figure 8.27.
Ollce the cenlral falsework was ill place and tl\e
location of the crown exactly positioned, cement
mortar was packed in the g-ap bet ween the ends
01 Ihe cenlral falsework and Ihe quarter-span
falsework, and eXIra-flat sand boxes were em­
bedded in the joint for subsequent slripping of the
celllral falsework.
After two days, the steel tie cables on the central
falsework were released and the winches support-
~e()metn
FIGURE 8.25.
truss.
Caracas Viaducts. lifting one wooden
GENERAL
ELEVATloti OF
FALse WORK
x
"-- - - ~~~ P.
"'.. '----.~
-
~. ~
.::>..~
--- -- ."",'L~l't---"
_J_
-~
,,<J L41 i
Jo·IAf!D SUEt AO.Jl"U11I6!!.11~ (~r!M!:t.
OF &4 HARD 51EEl "IJlE3 ,S·...... ;PU «'.11
~'';
'"
/;:::;;:: .X­
,/
~ snlAJ1~ 7je-, M~f ROP~ :
1j~~111 \IY,-~g ~~rt
FO~ liFTING
or
CENTRAL'~
SECTION wn::i.mtlG
!o!
tfoTOII~
:
!;L~5;~~lC WIMC~fS
fALSfWOltK
2:61 ifET
;l'4fEfT
220 tOMS
DETAIL OF JOINT OF LOWER MEMBER
AND DIAGONALS
I10!
DETAIL OF JOINT OF TOP MEMBER
AND DIAGONALS
.;::::~~~;;fj~?:;lfLJ
",.:iF
•o!h.
..- - _ . - - ,.
~~ >
i.~:·'
~~:;
4·x"" I>IAGOtiAlS
80TTOtA
TOP MEMBER OF FALSf. WOMI(
C~~!Lf!30Fbl<d.~TIMSfJtSSlot·~I'·"
,
51l0'Mi'IoG T\o!£
ARE.
DETAIL OF COtlCRETE END Of FALSEV\OIlIC
AHCHOI:IACiE OF
liARD 5lEtL W(RES Of TIES
.!
II
lL.IL.ll!Li.JI .
FIGURE 8.26.
vo
c::r>
I.C
~
5£.l'A.UTE
A55EM8LEO
~
.
3~OW'II'IO
MEt.
~~."f~~S~~~!<""C!l!l~';!'":?,,2!'.
CROSS SECTION OF FALSE WORK
TIMBER
ARCI-IES
INTO ONE. COMPLETE
FORMH'I(i
A~,Q
THE5~
FALse WORK
RIOH) -LIMIT Ely Mt:AI'tS Of'
IHOt'PENDAflT ARCHES
VARIOUS
8RAClHGS
0.48'"
0"-
018"
171
. . . 1". _
~
. I···· !;:
.$.~o'"
=i~___ ':
II 11.11 II
,F
•
-=.
T
~i
WHif':
~RAC!Na~
C;lra(a~ ,'j;ldllCb, ('i'CCIiOIl of c('Iller
'.
MU
UIlJ
'I
1f U
of an h fabcwork.
jJrPLYWOOO bDTTOM WfW&tR
DETAIL Of END JOINT OVER SUPPORT A
370
.'
Concrete Segmental Arches, Rigid Frames, and Truss Bridges
­
FIGURE 8.27.
Carac;t,
Viaducts.
lifting
c(,lIter
ing the section were loosened. At this point the
cOlllbination of the central trussed falsework and
the cOllcreted quarter-span units acted as a com­
pletc arch frOlll abutment to abutmellt.
:'\ cxt, t he bottom Aa nges of the arch ribs were
cOllcreted, in a previousl\' arrallged sequence, IIp
to the crown Oil each side, and temporary crown
hillge blocks were placed. The other temporal'\'
hinge~ hctweell clements of the quarter span were
hlocked alld the cable stays up to stay D removed.
The cOlllbillation of timber falsework and partly
huilt concrete arch ribs contillued to be held in po­
sition Iw sta\'s D, E, and F, with a temporar\' hinge
at F onlv.
Thc vert ical webs of the arch ribs over the cen­
tral sectioll were then concreted lip to the crown
Ilillge; cable st,l\' D was released; crown concrete
was cOlllpleted; the remaining construction joints
were tied with prestressing tendons; and the last
cable stays E alld F were released. At this point the
concrete arch ribs, less the top Aange over the
center 260 ft (79.25 m) section, carried themsehes
as well as the dead load of the entire falsework.
I\:ext, the cement joints at the ends of the
falsework were destroyed, sand boxes emptied,
and, after the steel cable ties had been retightened,
the central section of falsework was lowered, Fig­
ure 8.28. Falsework elements in the quarter-spans
were lowered by hand winches.
Spandrel columns were constructed next. Then,
following a carefull, \\'orked out sequellce, the top
flanges of arch ribs over the central section were
concreted. Upon completion of the arch ribs the
deck beams and slabs were placed, ill the manner
previoush' described for the approach viaducts, in
a s\'ll1metrical and simultaneous manlier on both
sidcs of the crown ...\fter the deck had bcen pre­
st ressed transverseh', it was prest ressed longit udi­
lIall, ill the same lllallncr as the approach \'iaducts.
Finishcd Viaduct I is shown in Figure 8.29.
.
In 1973, twellt\'-one \,ears after the construction
of the~e arches, t he\' were reevaluated to see how
they \\'Oldd IIOW be desiglled and cOllstructed. Fig­
ures tl.30 alld 8.31 compare the actual project COII­
structed ill 1952 with the structure as it wmIld have
been designcd in 1970 (two boxes) and in 1973
(single box). The three-arch-rib and eight-bealll
su perst ruct u re would be replaced by a variable­
depth box section (cantilever construction using
precast segments) supported on slip-formed piers.
The arch remains an appealing and aesthetic
structure and might still prove to be competitive;
but perhaps the construction technique suggested
in the :'\ecbrburg Bridgc (Section 8.5.2) might
be lllore appropriate today, either cast in place or
precast.
<'IF..
~
"""
.
~.
/'.
~' .r.fF-~ '.
."...
;
FIGURE 8.28.
f'aJsc\\'ork.
Caracas
Viaducts.
lowering
center
FIGURE 8.29.
Caracas Viaducts, finished Viaduct 1.
371
Gladesville Bridge, Australia
I
---~'5p~ht -----40---~.,t:..oo~J
As constructed in 1952
so 00
r----165 ft
'
I
264 ft
Possible alternative in 1973
FIGURE 8.30.
8.4
Caracas \,iacluCls. cOlllparisoll of l()n~illldjl1al sl'CliollS.
Gladesville Bridge, Australia
This precast segmental arch bridge, cOlllpleted in
19G4, spans the Parramatta River between Glades­
ville and DrunI111()\'lle and selTes a large seuioll of
the northern ~Irea of the Snlnev Metropolis, Fig­
ure H.:12.
A fter award of con tract the cont ractors submit
ted ,Ill alternative desi.!.{ll. Thev proposed that the
arch be built 011 fixed falsework. whereas in the
original design part of I he arch was to be built on
floating falsework and lOwed illto positioll. The
original design called for an arch span of 910 ft
(277.4 III). The alternate design increased the dear
SP;llI of the arch to 1000 ft (305 m) and eliminated
the necessitv for deep-water excavation for the
arch foundations on the Gladesville, or nonhern,
side of the river.!
Total bridge length between 'lbulinents is 1901
ft 6. in. (579.6 m). The 1000 ft (305 111) clear span
arch consists of four arch ribs, Figure 8.33, sup­
ported on massive concrete blocks. known as
"thrust blocks," founded on sandstone on each side
of the river. Roadwav width is 7'-2 ft (22111) with 6 ft
(l.8 m) wide sidewalks on each side. The roadway
has a grade of 6~:t at each end, and the grades are
lonl1~cted In' a vertical curve 300 it (91.4 m) in
length over the center portion of the structure.
The arch has a maximum clearance. at the crown,
of 134 ft (40.8 111) above the water and not less than
1'-20 ft (36.6 Ill) above water level for a width of 20(]
ft (61 Ill) in the center of the river.
COllstruction of the bridgc involvcd t hc follow­
ing main opcrations 4 :
I. Excavation for fOllndation of:
a. Arch Il1mst blocks 011 each ~idc of the rivcr
at the shoreline and partly below wat.er.
b. Abutments at the ends of the bridge.
c. Shore pier columns of the approach spans
on eaLh sidc of the river.
<)
Concreting of the arch thrust blocks, the
abutments and columns.
3. Driving of falsework piles in the river amI
erection of steel falsework to support the hol­
low COllcrete blocks and diaphragms forming
each of the four arch ribs.
4. Casting of the box-section segl1lents of the arch
and diaphragms and the erection of the fOllr
arch ribs one at a time.
5. Jacking each rib to raise and lift it off the
falsework.
6. Casting of concrete deck beams on each side of
[he river.
7. Erection of the deck beams to form the road­
wav over the arch.
8. Paving of the concrete roadwav and final com­
pletion of the structure.
..,
!
~
If!
,
II
j
I
I'
,
="
I
;il
t
I
I
;~~:i
~il
c:.
~
r
i
I
I
~
!
!
i
'0
l
l
'
.
~
••
_____ h
• _ _ ••••••
~
As constructed in 1952
____ _
...
i
't
I'
,\
-~~~~..7,~~.=.=.=.='~}?~~~==~~==~~~
I
~ - - - - - - - . , - , , " i . . - - - - . - ~­
I
Possible alternative In 1970
20.50
Possible alternative in 1973
FIGURE 8.31.
372
Caracas Viaducts, comparison of cross sections.
Gladesville Bridge, Australia
FIGURE 8.32.
reference 4.
373
Gladcs\'ille Bridg-e, aerial view, from
The roadway deck is supported on pairs of pre­
stressed concrete columlls, Figure 8.33. The wall
thickness is 2 ft (0.6 m), except ill the tal! colullllls
above the arch foulldation where the wall thickness
is increased Iw 6 in. (152 ll11l1). At the top of each
pair of colullln~ there is a reinforced COllcrete cap
beam to support the deck giJ:!lers.
During construction it was necessarv to provide
blsework to support the box segments ami dia­
phragms tlmt make lip cadi of the four arch ribs
in the arch. The falsework was made up of steel
tubuh\r columns 011 steel tubular pile trestles car­
ning spans of steel beams 60 ft (18.3 Ill) long and a
steel tl'lISS spall of 220 ft (67 Ill) over a navigation
opening in the Gbdesville (Ilonhel'll) half of the
FIGURE 8.34. Gladesville Bridge, arch rib Ctlscwork
and positioning of arch rib SCg:I11CIH, from refcrcllceL
falsework. These falsework units were tied to­
gether and anchored at each end to the thrust
blocks, Figure 8.3-L Piling was taken down to rock
ill the river bed.
Steel columns, braced together, forllled a tower
extending transverseh the full width of the bridge
at the center of the falsev·/Ork. rranwerse lIlell1­
FIGURE 8.33. Gladesville Bridge, schematic of four arch ribs, col­
umns. and deck. from reference 4.
374
Concrete Segmental Arches, Rigid Frames, and Truss Bridges
hel'S, extending the full width of the bridge. above
the waterline connected the pile trestles, Figure
R.34. The balance of the falsework was of sufficient
width to support one arch rib. Upon completion of
erection of an arch rib, the falsework was moved
transversely on rails on the transverse members of
the pile tr~stle to a position to enable erection of
the adjacent arch rib, until all arch ribs were
erected.
Equipment installed 011 the central tower lifted
the arch box segments and diaphragms from water
level and positioned them. The tower also sened
as a lateral bent to stabilize the individual arch ribs
alter they were self-supporting alld until thn were
tied t oget her. 4
The hollow-box segments and diaphragms were
cast;) lIliles (4.8 kl1l) dowllstream h'om the bridge
site. The casting \anl was laid out to accommodate
the lllallilfacture of one arch rib at a time. Each
arch rib consists of 108 box segments amI 19 dia­
phragms. Each arch-rib box segment is 20 rt (6 m)
wide, with depths decreasing from 23 ft (7 Ill) at
the thrust block to 14 It (4,3 Ill) at t he crown of the
arch. measlIred at right angles to the axis of the
arch. The lengt h 01 t he box segments a long
the arch varies from 7 It 9 in, (2.:~6 111) to 9 It :) ill.
(:1.1-12 III). After the box ullits were llI<llluractured,
lilt'\' were loaded Oil harges and transported to the
hridge site. The box segments and diaphragms
were lifted from the barges to the crOWIJ or the
arch lals('work and winched down to their proper
positioll, Figure R.:~4. Diaphragms are spared at
IIltervals of :>0 ft (15.24 III). sen-ing not olliv to
support the slender columns that support the
roadwa\' abO\'(' hut also to tie the four arch ribs to­
gcther.
\,\'hen the units were located in position on the
I~tlsework, a ;) in. (76 111m) joinl belween lhe pre­
cast segnlcllls was Gist in place. At two points in
elch rib, four la\'ers or Fre\ssinet Hat-jacks were
inserted. with 5G jacks ill each layer. The rib was
thCl1 jacked IOllgitllClinalh by inflating the jacks
with oil Olle laver at a time, the oil being replaced
In grout and ;t1J()\\'ed to set before the 'nexl layer
was inflated. Inflation of the jacks increased the
distance between the edges of lhe segments adja­
CCllt to the jacks and lhus lhe overall length of the
arch along its centerline. In this manner a camber
was induced into the arch rib, causing it to lift off
tlte supporting falsework. The faisework was then
shifted laterally into posilion to support lhe adja­
cellt arch rib and repeal the cycle. Figure 8.35 is a
view of the completed four arch ribs, and Figure
8.36 shows t he completed bridge.
FIGURE 8.35. Glades\ille Bridge. C'OInpleled liHIl'
arcli rihs. frolll reference ..t.
8.5
Arches Built in Cantilever
Cntil the appearance of the concrete cable-stay
bridge starting in 1962 (see Chapter 9), long-span
concrete bridges were t he domain or the arch
type 01 structure. Clitil 1977, with lhe (()mplelion
01 the Brotonne Cable-Stay Bridge ill France with a
span of 1050 It (320 m), the record length for a
concrete hridge had alwavs been held by an arch­
tq)e bridge. When the Kirk Bridges in Yugoslavia
were completed in 1980, the larger arch with a
span of 1280 ft (390 Ill) once again regained for the
arch the record of longest concrete span.
FIGURE 8.36.
bridge.
Glades\'ille Bricl!J;e, vicw of compleled
Arches Built in Cantilever
375
Here is a brief chronology of record concrete
arch spans up to 1964:
1930, Plougastel Bridge, France: three spallS of
611.5 ft (186.40 m)
1939, Rio Esla, Spain: 631 ft (192.4 111) span
1943, Sando, Sweden: 866 ft (264 m) span
1963, Arrabida. Portugal: 886 ft (270 m) span
1964, 19uacu, River Parana, Brazil: 951 ft (290 111)
span
1964, Gladesville, Sydney, Australia: 1000 It (305
m) span
The concrete arch bridge does not enjov the
favor it once did. \Iodern methods of bridge con­
struction utilizillg prestressing, cable stays, and
segmental construction have all but eliminated it
from contention as a economical bridge type.
However, with the application of these modern
methods to the older form, and givell the proper
site conditions, concrete arches may regain some of
their lost popularity.
(aJ
(b)
(d
8.5.1 REVIEW OF CO.\'CEPT; SU.H.\URY OF
STRUCTLRES WITH TEJliJOR."IR'( STAYS
The use of temporary staYs to facilitate the con­
struction of arch bridges begall. perhaps, with the
Plollgastel Bridge. Tem porarv prest ress tendons
were used to provide stabilitv to the short arch
cantilever sections emanating from the arch foull­
dations (see Figure 8.5). Prestressing telldolls \'.;ere
used to support the falsework of the Rio Esla
Bridge and were incorporated into the structure,
However. the l)1ore novel Illethod, which is the
birth of today's technology, was emploved in the
construction of the Saint Clair Viaduct at Lvon,
France, by ),1. Esquillan. The stabilitv of precast
segments was obtained bv the use of temporary
stays.
In the construction of the Caracas Viaduct,
Freyssinet extended this concept bv using tempo­
rary stays to support the falsework and construct a
mu<;h longer cantilever section of the arch. This
same stay system was then used to accommodate
the forces produced by lifting the center arch sec­
tion falsework (see Section 8.3). This concept was
partially recaptured for the construction of the
Iguacu Bridge in Brazil, where the falsework of the
central portion of the arch was supported by tem­
poraI;y stays.
The first arch bridge to be constructed using the
concept of supporting segmental sections of the
FIGURE 8.37. COllcrCIC arches built in calli ilc\cr v,il II
teillporar\' slavs. (0) With SlaVS alld pvlOIlS. (ii) With slays .
.' palldrel COIUIIlIlS, alld P\"IOllS. (I") Wil h spalldrel col­
1l1l1llS. lie diagonals and ,ta\s.
arch bv temporary sta\"S is the Sibellik Bridge in
Yugoslavia. Falsework for an approxilllate lellgth
of 88.6 ft (27 Ill) was supported on Bailev trusses.
which were in turn supported bv temporary suys.
Figure 8.37b, consisting of a combination of cables
and structural steel rolled shapes. This arch was
constructed in nine sections. f(Hlr on each side and
the central closure sectiolJ. A llIodificatiotl of this
concept was used for a secotld Yugoslav bridg'e at
Pag with a 634 ft (193.2 111) span constructed ill
seven sections. A further modiflcatiotl was used for
the Van Staden Bridge in Somh Africa, Figure
8.37a, with a span of 656 ft (200 m).
A somewhat different concept is wher'e, with the
assistance of spandrel columns, the stays act as
temporary diagonals during construction, Figure
8.37c. In this manner, the structure is built as a
variable-depth Pratt truss. This concept was used
for the Kirk Bridges in Yugoslavia. 111 some in­
stances these temporary diagonal stays may be in­
corporated into permanent diagonals such that in
the final configuration the structure is a truss and
not an arch (see Section 8.7.3).
In summarizing the construction methods using
temporary cable stavs. we find two basic categories:
@
(J)
I
I
-Sluftr,r](!
I
6IJ5'(J7
(])
CD
I
A~
!I
A4
I
"l
"'­
I
CD CD ®
II
(j)
I
®I ®,
@,
217%
a!5%
I
I
I
®
I
I
®
I
I
I
I
~I
~
I"
I
Longitudinal section
(a)
Erection scheme
(b)
a-a
at approaches
b-b
at arch
Cross-sections
376
(c)
®
®
I
Arches Built in Cantilever
377
FIGURE 8.38. (Opposite) :-':eckarburg Bridge. erec­
tion scheme and sections. from referellce 5. (a) LOIl­
gitudinal section. (h) Erection scheme. (e) Cross section.
Where the arch is supported directly by the tempo­
rarv stavs
Where the temporary slavs act as diagonals of a
Pratt truss during construction
Characteristics of the arch bridges using this con­
cept of temporary stays during construction are
presented in Table 8.2.
8.5.2
.YECKARBLRG BRIDGE. GERHLVY
This unique and contemporary arch-supported
structure, some 50 miles (80 kl1l) southwest of
Stuttgart, crosses the Neckar River near Rottweil,
Germany. It is a part of the federal expressway
:\-81 from Stuttgart to the west of Bodensee with a
connection to Zurich, Switzerland.
The original scheme proposed bv German au­
thorities cOllsisted of a steel girder structure sup­
ported on tall piers. Designer-contractor Ed. Zub­
lin. Stuttgart, developed an alternative design
consistillg of twin concrete arches to support the
roadway. The proposal was to construct the arches
segmentallv b~ the cantilever method and con­
strllct the twin single-cell trapezoidal box girders
for the roadway by the incremental launching
lechni<lue (see Chapter 7). The :\ustrian method
called the .\laucder system was used to construct
the arches without scaffolding.;;·f;
The roadway of this 1197 ft (364.98 m) long
structure is approximately 310ft (94.7 m) above the
~eckar River, Figure 8.38. The 507 ft (154.4 m)
arch span, Figure 8.39, has a rise of 164 ft (49.85
Ill). Total roadwav width is 102 ft (31.0 mi. The
FIGURE 8.39. i\;eckarburg Bridge, completed arch
(courtesy of Willhelm Zellner).
FIGURE 8'.40. :-':eckarburg Bridge, arch just belm'e
closure (COl! rtesv of \Villhell11 Zellner).
structure is constructed as two independent paral­
lel slructures with a 1.8 ft (0.54 m) gap in the me­
dian. Roadway spans are 98 ft (30 m) in the ap­
proach sections and 72.6 ft (22.14 m) over the arch.
Each independent arch rib is a two-cell box. The
arch ribs were constructed in symmetrical halves,
Figure 8.40. The curved form work was 43 ft (13. I
111) long, the first 23.3 ft (7.1 Ill) of the form
clamped to the previously constructed arch seg­
ment and the remaining 19.7 ft (6 m) remained to
cast the next segment incremellt. The first 2:3.3 ft
(7.1 m) of arch segment at the arch foundation was
constructed by' conventional forming methods.
There are 14 segments on each side of an arch rib
and a closure segment at the crown of each arch.
The exterior dimensions of each two-cell arch rib
are 21.3 ft (6.5 m) wide by 9.8 ft (:3.0 m) deep. Ex­
terior webs vary in thickness from 10 to 11 in. (260
.to 280 mm). and the interior web is 6.3 in. (160
mm) thick. The arch rib was cast in two operatiolls
-fi rst the bottom Hange and seconcl the webs and
top Hanges.;'
Piers supported by the arch or independent
foundations are of a constant section and slip­
formed by conventional methods. Sliding bearings
are used at the abutments and the short stiff piers 1
and 13. The remaining piers are hinged to the
superstructure deck such that the elastic piers can
follow the superstructure movement. 5.6
During construction, as each half-rib was can­
tilevered out from its foundation, it was supported
by a temporary system of Dvwidag bar stays, Fig­
ures 8.38, 8.41, and 8.42. After completion of the
arch, the temporary stavs were removed, except
those required to stabilize the arch during the in­
cremental launching of the superstructure deck.
Dywidag bar stavs were anchored either to a pier
foundation or to Dywidag rock anchors in the side
of the vaIley.5
1.>0
-.J
00
{:ounU\
YlIgo:-.I<I\I.j
"llgo... l;" 1;1
So"lh ,\hi..a
Austri:1
.lap,1Il
~ame
S,henik
P.lg
\'all Sladen
NlC-SCIl hachbriickc
Ilnkawa/H
1'17:1·· 71
I ~)i:\
,I;\\''\
a tempo!'an
diagoll,tl..
I, i \('
tempof.l!')
:}t)~
:-:i a Y"
tll'ed
v pdqn
ct...
a,ch di,n Ilv ",nh
Ille aid of an all'"
supporting Ihe
p)lon
('Ol1st rUt lion pro­
c{,(,tl". StIPP/H'l('d
l· Otl r 'ltay<;;. rdo­
(.\led gl a<lllaill '"
I1IHU"
..;upportcd ou (01­
heing .l<ldili()n,dl)
the lon,gt'l' ...fav
,ollc·d ""d
sl",p"s and "ahl,'s,
a1t\.ih,t1,~· pylo1l.
(I iO)
:l!ll
( 120)
C!OO)
ii!Hl
(I!I:U!)
Ab,,"1 I ~IIO
rill ('C 'Ia\',
/olIHcd trolH
n:H
I ~11)(j . il7
1'1"1,,,,
hHIt \t.n" formed
I, om !"Oiled "tcel
,h.,pcs and, ahles,
sopponlllg d;·
'T' ,1\ Ihe 'llch
\\itil all tllI:xilh,1I \
Hili
1211;)
1% I,on
s(.\~· ~h-thod
Iml
Sp.IIl,IL
e"';;j\,c
l'lli('('-I
ell
'C\
n'.1.III-
1.111-
.ISt
ast
(,T.d "Ia"ilil~
"I' I I It
(~A Ill) Icllglh.
segm(,l11>
tiol1 In
(('""i\('
(alltik\'CP,l)\
"'I(
(Otl\tI'lU­
ward.
'he
IIllIno\{'
(olumn .. \rter·
hI,
lI\()\;,hlc L1Isc"ork
... pan~by-~p<ln
(,on",nl< led in a
width 1m 1 C<ISe'''
s{'("tioll betw('en
til(' ahutmellt and
III1('a1"h- Irom 2{) to
:',211 ill 10 If> Ill) 10
""S<: ',0 II (FJ m)
clIlllinu()lI" 5palls
"pt it1giTl~". the
" slav 101 lile fi,sl
I he (II "I I\p'IIHlrd
Iiollow
IIUiO Ill) Ihid.­
,I.,,, 012 It
donhl('-'j "pan 01
1)'''(ill,:!IJIIl)
(:oIltiIlUOUS
',', n
IH'(,{
glnln" 01 71)". it
12:\'\11 Ill) 'p.Ill
made (Ol1tinUOlI';
Simpl!' prt·(
illddc (IHlllrltlIHl";
Simph' pn'ta.. . '
gil d(T' 01 7fi,·t It
12:1:10 "" '1';111
l{('cLmgul.1l l\\ 0-
1"\\0 parallcl1\nl­
(elf hox{'\.
rill ce·, ell
gulat box
gllbl hox
rn
D('ck '1\ 1'('
«,11 hox, :\ca, th"
Fonl/\',ot k par11,,11, '''p}",rl"d III
ment"
Hi.:') Ill) long I\C;';'
21 II
(Otl­
"U IIcfion of
"1l('{
Iwrmiltil1i{
for
Sq;llW1l1" )!Ul
(20 Ill) 1011l-(
Sn'Cll \('( lion, on
fa!.,('\\Ol k
:! ~ 1 III ~
I III ('C-i (·11
gul.lI ho\.
~·in(' "'('(lion" OJl
,\rc hl\ 1'''
I.,J,('\\ 01 k 01 H:"U;
and ~r') It (~7 and
COllsttwti[)11
..\1( h
Characteristics of Ardl Bridges Constructed with Cable Stays
(:OI1f"tl'lH tl()ll
Yf';tr of
TABLE 8.2
(,0[,­
Ih(' IWO
"pt'illgings 01 (he
arch
Ilillged ;)1
Fi"'d
Fixed
hall")"), of hr'
.II " .. lie jatk~
i'os... ihihly of cor­
the thru'\t
at Ihe cnnnt hy a
JT( linf.{
;J(
lhe no'\'\.'n h) "
hattery of 11y~
.il a,,)i, .lacks
n'( ling the thrllsl
Pot;sibliJtyof
Sialic
A, "It Scheme
1092 It (:1:l2,H
III)
10'.. of deck is R
(orillHltal (utva­
Remarks
~
7.
-
1:
'~
,g
--
...,..
­
~
;_~:~ i
"
~
:;. . u:
&:~
.. .:::
~
\:;
,.,:,..
;:: 1­
~
:...
-
y
!.I
-; '"
­
,:;:
~
..:
sc r-...:
;;;
:::;
­
r;
"r;
.", :::c
C,;:! ­
-::-:::
:::
r.
,",:
:5.,:":_
::
~
.:...
r;
~
379
380
Concrete Segmental Arches, Rigid Frames, and Truss Bridges
'"..
FIGURE 8.41. ~eckarburg Bridge, temporal): Dywi­
dag bar stays supporting cantilevered arch rib (cour­
tesY of Willhelm Zellner).
FIGURE 8.43.
Neckarburg Bridge. launching of deck
girder.
FIGURE 8.44. :":eckarburg
Bridge,
dose-up
01
launching nose.
FIGURE 8.42. :":eckarburg Bridge, temporary Dywi­
dag bar stays supporting cantilevered arch rib (cour­
tes\' of' Willhelm Zellner).
The trapezoidal box girders of the superstruc­
ture deck were constructed behind the Singen
abunnent and incrementally launched "downhill"
toward the Stuttgart abutment, Figure 8.43. A
close-up of the launching nose is shown in Figure
8.44. Overall girder width is 48.8 ft (14.9 m) with a
constant depth of 7.5 it (2.3 m). Girder segments
were cast in lengths of 65.6 fl (20 m). The lift and
push combination of hydraulic jacks (see Chapter
7) launched the girder in lOin. (0.25 m) incre­
ments. To maintain deformations of the arch and
piers. resulting from the horizontal forces of the
incremental launching operations. within allowable
limits, the tops of the piers were tied back to the
abutments and the arch was tied back bv the tem­
porary stays used during the arch construction. An
inno\'ation introduced bv Zublin on this project
was the use of bearings for the incremental
launching that remained as permanent bearings.
Prior procedure had employed a system of' tempo­
rary bearings for the incremental launching and
then a transfer to permanent bearings. s
8.5.3
NIESENBACK BRIDGE, AUSTRIA
This is a two-rib arch structure utilizing the free
cantilever construction method for each half-arch,
Figure 8.45. The arch has a span of 394 ft (120 m)
with a rise of 123 ft (37.5 m). Each arch rib is a
two-cell box with exterior dimensions of 16.4 ft (5
m) wide by 8.2 ft (2.5 m) deep. The roadway con­
sists of a concrete slab and girder system with an
overall width of 57.7 ft (17.6 m). Although the lon­
gitudinal axis of the arch is in a straight line, the
381
Arches Built in Cantilet'er
Final structure
Structure during construction
Hllfspylon
17.60
9.90
lSJO
FIGURE 8.45.
:-;iesenback Bridge. ele\3.tion. plan. and cross section. from reference 7.
roadway it supports has a centerline radius. in
plan. of l092 it (332.8 m).
The curved roadway structure has spans of 65.6
ft (20 m) over the arch and is supported by two 3.3
ft (1.0 m) square piers, one on each arch rib. At
the arch foundations, roadway support is by a wall
pier with dimensions of 4.6 ft (l.4 m) by 33.8 ft
(10.3 m).
'
Each two-cell box arch rib is constructed r.·v the
cantilever method. using a 41 ft (l2.5 m. long
traveling form. The form clamps to the prec--::ding
construction such that a 19,7 ft (6.0 m) se~~.ment
can be cast. A crew of seven men was able to ':ast a
segment on a weekly cycle.
To keep moments in the cantilevering arcC1 to a
minimum during construction, the cantik-,ered
Concrete Segmental Arches, Rigid Frames, and Truss Bridges
382
portion of the arch was supported by a S\'stem of
Dvwidag bar stays, Figure 8.45. Stay stresses are
monitored at each stage of construction to main­
tain a nearly moment-free condition in the arch.
Dywidag bal's used in the stays were 1 in. (26.5
111m) diameter and were used because they were
easily coupled and could be reused. 7
8.5.4
KIRK BRIDGES, rUGOSLAVIA
These structures connect the mainland with the
Island of Kirk in the Adriatic Sea. In between is a
small rocky olllcropping known as St. Mark, such
that from the mainland 10 SI. i\1ark is the world's
longest concrete arch with a span of 1280 ft (390
m) and from SI. Mark to Kirk is the seventh longest
concrete arch with a span of 800 ft (244 Ill), Figures
lAO amI H.4G.
Because the distallce between the shores of the
mainland and St. Mark is 1509 ft (460 m), the arch
support is partially founded in the sea, Figure 8.17.
The arch reaction of approximately 15,400 LOllS
(14,000 mt) is accoIllmodated by the inclined pier
in the sea, which takes 9900 tons (9000 mt) to the
rock, while the nearly horizontal box structure
:I ·
8.6
Rigid-Frame Bridges
Another bridge type thai lends itself to the con­
temporary segmental concept is the rigid-frame
bridge. Cnfortunately, segmental construction has
not often heen applied to this type of structure.
The reason is probably that the segmental concept
is associated with the conventional girder type
bridge, and designers have gin:n little considera­
tion to applying this method 10 the rigid-frame
bridge. Hopefully, the few examples that follow
will stimulate thinking about this t)'pe of structure.
-t~Jl_'Q--+
:
!
~
I"
.
I
above sea level takes the other reaction component
of 6600 tons (6000 mt).
A system of temporary stays was used to s.upport
the arch as it was progressively cantilevered out
from the springings, Figure 8.48. These temporary
stays were used as the top chord and diagonals of a
temporary variable-depth Pratt truss during con­
struction, Figures 8.48 and 8.49. The arch rib con­
sists of a three-cell rectangular precast box, which
was cast in segment lengths of 16.4 ft (5 m) and
assembled with <;:ast-in-place joints, Figure 8.48. A
view of the completed arch with spandrel columns
is given in Figure 8.50.
..
"1',1
--+
co
.
+
LW
--1
Section 1
Section 2
KERK
_~
ELEVATION
FIGURE 8.46.
I
2t' OO"--_--l:.:.:72~
Kirk Bridges, ele\'ation and sections.
Jeo
I
300 I
1
L:::;
I
i
! - 6.
~O
T -1<;1.00
.000
I
U,
I
J J. 50
FIGURE 8.47.
Kirk Bridge. foundation detail.
383
384
Concrete Segmental Arches, Rigfd Frames, and Truss Bridges
FIGURE 8.48:
tion.
.-...........
•
~~
..
-1"
Kirk Bridge, erection of first arch sec-
_"'0: _
'"
--......:.~--",
FIGURE 8.49.
FIGURE 8.50.
Kirk Bridge, completed arch.
'_
.
Kirk Bridge. erection approaching
(TOWll.
FIGURE 8.51. SainI l\1ichael Bridge. \iew of the
pleted structure.
COITI­
Ja;n'
FIGURE 8.52. Saint Michael Bridge, partial longitudinal sectioll.
8.6.1
SAI.\'"/' ,H/CHEL BRIf)GE IN TOULOUSE,
FRANCE
This beautiful structure, Figure 8.5 L appears as a
sliccession of arches with inclined legs, crossing the
two branches of the Garonne River in the southern
city of Toulouse, France. Typical dimensions of a
rigid frame are presented in Figures 8.52 and 8.53.
Because the bridge replaced an obsolete struc­
ture resting on masonry piers, it was possible to
construct the inclined legs on suspended scaffold­
ing using temporary ties anchored to the masonry
piers before they were demolished, Figure 8.54.
The longitudinal girders were cast in place be­
tween the legs to complete the rigid frame. Over
each pier an expansion joint with laminated bear­
ings is provided in the roadway slab, Figure 8.54.
Another view of the finished bridge is pre­
sented in Figure 8.55.
I
I
13:'1'"
FIGURE 8.53.
Saint :Vlichael Bridge, typical section.
Neopr~n~
b<torlns
\
.I
FIGURE 8.54.
Saint :Vlichael Bridge, constructioll sequence at tvpical pier.
FIGURE 8.55. Saim \'[ichael Bridge. finished struc­
ture.
385
386
(1.6.2
Concrete Segmental Arches,
Rigi~
BRIESLE MAAS BRIDGE, NETHERLAl'lDS
The Briesle Maas Bridge near Rotterdam, com­
pleted in 1969, is a distinctive structure with its
V-shaped piers, Figure 8.56. This bridge, crossing
the Meuse River, is situated in an area reserved for
pleasure boating and recreational purposes. It was
therefore considered essential to maintain a high
degree of bridge aesthetics. Although the design is
perhaps not the most economical, it was chosen to
meet t he aesthetic req uirements.
The three-span superstructure consists of a 369
f'l \ 112.5 m) center span with end spans of 264 ft
(!-iO.5 111). Trans\'erselv, the superstructure consists
of three precast singie-cell boxes, joined at iheir
flange tips by a longitudinal closure pour and
transverselv prestressed, Figure 8.57. The hollow
inclined legs of the V piers are structurally con­
llccted to the deck strllcture by post-tensioning, and
the V pier is snpported at its base through neo­
prene hearing pads on the pile cap foundation. Fig­
nres H.5H and !-i.59. 'rhe superstructure, with the
exception of a few cast-in-place closure joints, is
CO III posed of precast segments.
Shear forces, mainly concentrated in the webs,
Ilormally are transferred to piers or columns by a
diaphragm. Prefabrication prevented this solution
Frames, and Truss Bridges
in this project, however, as the additional weight in
the pier segments would have increased intolera­
bly. Shear stresses were maintained at an accept­
able le\'el by increased web thickness and by u-iaxial
prestressing.
At the moment that the midspan closure pour of
the center span is consummated, the bending mo­
ment at this joint is zero. With time this moment
increases, as a result of creep, to a significant per­
centage of what would occur if the bridge were
built as a continuous structure on falsework. 'Pre­
stressing to accommodate both conditions cannot
be gi\'ell maximum eccentricit\·, and it becomes
both difficult to execute and expemive. A consid­
erable amount of prestressing was saved b\'
eliminating the condition of zero stress at closure
and therefore preventillg creep. This was accol1I­
plished by inducing an upward reaction under
segmelli s 7 and 72. Figme H.59, ancr joi I1t closure.
Simultaneously with the increase of these reactio;1
forces, prestressing tendons in the central span
were stressed. Upon completion of the end spans
the illduced forces were released automatically by
prestressing the end spans.
Segmellts were produced at an existillg castillg
vanl 68 miles (1 IO kill) from the bridge site. A
long-line precasling bed (see Figure 11.37) was
I
~
~i
~
.._1
CROSS
FIGURE 8.57.
•123
EZl
CJ
SECTION
Briesle Maas Bridge, Irans\'el'se cross section.
LONGITUDINAL SECTION WITH CABLE PROFILE
FIGURE 8.58.
Briesle Maas Bridge, longitudinal section with tendon profile.
ospholl
prtrtrtuod
ConOllt~
prtslrtilled
CXltlcntt: (ill
rltnf{\f't.Wd
conerell
(p!af!t;.}
liholi
Rigid-Frame Bridges
387
_D_
A
B
C
D
E
Steel frame
Jacks
Rubber beanng pads
Joints
Counter weight
F=
G=
Joint
Temporary SUflPort
H"" Scaffol di ng
J = Joint
FIGURE 8.59.
Briesle \la;ls Bridge, erectioll sequence.
lIsed witl! a Ie!l(.ith equal to a half-spall-that is,
Olle cantilevcr. Three sets of sC(.illlent forllls were
elllploved to cast a total of 2:H segll1ents, avcragill(.i
7R reuses. Seg-ments were transported to the
bridge site b\' barge.
The variolls stages of erection are indicated in
Figure R.59..\ special structural steel frame was
used to position the inclined precast hollow-box
legs of t he piers a nd to su ppon the seven precast
road W;IV girder sCgll1ClltS hefore cast ing the joillts
at t he corners of the delta pier portion of the
structure. This frame was also utilizcd to balance
the pier during- erection of the remainder of the
roadway g-irder seglllcnts amI to adjust, by means
of jacks, thc loads ill the inclincd legs of the pier
during various stages of erection.
CpOIl cO!l1pletion of the balanced cantilever
erection about both piers, tcmporarv supports
were placed under segments 7 and 72 (the extreme
end seglllcnts of the partiall\ completed end spans)
so that thc temjJoran' steel frames under the piers
could be remmec/o At this point"both hahes of the
stnicture were in an unstable equilibrium condition,
therefore, counterweights were placed over the
supported segments, Figure 8.59, to prevent the
half-structures from toppling over.
Jacks atop the temporar\" suppOrts were used to
adjust the position of the bridge halves with respect
to olle another and to induce the upward vertical
reaction forces previollslv discussed. Also, dif­
ferences in elevation between the three box girders
were adjusted by these jacks. Arter castinJ4 Ihc
center-span closure joint and stressinJ4 in the
center spall, the remaining segments in the end
spans were placed Oil falsework, FiJ4llre H.GO; do­
SUI'C Joints were cast: and longitudinal and tran~­
verse prest ressing was completed.
All segments in the balanced call!ilever portion
of the structure were placed In a !loating crane.
Because of the crane's small reach, it could not
place the last five segments need cd to complete the
end Spall. Therefore, it placed thcm on a 'illlail
doll v installed 011 top of the falsework, which
would roll them into their final positions. To ~I\()id
dismantling the falsework after cOll1pleting (Jilt'
girder and reinstallillJ4 it under the lIext, II was
constructed so that it could bc lowered ~lI1d m()\cd
transverselv into position, Figure R.60.
A close-up of tlte piers of the flnished ~!rllC!lln>
is shown in Figure 8.61.
8.6.3
BOXflO.H.HE BRIDGE. FR.·/SCE
The Bonhomme Bridge over the 81;1\'et River ill
Brittany, France, was designed and built between
1972 and 1974, Figure 8.62. This three-spall
slant-leg portal-frame bridge has a center span of
481 ft (146.7 111) and end spans of223 ft (6i.95m),
Figure 8.63. The span between the foundations of
the slant legs is 611 ft (186.25111). A tubular steel
framewOI'k was used to support the slant legs tem­
porarilv until closure at midspan, Figures 8.64 and
Concrete Segmental Arches, Rigid.frames, and Truss Bridges
388
FIGURE 8.60.
span.
Briesle :V{aas Bridge, erection falsework for hlst fi\'e segments ill the end
8.65. This structure was huilt h:' the cast-in-place
balanced cantilever method.
For adjusting the geometry of the bridge, flat
jacks were placed under the legs and at midspan. A
detail of the ;tCUustillg jacks placed on top of thl:;
temporary support is shown in Figure 8.66. Flat
jacks and sand boxes were used both to adjust
the geometry of the bridge before closure was
achieved at midspan and later to release the energy
stored in the legs of t he temporary supports, which
were loaded with the full weight of the bridge.
FIGURE 8.61.
\' piers.
Briesle Maas Bridge, close-up \'iew of
FIGURE 8.62.
Bonhomme Bridge over Blavet Ri\'er.
~ORIENT
~
~
______________________________
~2~8~2~,~60~
KERVIGNAC,..
________________________________
~~
____~6~7~,9~5~____~______________~1~~~6~,7~O~________________T-______~6~7~,9~5~__~~
FIGURE 8.63.
Bonhomme Bridge, eie\'ation.
FIGURE 8.64.
Bonhomme Bridge. construction stages .
..
+
••
++.~
• +
G RANI T E
FIGURE 8.65.
••••
+ + •
+
Bonbomme Bridge, temporary support.
389
390
Concrete Segmental Arches, Rigid Frames, and Truss Bridges
The scheme is a ven satisfactory one in terms of
both the aesthetics of the finished structure and
simplicity of construction. However, it may be used
only when site conditions allow the foundations of
the temporary supports to be established safely at a
reasonable cost. Figure 8.67 shows the temporary
supports during the balanced cantilever construc­
tion of the bridge.
8.6.4
FIGURE 8.65.
(Continued)
MOTORWA}' OVERPASSES iiI,' THE
MIDDLE EAST
The use of precast segmental construction for the
Alpine Motorways in southern France was de­
scribed in Section :~.15. It was shown how mass
production could be applied to the construction of
a large number of similar overpasses.
This experience was repeated recentlv in a mid­
dle eastern country for the cOllstruction of 17
overpass structures over an existing freeway, Fig­
ure R.6R, To minimize disturbance of freeway
trafflc, it was fdt that a three-span rigid-frame
structure with inclined legs would be an attractive
solution.
Dimensions are shown in Figures R.69 and 8.70.
The total deck length of 252 ft 3 in. (77 m) is di­
vided into 32 precast segments for each of the twin
box girders. Deck wjdth of the overpasses is either
36 ft (II m) or 46 ft (14 m). The same box section is
used for all structures, and the cast-in-place lon­
gitudinal closure strip varies as required.
The slant legs are precast in the same plant
where the deck segments are produced. The typi­
cal erection sequence is shown in Figure 8.71. A
temporary bent founded at the edge line of the
new freeway is used to place and adjust the precast
legs on either side of the bridge. Segments are
placed in balanced cantilever from the special seg­
ment located atop the slant legs. A light temporary
bent in the short side spans is used to reduce the
bending moment in the slant legs during construc­
tion.
After completion of the cleck and removal of all
temporary supports, the structure is in effect a
two-hinged arch with vertical restraints at both
ends. The bridges were analyzed for earthquake
and large thermal variation loads (seasonal varia­
tion of 120°F and temperature gradient between
top and bottom flange of 18°F).
Figure 8.72 shows a detailed view of the inclined
legs and the temporary support during construc­
tion.
ra
iO!
II
FIGURE 8.66. Bonhomme Bridge,
details of bearing of concrete can­
tilever on temporary support.
1
1
10----1
I
I
I
I
I
1
1
-+-----1 I ­
1
1
I
I
,
10
rOI
I
'
AND 'SAND
BOX
1
I
4-_._ _ _ _ 11
!
~
IOi
L ____
J'
391
392
FIGURE 8.67.
Concrete Segmental Arches, Rigid Frames, and Truss Bridges
BOllhomme Bridge, during call1ile\'er
cOIlSlnIC{ion.
Plain
19'-0"
FIGURE 8.68.
\1otorw;1\ O\'el'jl<lss Frames, gellend
19'-0"
FIGURE 8.70. Motorwav O\'erpass Frames, cross sec­
tioll and elevation of inclined legs.
new.
8.7.1
8.7
Truss Bridges
As with rigid frames, segmental construction has
seldom been applied to truss bridges. Once again
the designer must realize that the principles of
segmental construction, together with imagination,
can be applied to bridge structures other than the
mllventionaJ girder bridge.
RETROSPECT ON CONCEPTS FOR CONCRETE
TIWSS BRIDGES
Trusses were used in all long-span cantilever steel
bridges, and it was logical to conceive of the appli­
cation of this type of structure to prestressed con­
crete. An interesting example of such an approach
is presented in Figure 8.73, in which an origi­
nal sketch made in 1948 by Eugene Freyssinet for
the design of a precast prestressed concrete truss
is reproduced. The studies were applied to two
specific exam pIes:
149.3
FIGURE 8.69.
Mowrway Overpass Frames, longitudinal section.
Truss Bridges
393
(a) '-­_ _ _ _ _ _---.l
(b)
L ­_ _ _ _~_..::;
(c) '---:::­_ _ _ _ _ _-.-::J
(d)
~
____ ...._ _ _ _. J
~Iororwa\' O\'erpass Frames, erection sequence,
Stage L (b) Stage 2, (e) Stage ,~. (il) Stage 4.
FIGURE 8.71.
(tI)
A bridge over the Hanach River near Algiers.
Algeria, with a clear span of 400 ft (123 m), Figures
8.14 and 8.75.
A major crossing of the Rhine River at Pfaffen­
dorf, Germany, with a main span of 600 ft (180 m)
FIGURE 8.72. Motorway Overpass Frames, detail of
inclined leg and temporary support.
These studies were very encouraging from the
viewpoints of both economy of materials and
simplicity of construction. The deck was to be en­
tirely precast, with members assembled by pre­
stressing. Construction would proceed in balanced
cantilever from the main piers until reaching
midspan closure, where adjustment of the deck
geometry and loads in the members was provided
by jacks.
...'-'"
!J:)
A
--=
,
J.. B
for a cOllcept
(t~J.OJ
_ _ ELEVATION
,ketch of E.
:.;<'~~--=r;.~""",
\.<?>:~
e
40,00
1%
L?
'A
51
12300
Concept
:sc=-
f'IGURE 8.74.
,e
vrSlSIO>' SI $1
or prcstrc"cd
or a
truss
~ iz
1.l:"_"""""'''''F~T',",''r'''Y-'T ",.-rT_:r_r-r_T""r:--r'-J'7-.r'!""'T-,--,,....,.,"~,--r~:r-"-r-"---T
:\~,
FIGURE 8.73.
COllcrete truss (1 \HH).
-->
/'
precast
t.O.(JQ
~~-
JI'jJ\
ir-~,
395
Truss Bridges
112 COUPE B_ B
+--_--<~-..- - - - - - 9 - 0 - 0 - - - - -..-~-~+_~----..~~.- ..----9-00..-.___....._ _ _ _. .
-+
,
,
J
J(
..
J(
:." q,,,.,",
..
~ '",
.
J
"~'!
-
'.' .
)(
J
, ,
."
J(
I
!
I
i
I
1
Jl
J(
I
I[
I
t
'
.0,
7.
I
i
I 150
i
J
L
J
1
I
I
J
IIJ
L
i
L
J
I
j
i
FIGURE 8.75. Concept of a truss bridge.
The use of I girders at 7 ft (2 m) spacing for the
precast deck would not be considered today as the
optimum design. One of the authors, who was in­
volved in the studies with E. Fr-eyssinet, remembers
also that many technological problems such as the
connection details between diagonals ,and chords
were not completely solved.
Neither of these two designs reached the con­
struction stage, and the concept was rapidly for­
gotten before its potential could be objectively as­
certained.
Oddly enough, the designers of steel structures
followed a similar path. Abandoning prematurely
the concept of truss structures, which had allowed
st,lch outstanding structures as the Firth of Forth
Bridge to be built all over the world, they turned to
web girder structures and closed box sections with
all the critical problems they entailed, such as elas­
tic stability. Perhaps it is time to reassess some
major design approaches in both steel and concrete
for very long spans.
8.7.2
anced cantilever, as construction started at one
abutment and proceeded to the opposite abutment
by progressive placement. Temporary interme­
diate piers were used as required to reduce the
cantilever stresses.
Figure 8.77 shows an interior view. The lower
flange is used as a walkway for pedestrians and for
bicycles. The railing in the center surrounds an
opening in the bottom flange where stress condi­
tions do not require the concrete area. Figure 8.78
is an interior view looking through one of the floor
openings, and Figure 8.79 is another interior view.
8.7.3
RIP BRIDGE, AUSTRALIA
The recently completed Rip Bridge, Figure 8.80,
north of Sydney, Australia, has a center span of
lHANGFALL BRIDGE; AUSTRIA
The Mangfallbrucke in Austria, Figure 8.76, on
the autobahn between Munich and Salzburg was
constructed in 1959. This structure is perhaps best
described as a large box girder with the webs being
a trusswork. Total length is 945 ft (288 m) from
abutment to abutment; the center span is 354 ft
(108 m) with side spans of 295.5 ft (90 m). It was
constructed as cast-in-place segmental using the
free cantilever method. However, it was not bal­
FIGURE 8.76.
Mangfallbrucke, general view.
396
Concrete Segmental Arches, Rigid Frames, and Truss Bridges
I
~
FIGURE 8.77.
Iruss\\'orL
Mangfalllwiicke, illterior "lew showing
FIGURE 8.80.
FIGURE 8.78. MangfalJbriicke, interior "iew looking
through 1I00r opening.
FIGURE 8.79.
:'-.1angfallbriicke, general interior view,
Rip Bridge, general \·iew.
600 ft (182.88 m). The identical cantilever trusses,
which sit symmetrically on either side of the cross­
ing, reach out 240 ft (i3.56 m) toward each other
to support a 122 ft (3i 01) drop-in simple span at
their extremities, Figure 8.81.
The erection scheme is illustrated in Figure 8.82.
Note that cable stays were used as diagonal mem­
bers during construction to support the arch seg­
ments. Temporary falsework bents were used at
each panel point of the truss on the landward side
of the main piers. Precast concrete elements were
delivered from a precasting plant some 80 miles
(130 km) from the site.
Each panel of the lower chords of the truss was
assembled from five precast I-shaped elements
with a 1 ft (0.3 m) longitudinal pour strip between
the flange tips. Similarly, the upper chord was as­
sem bled from five rectangular two-cell precast
members. Erection of one of the lower chord
members is shown in Figure 8.83. The exterior two
I-shaped lower chord members are supported by
the diagonal stays, while the interior three ele­
ments of the lower chord are supported by a trans­
verse beam arrangement from the exterior two
during construction.
Each diagonal member was assembled from lon­
gitudinally split halves, which, when brought to­
gether, encase the diagonal prestress tendon stays,
incorporating them into the structure by concrete
poured in place between the two halves. The upper
chord or deck members are erected after the verti­
cal members along with temporary falsework to
support the deck panels, while the cast-in-place
concrete is placed between the deck elements and
transversely prestressed.
Truss Bridges
397
6
c·c
a·a
A·A
1
FIGURE 8.81.
Rip Bridge, eic\;uiol1 and cross sections.
Prestress cable to
support lower member
r In-situ panel
. rAbutment
FIGURE 8.83.
Rip Bridge, erectioll of lower chord .
The deck performs as a prestressed concrete
tension member. As construction proceeds, addi­
tional prestress is progressively added to ensure
that the deck remains in compression.
H.7.-ILocation of
1F=~~~#~=';?'ii'''=;F~~~~~~), flat
jack
temporary
hinges for
shape correction
CO.VCEPT FOR.i CROSSlXC OF THE
ENGLISH CHANNEL
Certain projects rOt, crossings, such as of the Eng­
lish Channel between France and Great Britain.
the Straits of Messina, and even the Straits of Gi­
braltar. have exerted a powerful fascination on the
minds of the great engineers of this century.
FIGURE 8.82.
Rip Bridge. erection sequence,
,~
"&
t...;
:::
~
'::;'
;!;
:;
.
.
;..
;;
':
'-'
~
-
ri:
~
~
-"
398
References
Eugene Frevssinet was no exception, and he
spent the last vears of his long professional career
studying the crossing of the English Channel with a
series of 2000 ft (612 m) long prestressed concrete
spans. The many worthwhile ideas contained in
this COIKept are not likely to be developed soon, or
even bv the lUrn of the centurv.
Figure 8.84 presents all elevation of a typical
2000 ft (612 Ill) span, which was contemplated as a
prestressed concrete composite truss. :'1ajor mem­
bers of the truss were not of conventional pre­
stressed concrete, because such high stresses had to
be accepted to keep the weight of the span within
acceptable limits. A new material to be used for
that purpose had occupied Freyssinet's mind for
several years and had even beel! laboratorv t.ested
for confirmation of the concept. \Vhen a concrete
member is cOlllpletely confined in an envelope that
creates perlllanently biaxial transverse compressive
stress, it will resist safelv much higher stress than if
subjected to a lTlonoaxiai stress or reillforced COII­
ventionall\' with ulltensioned transverse reinforc­
ing (such as spirals in a circular column).
From a tecllllolo){ical point of view, the perrna­
llent active restraint creating tt1e biaxialt ransverse
compressio:1 is easilv achieved in a Illelllber that
h<IS a circular cross section bv continin){ it ill a
high-stren~th steel pipe or within a contillllOllS spi­
ral of prestressill~ steel wires, \V"hich are pre­
stressed at the time the concrete is cast.
This IHateria!' which could be called "pre­
confilled cOllcrete," has extraordinarv properties
such as total absence of brittleness and a capabilit\
,
'
399
to sustain several times as much longit udinal COIll­
pressive stress as a reinforced concrete member
without excessive strains, provided it is initiaIlv
loaded to ofTset the initial strain.
Such a project and such a material could not be
developed in a short period of time, They are
mentioned here at the close of this chapter as a
conceptual heritage, which it is onr dutv to make
fUllctional.
References
I. E. Frc;"ssinet, "Larsest Concrete Spans of the
Americas-Three '.follllllletltal Bridses Built ill
Venezuela," Ci<'il EII,l..,riIlPl'rill[;-tlSCE. '.larch 195:1,
;2, Jean
.\Iuller, "Largest Concrete Spans of the
Americas-How the Three Bridges Werc De­
signed," Citlil E II!-,riIlPl'rillg-ASCE, '.farch I ()5:l,
:3. Rober! Sham<l, "Largesl Concrete Spans of Ihe
"\mcricas-Ilo\\' ·lilcI \\"crc Built:· CIi'1i
ill,U,-.·ISC/:", .\Lmil I ~I"-d.
":\ew Brid~e over Panamatta Rilcr at
(;I;H!es\'ille," ,Hllill ROi/d" Journal of the lkpartlllcill
of \bill Roads, :\ew SOllth Wales, DeccmiJer 19(i4.
"J.
.\11011"
5.
:\11011.,
"'!"albrijcke ROllwcil-:\cckarhul'){," ZlIhlill­
Hefr 7/H. DezcHlllcr 1971), StUtl,l-iart,
Ct'l'm<l fl \.
Rlllld\rllfl1l,
6. ",\rcl1 Slipforlller ShUll", (;rollfld Support In Crm'i
Valle<' FII.!.,rillI'Prwi.( .\'fIl'.I-UI'(IJTlI, JUIIC I. 197H.
7, ,\110IL, ":\iesenhachbriickc, Bog-en illl Freit'll Vm­
h;IlI:' ;\ustria 1~170-74, FIt' COlll-{re;,s HI7,!, :\('\\
York.
i
L
9
Concrete Segmental Cable-Stayed Bridges
9.1
INTRODUCTION
9.2
9.3
9.4
9.5
9.6
9.1.1 Historical Review
9.1.2 Advantages of Concrete Cable-Stayed Bridges
9.1.3 Structural Style and Arrangement
LAKE MARACAIBO BRIDGE, VENEZUELA
WADI KUF BRIDGE, LIBYA
CHACO/CORRIENTES BRIDGE, ARGENTINA
MAINBRUCKE. GERMANY
TIEL BRIDGE. NETHERLANDS
9.1
Introduction
The concept of supporting a beam 01' bridge bv in­
clined cable sta\,s is not new, and the historical
evolution of this type of structure has been dis­
cussed in the Iiterature. 1- li Although the modern
renaissance of cable-stayed bridges is said to have
begun in 1955, with steel as the favored material,
in the last 1>\'0 decades a number of cable-stayed
bridges have been constructed using a reinfOI'ced
or prestressed concrete deck system. In recent
years several concrete cable-stayed bridges have
been built in the long-span range. In 'at least four
current projects, alternative designs in concrete
and steel have been prepared for competitive bid­
ding. Cable-stayed bridges are extending the com­
petitive span range of concrete bridge construction
10 dimensions that had previously been considered
impossible and reserved for structural steel. To
date, approximately 21 concrete cable-stayed
bridges have been constructed, and others are
either in design or under construction. A tabular
summary of concrete cable-stayed bridges is pre­
sented in Tables 9.1 and 9.2.
400
9.7
9.8
9.9
9.10
PASCO-KENNEWICK BRIDGE, U.S.A.
BROTONNE BRIDGE. FRANCE
DANUBE CANAL BRIDGE. AUSTRIA
NOTABLE EXAMPLES OF CONCEPTS
9.10.1
9.10.2
9.10.3
Proposed Great Belt Bridge, Denmark
Proposed Dame Point Bridge, U.S.A.
Proposed Ruck-A-Chuck), Bridge. U.S.A.
REFERENCES
9.1.1
Hl-5TOR1CAL REVIEW
Since the beginni ng of the cable-st<l\ renaissance ill
] 955, whether for technical or other reasons,
structural steel has been the preferred construc­
tion material. In ] 957, however, considerable ex­
citemenl was generated when Prof. Riccardo
Morandi's prize-winning design of a prestressed
concrete 1312 ft (400 m) cenler span cable-stayed
bridge for the Lake ~aracaibo crossing was an­
nounced. Regrettably the Lake Maracaibo Bridge
was not constructed as originally conceived. The
modified structure, built in 1962, is generally con­
sidered to be the first modern cable-stayed bridge.
However, the Lake Maracaibo Bridge was pre­
ceded by two little-known concrete cable-stayed
structures.
The first concrete structure to use cable stays was
the Tempul Aqueduct crossing the Guadalete
River in Spain." Designed by the famous Spanish
engineer, Prof. Torroja. who has introduced many
original concepts in prestressed concrete, this
structure has a classical three-span symmetrical
cable-stayed bridge configuration with two pylons.
401
Introduction
TABLE 9.1.
Location
Type
Guadalete River, Spain
Yakima River. Wash., C.S.A.
Venezuela
Kiev, U.S.S.R.
Obourg, Belgium
Genoa. Italy
Rome, Italy
Denmark
Denmark
Pretoria, S. Africa
Geelong, Australia
Perth, Australia
Libya
Londonderry, :-.i. Ireland
Hoechst, West Germany
Parana River, Argentina
Tiel, Holland
Barranquilla. Columbia
Vienna, Austria
Taiwan
;\.'ormandy, France
Province Poetenza, Italy
State of Wash .. C .S.A.
Chertsey. England
Auburn, California, C .S..-\.
Jacksonville, Florida. U.S.A.
Eas't Humington, W.Va., U.S.A.
Weirton, W,Va., C.S.A.
Aqueduct
Highway
Highway
Highway
Pedestrian
Highway
Highway
Highway & rail
Highway & rail
Pipe
Pedestrian
Pedestrian
Highway
Highwav
Highway & rail
Highway
Highway
Highway
Highway
Highway
Highway
Highwav
Highwav
Rail
Highway
Highway
Highway
Highway
Bridge
Tempul
Benton City
Lake Maracaibo
Dnieper River
Canal du Centre
Polcevera Viaduct
Magliana
Danish Great Belr'
Danish Great Belt"
Pretoria
II Barwon River
12 Moum Street
13 Wadi Kuf
14 Richard Foyle
2
3
4
5
6
7
8
9
10
15
16
17
18
19
20
21
22
2:)
24
25
26
27
28
~Iainbriicke
Chaco/Corrientes
River Waal
Bananquilla
Danube Canal
Kwang Fu
Pont de Brotonne
Carpineto
Pasco-Kennewick
~I-25 Overpass
Ruck-A-Chuck)",
Dame Point"
East Huntington"
Weirton-Steubenville"
Concrete Cable-Stayed Bridges-General Data
Spans (ftyl
66-198-66
2@57.5-170-2@57.5
525-5@771-525
216.5-472-216.5
2@220
282-664-689-460
476-176
multispans 1132
multispans 1148
2@93
180-270-180
2@116.8
320-925-320
230-689
485.6-308
537 -803.8-5:)7
312-876-312
228-459-228
182.7-390-182.7
220-440-440-220
471-1050-471
100-594- 100
406.5-981-406.5
2@180.5
1:>00
650-1300-650
158-300-900-608
820-688
Year Completed
1925
1957
1962
1963
1966
1967
1967
Delayed by funding
Delayed by funding
1968
1969
1969
1971
Project abandoned
1972
1973
1974
1974
1974
1977
19i1
1977
1978
1978
Design completed
Design completed
C nder construction
In design
a Design by White Young and Partners.
"Design by Clrich Finsterwalder.
"Alternative design with structural steel.
I ft = 0.305 m.
The stays were introduced to replace two piers that
were found to be too difficult to construct in deep
water. Thus, the stays were introduced to provide
!ntermediate support in the main span.
OnJuly 5,1957, a stayed structure crossing the
Yakima River at Benton City, Washington, was
opened to traffic. Designed by Homer M. Hadley,
the structure has a total length of 400 ft (122 m)
with a center span of 170 ft (51.9 m) flanked on
each side by twO continuous spans of 57.5 ft (17.53
m) each. A 60 ft (18.3 m) central drop-in span of 33
in. (0.84 m) deep steel beams is supported by
transverse concrete beams, supported in turn by
structural steel wide-flange stays. Continuous lon­
gitudinal concrete beams comprise the remainder
of the structure and receive support at their ex­
tremity, in the center span, from the transverse
concrete beams and si:eel stays.4.8
In the more than half-century that has elapsed
since.Torroja's Tempul Aqueduct. 21 cable-stayed
bridges have been constructed (Table 9.1). Thir­
teen, or 62%, of these structures have been con­
structed in the past decade. In the last five years
nine have been completed, representing 43% of
the total. Within the last three vears the span of
1000 ft (300 m) has been exceeded, and a current
design contemplates a span of 1300 ft (400 m). It
has taken almost a quarter-century to reach a span
contemplated by Prof. Morandi in his original de­
sign concept for the Lake Maracaibo Bridge. Be
that as it may, it is obvious from the statistics that in
recent years the concrete cable-stayed bridge has
been accepted as a viable structure.
9.1.2
ADVA.YT,1GES OF CONCRETE CABLE-STAYED
BRIDGES
As engineers, we are aware that no particular con­
cept or bridge type can suit all environments, con­
siderations, problems, or site conditions. The
selection of the proper type for a given site and set
of circumstances must take into account many
parameters. The choice of material, in addition to
Concrete Segmental Cable-Stayed Bridges
402
TABLE 9.2.
Bridge
Telllp,,1
Cit\
:1 I.ake \Iar'acaibo
t DlHcpl'l' River
:) Canal till Ct'llllT
Polec\!'r'a \. iad lIC!
i \Iagliana
ii Ibrllsir (;rcaf Bell"
~I
Ibrllsh (;n'at Heir"
1O Pt ('loria
II B~rn\ Oil Ri\ ('I
12 \Ioll!l! Street
1:\ \\adi I\.u!
1·1 ]{i\n I'ovlc
I C, \Loi nbriHke
It; l :han',!( ;Ollit-II tes
Ii Rl\,'r Wa."
Ii> B;'IT;u)(llIilla
I ~l Dalllll)(' Callal
20 I;. hang I'll
21 1'0llt de Brotollll('
;2~
( :arpilll'io
2:\ t'asn)' l\.('nl)(·\\I(\-.
2,1 ;\!_:!c, ()verpa'"
')
_:) Rtlc\-'-A-( :lllIcb
;2(i J),mte 1'01111
.)­
_f
\-:;"t Illlntingroll
:2H \\' "i rtoll,Slelll)('miJle
2
lklllOll
"
­
Stav
Planes
2
2
2
2
2
2
Concrete Cable-Stayed Bridges-Dimensional Parameters
Stay
:\0­
Stavs Arrangement
:1
4
1
Radiating
Radiating
2
Radiating
Harp
Radiating
Fan
1(;
2
2
2
14.1
0.07
2
I :{
2
2
139.4
95
65.6
I4H
111.5
(J.IH
0.20
315
41
43
1'11.H
0.27
0.44
0.16
0.42
0.19
0.52
0.3H
0.19
(l.11
52.Fl
() 15
2:11
94,75
0.22
~9
2
2
2
2
(ft)
Pvlon
Heightto-Span
Ratio'
Harp
lIar],
Radiating
Radiating
177.5
:{60
172
J[J5
O.:~O
0.21
0.23
:>
2
2
2
2
:!
"
.)
2
2
Deck
Width
(It)
Girder
Depth
( rt)
6.9
3.~5
2
:1
2
2
2
Pylon
Height
All(lV'e
Deck
2
21
IH
.)
20
21
15116
24
Radiating
Lm
Radiating
Fan
220
il
0.16
0.22
0.:19
Harp
Radiatitlg
Radiating
:,02
279.4
:l33.2
0.2:1
0.:1J
0.41
57
5.H7
59
79
:11.7Y
46
15.8
6
15.75
42.5
9H
101.5
~7
101
:17
'1l.H
Gi
G:1
·11 ,~V
79,H
39
.,}4
105.75
41
103.5
16.4
4.H
1.94
15
9oH-13.2
2:1.5
2,95
3
2
11.5-23
1l.5
SpantoDepth
Ratio'
Girdn
Construction
Type"
2H.7
52.3
46.7
9i'1.75
113
46
:{6
4ii
390
31
:{H.5
5HA
70
60
ell'
Clp/pC d-i-,
PC
PC
CII'/PC d-i-s
CII'!pC d-i-s
PC segments
CI P segmeuts
ell'
Ul'
ell'
CI Pipe d-i-s
PC seglllen ts
57
H.5
I 1.5
II.c)
10
9.2
70
76
-16
4"~.3-
12,5
H4
I 1.:,
i
9
H,5
'1-6
5
!l.5
52
140
20
I '1:~
260
IHO
96.5
ClP
UP
PC/CIt' d-i-s
PC and ell'
CI I' segments
PC and ell'
PC
PC and ell'
ell'
PC segmetlls
ell'
PC scgments
ell' and PC
Composite
Composite
., Design Il\' Wilile Young and Partners.
/. ])csign b\ t 'Iri," I-ir"ler\\'aldel'.
. Sct' Tahk ~I.I lor malor 'pall dilllcllsions.
"(:II' ~ (,;lst-in-place. PC = precast. d·i-s = drop-in·span.
, Forlll Inver""lit paraholoid in space.
! Pel single-cell box.
I It = O.:HJ:, Ill.
material properties, depends on availability and
Ihe prevailing economics al a particular time as
well as Ihe specific localion of the site. The process
of weighting and evaluating Ihese parameters for
variolls tvpes of bridges under consi~eration is
certailllv Illore an art than a science.
III e,,;du:ttillg a concrete cable-stayed bridge, the
designer should be aware of the following advan­
tages:
I.
The main girder can be very shallow with re­
spect 10 the span, Span-to-girder-depth ratios
vary from 45 to 100. With proper ael'Odynamic
streamlining and multistays the deck structure
call be slilll, having span-to-depth ratios of 150
10400, and lIot convey a massive visual impres­
SIOIL
2.
3.
4.
5.
Concrete deck structures, b" virtue of their
mass and because concrete has inherently
favorable damping characteristics, are not as
susceptible to aerodynamic vibrations,
The horizontal component of cable-stay force,
which causes compression with bending in the
deck structure, favors a concrete deck struc­
ture. The stay forces produce a prestress force
in the concrete, and concrete is at its best in
compression.
The amount of steel required in the stays is
comparatively small. A proper choice of height
of pylon with respect to span can yield all op­
timum solution. 9
Live-load deflections are small because of the
Iive-Ioad-to-dead-Ioad ratio, and therefore
Introduction
6.
403
concrete cable-stayed bridges are applicable to
railroad or mass-transit loadings.
Erection of the superstructure and cable stays
is relatively easy with today's technology of
prestressing, prefabrication, and segmental
cantilever construction.
9.1.3
STRUCTURAL STrLE ASD ARRASGE,\lE.YT
Many of the concrete cable-stayed bridges have
been designed by -"1orandi or have been strongly
influenced by his style. Commencing with the Lake
Maracaibo Bridge, of the 12 bridges constructed,
excluding pedestrian and pipe bridges (see Table
9.1), six have been designed by -"{orandi, Figures
9.1 through 9.6. A third prize winner in the 1967
Danish Great Belt Bridge Competition was the
Morandi-style design proposed by the English con­
sulting firm of White You ng and Partners, Figure
9.7. The Chaco/Corrientes Bridge, Figure 9.8, very
much resembles the Morandi style.
FIGURE 9.3. Magliana Viaduct (courtesy of L'lndus­
tria Italiana del Cemento).
FIGURE 9.4. Wadi Kuf Bridge, general construction
view (collrtesy of Prof. R. MOl'amli).
FIGURE 9.1. Lake :Vlaracaibo Bridge, general "iew,
from !'eferen<:e 1 I (courtesy of Julius Berger-Bauboag
Aktiengesellschaft).
FIGURE 9.2.
Polcevera Creek Bridge, general view.
FIGURE 9.5.
Garrido).
Barrallquilla Bridge (courtesy of L. A.
404
Concrete Segmental Cable-Stayed Bridges
FIGURE 9.6. Carpineto Yiaducl (courtes\' of L'II1­
ciuslria Italiana del Cemento).
FIGURE 9.7. Dallish Great Belt Bridge, anist's rend­
ering (courtesy of \'.'hite Young and Partners).
These structures, with the exception of the Ma­
gliana, Barranquilla, and Carpineto bridges, are
typified by the A-frame pylon positioned in the
plane of the stays and an auxiliary X frame- or in­
clined struts to support the deck structure at the
pylon. Thev are staticallv determinate systems so as
to preclude am' possible damage from differen­
tial settlements of the bridge piers and pylons or
from light seismic shocks.
A simple schematic of the structural scheme is
shown in Figure 9.9, which consists of a series of
independent balanced systems, each carried by an
individual pier and pylon. These systems are then
connected by drop-in girders, which are simple
span girders spanning between independent sys­
tems. IO The cantilever girder is supported at two
points (C and D) by a pier system and elasticany
supported at two points (B and E) by the cable
stays, thus producing a tbree-span girder with
cantilevers on each side. The stays are supported
bv a pylon ponal frame that is independent of the
pier system supporting the girder.
Another entry in the 1967 Danish Great Belt
Competition by Ulrich Finsterwalder, of the Ger­
mall firm Dyckerhoff & Widmann, deviated from
the Morandi style and was awarded a second prize.
Finstcrwalder's design proposed a multiple-span,
multistay system using Dywidag bars for the stays,
Figure 9.10. The deck was envisioned as being con­
structed by the cast-in-place balanced cantilever
a
b
c
e
FIGURE 9.9. Schematic oj !'.iorancii-st,le structural
scheme, from rei'erence 10 (cot! rtesv of the America n
COllcrele I nstilUle).
FIGURE 9.8. Chaco/Corrientes Bridge, general view,
from referellce 13 (courtesy of 'lJormer Gray).
FIGURE 9.10. Danish Great Belt Bridge, artist's rend­
ering (courtesy of Ulrich Finsterwalder).
Lake Maracaibo Bridge, Venezuela
segmental method, each segment being supported
by a set of stavs. This concept was later to be con­
summated in the )'lain Bridge and in the design of
the Dame Point Bridge.
The choice of geometrical conflguration and
number of stays in a cable-stayed bridge system is
subject to a wide variety of considerations. If cable
stays are few, they result in large stay forces, which
require massive anchorage systems. A relatively
deep girder is required to span the large distance
between stays, producing span-to-depth ratios vary­
ing from 45 to 100 (see Table 9.2). Depending
upon the location of the longitudinal main girders
with respect to the cable-stay planes, large trans­
verse cross girders may be required to transfer the
stay force to the main girder.
A large number of cable stays, approaching a
continuous supporting elastic media, simplifies the
anchorage and distribution of forces to the girder
and permits the use of a shallower girder, with
span-to-depth ratio varving from 150 to 400 (see
Table 9.2). The construction of the deck can be
erected roadway-width by free cantilever methods
from stay to slav without auxiliary methods or
stays. If the depth of the r<..>adway girder can be
kept at a minimulll. the deck becomes, more or
less, the bottom chord of a large cantilevering
truss; it needs almost no bending stiffness because
the inclined stan; do not allow any large deAections
under concentrated loads. 6
In the 55 years since Torroja's Tempul Aque­
duct the concrete cable-stayed bridge has evolved
from basically a statically determinate structure
with one stay on each side of the pylon to a
highly indeterminate system with multistays. As
demonstrated by the Danish Great Belt Bridge
·Competition. the Pasco-Kennewick Bridge, and
the Pont de Brotonne, spans of approximately
1000 ft (300 m) are practical and have been ac­
complished. The practicality of spans of 1300 ft
(400 m) is demonstrated by the Dame Point
Bridge. and spans approaching 1600 ft (500 m) are
considered technically feasible. Leonhardt 6 has
projected that with an aerodynamically shaped
cOI,nposire concrete and steel deck a span of 2300 ft
(1500 m) can be achieved. With today's technology
of prefabrication, prestressing, and segmental
cantilever construction, it is obvious that cable­
staved bridges are extending the competitive span
range of concrete bridges to dimensions that had
previously been considered impossible and into a
range that had previously been the domain of
structural steel. This technological means exist;
they only require implementation.
9.2
405
Lake Maracaibo Bridge, Venezuela
This bridge, Figure 9.1, has a total length of 5.4
miles (8.i km). Five main navigation openings COII­
sist of prestressed concrete cable-stayed structures
with suspended spans totaling 77 I ft (235 m). The
cantilever span is supported on four parallel X
frames, while the cable stays are supported on two
A frames with a portal member at the top. There is
no connection anvwhere between the X and A
frames, Figure 9.11. The continuous cantilever
girder is a three-cell box girder 16.4 ft deep by 46.7
ft wide (5 ~ by 14.22 m). An axial prestress force is
induced into the girder as a result of the horizontal
component of cable force, thus, for the most part,
only conventional reinforcement is required. Ad­
ditional prestress tendons are required for nega­
tive moment above the X-frame support and the
transverse cable-stav anchorage beams. II
The pier cap consists of the three-cell box girder
with the X frames continued up into the girder to
act as transverse diaphragms, Figures 9.12 and
9.13. After completion of the pier, service girders
were raised into position to be used in the con­
struction of the cantilever arm. Owing to the addi­
tional moment, produced during this construction
stage by the service girder and weight of the can­
tilever arm, additional concentric prestressing was
required in the pier cap, Figure 9.13. To avoid
overstressing of the X frames during this opera­
tion, temporary horizontal ties were installed and
tensioned bv hydraulic jacks, Figures 9.13 and
9.14.
FIGURE 9.11.
Lake Maracaibo Bridge, pier cap with
X frames, from reference 11 (courtesy of Julius
Berger-Bauboag Aktiengesellschaft).
;.-1
FIGURE 9.12.
reference 11
~Jlall IOwel ,md X-frallles, f rolll
of Julius Berger-BalllJo<lf,i AklicngesellsciIafr),
Lake Maracaibo Bridge, main
(colirtesY
f-.E-r"----------48,55
\
\
\
\
\
\
\
\
\
\
\
\
\
\
Service girder for
cantilever arm
~
II
""
""
"
""
;~-,a.i:~7-:-7III
: \..J,/
I
I
/
\~~
/
'{/: \.:,/
,I
/
'\. I /
. . _____
..:-~~V
FIGURE 9.13. Lake Maracaibo Bridge, pier cap of a main span and service
girder, from reference II (counesy of Julius Berger-Bauboag Aktiengesell­
schaft).
406
Wadi Kuf Bridge, Libya
FIGURE 9.14. Lake ~laracaibo Bridge, brace mem­
hers bear agaillSl X frames after being tensioned by hy­
draulic jacks, from reference 11 (courtesy of Julius
Berger-Bauboag Aktiengesellschaft).
In the construction of the cantilever arms, spe­
cial steel trusses (service girders) were used for
formwork. Thev were mpported at one end by the
completerl pier cap and at the other end by aux­
iliary piers and foundations, as shown in Figure
9.15.
•
The anchorages for the cable stays are located in
a 73.8 ft (22.5 m) long prestressed inclined trans­
verse girder. The reinforcing cages for these
members were fabricated on shore in a position
corresponding to the inclination of the stays. They
407
FIGURE 9.15. Lake \[aracaibo Bridge, placing ser­
\ice gir<ler (il!' forming cantile\'er girders, trom refer­
ence 11 (collrteS\ of Julius Berger-Bauboag Ak­
tiellgesellschaf't).
weighed 60 tons and contained 70 prestressing
tendons, Figu re 9.16. The cable stavs are housed in
thick-walled steel pipes, Figure 9.17, which were
welded to steel plates at their extremities and were
encased in the anchorage beam. A special steel
spreader beam was used to erect the fabricated
cage in its proper orientation. The suspended
spans are com posed of four prest ressed T sections.
9.3
Wadi Kuf Bridge, Libya
The Wadi Kuf Bridge in Libya, designed by Prof.
Morandi, consists of two independent balanced
FIGURE 9.16. Lake Maracaibo Bridge, fabrication of anchorage beam, from referellce
11 (courtesy of Julius Berger-Bauboag Aktiengesellschaft).
408
Concrete Segmental Cable-Stayed Bridges
9.4
FIGURE 9.17. Lake :Ylaracaibo Bridge, housing for
cahle slavs, fmm reference 11 (courtesy of jUJillS
Ikrgcr-Bauboag Akliengesellschaft).
cable-stay systems having their ends anchored to
the abutment by a short hinge strut. The cable-stay
systems are connected by a simply supported
drop-in span, Figure 9.4.
This structure consists of only three spans. The
center span is 925 ft (2S0 m) long and the two end
spans are each 320 ft (97.5111), for a total length of
1565 ft (475 111). The simply supported drop-in
center portion of the main span consists of three
double-T beams ISO ft (55 111) in length; each beam
weighs approximately 220 tons (200 mt).12
The A-frame towers are 459 ft and 400 ft (140
and 122111) high and the roadway deck is 597 (1S2
Ill) above the lowest point of the valley beneath the
Slrllct ure. 12 The su perstructure is a single-cell box
gilder that varies from 13 ft (4.0 m) to 23 ft (7.0 111)
at the pylons. The single-cell box is 24 ft (7.4 m)
wide and with cantilever flanges forms a 42.7 ft (13
111) cleek.
The contractor made good use of traveling
forms to construct the box girder and deck, using
the balanced cantilever technique to build on both
sides of the pylons at the same time. Traveling
forms were used because extreme height and
difficult terrain made other conventional con­
struction methods impossible or too. costly. The
deck was constructed by progressive cast-in-place
segments, attached to the previously completed
segments by means of temporary prestress ties and
subsequent permanent post-tensioning Dywidag
bars. The procedure adopted required temporary
cable stays to support the cantilever arms during
the construction sequence as the superstructure
progressed in both directions from the pylon.
When the superstructure extended sufficiently, the
permanent stays were installed, and the structure
was completed in the same manner.
ChacolCorrientes Bridge, Argentina
The Chaco/Corrientes Bridge (also referred to as
the General Manuel Belgrano Bridge) crosses the
Parana River between the provinces of Chaco and
Corrientes in northeast Argentina and is an im­
portant link in one of the highways between Brazil
and Argentina, Figure 9.8. It has a center naviga­
tion span of 803 ft lOin. (245 m), side spans of 537
ft (163.7 m), and a number of 271 ft (82.6 m) ap­
proach spans on both the Chaco and Corrientes
sides of the riv<:;r. The vertical clearance in the
main spans above flood level is 115 ft (35 m).13.14
The superstructure of this bridge consists of two
cast-in-place concrete A-frame pylons, which sup­
port a deck of precast segmelllal post-tensioned
concrete. The pylons are flanked by concrete
struts, which reduce the unsupported length of the
deck, Figure 9.18. Although the pier cap section of
the deck (between inclined struts) is cast in place,
the cantilever portion consists of precast segments.
The drop-in spans are cast in place.
The deck structure consists of two longitudinal
hollow boxes 8 ft 2Y2 in. (2.5 m) wide and with a
constant depth of II ft 6 in. (3.5 m), which support
precast roadway deck elements, Figure 9.19. The
precast girder elements were match-cast on the
river bank in lengths of 13 ft I Y2 in. (4.0 m), with
the exception of shorter units at the point of stay
attachment, which contain an inclined transverse
anchorage beam, Figure 9.20. Units were cast by
the long-line method on a concrete foundation
with the proper camber built in. Each ullit was cast
with three alignment keys, one in each web and
one in the LOp flange. The units were erected as
balanced cantilevers with respect to the pylon to
minimize erection stresses. After a unit was hoisted,
an epoxy joint material was placed over all of the
butting area; then the unit was placed against the
already erected unit and tensionedY
To eliminate the need for falsework, the inclined
struts and pylon legs were supported by horizontal
ties at successive levels as construction proceeded,
Figure 9.21. The legs were poured in segments by
cantilevering the formwork from previously con­
structed segments. When deck level was reached,
the girder section between the extremities of the
inclined ties was cast on formwork. To further stif­
fen the pylon structure, a slab was cast between box
girders at the level of the girder bottom flanges.
This slab is within the limits of the cast-in-place box
girders and inclined struts and serves as an addi­
tional element to accept the horizontal thrust from
the cable stays. The upper portion of the pylon was
Chaco/Corrientes Bridge, Argentina
409
157~
Precast
segments
(10.00 m)
4 ft 1ij in. (1.50 m)
Precast construction
-+Cast·in·place
369 ft 1 in. (112.50 m)
-.;- Precast construction
369 ft 1 ih. (112,50 m)
_ 8 0 3 ft 10 in (245,00 m ) - + - - 5 3 7 ft 0 in. (163.70m)~
Center span
Side span
FIGURE 9.18. Chaco/Corrientes Bridge. longitudinal geometry. from refer­
ence H (courtesy of Civil Engineering-ASCE).
8~ in,
9 It 2~
(2,80
In,
27 ft 3 in,
9 It 2i in.
8~ in,
(8,30 m)
(2.80m)
(22 em)
m)
Cast·in·place
concretei
2% down
'
2% down
-­
I
I
t. Bridge
8 ituminous
pavement
Box girder
I
I
~ 8 It 2~ in,~ 11
(2.50 m)
ft 3~ in.
(3.45 m)
I Symm. about t.
+'
~. 11 ft 5~ in,
(3.50 m)
channel
".
:±==::::J
7~ in, to 1 ft 7~ in. t;
,
I
(20-50 em)
J9~ in, to l1ij in.
11 ft 3~ in,~ 8 ft 2~ in.
(25-30 em)
(3.45 m)
(2.50 m)
FIGURE 9.19. Chaco/Corrientes Bridge. deck cross section, from reference
H (cOl1rtesv of Ci\il Engincering-ASCE).
FIGURE 9.20. Chaco/Corricllles Bridge. cable an­
chorage at girder, from refcrence 14 (courtesy of Civil
Engineering-ASCE).
then completed, using horizontal struts to brace
the legs until they were connected at the apex. Fig­
ure 9.21. 13• 14
The precast box girder units. with the exception
of those at the cable-stay anchorage. were cast 13 ft
1V2 in. (4 m) in length by the long-line. match-cast
procedure. The soffit bed of the casting form had
the required camber built in. Alignment keys were
cast into both webs and the top flange. Match cast­
ing and alignment keys were required to ensure a
precise fit during erection. Each 44 ton (40 mt) unit
was transported bv barge to the construction site
and erected by a traveling crane operating on the
erected portion of the deck. Since each box was
lifted by a balance beam, four heavy vertical bolts
had to be cast into the top flange of each box. The
lifting crane at deck level allowed longitudinal
410
Concrete Segmental Cable-Stayed Bridges
-'2.
3.
4.
5.
6.
7.
8.
Erect diaphragms between lines of boxes and
post-tension.
Place temporary and permanent stays as erec­
tion proceeds.
Remove temporary stays.
Remove temporary post-tensioning in the can­
tilever sections.
Place precast deck slabs between box girders.
Concrete the three 65 ft 8 in. (20 m) drop-in
spans.
Place asphalt p~\'ement, curbs, and railings.
9,5
FIGURE 9.21. Ch;lr()/C()lTiellle~ Bridge. crefllOll sc­
qll('Il(C of p\lOIl. fmlll reference 14 (courtes\ of Ci,il
b Igillecrillg-:\SCE),
1I1(l\CIl1Cllt of the suspellded box. Upon erection to
the proper elevation, the unit was held to within 6
in. (150 llllll) of' the mating unit while epoX\' joi1lt
1l1ateriaJ was applied. Bearing surfaces of the unit
w('re sand-blasted alld water-soaked before erec­
tioll, The water film was removed before erection
and application of the epoxy joint material. The
tra\eling deck crane held the unit in position
against its mating unit until it could be post-ten­
sioned into position. The crane was slacked off
without waiting for the joint material to cure. 13• 14
To minimize overturning forces and stresses in
the pylon, it was necessarv to erect the precast box
ullits by a balanced cantilever method on both sides
of the centerline of the pvlon, The erection sched­
ule delltalldcd simultaneous erection at each
pYlolJ, although the pylons are independent of
each other. \\'hen four precast box units were
erected ill the cantilever on each side of the pylon,
temporary stays were installed from the 'top of the
pylon to their respective connections at deck level.
After installation of the temporary stays, cantilever
erection proceeded to the positions of the perma­
nent stays, and the procedure was repeated to
completion of the installation of the precast box
units. 13
The erection sequence may be outlined as fol­
lows:
1.
Erect precast boxes and post-tension succes­
sively.
Mainbrucke, Germany
The Main Bridge near Hoechst, a suburb of
Frankfort, constructed in 1971 is a prestressed.
cast-in-place. segmental, cable-stayed structure
that connects the Fahwerke Hoechst's chemical in-.
dustrial complex on both sides or the River Main
in West Germany, Figure 9.22. It carries two
three-lane roads separated by a railway track and
pipelines. This structure, a successor to Finster­
walder's Danish Great Belt Bridge proposal, repre­
sents the first practical application of the Dywidag
bar stay.l:;
The hridge spans the river at a skew of 70° from
the high northern bank to the southern bank,
which is 23 ft (7 m) lower. The center navigation
span is 486 ft (148.2,3 m) with a northern ap­
proach span of 86 ft (26.17m) and southern ap­
proach spans of 55, 84, 95, and 129 ft (16.91,
25.65, 29, and 39.35 m), Figure 9,23.
Railroad track and pipelines are in the median
between the two cantilever pylon shafts and are
supported on an 8.7 ft (2.66 111) deep torsionally
stiff box girder, Figure 9,24. The centerline of the
FIGURE 9.22.
Mainhriicke, [rom reference 16.
Mainbrucke, Germany
FIGURE 9.23.
Mainbrticke, elevation and plan, from reference 16.
aUERSCHNITl DER
S~ROM OFFNUNG
!;
I
I,
:!
I~
1
aUERSCHNITT DER
VORLANDOFFNUNGEN
FIGURE 9.24.
:\lainbrticke, cross sections, from reference 16.
longitudinal webs of the box girder coincides with
the centerline of the indi\'idual cantilever pylons,
, and they are 26.25 ft (8 m) apart. Transverse cross
beams at 9.8 ft (3 m) centers form diaphragms for
the box and cantilevers, which extend 39 ft (11.95
m) on one side and 36 ft (II m) on the other side of
the central box to support the two roadways, Figure
9.25.
The cross section of the towers consists of an an­
choring web in the center, san9wiched by two flat­
pl;,lte flange elements, Figure 9.26. In a transverse
elevation of the pylons, the width of the pylon in­
creases from the top to just below the transverse
strut, where it decreases to accommodate clearance
requirements for both modes of traffic, Figure
9.26. The stay cables (Dywidag bars) are in pairs,
horizontal to each other in the main span and ver­
tica~ in the side span, thus simplifying the anchor­
age detail at the pylon. Figure 9.26. 16
FIGURE 9.25. \Iainbrticke, view of deck at pylon
(courtesy of Richard Heinen),
411
,1
I
I
412
Concrete Segmental Cable-Stayed Bridges
ANSICHT'
QUER
'
VERANKERUNG DER
SCHRXGSEILE 1M PYLON
FIGURE 9.26.
l\lainbnjcke, pYlon and cable configuration, from refer­
ence 16.
COllstruction of the bridge superstructure was
hy the cast-in-place segmental method. Figure
9.27. Segments in the river span were 20.7 ft (6.3 m)
in length, corresponding to the spacing of the
stays, Segments in the anchor span were 19ft (.5.8
Ill) ill lellgt 11. Segments in the allchor span were
concreted before the corresponding segment in
the river span to maintain stability. The pylon
segments were associated with the superstruc­
ture segments. and each pylon segment was slip­
formed.
Figure 9.28 shows the partially completed
structure and the falsework necessary to install the
stays. Each stay is composed of twenty-flve 16 mm
(% in.) diameter Dywidag bars encased in a metal
duct. which is grouted for corrosion protection
similar to post-tensioned prestressed concrete con­
struction.
FIGURE 9.27. Mainbriicke, casting of deck segments
(courtesy of D}'ckerhoff & Widmann).
9.6
Tiel Bridge, The Netherlands
The Tiel Bridge,17 Figures 9,29 and 9.30, crosses
the Waal River, which, together with the Maas and
the Rhine. flowing east to west, divides the
FIGURE 9.28. Mainbrucke,
partially
structure (courtesy of Richard Heinen).
completed
r.,;o
-"'"
!):;tu
i
NORD _NORTH
II¥!
VIAOUC O'ACCE5
-1W....-
APPUIS GLlS5ANTS
SliOING BHRING5
-l
aXl
-
6
r
._&».
~--,
APPUIS CAOUTCHOUC
RUBi:lER BEARINGS
r~~~~
_"''D
_ _ _ ,JD)
_ _ ~~
FIGURE 9.29. Tiel
]I'd!l
APPUIS GLiSSANT5
SLIDING BEARINGS
APPROACH VIADUCT
10
~
__
OUVRAGE PRI NCIPAL
14
15
MAIN BRIDGE
~.=:
414
FIGURE 9.30.
CotlCrete Segmental Cable-Stayed Bridges
Tiel Bridge, main spam,
\;etherlands into northern and southern parts,
struCl ure pr()\ides a needed t rafflc link be­
tween the town of Tiel and the south of the (OUI1­
tn' and is a lIlajor north-south route,
The structure has an overall length of 4656 ft
(1419 111) and consists of a 2644 ft (806 Ill) curved
viaduct on a 19,685 ft (6000 111) radius, which in­
cludes ten continuous 258 ft (i8,5 111) long spans
alld a 200H ft (G12 Ill) straight main structure CO!1l­
prising three ~t,l\ed spans of 312,876, and :112 ft
(95, 26i. and 95 Ill) and two 254 ft (ii.5 111) side
spans.
The cross section cOllsists of two pI'eGlst concrete
boxes. each supporting two vehicular and one bicy­
de lane, The total width of the superstructure,
which is R9 it (2i.2 Ill) in the access viaduct, Figure
9.:11. is elliarged to 103 ft (31,5 m) over the main
~tnl('lllI'e so a~ 10 accommodate the pdon sup­
porting the sta,'s,
The structure crosses not only the "Vaal Ri,'er but
also a flood plain, which is under water during the
willter months. :'\avigation requirements dictate a
horizontal de,lI'allee of 853 ft (260 m) and a verti­
cal clearance of30 ft (9.1 m).
Thi~
FIGURE 9.31.
Tiel Bridge, approach ,'iaduCL
The ten-span 2648 ft (806 m) long access viaduct
is continuous over iL~ entire length. The super­
structure is supported on the piers by sliding
teflon bearings, except at the three center j)iers
where it is supported on neoprene bearings, hav­
ing a thickness such that they fix the viaduct at
these piers. Expansion joints are located at piers 1
and II. The superstructure in the access viaduct
consists of two precast rectangular boxes of a con­
stant depth of 11.5 ft (3.5 m) and width of 21 ft 8
in. (6.6 111). The top flange including cantile\ler
O\'erhangs has a width of 44 ft (13.44 m). The
l)Verall width of the approach viaduct deck is 89 n
3 in. (2i.2 111), including a longitudinal pour strip.
The viaduct was constructed by the precast bal­
anced cantilever met hod with cast-in-place closure
pours at the midspans. To accommodate the can­
tilever compressive stresses in the hottom flange
()\er the piers, the thie Kness of 1 he ilOll om flange is .
linearly increased from a minimum of 8 in, (200
1ll!1l) to 24 in. (600 111m) over a length of 33 ft (10
m) on each side of the pier. Each pier segment
cOJltains a diaphragm.
Because of the potential flooding of the river
from A, pril through December a nci the consequent
loss or damage of fabework and loss of time, it was
decided to build the access viaduct utilizing precast
segments in the balanced or "free" cantilever con­
su'uction. The segments could be cast during
flooding and placed in storage. Erection of the
segments, which WOUld take less time than the
casting, could be accomplished after the Hood had
subsided.
The precast segments, weighing 132 tons (120
mt), were cast in I11m'able forms on a casting bed
baving the length of one span (by the long-line
method, see Section 11.6.2). Segments were Slored
by and parallel to the casting bed and handled by a
130 ft (40 m) span gantry crane, Figure 9.32. They
were transported to the site (access viaduct abut­
ment) by means of a 132 ton (120 I1lt) capacity
trolley and then placed in the structure by the same
gantry crane used in the precasting yard for han­
dling, Figure 9.33. The trolley was used to trans­
port the segments because the gantry was usually
engaged in the precasting yard or in placing seg­
ments in the viaduct. The gantry crane was such
that it spanned over the twin boxes in the super­
structure and 'the trolleyway used to transport the
segments.
Segment joints are of the epoxy-bonded type
(see Section 11.5). Cantilever imbalance is accom­
modated by a temporary support adjacent to the
pier, Figure 9.33. Five temporary prestress bars
Tiel Bridge, The Netherlands
415
FIGtJRE 9.32. Pn~castillg plant. (1) Casting hed, (~)
re-bar srorage, (C) segment storage, (cl) {oncrete hdtch
plant, (5) office, (6) gamry crane, (7) hridge approach.
are used as provisional prestressing to hold the
segments in position until permanent prestress
tendons can be threaded into the ducts and
stressed.
The sVlTlmetrical box girder main structure
consists of a 254 ft (7i.5 m) 'Side span, a 312 it (95
m) side stayed span, and a 331 ft (101 111) section of
staved center span cantilevering toward the center
of the bridge. The center section between the
staved cantilever ends is made up of four 213 ft (65
m) suspended lightweight concrete girders.
Two alternatives were considered for the cable­
stay pylons: a single p\'lon located on the 1011­
gitudinal centerline of the bridge or a ponal-type
pylon. To simplify the project, the portal-type
pylon was selected. The portal pylon is fixed to the
.pier and passes freely through the superstructure.
Figure 9.34. The superstructure is fixed at the
pylon piers except l'or rotation. It is allowed to
move longitudinally at succeeding piers.
Two alternatives were also considered for the
stay system: a multiple stay system supporting the
deck almost continuously and a system consisting
of a few large staY's. As prestressed concrete stays
had been selected, the second solution became
somewhat mandatorY" Construction of prestressed
FIGURE 9.33.
FIGURE 9.34.
Free pas.sage of pYlol1 t 11 Hlllgil deck.
concrete stays is a costly operation requiring extell­
sive high scaft'olding, Figure 9.35; thus it is advan­
tageous to reduce the number of stays.
The short stays of the bridge have a slope of I: 1
and the long stavs a slope of I :2. Their points of
anchorage to the deck are respectively at 156ft
(47.5 111) and 312 ft (95 m) OIl both sides of a pvlon.
The long stays have a cross section of 3 by 3.:; ft
(0.9 by 1.0 m) and are prestressed bv 36 tendons Oil
the bank side and bv 40 tendons on the river side,
because of the larger load on that side, Figure
9.36a. The effect of the different loads on the stays
introduces a flexural moment into the pylon. The
short stays have a cross section of 2.13 by 3.3 ft
(0.65 by 1.0 m) and are prestressed by 16 tendons
Placing of segme!l!s bv gal1lry crane.
Concrete Segmental
416
Ca~le-Stayed
Bridges
Three loading conditions were considered for
the stays from a statics point of view:
1.
2.
3.
FIGURE 9.35. Fabcwork for sta\' construction.
the hank side and 20 tendons on the river side,
Figure 9.36b.
The concrete of the stays has a 2H-day stl-ength
01 approximately 8700 psi (60 ,\IPa). Its function is
llot only to protect the tendons, hut also to increase
the rigidity of the stays, which is four times that of
the tendoJ]s alone.
011
(a)
Short stays
20/16 cables
(b)
FIGURE 9.36.
1
Cross section of stays.
For the self-weight of the stays and dead toad
of the superstructure, the deck is considered as
supported on nonyielding supports. which are
the stay anchorage points, and the load in the
stays results from the reactions at these points.
For design live load, the deck is considered as
supported on yielding supports, the rigidity of
which is determined by the rigidity of the pre­
stressed stays. .
The prestress of the stavs was calculated with a
safety factor against cracking of 1.1 for dead
load and 1.3 for live load, without allowing an~
tension in the concrete. The ultimate load
safety Elctor is 1.8. For the load condition be­
tween cracking and collapse the stay rigidity is
reduced to the rigidity of the tendons alone ..
Their excessive elongation, in case they
yielded, would lead to an excessive deflection
of the box girder and a premature collapse be­
fore the proposed safety limit. Therefore, it
was necessary to reduce the initial stress of the
tendons to 40 to 45o/c of their ultimate strength
in order to keep them in the elastic range up to
ultimate load determined by the safety factor
of the structure as a whole.
The sag of the long stay is 2.3 ft (0.70 m) in a
length of 328ft (l00 m) under dead load. Under
live load the sag is reduced to 1.8 ft (0.55 m). The
cross section of the staYs at their extremities is in­
creased slightly to resist bending stresses. These
stresses were calculated by the method of finite dif­
ferences.
In the longitudinal direction the girders are
prestressed primarily by the horizontal components
of the stay forces. The unstayed end spans are pre­
stressed with 54 tendons. In the other spans addi­
tional prestressing is provided by 10 tendons that
overlap each other at the supports. These tendons
were required until such time as the stay forces
were applied and, at completion, to provide safety
against cracking and collapse. The deck slab is pre­
stressed transversely by tendons spaced at 12 to 17
in. (0.30 to 0.44 m).
The suspended 213 ft (65 m) span is composed
of four precast lightweight concrete girders with a
6500 psi (45 MPa) concrete. The cast-in-place deck
slab is increased from a thickness of 9.8 in. (250
mm) in the box girders to 12.6 in. (320 mm), owing
to the smaller restraint of the slab in the one web
girders.
Tiel Bridge, The Netherlands
The following restraints and conditions were
considered in the determination of the construc­
tion procedure for the main spans of the structure:
I.
2.
3.
4.
The exclusion of falsework from the river be­
cause of navigation requirements.
The potential for flooding.
The presence of the precasting plant on the
north bank.
The possibility of adjusting the attachment
points of the stay to the deck.
417
"'''' .41
!--~=
II
12
PHASE 2
12A
13
~
!~~_~~=I=
I
I
I
I 475~
72.50
4750
4750
PHflSES DE CONSTRUCTiON DE
L' OUVRAGE PRINCIPAL
Construction was executed in increments limited
by the attachment points of' the stays to the deck.
The stays were prestressed progressively, by in­
creasing the number of stressed tendons as the
load in the stays increased. However, during cer­
tain construction phases when the load in the stays
decreased, some of the tendons were detensioned
or slacked otT.
Using the north side (access viaduct side) as an
example, the construction was divided into the
following phases, Figure 9.37:
PIlil ,I I' 1:
C()n~I/'l1cti()n
o/thl' mller .lImns-that i,l, the
stay-supported side span and/lanking span
Superstructure from pier 11 to pier
12 and a 72 ft (22 m) cantilever into
the next span
b. Extension up to temporary support
l2A
c. Extension up to pier 13 with a 26 ft
(8 m) cantilever into the center span;
simultaneous construction of the
pylon
MAIN BRIDGE
CONSTRUCTiON PHASES
FIGURE 9.37.
~lain
bloidge construction phases.
a.
. Phase 2:
Construction of the first section Ol'er the river
and the short forestay,
Phase 3:
Construction of the second section over the
riNr and the long/oresta}.
The external spans on the north side were con­
structed on falsework during the dry season.
Ctilizing the precast plant on the north side, pre­
cast segments 16.7 ft (5.10 m) long weighing 132
tons (120 mt) were assembled on the falsework.
Segments were joined by tin. (5 mm) cast-in-place
joints. Placing of the segments was carried out by
the same gantry crane as for the access viaduct. On
the south bank, where there was no precasting
plant, the external spans were cast in place on
false.work.
The cantilever river spans were built on 157 ft
(48 m) long steel falsework, consisting of four 10ft
(3 m) deep girders on 23 ft (7.10 m) centers. This
falsework was suspended at one end by prestress­
ing strands from the top of the pylons. At the
lower end. the temporary support strands were an­
chored in a cross beam that supported the steel
falsework by four 350 ton (315 mt) jacks. The 3 ft
(1.0 m) stroke of the jacks allowed adjustment of
the level of the suspension points, and the jacks
were used also to release the temporary prestress
suspension strands when the final stays were in­
stalled. At the opposite end, the steel falsework was
hinged. The horizontal force component on these
hinges was transmitted directly to the completed
part of the deck, and the vertical component was
taken by 1 in. (26 mm) bars.
In Phase 3, the temporary stays were deflected
by means of 95 ft (29 m) booms. This provided the
advantage of maintaining the angles at the lower
connection equal to that of Phase 2 and keeping
approximately the same force level in the tempo­
rary stay.
The falsework used in Phases 2 and 3 was car­
ried on a barge; it was positioned by two derricks
located on the completed part of the deck and by a
floating crane. After the box girders were cast, the
level of the falsework was adjusted, the last joint
418
Concrete Segmental Cable-Stayed Bridges
was cast, and the concrete was prestressed. The
next steps were constructing the stays, prestressing
them, releasing the temporary stays, and removing
the blsework.
In order to reduce creep and shrinkage, the
stays were made of 17 ft (5.15 Ill) long segments
with protruding reinforcement and 16 in. (0.4 m)
cast-in-place joints. The building of the falsework
for the stays and the handling of the precast segIllents were carried out with the hel p of a 16 [on
(15 mt) tower crane 213 ft (65 m) high, running on
the deck.
The precast 213 ft (65 m) suspended span gird­
ers weighed 468 tons (425 mt) and were trans­
ported by barge.
9.7 Pasco-Kennewick Bridge, U.S.A.
The hrst cable-stmed bridge with a segmental con­
crete superstructure to be constructed in the
United States is the Pasco-Kennewick Intercity
Bridge crossing the Columbia Rh'er in the state of
\Nashingloll, Figure 9.3R. ConstruClioll began in
August 1975 and was completed in May 1978. The
overall length of this structure is 2503 ft (763 m).
The center cable-stayed span is 981 ft (299 111), and
the stayed flanking spans are 406.5 ft (124 m). The
Pasco approach is a single span of 126 ft (38.4 m),
FIGURE 9.38. Pasco-Kennewick
(courtesy of An'id Grallt).
Intercity
Bridge
-while the Kennewick approach is one span at 124 ft
(37.8 m) and three spans at 148 ft (45.1 m).4.15.18.19
The girder is continuous without expansion
joints from abutment to abutment, being fixed at
the Pasco (north) end and having all expansion
joint at the Kennewick (south) abutment. The con­
crete bridge girder is of uniform cross section, of
constant 7 ft (2 m) depth along its entire length and
79 ft 10 in. (24.3 m) width. The shallow girder and
the long main spans are necessarv in order to re­
duce roadway grades to a minimum, to provide the
greatest possible na\igation clearance below, and
to reduce the number of piers in the 70 ft (21.3 m)
deep ri\·er.
The bridge is not symmetrical. The Pasco pylon
is approximately 6 ft (1.8 m) shorter than the Ken­
newick pylon, and the girder has a 2000 ft (610 m)
vertical curve that is no[ symmetrical with the main
span. Therefore, the cable-stay pairs are not of
equal length, the longest being 506.43 ft (154 m).IH ,
There is no attachment 01 the girder at the py­
lons, except for vertical neoprene-teAon bearings
to accommodate transverse loads. The girder is
supported only by the stay cahles. There are, of
course, vertical bearil1g~ al the approach piers and
abutments. It is estimated that the natural fre­
quency of the girder, where it will respond to
dynamic acceleration (i.e., earthquake), is 2 cycles
per second. If the siluatjon occurs where the lon­
gitudinal acceleration exceeds this value, the ver­
tical restraint at the I:asco (north) abutment is de­
signed to fail in direct shear, thus changing the
structure frequency to 0. I cycles per second, which
renders the system illSensitive 10 dynamic excita­
tion. The three main spans were assembled from
precast, prestressed concrete segments, while the
approach spans were cast in place on falsework,
Figures 9.39 and 9.40.
Deck segments were precast about 2 miles (3.2
km) downstream from the bridge site. Each seg­
ment weighs about 300 tons (272 mt) and is 27 ft
(8.2 m) long, Figure 9.41. The segment has an 8 in.
(0.2 m) thick roadway slab, supported by 9 in. (0.22
m) thick transverse beams on 9 ft (2.7 m) centers,
and is joined along the exterior girder edges by a
triangular box which serves the function of cable
anchorage stress distribution through the girder
body, Figure 9.42.6 Each match-cast segment re­
quired approximately 145 yd3 (111m 3 ) of concrete,
continuously placed in a previously adopted se­
quence within six hours. After initial curing in the
forms, the girder segments were wet cured for two
weeks in the storage yard, air cured for an ad­
ditional six months, prestressed transversely,
Brotonne Bridge, France
FIGURE 9.39. Pasco-KcIlnewick Intercitv Bridge.
precast segmellts ill maill spans (courtesv of An'id
Granl).
FIGURE 9.40. Pasco-Kennewick Intercity Bridge, ap­
proach spans cast in place on falsework (collrtesy of
Waltcr Brvant, FHWA Region 10).
419
cleaned, repaired, completed, loaded on a barge,
and transported to the structure site for illStalla­
tion in their final location. F01' possible unpredictcd
developments a shimming process was held in re­
serve for mainta1l1111g the assembled girder
geometry correctness, but it was not used. There
are no shims in the segmentally assembled,
epoxy-joined prestressed concrete girder.I.;·lH.l!>
The sections were barged directly beneath their
place in the bridge and hoisted into position, Figure
9.43. Fiftv-eight precast bridge girder segments
were required for the project.
The stays are arranged in two parallel planes
with 72 stays in each plane-that is, 18 stays 011
each side of a pylon in each plane. Thev are held at
each pvlon top, 180 ft (55 111) above the bridge
roadwaY', in a steel weldment, Figure 9.44. Stay all­
chorages in the bridge deck are spaced at 27 ft (8.2
11l) to correspond with the segment length. The
stays are composed on in. (6 mm) diameter parallel
high-strenglh steel wires of the EER type. The
prefabricated SlaVS, manufactured bY' The PreSCOll
Corporation, arrived on the job site on reels, Fig­
ure 9.45, and contained from 73 to 283 wires, de­
pending upon their location in the structure. They
were covered with a ~ in. 00 mm) thick poly­
ethylene pipe, and after installation and final
adjustment were protected against corrosion by
pressure-injected cement grout. cl'he outside di­
ameter of the pipe covering varies from 5 to 7 in.
(0.12 to 0.17 m). Design stress level for the stays is
109 ksi (751.5 MPa). Stay anchorages <Ire of the
epoxy-steel ball (HiAmp) fatigue type produced bv
The Prescon Corporation.
This structure was designed bv Arvid Grant and
Associates, Inc., of Olympia, Washington, in pro­
fessional collaboration with Leonhardt and Andra
of Stuttgart, Germany.
9.8
Pasco-Kennewick Intercity Bridge,
precast segments in casting yard (courtesv of An'ill
Grant).
FIGURE 9.41.
Brotonne Bridge, France
The Pont de Brotonne, designed and built by
Campenon Bernard of Paris, crosses the Seine
River downstream from Rouen in France. Because
of increased navigation traffic in the area, a second
crossing over the Seine River was urgently needed
between the two harbors of Le Havre and Rouen.
The first one, the steel suspension bridge of Tan­
carville, was opened to traffic in 1959. The second,
the Brotonne Bridge, the world's largest cable­
staved prestressed concrete bridge, was opened to
traffic in June 1977. 20 A model of the structure is
I
22.50 m
CROSS -SECTION
OF
CONCRETE
BRIDGE
sleeve
cushion
I
4A
48
SECTION
A - A
SECTION. ELEVATION 8 - B
FIGURE 9.42. Pasco-Kennewick Intercity Bridge, cross section alld allchorage of st<l\
callies (courteS\'
Prof. Fritz Leonhardt).
or
FIGURE 9.43. Pasco-Kennewick Intercity Bridge.
erection of precast segments from barge (courtesy of
Arvid Grant).
420
FIGURE 9.44. Pasco-Kennewick Intercity Bridge.
pylon and stay attachment steel weldment at top (cour­
tesy of Arvid Grant).
Brotonne Bridge, France
FIGURE 9.45. Pasco-Kennewick
prefahricatcd cahle stay on rcel.
Intercity
Bridge,
shown in Figure 9.46 and the general layout in Fig­
ures 9.47 and 9.4:8. The box girder carries four
lanes and replaces ferry service between two major
highways that run north and south of the Seine.
Because large ships use this section of the river to
approach the inland port of Rauen 22 miles (35
km) to the east, vertical navigation clearance is
164 ft (50 m) above water level, which results in a
6.5% grade for its longer approach. 15.21
Total length of structure IS 4194 ft (1,278.4 m),
consisting of the main bridge and two approach
viaducts. The main crossing has a span of 1050 ft
(320 m). On the right bank, the transition between
the main span and the ground is quite short be­
cause of a favorable topography where limestone
strata slope upward to a relatively steep cliff. On
the left bank, the terrain is flat and occupied by
meadows. With an allowable maximum grade of
6.5% and a maximum height of fill of 50 ft (15 m),
a nine-span viaduct was required to reach the main
·bridge. In a structural sense, the bridge is divided
into two sections separated by an expansion joint at
a point of contraflexure in the left-bank viaduct
span adjacent to the cable-stayed side span, Figure
9.48. 20
FIGURE 9.47.
Brotonne.
2.
Model of the Pont de Brotonne.
Artist's rendering of the Pont de
The prestressed segmental concrete deck con­
sists of a single-cell trapezoidal box girder with
interior stiffening struts, Figures 9A9 and 9.50. In
the approach spans. web thickness is increased
from 8 in. (200 mm) to 16 in. (400 mm) near the
piers, and the bottom flange thickness is increased
to a maximum thickness of 17 in. (430 mm). The
only portion of the segment that was precast is its
sloping webs, Figure 9.51, which were precast at
the site. The other portions of the cross section,
including top and bottom flanges, interior stiffen­
ing struts, and cable-stay anchorages (in the main
structure only), were cast in place. Each segment is
9.8 ft (3 m) long.
Extensive use of prestressing was made in the
deck to provide adequate strength to this light
structure. To resist the extreme shear stresses it
was decided to place vertical prestressing in the
webs. Pretensioned units were stressed on a casting
bed, Figure 9.52, and equipped with specially de­
signed button heads. thus producing a combina­
tion of pretensioning and anchorage plates. This
system has the advantage of ensuring a perfect
centering of the prestressing force together with a
very rapid transfer of this force at both ends. In­
tensive rupture tests proved that an extremely
high resistance to shear was created by this sys­
tenl. 20
Finally, prestressing was also used as follows,
Figure 9.53: 20
1.
FIGURE 9.46.
421
Transversely in the top flange to provide
flexural strength to the thin 8 in. (200 mm)
slab.
In the inclined internal stiffeners, to accom­
modate tensile forces created by the transfer
of loads from the box girder to the stays.
.c..
N)
Nl
! \
+.58,50._ ~5850
____ . __320,00
I
'
,')
464 40
.12'840
FIGURE 9.48.
Ccm'r;d
or Brolollllc
,
• 5,5,iQ., nOO~
(63')
19.20
t
r s o 6.S0
15')(21')
1.60
(5')
ROADWAY
I
(18')
(13')
FIGURE 9,49.
FIGURE 9.50.
Bridge.
Illtel'ior
vIew
of
deck,
b:..:lkhead
ROADWAY
( 18')
Cross sectioll of BroHlIIIH:
FIGURE 9.51.
cou?ler for
steel forms
(21 ')
(13')
Brotonnt'
tensi(;n~ ::"cc S
1.50
( 5')
6.50
160 •
(5') •
Brid~e.
Precast webs, Brownnc
";;ensioning jack
distributiun
be~~
36 mm d i~te.1~i~n-;:-od~
?lcju3table
adjustable
brackets'
brackets
"Y',,!dag nut
Brid~c.
11~36 mm
,-,,""...- ..~~.
Dywidag
"-­
tension bar.
FIGURE 9.52.
Casting bed for pre tensioned webs.
423
424
Concrete Segmental Cable-Stayed Bridges
FIGURE 9.53.
;).
4.
Various prestressing systems in the box girder.
Transversely in the bottom flange, to coun­
teract tensile forces created by the stiffeners.
Longitudinally near the center of the main
span, to allow for a reasonable margin of the
order of 300 psi (2 MPa) of compressive stress
in view of creep and secondary tensile stresses.
Before erection of the superstructure, the
bridge's 12 approach piers were slip-formed, nine
on the left bank and three on the right. The pier
shaf'ls have an octagonal curvilinear cross section
inscribed inside a l3 by 29 ft (4.0 by 8.75 m) rec­
tangle, Figure 9.54. The same section was used for
all the approach-span piers, whose height varied
from 40 to 160 ft (12 to 49 m). The shape of the
piers did not substantially increase costs but did in­
(Tease the aesthetic appeal of the piers. The piers
bear through a reinforced concrete footing on four
rectangular slurry trench walls used as piles with a
maximum length of60 ft (18 m), Figure 5.17.
The pylon pier shafts also have an octagonal
curvilinear shape inscribed inside a 30 ft (9.2 m)
square to produce equal bending resistance about
both principal axes. They are supported on foun­
dation shafts having a diameter of 35 ft (10.86 m)
with a maximum wall thickness of 6 ft 8 in. (2.03
111). The foundation shafts transfer the loads to a
limestone stratum at a depth of 115 ft (35 m) below
ground level. Foundation shafts were built inside
a circular slurrv trench wall, which was used as a
cofferdam for dewatering. 20
When slip-forming of the piers reached deck
level, the piers were prestressed to their founda­
tion so as to stabilize them for erection of the deck
segments. As the precast deck units were erected,
w
18
8
!Jeeticm A-A
FIGURE 9.54.
spans.
Pier and
Section B-B
foundation
of approach
Section C-C
Section D-D
120,oa
Longitudinal Section A-A
FIGURE 9.55.
Half center span and pylon.
__ 8..-l0 __ . _ _ _
connection between pylon and pier
FIGURE 9.56.
~
layout or neoprene bearings
Connection between pvlon, deck, and pier.
425
426
Concrete Segmental Cable-Stayed Bridges
the pylon was constructed by conventional
methods.
Two single-shaft pylons carry a svstem of 21
stays located on the longitudinal axis of the struc­
ture, Figure 9.55. The reinforced concrete pylons
required limited cross-sectional dimensions to pre­
clude an unnecessary increase of the deck width
while providing sufficient dimension to accommo­
date bending stresses from a transverse wind di­
l'cction. Total pvlon height above the deck is 231 ft
(70.5 m). Construction of the pylon required leap­
frog forms with 10 ft (3 m) lifts. An interesting
feature is the total fixity of the pylon with the box
girder deck. Because the bending capacity of the
pYlon pier and foundation had to be such as to ac­
commodate unsymmetrical loads due to the can­
tilever construction, a decision was made to take
advantage of this requirement in the final structure
to reduce the effect oflive load in the deck. There­
fore, the pylon was constructed integral with the
deck at its base, both pylon and deck being sepa­
rated from the pier by a ring of neoprene bearings,
Figure 9.56. 20
FIGURE 9.57.
Cable-Slay anchorage.
All deck loads are carried to the pylon piers by
21 stays on each pylon. Each stay consists of 39 to
60-0.6 in. (15 mm) strands encased in a steel pipe,
which is grouted after final tensioning. Stay 1ength
varies from 275 to 1115 ft (84 to 340 m). Anchor­
age spacing of the stavs at deck level is every 19.7 ft
(6 m), even other segment, where the inclined stif­
feners in the deck segments converge, Figures 9.53
and 9.57. A special deck anchorage block was de­
signed to accommodate the variable number of
strands in the stay as well as to allow full adjust­
ment of the temion in the stavs by a simple an­
choring nut, Figure 9.58. The anchorage of the
stays is such that it is possible at any time during
the life of the structure to either readjust the ten­
sion in the stay or replace it without interrupting
traffic on the bridge. Permanellt jacks are incorpo­
rated into the anchorage, Figure 9.59, such that by
tensioning the stav the <l<Uusting nut can be slacked
ofT. Stays are continuous through the pyl<)n
where thev transfer load to the pvlon bv a steel
saddle. The pipe wall thickness is increased near
the anchorage points and near the pylon so as to
improve fatiguc rcsistance of the stavs with regard
to bending reversals. ~o
III constructing the deck girder, the operation
was to extend the bottom flange form from a
traveling form at the completed segment, placing
the precast web units that form the basic shape and
act as a guide for the remaining traveling form.
After placement of'the precast webs the interior
steel form was jacked forward to cast the bottom
flange struts and the top flange. Tower cranes at
the pylon placed, as far as they could reach in both
directions, the precast webs, Figure 9.60. Beyond
the range of the tower cranes, gantry cranes run­
ning on rails on the top flange and extending 9.8 ft
,;,J""
renr-
FIGURE 9.58. Jacking of stay.
-­
427
Danube Canal Bridge, Austria
concrete
cover
FIGURE 9.59.
Permanent stay anchorag;e.
FIGpRE 9.60. \l<Iin pier. pylon. and deck during
construction. from reference 20.
(3 m) beyond the end of the completed section
were used to place new elements.
The strucwre is shown at the start of main span
construction in Figure 9.61, before closure of the
main span in Figure 9.62. and completed in Figure
9.63. 20
FIGURE 9.61.
reference 20:
Start of main span cOBstruction. from
FIGURE 9.62.
erence 20.
Before closure of main span. from rd­
FIGURE 9.63. Aerial view of the Brotonne Bridge.
from reference 20.
9.9
Danube Canal Bridge, Austria
This structure is located on the West Motorway
(Vienna Airport Motorway) and crosses the
Danube Canal at a skew of 45°. It has a 390 ft (119
m) center span and 182.7 ft (55.7 m) side spans,
Concrete Segmental Cable-Stayed Bridges
428
I,
I
182.7 ft
390 ft
55.7 m
110m
FIGURE 9.64.
.,
d,
Construction of half-bridge on bank of
FIGURE 9.66.
·1·
55.7 m
·1
EIe\'ation of the Danube Canal Bridge.
Figure 9.64. It is unique because of its construction
technique. Because construction was not allowed to
interfere 'with navigation on the canal, the struc­
ture was built in two 360.8 ft (110m) halves on
each ballk and parallel to the canal, Figure 9.65.
Cpon completion the two halves were rotated into
FIGURE 9.65.
c<lnal.
182.7 ft
final position and a cast-in-place closure joint was
made, Figures 9.66 through 9.69. In other words.
each half was constructed as a one-time swing span.
The bridge superstructure is a 51.8 ft (15.8 01)
wide trapezoidal three-cell box girder, Figure 9.70.
The central box was cast in 25 ft (7.6 m) long seg­
ments on falsework, Figure 9.71. After the precast
inclined web segments were placed, Figure 9.72.
the top slab was cast.
Each half-structure has two cantilever pylons
fixed in a heavily prestressed trapezoidal crosshead
pmtruding under the deck with a two-point bear­
ing on the pier, Figure 9.73. At the cleek level the
stays attach to steel brackets connected 10 pre­
stressed crossbeams, Figures 9.74 and 9.75.
Each stay consists of eight cables, two horizontal
by four vertical. At the top of the pylons each cable
is seated in a cast-irol,l saddle. The cable saddles are
stacked four high, Figure 9.76, and are fixed to
each other as well as to those in the adjacent plane.
The cables were first laid out on the deck. fixed to a
saddle, and then lifted by a cralle for placement at
the top of the pylon. The cables were then pulled
Plan of Danube Canal Bridge during construction and final state.
Danube Canal Bridge, Austria
FIGURE 9.67.
Danube Canal Bridge during rotation.
FIGURE 9.69.
FIGURE 9.68.
429
Closure joint. Danube Canal Bridge.
Danube Canal Bridge during rotation.
FIGURE 9.70.
Cross section. Danube Canal Bridge.
at each extremity by a winch rope to their attach­
ment point at the deck level.
During rotation of the two half-bridges, the dec k
and pylon sat on a bearing consisting of five
epoxy-glued circular steel plates. The top plate was
coated with teflon, sitting in turn on a reinforced
concrete block that sat on a sand box. After rota­
tion the structure was lowered to permanent
bearings by emptying the sand box.
At the canal-bank end the deck had a concrete
wall on its underside, bearing on a circular con­
crete sliding track, Figure 9.77. The bearing be­
tween the wall and the track was effected by two
concrete blocks clad with steel plates, under which
430
Concrete Segmental Cable-Stayed Bridges
FIGURE 9.71.
HI idge.
Comtl'uClioll
Oil
ballk. Danuhe Canal
Trapezoidal U'osshead. Danube Canal
Bridge.
FIGURE 9.72.
Precast \\cbs. Dallube Callal Bridge.
tclloll-coated neoprene pads were introduced
during the rotation 1110vemel1l (similar to the in­
rrementallaullching method). The pivoting was ac­
complished by means of a jack pulling on a cable
anchored in a block located near the sliding-track
elld.
After rotation the two haJ"es of the structure
were connected by a cast-in-place closurejoint, and
continuity tendons were placed and stressed. 22 The
filial structure is shown in Figure 9.78.
9.10
9.10.1
Notable Examples of Concepts
PROPOSED GREAT BELT BRIDGE,
DENMARK
The competitIon for a suitable bridge design in
Denmark produced many new concepts and ar­
chitectural styles. The design requirements spec­
ified three lanes for vehicular traffic in each direc­
tion and a single railway line in each direction.
FIGURE 9.74. Jacking of stays. Dallube Canal Bridge.
The rail traffic was based on speeds of 100 mph
(161 km/hr).2:! Navigational requirements stipu­
lated that the bridge deck be 220 ft (67 m) above
water level, and the clear width of the channel was
to be 1130 ft (345 m).
A third prize winner in this competition was the
Morandi-style design proposed by the English con­
sulting firm of White Young and Partners, Figure
Notable Examples of Concepts
FIGURE 9.75.
Bridge.
431
Cable-stav attachment. Danube Canal
FIGURE 9.77. Circular concrete sliding track. Dan­
ube Canal Bridge.
FIGURE 9.78.
.-
,
'11
,
FIGURE 9.76. Stav saddles at pylon. Danube Canal
Bridge.
9.7. This design embodied the principles of a
cable-stayed bridge combined with conventional
approaches of girders and piers with normal spans.
The principal feature of this bridge design is the
three-plane alignment of cable stays. This feature
may become more important in urban areas, where
trends in the future may dictate multimodal trans­
portation requirements and an increase in the
Completed Danube Canal Bddge.
number of automobile traffic lanes. The deck COI1­
sists of two parallel single-cell prestressed concrete
box girder segments. Figure 9.79. The rail traffic is
supported within the box on the bottom flange
and the road traffic is carried on the surface of the
top flange.
The box girder contemplated a depth of 23.5 ft
(7.2 m) and width of 27.75 ft (8.45 m) with the
top flange cantilevered out 12 ft (3.7 m) on each
side. The piers and towers were to be cast-in-place
construction to support the deck segments, which
were to be precast at various locations on shore and
floated to the bridge site for erection. The
maximum weight of a single box segment was es­
timated at 2200 tons (2000 mt). All segments of
the superstructure were to be of reinforced and
prestressed concrete.
Up to this point in time, when the competition
for this structLre was conducted, all the concrete
cable-stayed bridges had been either designed by
Concrete Segmental Cable-Stayed Bridges
432
_
3.675 m
8.'\5 m
------.;.-~--<E--
3.675 m----o-
Main longitudinal
prestressing tendons
I
7.20 m
Vertical prestressing
bars
FIGURE 9.i9. Danish Great Belt Bridge. section through deck beam at ex­
pansion and constructioll joint. frolll reference 23.
;'vloralldi (Lake Maracaibo, Wadi Kuf, and so on)
or strongly influenced bv his style (Chaco/
Corrienles). They were typified, for the most part,
bv the transverse A-frame pylon with auxilian
X-frame support for the girder. However, an entry
in the Danish Great Belt Competition by Ulrich
Finsterwalder of the German firm of DyckerhofT
& Widmann deviated from this style and wa~
awarded a second prize.
Finsterwalder proposed a multiple span, multi­
stay system using Dywidag bars for the stays, Fig­
ure 9.10. This proposal contemplated a spacing
between pylons of 1148 it (350 m) and a spacing.of
the stays at deck level of 32.8 It (10 111). P\"lon
height above water level was 520 ft (158.5 m). 1n a
transverse cross section the deck was 146 (44.5
m) wide with two centrally located vertical stay
planes 39 ft 4 in. (12 m) a part to accommodate the
two rail traffic lanes, and three automobile traffic
lanes in each direction outboard orthe stay planes,
Figure 9.80.
The solid concrete deck had a thickness of 3 ft
(0.9 m) in the transverse center portion, under the
rail traffic, and tap~red to a 1.3 ft (0.4 m) thickness
-1.;.158,50
:.12,50
form
I
F'"
~.--.~.--.l._-------- 350,00 -~·-----""'---175,OO --~
- - - ------------------ -r­
~-
,
,!
JA:=~=~===~==~:::==::::;::::::::==~::::=====i::======.!i. c'i 0,40
Ij"": - - - - 15,25 ----."'!2,OO:...-lO,OO-----.i2,OO:..-~-- 15,25 _
1...---------
------44,5O~·--·--------·
..--.--­
FIGURE 9.80. Danish Great Belt Bridge, elevation and cross section (courtesy of
DyckerhofJ & \\'idmann).
.:!:, 0,00
Notable Examples of Concepts
at the edges. The deck was to be constructed by the
cast-in-place
balanced
cantilever
segmental
method, each segment being supported by a set of
stays.
9.10.2
PROPOSED DA.'vlE POIST BRIDGE, U.S.A.
The proposed Dame Point Bridge over the St.
Johns River in Jacksonville, Florida, as designed
by the firm of Howard ;-';eedles Tammen &
Bergendoff, is a cable-stayed structure with a con­
crete and a steel alternative. An artist's rendering
of the concrete cable-stayed bridge alternative is
shown in Figure 9.81. Navigation requirements
dictate a 1250 ft (381 m) minimum horizontal
opening and a vertical clearance of 152 ft (46.3 m)
above mean high water at the centerline of the
clear opening. The proposed concrete cable-stayed
main structure will h;l\'e a 1300 ft (396 m) central
.
--..,..;:,:..""
/
~~~:.
FIGURE 9.81. Dame Point Bridge. arris["s rendering
of Ho\\'ard :\cedles LlIl1l11en & Bergendoff).
«Olll'lCSV
433
span with 650 ft (198 m) flanking spans. The layout
of the main structure is shown in Figure 9.82.24
Structural arrangement of the bridge deck is
shown in Figure 9.83. The bridge deck, which will
carry three lanes of traffic in each direction, will
span between longitudinal edge girders on each
side. The longitudinal edge girder is in turn sup­
ported by a vertical plane of stays arranged in a
harp configuration. The concrete deck and edge
girders take local and overall bending from dead
and live load in addition to the horizontal th rust
from the stavs. 25 The stay cables are anchored in
massive ver:tical concrete pylons, two at each main
pier, which carry all loads to the foundations, Fig­
ure 9.84.
In the center span, at each edge of the deck, the
stays are in a single plane spaced 30 in. (0.76 m)
vertically, Figures 9.84 and 9.85. Stays in the side
spans, along each edge, are in two planes spaced 30
in. (0.76 m) transversely. Spacing of pairs of stays
along the edge beam is approximately 30 It (9.1 111).
Preliminary design contemplates 7 to 9 Dywida~
bars per stay, It in. (31.75 mm) in diameter, the
number of bars per stay being a function of stre~s
in the stay. The Dvwidag bars are to be encased in a
metal duct. During erection the fabricated length
of duct is left uncoupled. After final adjustment
the lengths of duct are coupled and pressure­
grouted. Thus, the steel encasing tube will thell be
composite for live load and secondary dead loa<l.2;;
Construction proceeds bv conventional methods
from the top of the pier bases at elevation 15.0 It
(4.6 m) to the level of the roadway at elevation
144.6 ft (44 m). At this point, a fixed formtable is
secured and the first elements of the pvlon and
edge girders are cast. Erection of the deck is bv the
llev. !5f
(396m
(198m)
1
2600 Main River Bridge
( 793m)
FIGURE 9.82. Dame Point Bridge. concrete cable-staved alternative, from reference
(courteS\' of Ho;,-ard :\eedles Tammen & BergendofO.
~l
105'-10" (323m)
43'-6"Roadway (06m)2'
43'-6" Roadway
(133m)
(!33m)
Cables
C~llit
in
abies
plact' Declo.
i
~Pfecast
Cast- in-situ Beam
<EM Sp.nl
T Beam
FIGURE 9.83. Dame Point Bridge. structural arrangemellt of bridge deck. from
reference :24 ("(Jurtes\ of HO\\'ard '\c(,dlcsLlllllllCIl &- lkrgcmio!f).
-,
c
c
0
0
0­
0.
(f)
Slrul
(f)
c:0
c
'"
IJ.J
::;:
.,
~
:is
0
u
.0
0
u
\
"
J
Tow~r
jDeCk
PedeSlal
". _."I(t\.'
SIDE VIEW
FRONT VIEW
FIGURE 9.84. Dame Point Bridge, pylon <lrrangment, from reference 24
(courtesy of Howard l'\eedles Tammen & Bergendoff).
434
""
~
u-.
HOw,"D
N:~o':~>":~~·::;~~·cR.G:~o.o::IHNTB
FIGURE 9.85. Dame Poillt illidge, snpnSlrnUllrt'
of Ilowan/ :\ccdlcs LlIlIIlICIl & Bcrgelldofl).
(l()llne~V
ISOMETRIC VIEW OF ERECTION SEQUENCE
lal iOll,
\7
from
",
BECI~
ERECT I ON SEQUENCE
or
CAS.T'IIl~?LAC£
CASLES
sap
S
RFplAT STEP 8
(621;0) PR£CAS1 T BEAM
NOH:
:!:'>
1.0NSTRIJCT
lOS- COh!.TRIJCT
TOPf'IN4 [)UII::IIfG EACH (YClf.
SEAM AT H?AttSION
DAMES POINT BRIDGE
CAST~Itl-PlACE
CASTwl~'PLAtE
10,-- ERECT (6)RO) PFlECAST T firM.
lo6,~, [FlECl
JOI~TS
GIRDER SEGMENT
tS- REPEA; STEPS 10 THRU )'< TO STEP lOS
14- RfPlAT STEP 6
13·- REPEAT STEP 1
12- REnAT ST[P 9
I! -
10- REPlAl
9- ERECT (4TH) PR£{AH T BCAM
r SEAM
(;A5T-IN~f>LACf
6- OiHT (3RD) PHECAlT
at. Tli(:(N
CONSTRUCT n{>!(,Al
ERECT (7-NOl PRECAST T BEAM
IRGIN TYPICAL HQtJHlCt Of (ABtES. GIRDER ArlD
CUNSTRLlCTIOll
4- afGIN CONSTRI.lCTlOk Of rOVER
(OCE
CA$i"IIi-f'LMf OfCK BHIJ(U4 T(lIJfk,
CO)-I!;.TRuCTIDti
(G~STRtJ(!
19
3- ERECT fiRST PRUAST T BEAM
2--
ll'rt'll'IlC(,
\Il
PLATE 17
Concrete Segmental Cable-Stayed Bridges
436
balanced cantilever method. Two pairs of traveling
forms are then used for sequential casting of 17.5
ft (5.3 m) lengths of edge girders on each side of
the pylon. The bridge deck consists of single-T
precast Hoor beams spanning between longitudi­
nal edge girders and a cast-in-place topping. The
precast T's are pretensioned for erection loads.
After erection the entire deck is post-tensioned to
provide positive precompression between edge
girders under all conditions of loading, Figure
9.85. 24 ,25
A hinge ex pansion joint is provided at the cen­
terline of the main span to allow for changes of
superstructure length due to temperature, creep,
and shrinkage. Similar joints are provided at the
end piers, and link connections are used to prevent
vertical movement of the superstructure.
0./ 0.")
1)IUW()S/~n
fa ·C'l(-.·}-UIL 'CAl'
HW n(;/:', C.S ..·/.
The site for the proposed Ruck-A-Chucky Bridge
designed In T. Y. Lin International, Figure 9.86, is
approximateh' 10 miles (16 kl1l) north of the pro­
posed Auburn Dam and about 35 miles (56 kill)
northeast of Sacramento, California, crossing the
middle fork of the American River. The river at
this location is about 30 ft (9 m) deep and 100 ft
(30.5 m) wide: however, upon impounding of the
water behind the proposed dam, the river will be­
come 450 It (137 m) deep and 1100 ft (335 m)
wide. 2 (;
In order to provide a 50 ft (15 m) vertical clear­
ance above high resenoir water level, a bridge
length of 1300 ft (396 m) will be required between
the hillsides, which rise at a 40° angle from the
horizontaL Two existing roads parallel the canyon
faces; a straight bridge across the river would re­
quire extensive cuts into the rock faces of the can­
yon to provide the necessary turning radiu~ at the
bridge approaches. This would be not only expen­
sive but would also be damaging to the environment.
Conventional piers in the river provide prohibitive
design constraints, not only because of the 450 ft
(137 m) water depth, but also because of the seis­
micity of the area. The hydroseismic (seiche effect)
forces provide a formidable design load.
After extensive studies, the proposed final solu­
tion was that of a hanging arc, Figures 9.87 and
9.88. The geometric configuration of this structure
is such that the stays are tensioned to control the
stresses and strains, in order to balance all the dead
load with zero deHection; the curved girder carries
the traffic and absorbs the horizontal component
of the stays as axial compression. The stays are an­
chored on the slope according to the design form~­
tion to control the line of pressure in the girder.
Thus, an ideal stress condition is achieved with
almost no bending or torsional moments. After
numerous studies and trade-olfs a final radius of
cunature was selected at 1500 ft (457 m).26
Two alternative designs have been prepar,=d for
this structure, one with a steel box girder and one
with a lightweight concrete box girder. The con­
crete box girder, Figure 9.89, is fixed at the abut­
ments and has no hinges or expansion joints in the
1300 ft (396 m) spcin. Depth of this box girder is
8.5 ft (2.6 m), so as to provide vertical stiffness and
to distribute live load and construction loads on the
deck to a sufficient number of adjoining cables.
Stay anchorage at the girder is at 30 ft (9 m) inter­
vals, based on construction and aesthetic consider­
ations. 26
FIGURE 9.86. Ruck-A-Chucky Bridge, artist's rend­
ering (courtesy of T. Y. Lin).
.10
c"o
....
lercn'llCl' ~ti .
FIGURE 9.87.
BRIDGE
RlIck-.\-Chuckv Hlidgc,
~~
of
12'9.691
CHOj1tD· LIN,rN
C>
It
~
O·
o
o
o
1300:'0'
I..I,,.,,.,EI'I(' IEO"""'6 .. ,
. ..- t
II it II (OIllTl'lc ailt'rllalc. from
SPAN
'-..PE:O€SrALS
sourH INSIO€
\.
\
\.
\
\.
\
,\
\.
.\
'~
\\..
,
,
\'
, \,
'\.
\
'\
\.
"\~\.
.­
~J
•
00
00
U
~
=
ai ~
'/: j
f<:-':;,__ ./
"
-/
I
if,f'
',',,1,,',',,"
,'r;
":'?;-'->./
, ' i'ii ,z;,
! - "':/
; / ;'t::t.l
/
438
/
/
/'
.
/
... -=
:::::: :;
;:,
(,!l
;::
:5
t;:~
References
439
54'-0"
~
_________________2~7_'_-0_"________________~4-______________2~7_'~-O~" ____________________~
5' -9"
i agonal
Struts lO"xlO"
e'-5t"
\05:...'_-_4,,:...'_'
6'-6"
I
-----r-d
_+-__8_'-_8_~_"'____--I______________::::25=-'_-_1:...1'_'_______________--1-_-8 _'-_B,,-t'_'
FIGURE 9.89.
Ruck-A-Chuch Bridge, cross section of concrete box girder alternative,
from reference ::6.
10. R. Morandi, "Some Types of Tied Bridges ill Pre­
stressed Concrete," First International Symposium,
A. Feige, "The Evolution of German Cable-Staved
Concrete Bridge Design, ACI Publication SP::3,
Bridges--An Overall Survey," Acier-Slahl-Sleel, :\0.
Paper 23-25, American Concrete Institute, Detroit,
12, December 1966 (reprinted in AISC Engineering
1969.
journal, july 1967).
II. Anon., TIll" Brid!il' S/JIlnnmg I.rlkp .H{/mmilJl) 1/1 Vrn­
ezw11l. Wiesbaden, Berlin, Bauverlag (;m 1)I-L,
H. Thul, "Cable-Staved Bridges in Germany," Pro­
ceedings, Cunference on Structural Steelwork, I flstilutiun
196~\.
of Civil Engineer>, Sl'ptember 26 to 28, 1966, London.
I::. Anon., "Longest Concrete Cable-Stan~d Span Can­
tilevered over Tough Terrain," Enginfenng NPll',\­
W. Podolny, jr., and J. F. Fleming, "Historical De­
Record, julv 15, 1971.
velopment of Cable-Staved Bridges," journal uj the
Structural Divisiun, ASCE, Vol. 98, No. ST9, Sep­
13. ::\. Gray, "Chaco/Corrientes Bridge in Argentina,"
tember 197::.
JJ unicipal EngillCPrs journal, Pa per :\1). 380, Vol. 59.
W. Podolny,jr., and]. B. Scalzi, "Construction and
Fourth Quarter, 1973.
Design of Cable-Stayed Bridges," john Wiley &
14. H. B. Rothman, and F K. Chang, "Ll)ngest Precast­
Sons, Inc., :--Jew York, 1976.
Concrete Box-Girder Bridge in Western Hemi­
sphere," Civil Engineering, ASCE, March 1974.
~L S. Troitsky, "Cable-Staved Bridges-Theory and
Design," Crosby Lockwood Staples, London, 1977.
15. W. Podoiny, jr .. "Concrete Cable-Stayed Bridges,"
Transportation Research Record 665, Bridge En­
F. Leonhardt, "Latest Developments of Cable­
gineering, Vol. 2, Proceedings, Transpurtatiun Research
Stayed Bridges for Long Spans," Saetryk af
Bygoningsstatiske ivfeddelelser, Vol. 45, No.4, 1974
Board Conference, September 25-27, 1978, St. Louis,
Mo., National Academy of Sciences, Washington,
Denmark).
D.C.
'E. Torroja, Philosophy of Structures, English version
References
I.
2.
3.
'4:,
5.
6.
7.
by J. ]. Polivka and !¥filos Polivka, V niversity of
California Press, Berkelev and Los Angeles, 1958.
8. H. M. Hadley, "Tied-Cantilever Bridge-Pioneer
Structure in V.S.," Civil Engineering, ASCE, january
1958.
9. F. Leonhardt and W, Zellner, "Vergleiche zwischen
Hzmgbrucken und Schragkabelbrucken fur Spann­
weiten tiber 600 Ill." Intemationnl dssociation j(n
Bridge and Structural Engineering, Vol. 32, 1972.
16. H. Schambeck, "The Construction of the Main
Bridge-Hoechst to the Design of the 365 m Span
Rhein Bridge Dusseldorf-Flehe," Cable-Staved
Bridges, Structural Engineering Series No.4, june
1978, Bridge Division, Federal Highway Adminis­
tration, Washington, D.C.
17. Anon., "Tiel Bridge," Frey'>sinet International, STUP
Bulletin, March-April 1973.
IR. A.l'vid Grant, "Pasco-Kennewick Bridge-The
440
Concrete Segmental Cable-Stayed Bridges
Longest Cable-Stayed Bridge in !'\orth America."
Ch'l} Ellginrrring, ASCE, \'o!. 47, :\'0. 8, August
1977.
19. Arvid Grant, "Intercity Bridge: A Concrete Ribbon
on']' the Colu!I1bia River, Washingtoll," Cablc­
Staved Bridges, Structural Engineering Series No.
4, June 1978, Bridge Di\'ision, Federal Highway
Administration. \\'ashington. D.C.
20. C. Lenglet, "Brotonne Bridge: Longest Prestressed
Concrete Cable Stayed Bridge," Cable-Stayed
Bridges, Structural Engineering Series !'\o. 4, June
1978, Bridge Division, Federal Highwa\' Adminis­
tration, \\'ashington, D.C.
21. Anon., "Cable-Staved Bridge Goes to a Record with
Ihbrid Circlel Design." Lligill(,l'Iill{!, .\'('il',I-R('rou/,
October 28. 1976.
qq
AIIOIl., "The Danube Callal Bridge (Austria),"
~
Frl'"),ssinet international, STUP Bullrtill, May-June,
1975.
23. Anon., "Morandi-Stde Design Allows Constant Sus­
pended Spans," COl/.witing Eligilll'l') (l,ondon),
~1arch 1967.
24. H. J. Graham, "Dame Point Bridge," Cable-Stayed
Bridges, Structural Engineering Series No.4, June
1978, Bridge Division, Federal Highway Adminis­
tration, Washington, D.C.
25. Anon., "Dame Point Bridge," Design Report, How­
ard :\'eedles Tammen & Bergendoff, ;'\ovember
1976.
26. T. Y. Lin, Y. C. Yang, H. K. Lu, and C. M. Redfield,
"Design of Ruck-A-Chucky Bridge," Cable-Stayed
Bridges, Structural Engineering Series No.4. June
1978, Bridge Division, Fecleral Highw;1\ Adminis­
tration, Washington, D.C.
10
Segmental Railway Bridges
10.1
INTRODUCTION TO PARTICULAR ASPECTS OF
RAILWA Y BRIDGES AND FIELD OF APPLICA·
TlON
10.2
LA VOULTE BRIDGE OVER THE RHONE RIVER,
FRANCE
MORAND BRIDGE IN LYONS, FRANCE
10.3
lOA
10.5
10.6
10.i
10.1
CERGY PONTOISE BRIDGE NEAR PARIS,
FRANCE
MARNE LA VALLEE AND TORCY BRIDGES FOR
THE NEW EXPRESS LINt NEAR PARIS, FRANCE
CLICHY R.-\ILWAY BRIDGE l'iEAR PARIS,
FRANCE
OLIFANTS RIVER BRIDGE, SOUTH AFRICA
Introduction to Particular Aspects of Railway
Bridges and Field of Application
Construction of segmental post-tensioned bridges
for railway structllres started in France in 1952
. with a bridge <Tossing the Rhone River at La
Voulte, Figure 10.1. It has been used extemively
since that time in many countries. Precast seg­
mental cOllstruction was introduced in railway
structures in France with the ;Vrarne ]a Vallee Via­
duct and in Japan with the Kakogawa Bridge,
while incremental launching was adopted for sev­
eral large railway crossings including the world's
longest bridge of this type: the Olifant's River
Bridge in SOLith Africa (see Section 7.5).
The m,~()r characteristic distinguishing railway
bridges from highway bridges is the magnitude
and application of loading. Live loading on a rail­
way structure is two to four times larger than that
applied to a highway bridge of comparable size.
Every time a train crosses a railway bridge, the ac­
tuat load applied to the structure is much closer to
design live load than for a highway bridge, where
even dense truck traffic usually represents only a
10.8
INCREMENTALLY LAUNCHED RAILWAY
BRIDGES FOR THE HlGH·SPEED LINE, PARIS
TO LYONS, FRANCE
10.9
SEGMEl'iTAL RAILWAY BRIDGES Il'i JAPAN
10.10 SPECIAL DESIGN ASPECTS OF SEGMEl'iTAL
RAILWAY BRIDGES
10.11
10.10.1 Magnitude of Vertical Loads
10.10.2 Horizontal Forces
10.10.3 Bearings
10.1 0.4 Stray Currents
10.10.5 Durability of the Structure
10.10.6 Conclusion
PROPOSED CONCEPTS FOR FUTURE SEGMEN·
TAL RAILWAY BRIDGES
moderate proportion of the design load. Fatigue
and durability of railway structures, therefore, are
essential problems and need careful consideration,
particularly in view of the fact that maintenance
and repair of railway structures under permanent
FIGURE 10.1. La Voulte Bridge. new of the com­
pleted structure.
441
Segmental Rc;ilway Bridges
442
trafflc is a very critical operation that can lead to
unacceptable disturbance in a railway network.
10.2
La Voulte Bridge over the Rhone River,
France
This first segmental prestressed concrete railway
bridge is a notable structure and a landmark in the
development of prestressed concrete. Constructed
in 1952, it carries one railway track over the Rhone
River near la Voulte, 80 miles (128 km) south of
Lyons, in the southeastern part of France.
The structure has five spans, each 164 ft (50 m)
long. Each pier is made up of two inclined legs. and
each span is an independent frame supported by
an inclined leg at each end. Between the inclined
legs on each pier, the deck is supported by a small
beam resting on simple bearings.
Construction proceeded using the cantilever
schellle, with poured-ill-place segments. The form
travelers wcre supported by a temporary sted truss
i>ridge, Figure 10.2. The cantilevers were built
sYlllllletrically III ol1e span. the unbalanced
moments being taken care of by temporary
post-tcnsioning connecting t he two inclined legs
ali(I the independent beam on one pier. The seg­
lllellts were 9 It (2.75 m) long. Tbe bending mo­
mellls 01 each completed frame were adjusted by
jacks placed at midspan and by continuity post­
tellsionillg tendons. Figure 10.3,
10.3
Morand Bridge in Lyons, France
This structure is a combined highway and mass­
transit bridge over the Rhone River in Lyons,
t:
.'
jC._"i:.L'." ~," i W~
FIGURE 10.2. La Voulte Bridge, aerial view of [he
deck under construction.
FIGURE 10.3. La Voulte Bridge. cantilever' deck con­
struction in progress.
France's third largest city. It is a three-span con­
tinIlous struclllre witll span lengths of 160, 292,
and 160 ft (49,89, and 49 m), resting on two river
piers and two end abutments, which allow the tran­
sition of highway and railway traffic on both banks.
The deck is made lip of two parallel box girders
carrying at the upper le\el three lanes of highway
traffic including sidewalks. Inside each box girder
is a railway track for the mass-transit system, Fig­
ure 10.4.
.
This final scheme proved to be significantly less
expensive and more efficient in terms of the layout
of the railway system. than did the initial proposal,
which contemplated a submerged tunnel for the
railway crossing and a separate bridge for the
highway traffic.
Dimensions of the structure in cross section are
shown in Figure 10.5. The railway clearance of 13
it 5 in. (4.12 m), including ballast and rail, calls for
a 15 fl (4.56 m) structural height in excess of the
normal requirements for a maximum span length
of 292 It (89 m). A constant-depth girder could
thus be maintained throughout the river crossing
except in the vicinity of the river piers. where short
straight haunches allow the depth to be increased
to 22 ft 7 in. (6.90 m). Over the piers a strong
transverse diaphragm connects the two box
girders, and the additional height over the pier
allows the continuity of the diaphragm over the
height of the haunch while the full clearance of
the trains is maintained inside the box girders.
The deck was built in balanced cantilever with 10
ft (3.0 m) long cast-in-place segments using one
pair of travelers on a typical one-week cycle, Fig­
ures 10.6 and 10.7.
Typical quantities of materials are as follows for
the deck alone:
443
Morand Bridge in Lyons, France
FIGURE lOA.
ON PIER
Morand Bridgc, pcrspecti\c \'iew of the structurc.
..
AT MID-SPAN
(
1
...
~
E3
136
36
~
~
1
..,1
-1..
7
I
.
r .
.1e6
I
....'"
H2
I
it27
... ,~2715:50
4.62
mW
.. !
r"
FIGURE 10.5.
i,.e61
.~
\Iorand Bridge, typical cross section.
Deck area
Concrete
Reinforcing steel
Prestressing steel
(longitudinal and
transverse)
31,200
3,100
618,000
256,000
ftZ
yd:l
lb
Ib
2,900 m 2
2,400 m:!
280,000 kg
116,000 kg
FIGURE 10.6.
su perstructure.
Morand Bridge, construction of the
Both concrete and reinforcing steel quantities far
exceed those required for a typical highway be­
cause of the very important increase of loads due
to the railway lines in the box girders.
The structure was completed and opened to
traffic in 1977.
444
Segmental Railway Bridges
single box carries the twin tracks, with the depth
varying between 13.6 ft (4.15 m) and 17.9 ft (5.45
m) for the maximum span length of 280 ft (85 m)
as shown in Figures 10.9 and 10.10. The segmental
deck was cast in place, with travelers working in the
conventional balanced cantilever fashion.
10.5
The extension of the Paris mass-transit system in
the highly populated southeastern suburbs was the
occasion for building a long elevated segmental
prestressed concrete railway structure in a sensitive
urban environment, Figure 10.11. This structure,
located in the city of Marne la Vallee, includes a
bridge over the Marne River and a long viaduct
carrying two parallel railway tracks. Near the tran:
sition between the river bridge and the viaduct a
passenger station is carried by the bridge structure.
Three major considerations guided the choice of
the structure:
FIGURE 10.7. \loralld Bridge, constructioll of
supcntructlln'. :--';otc pier segment for second parallel
box girder.
10.4
Cergy.Pontoise Bridge near Paris, France
:\ 11(,\\
railway lille \\'as completed ill 1977 between
Marne la Vallee and Torcy Bridges for the
New Express Line near Paris, France
Paris alld the new satellite W\\'n oj Cergy.Pontoise.
A major prestressed COllcrete structure carries this
line onT sen'ral ohstacles, including an inter­
change between two expressways (A-~6 alld :\-14)
alld two brallches of the Seine Ri\·er.
Maintain maximum clearance at ground level, not
only to reduce the visual disturbance to the
neighboring population, but also to allow all piers
of the new structure to be fully compatible with the
layout of all existing and future roads.
The treslle structures have a solid slab deck with
spans varying between 65 ft (20 m) and 117 ft
(35.60 m). T\'pical dimensions of the two main
bridges over the Seine are shown in Figure 10.8. A
Elevation
(a)
Typical cross section
(b)
FIGURE 10.8.
section.
Cergy-Pontoise Bridge, dimensions.
(a)
Ele\'<l{ion. (b) Typical cross
Marne La Vallee and Torcy Bridges near Paris, France
445
----~.
~
FIGURE 10.9. Cergv-Pontoise Bridge, cantilever con­
struction.
FIGURE 10.10.
c1osurc.
Cergv-PoI1toise Bridge. mam span
Produce a structure that is aestheticallv pleasing
when seen constantly from nearby.
Protect the neighbol'ing population from unac­
ceptable noise aggression.
Basically, the structure is a single box of constant
depth built of precast segments assembled by pre­
stress into a continuous beam; the beam rests upon
vertical piers provided with an architectural shape
and regularly distributed at distances of 90 ft (27
m) to 120 ft (36 m), Figure 10.12.
Both parallel tracks are laid on the transversely
prestressed deck slab of the box girder and on a
crushed-Slone bed retained sidewavs bv three conlinuous reinforced concrete walls. A central noise
barrier separates the two opposite tracks and pre­
vents the noise of a train riding one track to travel
across to the other. At the edge of the concrete box
girder. precast concrete panels manufactured with
spe~ial white cement improve the appearance of
the structure while providing the outside sound
barriers.
I
;'
FIGURE nUl. Marne la Vallee Bridge, aerial view
of the completed structure.
FIGURE 10.12. :'/arne la Vallee Bridge.
finished structure from ground level.
VICW
of
In plan, the structure is laid out on a curve with a
minimum radius of curvature of 1640 ft (500 Ill).
Figure 10.11. Characteristic dimensions of the
Marne la Vallee Viaduct are shown in Figures
10.13 and 10.14 and are summarized as follows:
L
Bridge over the Marne River:
a. Total length, 528 ft (161 mi.
b. Three-span continuous bridge with spans
of 157, 246, and 125 ft (48, 75, and 38 m).
c. Cross section: constant-depth box section
with depth of 12.8 ft (3.90 m), web thick­
ness varying from 20 to 35 in. (0.50 to 0.90
m) and bottom flange thickness from 7 in.
(0.18 m) at midspan to 51 in. (1.30 m) over
the river piers. Length of precast segments
5.6 ft (1.71 m).
d. Two river piers are founded on large­
diameter bored piles and support the
su perstructure through special teflon
bearings.
1205
o
<0
N
6.00
~
(3955)
II
••
j
\
,-J'; -4- ..... Lt••.
: ; : :
•
ALLUVIUM
DEPOSITS
ALLUVIUM
DEPOSITS
I
•
II' ,.1
..
,
iLL~
Jj~
~ ~J.
,
-.
:
I
,-
I
\1
: :::
r
.11
I
,If
~:~~:;:
..
~.::::
I
~
I , 'I
::
I.,
I
,
L _ ;.
LIMESTONE
SAND
FIGURE 10.13.
446
Marne la Vallee Bridge, typical sections of deck and piers.
Marne la Vallee and Torey Bridges near Paris, France
f.
g.
470
_250___ _
1100
12 MID
12 CROSS
SECT ION ON i>IER
SPAN
CROSS SECTION
447
All bearings in the viaduct are standard
laminated elastomeric pads.
Piers are made of twin columns located
under the webs of the box girder and con­
nected at ground level by a common foot­
ing, which transfers the loads to deep
slurry trenched walls anchored in lime­
stone. The number and position of these
bearing walls under each pier has been
determined in relation to the magnitude
of the transverse and longitudinal hori­
zontalloads transferred by the superstruc­
ture, particularly in the curved portion of
the viaduct.
(a)
4.70
1100
(b)
FIGURE 10.14. \Iarne la Vallee and Torev Viaduct,
l\pic~t1 deck sections. (a) .\larne la Vallee l;'estle and
['orey Viaduct cross section. (h) \!arne la Vallee Bridge
over lhe .\£arne River.
2.
Elevated viaduct:
a. T Ofal length. 4482 ft (1367 m).
b. The viaduct is divided into 11 sections
separated by expansion joints. allowing
compatibility of thermal stress between the
continuous welded rails and the concrete
superstructure. The typical section is 412
ft (126 m) long with four spans of 88, 118,
118. and 88 ft (27,36,36, and 27 m).
e. The two south viaduct sections adjacent to
the main river crossing carry the passen­
ger station and have _shorter spans 69
and 92 ft (21 and 28 m).
d. Typical cross section is a single box carry­
ing the two tracks with two main vertical
webs 35 in. (0.90 m) thick and two sharply
inclined facia webs used essentially for ar­
chitectural purposes to reduce the appar­
ent structural depth of the box and focus
the eye on the high parapet wall.
e. Average length of precast segments 7.5 ft
(2.:30 m).
The entire project was predicated on the use of
precast segments with match casting and epoxy
joints. A precasting yard on the south bank of the
Marne, using four casting machines, produced the
690 segments with a maximum weight of 60 tons
(55 mt) in eleven months. Segments were trans­
ported with a tire-mounted self-propelled carrier
over the finished portion of the deck and placed in
the structure with a launching gantry, Figure
10.15, in balanced cantilever. The gantry used on
that project was that designed and built earlier for
the B-3 Viaducts project.
The gantry allowed all operations to be per­
formed from the top in complete independence
from the ground and all its related constraints.
Placing of all segments was performed in a period
of nine months between March and December of
1976, including the three spans of the main bridge
and the forty-four spans of the viaduct. The entire
project was completed in 24 months (including
preparation of the final design), for a total deck
area of 190,000 ft 2 (l 7,600 m 2). Figure 10.16 shows
FIGURE 10.15. r-.larne la Vallee Bridge, precast seg­
ments placed with the launching gantry.
Segmental Railway Bridges
448
FIGURE 10.18.
FIGURE 10.16.
:>Iarne la Vallee Bridge. crossing the
\Iarne River and elevated passenger station.
Torey Viaduct, segment transporta­
tion frol11 l'Iarne la Vallee to Torc\,.
The total length of 1870 it (570 m) is divided into
three separate sections: one fou r-span unit, on<:;
nine-span unit, and one four-span unit.
FIGURE 10.17.
?-larne la Vallee Bridge, aerial view of
the rin~r crossing. a passenger station. and the elevated
viaduct.
Precast segments were placed in the structure
with an overhead launching gantry of a type
,.;lightly different from the one used previously,
although calling on the same sequence of mm'e­
ments. T\\'o parallel longitudinal trusses make
the track for a transverse overhead portal crane
carrying and placing the segments between the
trusses. Figures 10.19 and 10.20 show the general
view of the gantry a~d the detail of one segment
placing. The overall view of the finished bridge
appears in Figure 10.21.
the northern span of the river crossing and the ele­
vated passenger station. Figure 10.17 is an aerial
view of the overall project.
1n view of the success of this first application of
segmental construction in urban railway elevated
structures, the Paris Mass-Transit Authority de­
cided to extend the same concept to construct an­
other large structure a few miles eastward: the
Torcy Viaduct. Fortunately, the precasting yard
for the first bridge was still available and all seg­
ments could be manufactured there and trucked to
the second bridge site, Figure HU8.
Dimensions of this new bridge are as follows:
Cross section: exactly the same as for the Marne la
Vallee elevated viaduct.
Distribution of spans: 17 spans with typical span
length of 115 ft (35 m).
FIGURE 10.19. Torey Viaduct, precast segment plac­
ing with launching gantry.
elichy Railway Bridge near Paris, France
FIGURE 10.20. Torcy Viaduct, detail of segment
handling between twin trusses of launching gantry.
~~l"~"':'~~
· ,~~",~CL
'}'Wm~'-"'" ;J.:":"
ff!:~--:
"c::-'
.nt
~~~T»'C':'~
FIG:URE 10.21.
structure.
10.6
449
vated metro. It crosses the Seine River adjacent to a
new highway bridge between the cities of Clichy
and Asnieres, as shown in Figure 10.22. Layout
and principal dimensions appear in Figures 10.23
and 10.24.
The prestressed concrete segmental structure is
1350 ft (412 m) long with a 280 ft (85 m) main span
over the river with a deck of variable depth. The
river piers of the two railway and highway bridges
match exactly to minimize water flow and barge
traffic disturbance. A provision is made for a sec­
ond future highway bridge at the other side of the
railway bridge, as seen clearly in Figure 10.25a.
The rest;icted transverse clearances between the
three structures and their corresponding traffic
explains the special shape of the piers for the
center railway bridge, which was carefully studied
architecturally to enhance the appearance of the
project. Foundations were very close to one an­
other but could be maintained structurally inde­
pendent to better control settlement and avoid vi­
bration interference between bridges and in the
ground.
To carry the two railway tracks, the deck has a
typical cross section consisting of three precast
webs connected by a bottom slab, which forms es­
sentially the compression Aange over the piers, and
an intermediate slab, which receives the ballast,
Figures 1O.25b and 10.26. The depression thus
realized between the web top flange and the tracks
has several advantages, including providing full
safety against derailing on one track and reducing
the noise level.
Construction of the superstructure included
match casting of all webs in a yard near the project
site. The webs were placed in balanced cantilever
with a light portal crane carried by the finished
Torcy Viaduct, view of the completed
Clichy Railway Bridge near Paris, France
At about the same time the two structures de­
scri~ed aboye were built, a large and innovative
railway bridge was constructed in the northeastern
suburb of Paris for another extension of the reno­
FIGURE 10.22. Clichy Railway Bridge, VIew of the
completed structure.
....
450
Segmental Railway Bridges
1
I'
ASNIERES
C'''''.~'f''''
d,,:
,
c~, .. '"
;
'1 •
,I'
LA SEINE
CLiCHY
(a)
(b)
FIGURE 10.23. Clichy Railw<.J) Bridge, layout and dCY<ltion of the' structure,
\'ic\\', (Ii) EIe\'alioll.
(a)
Pial!
~::::l=~~=F==~I:+
~+----,-1,6.'~+/971~34
_
("pG)
g_lI_CI~t~__ .__.SEIN.L13.!!g!L.
(7)7)
FIGURE 10.24.
(l'Ct) ,
(J>!J)
__
l __.~,s!>'IERES
(Plrp
(?lP
Clichy Railway Bridge, main dimensions of segmental structure.
portion of the deck, Figure 10.27. Maximum
weight of precast webs was 19 tons (17 mt),
whereas segments that included the full three-web
box (or even a more conventional single box for
the equivalent span length) would have weighed in
excess of 66 tons (60 mt), After assembly of precast
webs with longitudinal post-tensioning, the two
twin slab sections were poured in place between the
webs in balanced cantilever on very simple travel­
ers, Web segments were 7.3 ft (2.22 m) long for the
constant-depth part of the deck and 4.8 ft (l.48 m)
for the variable-depth part. In fact, the slabs were
cast in place between the three webs in two or three
increments of that length respectively (a length of
Clichy Railway Bridge near Paris, France
E~~~_
451
.--'"--_____.___
.2110)
------"­
l!G!:NDE
_
Ouvroge\ b con\frulre.
(a)
!}ur~J i, fJlJc~
Sl.b.s
.
'>-,
J
FIGURE 10.25, Clidn Ibih,<\\ Bridge, t\vicaJ SC(­
lions of pier, and dcck, (II) Flc\'<trioll of lalld and rl\er
pins. (hI DiIllt'llsiollS of lhe dcck (TOSS scerioll.
14-.6 or 4"+·1 m) to reduce the number of site oper­
;)tions. A three-day cYcle of operations could be
constantly maintained, including some overtime
work for the larger segments near the river piers.
Overall, construction in cantilever of the total
superstructure took one year between September
197.7 and September 1978.
A special design aspect, specific to railway
bl'idges, was the transfer of horizontal loads (in­
FIGURE 10.26. Clichv Railwav Bridge, pier seglllCIIt
and ca ntilever con~rrllerion.
duced through braking or starting of the trains
over the bridge), to the piers and foundations. A
single fixed bearing was provided over pier P6, the
foundation of which was designed to transfer to
Segmental Railway Bridges
452
,_
the need arise in the future. Two families of ten­
dons could be added:
."
. ."(.). . .
.. '
l .
:.v..~
Above the lower slab in the two voids of the box
section, anchors being provided in blisters already
built in the structure.
Atop the center precast web and on the outside
face of the two facia webs, anchor blocks and de­
viation saddles being prestressed by high-strength
bolts to the precast webs.
FIGURE 10.27.
Chehv Railw,1\ Bridge, placing pre­
cast \\Ths for can1 ile\"t'r constnlClion.
the limestone stratum the total maximum hori­
zontal load of 660 tons (600 Int) applied to the
bridge. There are three pot bearings between the
deck and the pier shaft, each capable of safelv
transferring half of the maximum horizontal load.
Each bearing can thus be changed under traffic
without I-educing the capacity of the structure.
Special provisions were also included at the de­
sign stage, Figure 10.28, to allow additional pre­
stressing to be incorporated in the structure should
The large precast architectural panels on hoth
sides of the deck could be temporarih' removed to
allow this work of additional prestressing to be per­
formed. Cpon completion, all additional tendons
would be full\' protected and concealed behind the
panels.
The new line has been open to traffic since May
1980, and the first months of operation confirm
that the precautions taken to reduce noise and vi:
bration disturbance through welded continuous
rails and sound-barrier panels make such elevated
structures an acceptable solution for mass-transit
lilies in urbanized areas.
10.7 Olifant's River Bridge, South Africa
(b)
FIGURE 10.28. Clichy Railway Bridge. (a) View of
adjacelll highway and railway hridges crossing the Seine
River. (b) Provisions for future additional prestress.
This structure is part of a line carning iron ore on
special heavy trains 7500 ft (2300 m) long made up
of 200 cars with a lotal weight of 19,000 tons
(17,000 mt) to connect the Sishen mines to the har­
bour of Saldanha 110 miles north of Capetown.
Olifant's River Viaduct is today the world's longest
incrementally launched prestressed concrete
structure (refer to Chapter 7) with a total length of
3400 ft (l035 m) and 23 spans of 148 ft (45 m),
Figure 10.29.
Shown in cross section in Figure 10.29, the single
box girder deck accommodates only one track on
ballast. The equivalent uniform live load of the 33
ton (30 mt) axles is 7.1 kips/lineal ft (l0.5 mt/lm),
which is increased by an impact factor of 1.29.
The 23 spans are divided into two II-span sec­
tions, each anchored to the end abutment, and one
single transition span at the center. This scheme
allows all horizontal loads to be transferred to the
abutments. The maximum horizontal reaction in­
cluding all thermal effects is in excess of 1200 tons
(1100 mt). The piers, which vary between 80 ft (25
m) and 150 ft (55 m) in height, are extremely flexi­
ble and do not, therefore, have an important effect
on the horizontal restraint of the structure, except
during construction. The pier shafts have an 1­
Incrementally Launched Railway Bridges
453
(b)
FIGURE 10.29. Olifallt's Rin'r Viaduct. (II) General
view of the structure. (b) '[\Vic~\ll"ross section.
shaped cross section with longitudinally tapered
faces. Neoprene bearings are used for the piers
near the abutments and teAon sliding bearings in
the center of the structure.
The deck was entirelv constructed behind one
abutment (see schematic view in Figure 7.29) and
incrementally launched in one direction. Construc­
tion time for the superstructure was nine months,
with a theoretical cycle of 10 working days for a
. typical 148 ft (45111) span realized after 10 spans; it
was further reduced to se\en days with two shifts
toward the end of the project. The total weight of
the superstructure of 14,500 tons (13,000 mt)
called for two 200 ton jacks for the push-out oper­
ations in increments of 3.5 ft 0.00 m). A 60 ft (18 m)
long launching nose was used in front of the first
span to reduce the variation of bending stresses in
the superstructure during the ·successive stages of
construction, Figure 10.30. The bridge nearing
completion is shown in Figure 10.31; it was opened
to iron ore trains in 1976.
10.8 Incrementally Launched Railway Bridges for
the High-Speed Line, Paris to Lyons, France
FIGURE 10.30. Olifant's River Viaduct, launching
nose reaching bevond a high pier.
build some new very-high-speed train lines (safe
maximum speed of 200 mph or 320 km/hr) and
started the construction of the first such line be­
tween Paris and Lyons, which included an entirely
new structure over a distance of 250 miles (400
km) with proper connections to the existing met­
ropolitan track and station system.
The new project required 400 bridges including
nine large viaducts. such as the structure shown in
Figure 10.32. A very comprehensive optimization
study followed, and a set of guidelines and struc­
tural standards were prepared for the French Na­
tional Railways by a team of engineers headed by
one of the authors. Results of the preliminary in­
vestigations and of this optimization study can be
summarized as follows:
L
To meet increased competition by domestic air­
lines, the French National Railways decided to
Track alignment is chosen to keep the curva­
ture in plan more than 10,500 ft (3200 m) and
preferably more than 13,000 ft (4000 m). The
Segmental Railway Bridges
454
4,
5,
6.
FIGURE 10.31. Olifallt's Ri\cr Viaduct. \'ie'\\" of the
s\ nln llre lIe'a ri IIg com plet ion,
FIGURE 10.32. Railwa\ Viaducts for Paris-Lnms
high-spcl'd lil1c, \'ie\\' of the \'iadun O\;er (he Saone
Ri\'er.
2,
3.
corresponding cross fall between rails is 7 in.
(180 111m),
All rails are to be continuously welded and
placed on a ballast bed with a minimum thick­
ness or 14 in. (0,35 m).
Maximum rigidity of the structures is obtained
by using a continuous box section with slen­
derness ratio of 1/14. The corresponding
maximum deflection under design load is
therefore 1/2000 of the span, whereas conven­
tional specifications for normal-speed lines
allow up to 1/800,
Adopt as much as possible single box girder
decks for the two parallel tracks with minimum
web thickness of 14 in. (0,35 m) and a
minimum top slab thickness of lOin, (0.25 m).
The optimum span length is between 150 and
170 ft (45 to 50 111), which lea\es the construc­
tion method open to various solutions (can­
tilever, spar1-b\'-span or increlnental launch­
ing).
The horizontal loads should be transferred to
one abutment equipped with a special fixed
bearing, allowing all piers to be relieved of am
appreciable longitudinal bending. A tvpical
H-section was adopted as the most appro­
priate except for certain specific locatioos
where a box section might be required.
Because many of the \'iaducts were located in en­
virolll11elltalh sensitive areas, all overall architec­
IUral study was also conducted to establish a unitv
or appearance for all hrid~es ill terms of t he shapes
of deck and piers, parapet or guard rails, abut­
ments and approach fills,
Of the nine viaducts, two were finally con­
structed with conventional methods and the re­
maining seven wert' incrementally launched, This
method proved economical in view of the moder­
ate span lengths, the depth of the box section avail­
able, and especially because the superimposed
dead and live loads were so much more important
than for a highway bridge that the increased
dead-load moments during construction were in
proportion of much less significance.
Table 10,1 gives the essential characteristics of
the seven segmental viaducts, including principal
quantities of materials for the superstructure. Ele­
\'ations or fi\'e hridges appear in Figure 10,33,
As an example of the construction method, some
details are given ror the bridge over the Saone
River, where a launching nose 93 ft (28.50 m) long
and weighing 71 tons (65 mt) was used in front or
the first span to reduce the stress variations in the
superstructure during launching, Figure 10.34.
"fhe bridge superstructure was cast in successive
increments in a fixed location behind the right
bank abutment in the length of a half-span,
Figure 10.35. A typical sequence of operations is
shown schematically in Figure 10.36. Each
superstructure section is in fact cast in two stages
~
(Jt
(Jt
(Ill))"
41.0
(12.50)
40.0
(12.10)
429
(131)
279
(il5)
Long. grade: 0.2%
Straight in plan
39.0
(11.90)
1260
(385)
-10.3
(12.30)
1112
(339)
39.0
(11.90)
41.0
(12.50)
662
(202)
1370
(419)
41.0
(12.50)
(ft)
Total
Witllh
662
(202)
!:Iritlg.:
Length
Long. grade: O.S5%
Slraight in plan
Long. grade: 2.5%
Straight in plan
Long. grade: 3.5%
Radius in plan:
10,61l0 ft (3250 Ill)
Long. gradt.:: 1.3%
Radius in plan:
20,000 ft (6000 m)
I.ong. grade: 0.95%
Radius in pia,,:
26,000 ft (8000 m)
Cin·ula. ptofile
in elevation:
R
130,000 h
(40,000111)
Bridge
I.ayolll
7.8
(2.37)
13.1
(4.(H»
(:UO)
10.8
10.8
(S.30)
11.5
(3.51)
10.8
(3.30)
10.8
(3.30)
(tl)
Heighl
19.0
(5.80)
190
(5.80)
IB.O
(5.50)
18.0
(5.50)
IS.O
(5.50)
111.0
(5.50)
IS.O
(5.50)
(It)
Box
Widlh
eft
12
(0.30)
24/35
(0.60/0.90)
10
(0.25)
(0.28)
II
12.5
(0.32)
24
(0.60)
12.5
(0.32)
12.5
(0.32)
II
(0.275)
11
(0275)
Top
(in.)
Pi.:,.
(III)]
(0.20)
8
12/20
(0.30/0.50)
14
(0.35)
14
(0.35)
43/105
43
(1'1)
36
(II)
43/115
(l:W5)
(! :I/:I:!)
2.30
(0.70)
2.30
(1l.70)
84
(50)
84
(50)
84
(50)
190
(110)
250
(150)
250
(150)
210
(125)
84
(50)
2.46
(0.75)
46
(14)
12.5
(0.32)
240
(140)
78
(46)
661148
(20145)
10
(0.25)
2.52
«(l.77)
[Ib/yd'
(kg/lll')]
Reinf.
Steel
240
(140)
[Ib/yd'
(kg/m")]
HT.
S.ed
Quantities of
neck
78
(46)
(m'/Ill")]
[fI'/ft'
:i.52
(0.77)
4611:i1
1ft
Heigh.
ConCi.
(HI:;7)
10
(0.25)
Bottom
(in.)
Flange Thick
24
(0.60)
20
(0.50)
18/49
(0.45/1.25)
(0.45/1.25)
IHI4!J
(in.)
Web
Thick.
Dimensions of Deck
or in. (m)]
Characteristics of Segmental Viaducts on the Paris-Lyons High-Speed Line
uSlfunures are nUlnhet eLI with increasing nlunbers, fronl Paris to Lyons.
109-S~v 144-109
(33.4 - 8 @ 44 - 33.4)
@ Roche
108 ­ 7 @ 149 - 108
(33.1 - 7 @ 45.5 - 33.1)
CD Sei1lE River
114 - 201-114
(34.8 - 61.1 - 34.8)
® Center Canal (length)
85 ­ 105 ­ 85
(26 - 32 - 27)
@ Digoille
Saulieu
115-3«v 144-115
(35 - 3 @ 44 - 35)
CID Sereill
115- 3 @ 144 - 115
(35 - 3 @ 44 - 35)
(J) Same River
155 - 5 @ 164 - 137
(47.2 - 5 (iiJ 50 - 41.8)
CD
1ft
Bridge
Location
and Span Lengths
Table 10.1.
Year
1978
1980
1978
1978
1979
1979
1978
Cmn­
pk,,·!!
...
LYON
Viii/due sur la Seine.
ttl
II
Viadue du Serrein.
t\l
It
Via due de la Digoine.
Viadue de /a RO'ihe.
I
I
tlUl
I
r=m=.
-~.~..
•-
=;;=a'""1I
ji
tuttli,
',."
~
'1.111­
!:==1~~~?F~~~::::,E*'
i
"J
",'
'"
,,',
JI'JOI
Viadue sur fa Sa6ne.
FIGURE 10.33.
456
Elevation of five segmental bridges for Paris-Lyon!> line.
Segmental Railway Bridges inJapan
457
(bottom slab during the first stage, webs and top
slab during the second stage). The typical con­
struction cycle allowed casting a half-span every
week-that is, constructing two spans per month.
The launching operation proper called for a
very efficient system, developed and perfected
previously in Germany, including under each web
of the box section:
One vertical jack with sliding plate
Two coupled horizontal jacks for actual launching,
allowing movements in 3 ft increments
FIGURE 10.34. Saone Ri\'er Bridge, launching nose
approaching pier.
Typically, launching of an 80 ft section took three
to three and a half hours, despite the large weight
of the concrete superstructure, reaching 9000 tons
(8000 mt) at the end of construction.
Figure 10.37 shows a completed structure, and
Figure 10.38 shows another aspect of the con­
struction of these seven viaducts.
10.9 Segmental Railway Bridges inJapan
Many railroad bridges have been built in Japan
using the segmental construction technique. The
sketches shown in Figures 10.39 through 10.42 de­
pict the elevation and the cross section of the fol­
lowing cast-in-place segmental bridges:
FIGURE 10.35. Saone River Bridge, aerial view with
casting vanl in behind abutment in foreground,
TE~PCRARY
SLiOINI>
FOR
PADS
50 DOm
-
SUPPORT
PUSHt£
(WITH JACK)
50.00
~-
4300
Kyobashigawa Bridge
Natorigawa Bridge
-
APPROACH
SPt.N
,­
PRECAST Yt.RO
23!10
....---~~.-~,.....
SITUATION DURING FABRICATION OF SEGMENT 7
-
2(\.50 1025 2070. 2500
-~
.......................25.00
--~.
SrTUATION AFTER PUSHING OF SEGMENT 7
GENERAL PRINCIPLE OF THE CONSTRUCTION METHOD BY PUSHING
FIGURE 10.36. Saone River Bridge. typical construction stages of incre­
mental launching.
Segmental Railway Bridges
458
FIGURE 10.37. Saone River Bridge, view of the completed structure.
FIGURE 10.38. Digoine Bridge, incremental launch­
ing over high piers.
Kisogawa Bridge
Ashidagawa Bridge
Figure 10.43 shows the Kakogawa Bridge during
construction. The superstructure is made of twin
constant-depth box girders, one box girder carry­
ing one railway track. The total length of the
bridge is 1640 ft (500 m), with typical span length
of 180 ft (55 m). Each box is 13 ft (4 m) wide and
11.5 ft (.3.50 m) deep. The precast segments were
handled by a launching gantry and assembled by
longitudinal post-tensioning tendons. The erection
used the balanced cantilever system.
The most outstanding prestressed concrete rail­
way structure, however, is the Akayagawa arch
bridge shown in Figure 10.44. Total length is 980
ft (298 m) and the center arch span is 410ft (126
m). The 13 ft (4.00 m) deep box girder carrying
two railway tracks is continued throughout be­
tween abutments and rests over the center gorge
on a very flat arch rib through ten spandrel col­
umns. The respective proportions are such that the
deck carries all bending moments and the arch rib
carries the normal load induced by its curvature.
The erection scheme was unique and called for
cantilever construction starting from both sides.
A very strong back stay made up of a prestressed
concrete member with a prestress force of 5300
tons (4800 mt) was installed diagonally between the
top of the main transition piers between the arch
structure and the approaches on one hand, and the
foundation of the adjacent piers in the approach
structures on the other hand.
While erection progressed, high-strength steel
bars were placed diagonally between the vertical
members, forming a temporary truss structure
until the crown was reached from both ends. Con­
trol of tensioning of those steel bars was very criti­
cal and complicated. Finally, all steel bars and the
two temporary back stays were removed after clo­
sure of the arch at midspan.
10.10 Special Design Aspects of Segmental
Railway Bridges
10.10.1
M.AGNITUDE OF VERTICAL LOADS
Most bridges carry tracks laid on ballast with a
minimum thickness of 10 to 14 in. (0.25 to 0.35 m).
Special Design Aspects of Segmental Railway Bridges
459
HAKATA
ELEVATION
CROSS SECTION
FIGURE 10.39.
Hvobashigawa Bridge, Japan.
Live loading used in design of railway bridges
varies between countries-Cooper loading for
Anglo-Saxon countries, new UIC loading for most
European countries-and also according to the na­
ture of the structure: mass-transit lines are usually
designed for much lighter loads than normal train
lines. The heaviest loadings are for are freight
trains.
To exemplify the basic diff.erence between a
highway and a railway bridge, Figure 10.45 com­
pares a typical 150 ft span and a 36 ft wide deck
normally designed for three highway lanes of
traffic or two railway tracks. The total superim­
posed dead and live load is 3.6 times greater for
the railway bridge. hi addition, the weight of bal­
last (representing 40% of the total load) must be
considered as a live load to cover the cases where
the ballast is removed from the deck or has not yet
been placed on a new bridge.
/0./0.2
HORIZONTAL FORCES
Railway bridges have to carry very important hori­
zontal forces, between five and ten times the hori­
zontal forces carried by a highway bridge of similar
size. The standard current practice for long via­
ducts is to have a fixed bearing on one abutment if
the bridge length is less than 1500 ft (450 m), and
on both abutments and on intermediate special
bents if it is greater. The order of magnitude of
this horizontal force on the abutments carrying the
fixed bearings is often 1000 tons for a two-track
viaduct.
The various forces involved are described below:
Long-itudinal Forces
Braking and acceleration forces
Segmental Railway Bridges
460
TOKYO
r
r-----------51.95
52.00
~---t--
524.90 m
•
~
-1- H
!Jl:Ur
'0
I
--
52.00 I 52.00 - 54.50 . 54.50 - 52.00 , 52.00
52.00
T"---r-O
·--~---T----·---I--------r..----..-'---....---
10,.
:~
--
0
MORIOKA
_ 5195
------~.
. '
[2
I
•
~#M~" 8·"~ Ff;1~ F9r­
ELEVATION
~---,;:-
- --
I]
-----1
-:
J
L...2:=====i' .. - - .. i
I
-----j
_-=-5::-9--t--t-....:2:::,:.2::..::5......,.1_-=-2.:.:.,75::...--li
2. £,5
6.00
I
I
2.45
~~-_---~--~l~l.l~O~m~------~
CROSS SECTION
FIGURE 10.40.
Natorigawa Bridge, Japan.
Forces due to box girder deformations: creep,
shrinkage, and temperature variations
Loads induced by the length variations of long
welded rails under temperature variations
Longitudinal component of wind forces
Braking and acceleration forces are one­
seventh of the total weight of live loads, with a
ceiling of 285 tons for braking and 53. tons for ac­
celeration (French regulations).
Forces due to longitudinal deformations of the
box girder vary because of creep, shrinkage, and
temperature variations. The bearing displace­
ments induce horizontal loads by distortion or
friction.
Length variations of the long welded rails due to
temperature variations create a horizontal force
parallel to the rail. This force can be estimated at
50 tons per rail (length of rail more than 100 me­
ters). For a two-track bridge it is 2 x 2 x 50 = 200
tons.
Longitudinal component of wind forces are de­
scribed in the AASHTO specifications for bridges.
Transverse Horizontal Forces Centrifugal horizontal
force can be very important for high-speed trains.
For the 200 mph train from Paris to Lyons this
force is more than 400 tons for some viaducts 1200
ft (380 m) long with two tracks and radius of cur­
vature of 10,500 ft (3200 m), The lateral accelera­
tion is more than 20% of that of gravity.
Transverse wind force is described in the
AASHTO standards (50 Ib/ft2 ).
10.10.3
BEARINGS
In order to gain complete control of these very
large horizontal forces, the bearings are specially
designed to take care of the vertical loads and ro­
tation of the box girder and simultaneously to pro­
vide all possible horizontal restraints (fixed bear­
ing, bearing free lengthwise or crosswise, or both),
Special Design Aspects of Segmental Railway Bridges
461
----1
m
---
I
HAGOn,
-=>­
ELEVATION
76
or-b5~~~:~
I-Iii
~1~IL
I
co
:1,
0
Ii ' 2.00
,I
1 '9
.u
'I'1
2 40
!.'
5:30
,. 2.00
9.30m
I
I
CROSS SECTION
FIGURE 10.11.
Kisogawa Bridge. Japan.
These bearings are specially manufactured for this
type of structure. Figures 10.46 and 10.47. The
sliding parts consist of a teflon-coated plate resting
on a stainless steel plate, and the restraints are pro­
vided by steel keys.
ference of potential with the ground may be mea­
sured at regular intervals, and a permanent con­
nection with the ground may be decided on as a
result.
10.10.5
10.10.4
DURABILITY OF THE STRUCTURE
STRAY CURREVTS
For structures carrying electrified railways there is
some uncertainty about the long-term effect of
stray currents generated near the power lines. In
order to preclude electrolytic corrosion of rein­
forcing steel and prestressing steel, the following
precautions are now taken in prestressed concrete
structures:
The deck is electrically isolated from the ground,
piers, and abutments by e1astomeric plates.
The reinforcing and prestressing steel svstems of
the entire deck are interconnected by mild steel
bars to equalize the electric potential. The dif­
Because very difficult problems of train traffic
would arise during repairs to these bridges, their
durability needs special attention. The following
provisions were established for the high-speed
bridges between Paris and Lyons:
Under the worst service loads the concrete must
remain under a 140 psi minimum compression.
For continuous bridges, the design shall be
checked by weighing the dead-load vertical force
on the bearings.
The stressing force of the post-tensioning tendons
shall be less than 80% of the ultimate strength of
the tendons.
462
Segmental Railway Bridges
HAKAlA
----::..
ELEVATION
FIGURE 10.42.
CROSS SECTION
Ashidagawa Bridge, Japan.
10.10.6
FIGURE 10.43. Kakogawa Railway Bridge, placing
precast segments with launching gantry.
The ultimate strength of the structure should be
capable of supporting the service loads increased
by 30%, if 30% of the post-tensioning steel were
missing.
Provisions shall be made for installing additional
tendons while the structure is under traffic. The
additional post-tensioning force shall be 15% of
the designed force minimum.
It shall be possible to replace all the bearings.
CONCLL'SlON
This review of specific design problems of railway
bridges should raise no doubts whatsoever about
the advantages of prestressed concrete and seg­
mental construction in this field. Prestressed con­
crete is the safest material known today to resist
indefinitely the large variations of loads such as
those applied to a railway bridge.
The problem of fatigue has been covered briefly
in Chapter 4, and the results mentioned there
apply particularly well to railway bridges. The
main objective in the design and construction of
prestressed concrete bridges should be to minimize
and even eliminate concrete cracking, which is al­
ways a source of weakness in a structure subject to
cyclic loading.
.
The use of the provisions laid down in Section
10.10.5 should result in practically crack-free
structures with an expected life free of major
maintenance.
(a)
Arch rib
(b)
FIGCRE 10.44. .\k;n;lg;ma I<.;lil\,·;I\ l)ridge. general dimciisiolls.
\.lliOl1. (/1) rq)ical ClOSS sectioll .\-.\.
55 k
125t)
5A ,<icF
18 t/ml)
III.'IIIIIIIIIII!IIIIIIU
j
55 k
(25t) .
55 k
(25!)
I
J
55 k
(25t)
(II)
Fk­
5A k/cF
j j
(8 t/ml)
1IIIIIIIIIIIIIlIIIIIIIIIIII
. 2.6'
I i80l
Railwav Bridge
Description
Span length
Deck width
:\ umber of lanes or t LICb
Superimposed dead load:
Ballast
Curb, pavement. etL
Total S.L.
Live loads:
Equivalent uniforlll
load
Impact bctor
Total L.L.
Total (S.L + L.t.)
150 ft (45 m)
150 ft (45 Ill)
%ft(lllll)
Three lanes
:.16 ft (11 Ill)
Two tracks
6.:3 kips/h
0.& kips/ft
L5'kipslft
i.O kipslft
1.5 kips/ft
6.8 kips/It
2.4 kipslll
30%
2.8 kips/ft
8.8 kips/ft
4.3 kips!!t
15.8 kips/ft
FIGURE 10.45. Venical loading on railway bridges. (II) Typical U Ie track loading.
COlllparison of superimposed dead and live loading on highway and r,lilw<lV bridges.
(b)
463
Segmental Railwa)' Bridges
464
10.11
...
... :.".
.,"
'
,",
·t~....: ......
'" '-.
, r ,...
"
.
• I'..
•
•
'"
.
.­ ..
)
~
,
.
.
.
FIGURE 10.46.
pOl bearillg \\'ith unidircc·
I jona! horizollla!lII01'cmclll.
Proposed Concepts for Future Segmental
Railway Bridges
We should note that many types of structur:es de­
scribed for highway bridges are equally appropriate
for railway bridges: the structures described in this
chapter were essentially girder or arch bridges
built in cantilever or incrementally launched.
Today, many design projects are based on stayed
bridges. As an example, Figure 10.48 shows a pro­
posed crossing of the Caroni Ri"er in Venzuela for
hea"y iron ore freight trains.
I
!
I
I
!
i
I
I
,
131',/31"129'
,-=-+-'.
~-.
t
!3/tJ'
318'.
FIGURE 10.48. Pmpmt'd
iron ore ]'ail"'<I\' lint',
('J()s~jng
of Rio Camni iOl
11
Technology and Construction
of Segmental Bridges
11.1
11.2
11.3
11.4
SCOPE AND INTRODUCTION
CONCRETE AND FORMWORK FOR SEGMENTAL
CONSTRUCTION
11.2.1 Concrete Design and Properties
11.2.2 Concrete Heat Curing
11.2.3 Dimensional Tolerances
11.2.4 FOTmwork for Segmental Construction
POST-TENSIONING MATERIALS AND OPERATIONS
11.3.1 General
11.3.2 Ducts
11.3.3 Tendon Anchors
11.3.4 Tendon Layout
11.3.5 Friction Losses in Prestressing Tendons
11.3.6 Grouting
11.3.7 Unbonded Tendons
SEGMENT FABRICATION FOR CAST-IN-PLACE
CANTILEVER COr-;STRUCTION
11.4.1
Conventional Travelers
Self-Supporting Mobile Fonnwork
11.4.3 Two-Stage Casting
11..1..1 Combination of Precast Webs with Cast-in-Place
Flanges
11.4.5 Practical Problems in Cast-in-Place Construction
Camber Control
CHARACTERISTICS OF PRECAST SEGMENTS AND
!\fATCH-CAST EPOXY JOINTS
11.6
11.6.1
11.6.2
11.6.3
11.6.4
11.6.5
11.7
11.8
11.1
Scope and Introduction
Certain problems are common to all tvpes of seg­
mental construction-for example, the selection
and control of materials. prestressing operations.
and choice of bearings, joints, and wearing surface.
Other prohlems are specific to a particular con­
struction method. The use of form travelers in
cast-in-place cantilever construction and the cast­
ing ~U1d handling of segments in precast cantilever
construction are two such examples. This chapter
covers these various topics in the following order:
Introduction
Long-Line Casting
Short-Line Horizontal Casting
Short-Line Vertical Casting
Geometry and Survey Control
Segment Precasting in a Casting Machine
Segment Casting Parameters
Survey Control During Precasting Operations
Survey Control During Construction
Conclusion
11.6.6 Precasting Yard and Factories
HANDUNG AND TEMPORARY ASSEMBLY OF PRE­
CAST SEGMENTS
PLACING PRECAST SEGMENTS
11.8.1 Independent Lifting Equipment
1 1.8.2 The Beam-and·Winch Method
11.8.3 Launching Girders
Launching Girders Slightly Longer Than the Span
Length
Launching Girders Slightly Longer Than Twice
the Typical Span
II.U
11.5
11.5.1 First-Generation Segments
11.5.2 Second-Generation Segments
11.5.3 Epoxy for Joints
MANUFACTURE OF PRECAST SEGMENTS
REFERENCES
I.
2.
3.
Problems common to all segmental bridges
Problems specific to cast-in-place cantilever
construction
Problems specific to match-cast segmental
bridges with particular emphasis on cantilever
construction, which is the most widely used
method.
In designing segmental bridges, it is important
to pay attention to certain details at the time of
conception, in order to keep the project as simple
as possible and thereby achieve economy and effi­
465
466
Technology and Construction of Segmental Bridges
nellC), during construction. The following guide­
lines apply to both cast-in-place and precast con­
struction:
1.
Keep the length of the segments equal, and
keep the segments straight even for curved
stnlCtures (chord elements).
<)
:\1aintain constant cross-section dimensions as
much as possible. Variations of cross-section
dimensions should be limited to change of
depth of webs and thickness of bottom slab.
~~. Corners should be beyelcd to facilitate casting.
4. Segment proportions (shear keys, for example)
should be such as to allow easy form stripping.
5. Ay(lid as much as possible surface discon­
tinuities on webs and flanges caused by anchor
blocks. inserts, and so on.
6. Use a repetitive lavout for tendons and all­
chors. if possible.
7. Minimize the number of diaphragms amI stif­
fencl'S.
H. Avoid dowels passing through fonnwork, if
possihle.
11.2
Concrete and Formwork for Segmental
Construction
11.2.1
COXCRETE DESIG.\' /i,VD PROPERTIES
Ullifonll qual it v of concrcte is essential for seg­
mental construction. Procedures for obtaining
high-quality concrete are covered in PCl and ACI
publications. 1.2 Both normal weight and light­
weight concrete can be made consistent and uni­
form by means of proper mix proportioning and
prod uction con t ro1s.
Ideal concrete will have a slump as low as prac­
ticable. notwithstanding the possible use of special
placing equipment such as pumps, and a 28-day
strength greater than the minimum specified by
structural design. It is recommended that statistical
methods be used to evaluate uniformity of con­
crete mixes.
The methods and procedures used to obtain the
concrete characteristics required by the design may
vary somewhat, depending on whether the seg­
mCllIS are cast in the field or in a plant. The j'csults
will be affected by curing temperature and type of
curing. Liquid or steam curing or electric heat
curing may be used.
In tem perate climates and where cu ring is car­
ried out in an isothermal enclosure, only small ad­
ditions of heat are required to maintain the curing
temperature, full advantage being taken of the
heat of h\'dration generated by the fresh concrete.
In this case heat demand will be a function of the
ambient temperature, more heat being required in
winter and little or no additional heat during hot
summer weather.
'Where segment production rate is not critical, it
may be possible to do without accelerated curing
and simplY use a normal curing period of a few
dm's, during which the concrete is well protected
against excessive temperature variations and a!J
exposed surfaces are kept moist.
A sufficient number of trial mixes must be made
to assure uniformity of strengt h and modulus of
elasticity at all important phases of construction.
Careful selection of aggregates, cement, admix­
tures, and water will improve strength and mod­
ulus of elasticity and will also reduce shrinkage and
creep. Soft aggregates anc! poor sands must he'
avoided. Creep and shrinkage data for the con­
crete mixes should he determined bv tests.
Corrosive admixtures such as calcium chloride
should nevcr be used, since thc\' can have a det­
rimental effect on hanlelled cOllcrete and can
cause corrosion of reinforcement and prestressing
steel. \Vater-reducing admixtures aud also air­
entraining admixtures that improve cOllcrete re­
sistance to environnienlal effects, such as de-icing
salts and freeze and thaw actions, are highlv desir­
ahle. Yen careful control at the batching stage is
required, however, since the advantages of air­
entrained concrete callnot be relicd upon ullless
the qualltitv of entrained air is within specified
limits.
The cement, fine aggregate, coarse aggregate,
water, and admixture should be combined to pro­
duce a homogeneous concrete mixture of a quality
that will conform to the minimum field-test and
structural design requirements. Care is necessary
in proportioning concrete mixes 10 insure that they
meet specif1ed criteria. Reliable data on the poten­
tial of the mix in terms of strength gain, creep, and
shrinkage performance should be developed to
serve asth~ basis for improved design parameters.
Proper vibration should be used to permit the
use of low-slump concrete and to allow for the op­
timum consolidation of the concrete.
11.2.2
CONCRETE HEAT CURiNG
An early concrete strength usually is required to
reduce the cycle of operations and to maintain the
Concrete and Formwork for Segmental Construction
efficiency of the special equipment used either in
cast-in-place or in precast construction. Two
methods may be used for this purpose, either sepa­
rately or together: (a) preheating the fresh con­
crete, before placing it in the forms or in the cast­
ing machines, (b) heat curing the concrete after
consolidation in the forms.
In the first case the concrete is preheated to
about 85 to gO°F (30 to 35°C). This operation is
achieved in several ways:
1.
2.
3.
Steam heating the aggregates-a simple solu­
tion that presents the disadvantage of chang­
ing the aggregate water content
Heating the water-a solution that has limited
efficiency, owing to the small proportion of
water in comparison with the other compo­
nents (water at l40°F raises the concrete tem­
perature bv only 20°F).
Direct heating of the concrete mix bv injecting
steam into the mixer itself-the best solution
and the one lllost easily controlled.
To avoid heat loss, the [or!11S are generally in­
sulated and some source of radiant heat is installed
inside the segment (radiators or infrared ele­
ments).
In the second case, the concrete is heated in its
mold inside a container in which low-pressure
steam is circulated. I n this way it is relatively easy to
obtain the strength required for prestressing oper­
ations [350n to 4000 psi (25 to 28 MPa)] after one
or two days, even in winter. If however, tensioning
operations are to be performed earlier, after 24
hours for example, modifications must be made to
the concrete in the anchorage zone.
Electrical resistances mav be embedded in the
concrete. or precast end-blocks may be used. Pre­
cast end-blocks were used notably for the Issy­
les-~IoulineaLlx, Clichy, and Gennevilliers Bridges.
For the Gennevilliers Bridge, despite the excep­
tional dimensions of the box girder deck, two
segments were cast each week .through an early
stressing of the prestress tendons.
In the case of precast segments, the accelerated
curing of the concrete must attain two apparently
contradictor\' objectives:
1.
2.
1.
2.
3.
467
Conventional kilns.
Direct heating of forms with electric resis­
tances.
Direct heating of forms with low-pressure
steam.
The use of a conventional kiln entails several
precautions. First, a constant temperature must be
maintained in the kiln. Second, the segment sec­
tions of varying thickness are all heated to the same
temperature, which may produce unacceptable
local thermal gradients and cracking if heat curing
is excessive.' Finally, the heated segment may be
subjected to a thermal shock when removed from
the kiln, if the difference between the ambient
temperature and the kiln temperature is greater
than 60°F. However, kiln curing is a simple solu­
tion and is acceptable for long curing cycles-for
example. of 10 to 14 hours.
Form heating by means of electrical resistances is
perfectly adapted to long curing cycles. This sys­
tem permits a wide range of adjustment per zone,
varying the temperature between the thick and
thin sections of the segment and thereby minimiz­
ing thermal gradients and eliminating the risk of
permanent damage to the concrete at the begin­
ning of its solidifying phase.
The heating of forms with low-pressure stearn is
preferable for short curing cycles lasting less than
five hours, as it permits the distribution of a large
quantity of calories over a short period, causing a
rise in the internal temperature of the concrete of
the order of 20 to 30°F (10 to l5°C) per hour. This
system, however, requires a complex regulator to
ensure an equal temperature in all the form panel
enclosures, at all times during the treatment, what­
ever their thermal inertia and the external
influences to which they are subjected, Figure 11.1.
Accelerated curing to permit rapid stripping.
Final compressive strength as near as possible
tQ thaL of the design concrete.
Several curing systems may be considered:
FIGURE 11.1.
Viaducts).
Heat-curing control system (B-3 South
Technology and Construction of Segmental Bridges
468
The different systems (kiln, electrical resistances,
and low-pressure steam) have all been applied suc­
cessfully to segmental bridges. The segments for
the Choisy-Ie-Roi and Courbevoie bridges were
kiln cured. Electric heating was adopted for the
construction of the upstream and downstream
bridges on the Paris Ring Road and the Blois
Rridge. among others. Form heating using low­
pressure steam was used for the Pierre Benite
Bridges. the Oleron Viaduct. and the B-3 South
\'iad ucts.
Whether forms are heated bv electricity or bv
steam, it is relatively easy to produce a long curing
ocle, and the desired final concrete strength is
easih' ohtained. A short curing cycle, on the other
hand, reguires a great deal of caution and meticu­
lous preliminary calculations. Particular attention
must be given to:
I.
2.
3.
Choosing a cement, the performance of which
is adapted to the accelerated curing of concrete
(preferred is artificial Portland cement with:
C"A ~ II (If and C: I S/C 2S ~ 3).
Consistently manufacturing concrete with a
minimum water content and a maximum tem­
perature ol9S"F (35°C) at the time of pouring.
Using sufficiently rigid forms to resist the
thermal expansion of the concrete in its plastic
state while heating.
212
In order to avoid a drop in the long-term me­
chanical properties of the concrete. the tempera­
ture curve during the heat curing must necessarily
include. see Figure 11.2:
An initial curing period of two to three hours,
during which the concrete is kept at the ambient
temperature
An increase in temperature at a low rate of less
than 36°F (200C) per hour
A period (depending upon the concrete strength
be attained) during which the temperature is
held constant and below 150°F (65°C)
to
A period during which the concrete is cooled at a
rate similar to that used for the temperature in­
crease
The loss of strength
greater:
III
If the initial curing period is short
It' the temperature increase is rapid
II the lIJaximum telllperature is high
As an example, the short-cycle treatment used
lor the B-3 Viaduct segments was the following,
see Figure 11.3:
Initial period of H hour at 95°F (35°C) (mixing
temperature)
PREHEATING ALTERNATIVE
95­
65-1---­
'-v--I~ '-----r----I\'---~.,------il
INITIAL TEMPERATURE
CONSTANT
CURING
INCREASE
TEMPERATURE
PERIOD
FIGURE 11,2.
the long term will be
COOLING
Heat-treatment cycle.
Concrete and Formwork for Segmental Construction
11.2.4
SHORT CYCLE
GO F
LONG CYCLE
f'1---- r--_
11.0'
FIGURE 11.3.
Example of shl-H·t and long cycles.
Temperature increase of 27°F (l5°C) per hour for
2 hours
A constant temperature of IS0°F (65°C) for H
hours
Figure 11.3 shows an example of long-cycle heat
treatment, the Conflans Bridge, which had a total
heat-treatment duration of 19 hours.
11.2.3
DI.HE.YSIOXAL TOLERAA'CES
Formwork that produces typical bridge box girder
segments within the following tolerances is consid­
ered to be of good quality~·4:
Width of web
Depth of bottom slab
Depth of top slab
Overall depth of segment
Overall width of segment
Length of match-cast segment
Diaphragm dimensions
FORMH'ORK FOR SEGMENTAL
CONSTRUCTION
Formwork along with its supports and foundations
must be designed to safely support all loads that
might be applied without undesired deformations
or settlements. Soil stabilization of the foundation
may be required.
Since economical production of cast-in-place or
precast segments is based on repetitive use of the
same forms as much as possible, the formwork
must be sturdy and special attention must be given
to construction details. Where form work is to be
assembled by persons other than the manufacturer
or his representatives, particular care must be
taken with erection details and assembly instruc­
tions. All elements of the formwork must be easy to
handle. 1.2
Formwork for structures of variable geometry
will need to be relatively flexible in order to allow
adaptation at the various joints. Both external and
internal forms are usually retractable in order to
leave a free working space for placing reinforcing
steel and prestressing ducts. 3
Special consideration must be given to those
parts of the forms that have variable dimensions.
To facilitate alignment or adjustment, special
equipment such as turnbuckles, prefitted wedges,
screws, or hydraulic jacks should be provided.
Tendon anchors and inserts must be designed in
such a way that they remain rigidly in position
during casting. Projecting anchorage blocks or
other such irregularities should be detailed to
permit easy form stripping. 3
If accelerated steam curing with temperatures of
the order of 130°F (55°C) is to be used, then the
deformations of the forms caused by heating and
cooling must be considered in order to prevent
cracking of the voung concrete.
In general, internal vibration using needle vi­
brators should always be applied. External vibra­
tors, if used, must be attached at locations that will
::d in.
+! in.
to 0 in.
±t in.
±~ of depth
with t in. min.
±iooo of width
with t in. min.
Hl.
±~
469
in.
10 mm)
(+ 10 mm to 0 mm)
(±S mm)
(5 mm min.)
{5 mm min.}
(±S mm)
(± 10 mm)
470
Technology and Construction of Segmental Bridges
achieve maximum efficiency of consolidation and
permit easy replacement in the case of a break­
down during casting operations. External vibration
may lead to f~ltigue failure in welded joints, and
regular inspection should be made to help prevent
am sudden failure of this kind. 3
Paste leakage through formwork joints must be
prevented by suitable design of joint seals. Nor­
mally this can be achieved by using a flexible seal­
ing material. This is particularly important at the
joint face with the matching segment, where loss of
cement paste can lead to poorlv formed joint sur­
faces and subsequent spalIing and loss of matching,
requiring repair. Special attention must be given to
the junction of tendon sheathing with the forms. 3 • 4
All form surfaces, especially welded joints in con­
tact with the concrete, must be perfectly smooth
and free from reentrant areas, pitting, or other
discontinuities, which could entrap small volumes
of UlllCl'ete and lead to spalling during form strip­
ping. 3
11.3
Ducts must have sufficient grouting inlets, shut­
off valves, and drains to allow proper grouting and
to avoid accumulation of water during storage.
Vent pipes should not be spaced more tha'J1 ap­
proximately 400 ft (120 m) apart. 7 This spacing
may have to be reduced, depending upon the ex­
pertise of the personnel performing the grouting.
Particular attention must be paid to the quality
of duct connections at the joints between segments.
At the joints, accurate placing is mandatory. The
method of duct connection depends on the type of
joint 3:
Telescopic sleeves pushed over projecting ducts
-wide joints
Screw-on type sleeves-wide joints
Internal rubber or plastic sleeves-malch-cast
joints
Gaskets or other special seals-match-cast joints'
No special provisions: clean ducts with a torpedo
after jointing to remove penetrated epoxv if
any-match-cast joints
Post-Tensioning Materials and Operations
11.3.1
CEA'ERAL
Techllical details relating to the different methods
available are described in the various post­
tensioning manuals 5 •6 and in the specific docu­
ments issued by su ppliers.
113.2
DUCTS
Ducts are used to form the holes or enclose the
space in which the prestressing tendons are lo­
cated. The ducts may be located inside or outside
the concrete section.
Although in some instances the tendons are
placed in the ducts before concreting (cast-in-place
and span-by-span construction), post-tensioning
tendons will normally be threaded into the ducts
after erection of the segments. The' duct cross
section must, therefore, be adequate to allow
proper threading; and in general it will be about t
in. (5 mm) larger in any direction than for ducts in
which the tendons are placed before concreting.
The duct dimension must allow not only the in­
stallation of the tendons but also free passage of
grout materials after stressing. The ratio or pro­
portion of cross-sectional area of the duct with re­
spect to the net area of prestressing steel should
conform to appropriate specifications or codes. 4 A
minimum value of 2 usually leads to satisfactory re­
sults.
Connection tightness is essential in order to pre­
vent penetration of joint material, water, or other
liquids or solids into the ducts, which would intro­
duce a risk of blockage, and also to prevent leakage
at the joint during tendon grouting operations. 3
,
11 33
TENDOlv' ANCHORS
Tendon anchors usually consist of a bearing plate
and an anchorage device either in combination or
as separate units. Shape and dimensions of the an­
chors must conform with the applicable specifica­
tions, particularly insofar as bearing stresses are
concerned.
Choice of anchor positions in the segments
should take into account the following considera­
tions;}:
Tendon layout requirements and installation se­
quences.
Stresses generated around the anchors.
Ease of tendon threading and stressing.
Ease of formwork preparation, stripping and con­
crete placing.
Certain anchorage positions, such as the anchorage
block on a thin slab shown in Figure 11.4, should
be avoided. If this type of detail cannot be avoided,
then particular care must be taken in design and
construction of the zone concerned.;}
,,
=
Post-Tensioning Materials and Operations
FIGURE 11.4.
.-\nchoragc
block
position
to
be
avoided.
Bearing plates are usually emhedded in the seg­
ment at the time of casting. In certain cases they
are installed against the hardened surface of the
concrete with a dry mortar bed or a suitable cush­
ioning material such as asbestos cement or syn­
thetic resin.
11.3.4
Construction sequence with respect to tendon
placing. segment casting (or erection), and other
construction imperat.ives
Standardization and repetition of essential fea­
tures, especialh· duct and anchor positions at joints
(in order to facilitate formwork design)
Various loading conditions throughout the con­
struction period and in service
When using large tendons. it is not advisable to
couplers or crossed splices. for reasons of con­
gestion and formwork complication. Also, couplers
and splices should not be located in areas where
yielding mav occur under ultimate load condi­
tions. 3
I n order to limit friction losses, and to facilitate
tendon threading. excessively curved tendons
should be avoided if possible.
u~e
Il.3.5
struction under ordinary working conditions and
supervision. The actual results obtained in a seg­
mental bridge built in Europe are given below by
way of example for the benefit of future project
designers.
Cantilever tendons were placed along a straight
profile in the roadway slab and anchored either on
the segment face or in a block-out inside the box
girder. Continuity tendons were either anchored
in a block-out at the bottom slab level or draped
upward in the webs and anchored in the same
block-out of the cantilever tendons. All tendons
were made up of twelve 0.6 in. diameter strands.
Soluble oil for reducing friction in the ducts was
not allowed by the consultant. The calculations
were carried out using the following values for
curvature and wobble friction coefficients:
TEVDON LAYOCT
This subject has been covered in Chapter 4 relating
to design. The choice of tendon layout must be
treated carefully, with special attention paid to the
following factors:
FRICTION LOSSES LV PRESTRESSI.VG
TE,VDOSS
Segmental construction usually calls for prestress­
ing tendons to be installed through a succession of
short duct lengths coupled to one another at the
joints between segments, these being at approxi­
mately 8 to 30 ft (2.5 to 10 m) intervals.
The friction factors (for curvature and wobble)
usually accepted for long tendons in cast-in-place
structures may not be realistic for this type of con­
471
f.L
0.20,
K
= 0.007/ft
0.0021/m
The Young's modulus of the tendon samples
tested in the factory or in the laboratory varied
between 28,000 and 29,000 ksi, and the variation
between various heats over the whole structure was
very low. According to direct tests carried out on
site, and a systematic analysis of all results of ten­
don elongations recorded during the stressing op­
eration, the actual Young's modulus of a (twelve
0.6 in. diameter strand) tendon at first tensioning
varied between 25,000 and 26,000 ksi, which is
only 90% of the value recorded during factory and
laboratory tests.
Figures 11.5 and 11.6 show values of the wobble
friction coefficient K measured for all the tendons
in the structure's 18 cantilevers. All the tendons are
shown in Figure 11.5, while Figure 11.6 shows only
those tendons in the spans without hinges. and
separates the tendons anchored on the segment
face from those anchored in block-outs (the ten­
dons had the same lavout except a rather severe
curvature at the end). It is obvious that:
1.
2.
3.
As construction proceeded and the quality of
manufacture and supervision improved, the
results got better.
At the beginning of the job, the effect of the
curved ends of certain tendons was lost in the
generally mediocre results. As these results got
better (value of K equal to that used in calcula­
tion from cantilever lIon), this effect became
preponderant, counteracting that of the im­
proved standard of work.
As the site staff became accustomed to the
work and the effort and supervision dropped,
the results became gradually worse (compare
cantilevers 13 and 17, for example).
472
Technology and Construction of Segmental Bridges
3+--------------­
2+-----------~-
+------~~----"~-"
;tV\
-+­
5
6
7 8
9 10 11 12 13 1" 15 16 17 18
CANTILEVER
2
3
"
FIGURE 11.5. Prcstressing in <I (;lIllilen'r IJridg(·. \'arialiol) of \wlJlJic frinioll
(oclliciclIt for clIlIiin'cr tendons ill each of file SlnlClUlC\ Ix spall;',
3
+----<~------ -----,--,~~~
2
+-~.__~..,....-__\---_T_ENDONS
ANCHORED
nO
IN
BLOCK - OUTS
TENDONS ANCHORE_~. It..T __
THE
SEGMENT
FACE
2
3
S
7
9
11
13
1S
I
I
17
18
CANTILEVER
FIGURE 11.6. Prestressing in a cantilever bridge. Wobble friction coefficient for can­
tilever tendons in the 10 spans without hinges.
As an example, a straight tendon in the top slab
fillet between slab and web was isolated. The wob­
ble friction coefficient depends on the care exer­
cised in fastening the duct to the reinforcing steel
cage as the concrete is poured (when the tendon is
in the slab rather than in the fillet, the accidental
deviations are much smaller). For the first seven
cantilevers (see Figure 11.7) the wobble coefficient
Post- Tensioning Materials and Operations
II')
-
I
I
FL EXI f3LE.
0...­
)(
:::t:.
RIGID
T
DUCT
3
473
­
DUCT
I­
Z
W
c,:?
lJ...
lJ...
w 2
0
()
z
Q
I­
~
a::
lJ... 1
W
...J
CO
OJ
~
2
3
"
5
6
e
9
10
11
12
13
1~
15 16
17 1!
FIGURE 11.7. Prestressing in a cantilever bridge. Wobble friction coefficient for a
'itraight tendon locat.cd in the upper fillet.
reached up to six times the assumed value used in
the calculations, and yet very careful construction
will enable this assumed value to be reached or at
least approached closely to obtain the desired pre­
stress with little room for uncertainty.
Th~ presence of hinged segments not only com­
plicates the tendon profile and the construction
phases, but introduces uncertainty about obtaining
the required prestress force. Owing to the techni­
cal restrictions imposed by the consultant, the tra­
ditional prestress layout employed in earlier
bridges could not be used. Consequently, long ten­
dons stressed only at the opposite end had to be
accepted. It was thought that a realistic value of the
final force for each of the tendons (twelve 0.6 in.
diameter strand) would be 350 kips (160 mt). It is
474
Technology and Construction of Segmental Bridges
fortunate that a direct check was made at the site,
which revealed the actual initial load at transfer to
be the following for the four tendons under con­
sideration: 130 kips (60 mt), 210 kips (96 mt), 130
kips (60 mt), and 200 kips (90 mt). The average
initial prestress load per tendon was therefore 170
kips (i8 ml), and the probable final force would
ha\'e been 150 kips (70 mt) as compared to the as­
sumed \'alue of 350 kips (160 mt). Fortunateh', the
situation could be easily corrected and remedial
measures put into effect as follows:
1.
:2.
The reinforcing steel and local prestressing
tendons allowed for a certain margin of safety.
11 was possible to restress t\\'o of the four cables
in the flrst cantilever and then to change the
profile and method of placing segments in
order to stress all the tendons at both ends for
the rest of the cantilevers.
'rhe above results, quoted rigoroush· so as to il­
lustrate se\'eral important aspens of friction losses,
must not lead the reader to suppose that the safety
of the structure was at any time compromised. The
force ill a tendon \'aries much more slowly than
any changes in the friction coefficients for ordinary
tendon profiles. For example, in a 270 it (80 m)
tendon stressed at both ends, if the friction
coefficients are multiplied by 4, the minimum force
in the tendon is reduced by only 16%.
It is interesting to examine the results for the
actual prestress obtained in cantilevers 2 and 3 (the
ones having the worst results) shown in Figure 11.8
for each section, compared with the prestress used
in the calculations. The lack of prestress, most
marked at midspan, was compensated by addi­
tional tendons to bring the force back up to that
required by the calculations in the first two spans.
Afterward, the Ol;jginally calculated prestress was
always sufficient.
To summarize, the authors wish to underline the
following points:
I.
2.
Bench tests should be performed on site to
determine a realistic value of the modulus of
elasticity of the tendons to be used 1.0 compute
the theoretical tendon elongations.
Realistic values of curvature and wobble fric­
tion coefficients should be used in the design
and further controlled on site. Direct friction
tests should be made together with a statistical
analysis of the measured elongations for all
tendons.
r----------.-.---- --------.----------------,
SUPPORT
\cXXl
0950
0.900
0.650
3
FIGURE 11.8.
Prestressing in a cantilever bridge. Effecti\'e prestress in spans 2 and 3.
Segment Fabrication for Cast-in-Place Cantilever Construction
3.
Provisions should be made at the design stage
for additional prestress to compensate for any
unexpected reduction in the design prestress
force due to excessive friction. This may be
done as follows:
a. By adding additional ducts over and above
the number required by design calcula­
tions; if this method is used, the unused
ducts at the end of construction must be
grouted to prevent water from seeping in­
side and subsequently freezing with disas­
trous effects on the structure.
b. By using larger than required sizes for
some of the ducts, so as to allow the use of
larger-capacity tendons if required.
c. By providing anchor blocks and possible
deviation saddles so as to allow the instal­
lation of external tendons located inside
the box girder but outside the concrete
section.
[f the correct approach is taken at the concep­
tion stage, perfect con trol of this aspect of prestress
rnav be obtained and very satisfactory structures
can be built that give maintenance-free long-term
performance.
I
"
II.J.6
..
used because it increases the moisture content of
the air and reduces the natural corrosion protec­
tion.
Another important and sometimes acute prob­
lem relates to potential grout leakage at segment
joints, which can lead to the passing of grout from
one duct to another. For this reason ducts must be
well connected and sealed at joints. To check the
grout tightness of the joints and to avoid blockages,
it is advisable to flush the ducts with water under
pressure before grouting. Any leakage points thus
detected may then be sealed. If communication is
discovered' between tendon ducts, the tendon
groups affected should be grouted in one opera­
tion after threading and stressing of all the tendons
involved. 3
If couplers are being used (notably for single-bar
tendons), precautions must be taken to limit the
risk of grout blockage at the coupling points.
Couplers must be housed in special enlarged en­
closures with two essential features:!:
1.
'
2.
Clear cross-sectional area for the passage of
grout equal to or greater than that for the rest
of the tendon.
Independent grout inlets and vent pipes.
GROLTI:VC
As in conventional post-tensioned structures, seg­
mental construction requires the grouting of pre­
stressing tendons after tensioning to provide cor­
rosion protection and to develop bond between the
tendon and the surrounding concrete. Current
recommendations and provisions of good practice
are therefore applicable to segmental bridges.
However, several important points need to be ex­
amined.
Grouting must not be carried out if the temper­
ature in the ducts is less than 35°F (2°C) or if the
surrounding concrete temperature is less than
32°F (2"C). This requirement virtuallv precludes
grouting operations during the winter months in
the northern and middle western United States,
unless very special winter precautions are used. It
is preferable to postpone all grouting operations
until the following spring, even though some ten­
dons may be left tensioned and ungrouted for a
long period. Attention must then be given to cor­
rosion protection of the high-tensile steel bars or
strands. Satisfactory protection is obtained by seal­
ing all tendon ducts at both ends after blowing out
with cool compressed air. Hot air should not be
475
11.3.7
USBONDED TESDONS
Unbonded tendons may be used in segmental con­
struction provided that the performance require­
ments of the post-tensioning steel are also met by
the tendon anchorage, notably with respect to
fatigue characteristics. In unbonded post-ten­
sioning a corrosion protection system must be
provided to guarantee at least the same degree of
corrosion protection as for bonded tensioning.
This may be achieved by enclosing the tendons in
flexible ducts (such as polyethylene pipes) and by
cement grouting after tensioning.
11.4
Segment Fabrication for Cast-in-Place
Cantilever Construction
11.4.1
CONVENTIONAL TR::lVELERS
The conventional form traveler supports the
weight of fresh concrete of the new segment by
means of longitudinal beams extending out in can­
tilever from the last segment in order to support
the forms and service walkways.
I
:1
476
Technology and Construction of Segmental Bridges
Form Travelers with Top Main Beams (Figure
2.83) The longitudinal main beams or girders are
usually located above the segment to be concreted,
in line with the webs. The outside forms, the bot­
tom forms, the work floor, and the service walk­
ways are hung from the main beams with the help
of cross beams. The inside forms are supported on
a trolley, which travels inside the deck.
The main beams are anchored to the previous
segment. In order to maintain stabilitv during the
pouring operation a counterweight is sometimes
used to reduce the uplift forces applied to the con­
crete section. When the traveler is transported to
its new position ready for the next segment, the
counterweight keeps it in balance between two suc­
cessive anchoring positions. The main beams that
suppon the load due to concrete, forms, walkways,
and so on are often subject to large deflections,
which can give rise to transverse cracking along the
joints between segments. These cracks appear at
the upper face of the bottom slab and at the con­
nection between web and top slab. This undesir­
able condition can be avoided by using a rigid
structure; the weight of the traveler is increased
together with the prestress required in the can­
tilevers. The form traveler used for the Oissel
Bridge weighed 120 tons (110 mt) and may be considered as a heavy form traveler.
.
If the travelers are light, care must be taken to
compensate deflections during concreting by ad­
justing jacks. This type of traveler weighs (exclud­
ing counterweight) a little less than half the
maximum concrete segment weight. An example
of a light form traveler is shown in Figure 11.9 for
the Tourville Bridge. Each traveler weighs 33 tons
(30 mt).
Form Travelers with Lateral Main Beams (Figure
11.10) Travelers with their main beams above the
bridge deck present the disadvantage of hindering
the construction operation concerning the upper
part of the segment. For this reason ·certain form
travelers have their main beams disposed laterally
parallel to the outside webs, underneath the bridge
deck. This solution leaves a clear working surface
and allows easy access to all surfaces to be formed,
reinforced, and concreted. In this way, the tech­
nology originally developed for precast segmental
construction can be applied to cast-in-place can­
tilever methods, resulting in shorter construction
cycles. The Moulin-Ies-Metz Bridge in eastern
France, Figure 11.1 I, was constructed using this
type of form traveler.
FIGURE 11.9.
eler.
11.4.2
Tourville-la-Riviere Bridge form trav­
SELF·SUPPORTING MOBILE FORAHV()RK
I n the case of traditional form travelers, the re­
sulting deflections seen during construction are
almost entirely due to the main beams. The
formwork as such IJ.sually acts only as a mold and
does not support any part of the total load, even
though it comprises very stiff walls.
In several recent bridges the traveler concept has
been modified so as to use the rigid form work as
the weight-carrying member, thus producing a
self-supporting rigid mold. Several advantages are
gained with this concept:
Surveying control and correction of bridge deck
geometry are easily obtained.
Cracking near the joints caused by the deflection of
conventional travelers is completely eliminated.
The work area is maintained completely free and
allows prefabricated reinforcing steel cages to be
used as in precast segmental construction.
This type of mobile formwork was first used for
constant-inertia bridge decks such as the Kennedy
Bridge, Dijon, and the Canadians Interchange in
Paris, Figure 11.12.
During the concreting operations, the mobile
formwork is prestressed to the existing deck. The
exact positioning of the formwork is obtained by
Segment Fabrication for Cast-in-Place Cantilever Construction
477
, _ CONCRETI NG PHASE
Rear support
Horizontal
'\
Pre5tre!>sed suspension /
rod!>
restress
Self su
form
2_ LAUNCHING PHASE
LIpunq
t'
"
I ey
..rOI
I
..
!
I
i
•
Vi I'\J
I
FIGL'RE 11.10.
FIGURE 11.11.
rypical form traveler with lateral main beams,
\Ioulins-les-\Ietz form traveler.
FIGURE 11.12. Canadians Viaduct (Paris), VIew of
form traveler in operation.
means of adjusting pins located at the rear in res­
ervations provided in the previously poured seg­
ments. The formwork is transported to its new po­
sition, ready for the next segment, on an overhead
trolley, which travels along short steel girders can­
tilevered out from the existing hardened concrete
in line with the webs.
A further refinement was to use pretensioned
reinforcing to add to the stability of the traveler
while pouring the segment. Figure 11.13 shows the
arrangement for the Canadians Viaduct in Paris,
France. Monostrands located in the webs are provi­
sionally anchored to the front of the traveler and
embedded in the webs of the concrete segments to
be incorporated in the reinforcement of the per­
manent structure.
The use of the self-supporting mobile formwork
was later extended to variable-depth bridge decks
478
Technology and Construction of Segmental Bridges
Is
fA
/l.JpperB~ar.Fixa1ion
1
i
I
Pre$tres$ Tendons ( 12 xO 6")
!
SIng 1~2t~and~~
(4x06~)
I
~
l§
SECTION B.B
SECTION A.A
. Uppe r Fiulio ns
"
Single
FIGURE 11.13.
~.!rands
Canadiam Viaduct
(Pari~).
as well as three-web cross sections, as in the Clichy,
Orleans, and Gennevilliers Bridges.
The structural members of the mobile formwork
are therefore the side forms of the exterior face of
the outside webs and the bottom forms of the
underside of the bottom slab, both of which are
stiffened transversely by front and rear frames
braced together for additional rigidity, Figure
11.14. In this manner a rigid box is formed, which
is prestressed to the existing deck. The change of
section height is achieved by vertical displacement
of the bottom forms, which are fastened to the
front stiffening framework and bottom slab of the
last segment.
The stability of the self-supporting mobile forms I
of the Gennevilliers Bridge was ensured by (Figure
11.15):
l.
2.
/
Two steel pins fixed to the top of. the outside
forms and matching imprints provided on the
outside face of the previous segment, the con­
nection being assured by high-strength bars
going through each web.
Two steel pins fixed to the upper surface of the
bottom forms and matching the corresponding
imprints provided in the last segment bottom
slab, again held by prestress bars.
The self-weight of the mobile forms and the fresh
concrete creates an overturning moment, which is
details of the self-supporting form Ira\'eler.
balanced by two forces F sustained by the previ­
ously described locating pins. Practically all the
shear force is taken by the upper pins. Because of
the large forces transmitted through the top pins
to the concrete, precast concrete elements are used
to avoid the transmission of high stresses to young
concrete, Figure 11.i6. These forces are transmit­
ted by friction between pin and concrete, and this
determines the necessary prestress force.
11.4.3
TWO-STAGE CASTING
The method of two-stage casting involves, first, the
fabrication of the bottom slab and the webs to­
gether with a small part of the top slab in order to
create a flange in which all or some of the can­
tilever tendons can be located. This operation, car­
ried out using a conventional form traveler, pro­
duces either a U-shaped or a W-shaped section,
depending on the number of webs, Figure 11.17.
After the cantilever tendons are stressed the form
traveler is moved to the next position, the top is
poured using a mobile formwork of relatively sim­
ple design. This second stage usually follows the
first with a minimum interval of two or three seg­
ments, and concrete can be placed in a simple pour
over the length of several segments.
This method has the advantage of reducing the
concrete volume to be supported by the form
traveler, thus reducing the weight of the traveler.
Segment Fabrication for Cast-in-Place Cantilever Construction
479
SII/{ suppllrtin
IIXtirior
Hobll,
truss
Bottom
FIGURE 11.14. Self-supporting mobile forms for \;ll'iable-depth bridge decks.
Concreting. (/I) ~IO\il1g forward.
In addition, the second stage is independent with
respect to the first and so is no longer on the critical
path of concreting operations.
The bridge decks of the Saint Isidore and Mag­
nan Viaducts on the Nizza A-8 bypass were con­
structed using this method. All of the 130ft (40 m)
spans of the Saint Isidore Viaduct were completed
for stage one only, including closure to the pre­
ceding> span, before the second stage was com­
pleted, using mobile formwork which rolled along
the bottom slab from one abutment to the other.
As regards the Magnan Viaduct, the second stage
followed the first with an interval or three seg­
(a)
ments, because of the long spans in this structure.
The same procedure was used for the Clichv,Join­
ville, and Woippy Bridges, Figure 11.18.
11.4.4
COAtBINATlON OF PRECAST WEBS WITH
CAST-IN-PLACE FLANGES
The preceding methods allowed a considerable re­
duction in the construction cycle. Two pairs of
segments could thus be completed every week, cor­
responding to an average rate of construction of 7
to 10 ft (2 to 3 m) per working day.
MOBILE
FIGURE 11.15.
FORM - STABILITY
Stabililv of the GellllC\illiers Bridge self-supporting lllobile forms.
PRECAST
JOIN T
Prestressing
FIGURE 11.16.
Precast gusset for GelllJ(.'\·ilJiers Bridge.
/
st
\ U' SECTION - 1
FIGURE 11.17.
480
STAGE
Two-stage construction of a two-web bridge deck.
bars
Segment Fabrication jor Cast-in-Place Cantilever Construction
_~a_'"':......... ~_--:::--~_ _ ~~_~~~ __
-
--
-
-~- _
-
481
~.-
~
FIGURE 11.18. \voippy Viaduct, France. Detail of the
self supporting form traveler and two-stage casting.
The main obstacle preventing further reduction
in the construction cycle and therefore a closer ap­
proach to the speed of precast segmental construc­
tion is the lack of strength of young concrete and
the consequent interference with stressing opera­
tions. Apart from several other methods already
discussed, the problem can be partially overcome
bv using precast end blocks or precast webs or
both. This was first tried for the construction of the
Brotonne Viaduct approach spans. Figure 11.19.
The webs, which were rather thin and heavily in­
clined, were precast in pairs and pretensioned.
Figure 11.20.
The deck was cantilevered out from the piers
using 10 ft (3 m) long segments assembled in two
phases. In the first phase. the precast webs weigh­
ing up to 18 tons (16 mt) were placed inside the
·form traveler, previously adjusted to the bridge
profile including the desired camber. The webs
were then prestressed to the preceding segment
with provisional prestress bars, the joint being
FIGURE 11.19.
rier.
Brotonne Bridge, mobile form car­
match-cast or cast in place. The second phase con­
sisted of casting the rest of the segment inside the
form traveler. which was now suspended from the
newly stressed webs.
This procedure, which requires partial prefabri­
cation of the segments using light casting equip­
ment, enables a considerable simplification of the
form traveling equipment, the limitation of total
weight to 39 tons (35 mt), and a reduction in the
construction cycle such as to produce, even for a
cable-stayed bridge, as many as four segments per
week for each pair of form travelers.
COUPLER FOR
\TENSION RODS
36 mm dia TENSION RODS
STEEL FORMS
7
DISTRI BUTION
BEAM
\
ADJUSTABLE
BRACKETS
BRACKETS
SOFFIT
BED FOR PRETENSION ED WEBS
FIGURE 11.20.
Brotonne Bridge, precasting of webs.
CASTING BED
482
Technolog), and Construction of Segmental Bridges
During construction of the Brotonne cable­
stayed bridge, the precast wehs were placed hy
tower crane traveling parallel to the bridge deck
above the river banks and by an overhead gantry
crane above the Seine River.
Another example of the use of precast webs is
found in the Clichy Bridge carrying the met­
ropolitan line over the Seine in the northwest of
Paris. The bridge deck with a 280 ft (85 m)
maximum span consists of a three-web box girder
without cantilever flanges and with the deck sup­
porting the live loads as low as possible in order to
reduce the length of the access ramps to the struc­
ture. The 8 ft (2.5 m) long segments were also con­
SI ructed in two stages, Figure 11.21.
The precast wehs, with epoxy match-cast joints,
are placed with the aid of a mobile handling system
rolling along the webs of the previously placed
segments. They are then prestressed 10 the existing
structure before the lOp and bottom slabs are
poured in place on the length of two segments.
11.4.5
PRACTICAL PROBLEMS IN CAST-IN-PLACE
CONSTRUCTlON CAMBER CONTROL
Before proceeding with the cantilever construction
proper, a starting base must first be completed on
the various piers. This first special segment, called
a pier segment or a pier table, is generally con­
structed on a temporary platform anchored by
FIGURE 11.21. Precast web placing equipment for
Clichy Bridge carrying the metropolitan line over the
Seine River.
E ~EV!~TlON
SECTION
7·
~/
J;
1:
nOll \
\
FIGURE 11.22.
Con~truClioll
of the pier segment for
a cast-in-place camile\'cr deck.
prestressing the pier top, Figure 11.22. This spe­
cial segment may either be given the minimum
length to insure adequate connection to the pier
for the stability of the future cantilever or else be of
such length as to allow both travelers to be installed
simultaneously, Figure 11,23.
Another important problem relates to the safety
of the travelers during construction. Chapter 4 de­
scribed the difficulties of ensuring pier safety in
the event a form traveler fell during transfer from
one position to the next. The difficulties would
even be greater in the event of an accident during
the casting operation. Consequently, all precau­
tions must be taken both at the design stage and
during construction to eliminate this potential
hazard. The load-carrying members of the traveler
must be carefully inspected and may even be load
tested before use so as to practically eliminate the
danger of structural failure.
The most critical areas are in the safety of the
suspension rods and the transfer of the traveler
reactions to the concrete. Preferably all suspension
rods and anchor bars should be doubled. Also, the
prestressing tendons must have an adequate mar­
gin of safety. Use of a single strand or a single bar
in each web of the box should be avoided. Rather a
multistrand tendon with individual anchors for
each strand or two prestress bars should be used.
Worldwide use of cast-in-place cantilever con­
struction has established an extremely good safety
record, much better than that for cast-in-place con­
struction on falsework. Accidents are very few and
far between; however, designers and constructors
must always be safety conscious.
Segment Fabrication for Cast-in-Place Cantilever Construction
3.
4.
5.
FIGURE 11.23_ Start of GlIltiIever construction from
the pier segment. (a) Short pieI- segment
succeSSIve
installatioll of tr;l\-elers. [iJ} Long pier segment
'-siIllultaneous installatiolJ of travelers.
The most critical practical problem of cast-in­
place construction is deflection control, partic­
ularly for long-span structures. There are five
categories of deflections (or space geometrical
movements of the structure) during construction
and after completion:
Deflection of the travelers under the weight of
the concrete segment. This value is given by
the manufacturer or may be computed and
checked at the site during the first operations.
2. Deflection of the concrete cantilever arms
,during construction. For each casting of a pair
of segments, the weight of the concrete seg­
ments and the corresponding cantilever pre­
1.
483
stress forces impose upon the cantilever a new
deflection curve.
Deflections of the various cantilever arms after
construction and after removal of the travelers
before continuity is achieved with the other
parts of the deck.
Short- and long-term deflections of the con­
tinuous structure, including the effect of
superimposed dead loads (curbs, railings,
pavements, utilities, and so on) and live loads.
Short- and long-term pier shortenings and
foundation settlements.
Using the data available on concrete properties
and foundation conditions, the designer should
compute the various deflections mentioned under
items 3,4, and 5 above, assuming the bridge un­
loaded for foundation settlements and long-term
concrete defltfctions and half the design live load
for computation of the short-term concrete deflec­
tions.
The sum of the various deflection values ob­
tained in the successive sections of the dcck allows
the construction of a camber diagram, which
should be added to the theoretical longitudinal
profile of the bridge to determine for each can­
tilever arm an adequate casting cUrve. This casting
curve is the goal toward which construction pro­
ceeds during cantilever casting. The essential
difficulty is that no absolute coordinates are avail­
able in a system where everything changes at each
construction stage (transfer of traveler, concrete
casting, or cantilever prestressing).
A very simple example may illustrate the solu­
tion of the problem of accommodating the deflec­
tions described under item 2 above. For simplicity.
assume only a four-segment cantilever arm. for
which a horizontal longitudinal profile is required,
Figure 11.24.
As outlined in Chapter 4 and summarized briefly
above, the designer analyzes the various deflection
curves for each construction step (casting segment
and precasting). The typical results are shown in
Figure 11.24. The cumulative deflection curve is
immediately obtained together with the camber dia·
gram, Figure 11.25. The use ofthe camber diagram
for determining the adequate deflection at each con­
struction stage is simple; however, it is much less
simple to use in a proper manner in the field, and
experienced surveyors have often made mistakes.
When properly used, the camber diagram allows
the determination at each joint, of offset values
such as YI-2, Y2-:l, and YH at each point, which will
484
Technology and Constructio:: of Segmental Bridges
I
ELEVATION OF TYPICAL CANTILEVER
--­
3
NOTE
8
I)
CD
Denotes projection of deflection
curve outboard in the following joints
Downward deflection is posItive
I
CASTING AND
PRESTRESSING
SEGMENT
(0
~-~
FIGURE 11.24.
struction sLage.
B
c0
Ed:V
(-23)
1-11)
(-17)
1
5
(9)
(13)
5
10
20
130)
8
18
29
49
+9
+22
41
69
-5
CD
0
8
TOTAL
DEFLECTION
I
I
VERTICAL DEFLECTIONS (in mm)
,
.
Partial deflections due to girder weighL and prestressing at each con­
bring the traveler in the proper position to realize
the desired final geometry. The sketch and table in
Figure 11.26 show how to use the camber diagram
properly. It is very important to realize that at no
construction stage does the profile of the cantilever
coincide with either the final deflection curve or
the camber diagram.
The natural tendency would be to build up the
traveler to the required offset to make its nose fall
exactly on the camber diagram. The results of this
improper procedure are shown in detail in Figure
11.27. The bridge is built with an undesired double
curvature, particularly undesirable toward the end
of the cantilever. When the mistake is discovered, it
is usually too late to put into effect any remedial
measures, because the final shape of a cantilever
depends essentially upon the accuracy of the
geometry near the piers, where the deck is sub­
Characteristics of Precast Segments and Match-Cast Epoxy Joints
485
C;lmber curve
\
.
\
\
o
FIGURE 11.25.
camber.
Cumulative deflection curve and choice of
b.
jeeted to the highest moments and where its
detleetions have the greatest effect at midspan.
2.
11.5 Characteristics of Precast Segments and
Match-Cast Epoxy Joints
In the finished structure after hardening:
a. To ensure the watertightness of the joints,
especially in the top slab.
b.
Developed originally to allow a rapid and safe as­
sembly of precast segments at the construction site,
the technique of match casting was progressively
refined as experience was gained. We shall de­
scribe the characteristics of segments in the early
structures to further highlight the latest improve­
ments and variations of the original concept.
11.5.1
FIRST-GENER1.TION SEGMENTS
In those early structures the epoxy resin played
several important roles:
1.
During assembly before hardening:
a. To lubricate the mating surfaces while
final positioning took place.
To compensate for minor imperfections in
the match-cast surfaces.
To participate in the structural resistance
by transmitting compression and shear
forces. However, before hardening of the
epoxy resin, the joints present no shear re­
sistance whatsoever, because the epoxy
behaves like a perfect lubricant. It was
therefore necessary to provide shear keys
in each web in order to ensure the shear­
force transfer between segments. These
keys, as well as those situated in the top
slab, also allowed a very accurate assembly
of one segment with respect to another.
During assembly of the deck, some sort of tem­
porary fixation, either mechanical or by means of
prestress bars, allowed the placing equipment
(launching girder, crane, and so on) to be quickly
486
Technology and Construction of Segmental Bridges
/J
CD
i
i SEGMENT
cD
i SEGMENT
CAMBER
L .
LOADS
TOT~L
CAMBER
0
+~'
0
SEGM£NT
LO~D5
TOTAL
-13
CAMBER
0
0
LOADS
:,
10
TOTAL
8
I
0
I
I
-18
29
C
0
0
+B
+18
+ 29
0
0
a
- f
j
! .
FIGURE 11.26. Follow-up
camber diagram.
j-
or
ullloadcd without wailing for the cantilever len·
dons to be stressed.
Figure 11.28 shows how a typical first-generation
segment can be assembled to the existing structure
using a temporary apparatus'located on the top
and boltom slabs, which is used to create forces F I
and F2 which ensure the equilibrium of the new
segment at the joint.
These two forces, combined with the weight W
of the segment, give the resultant force R, which is
inclined with respect to the joint. Because of the
very small coefficient of friction of the epoxy, the
shearing component of R produced by W can
be balanced only by the vertical component of the
reaction C, which exists normal to the bottom face
of the web shear keys, Figure 11.28. The resultant
R is composed, therefore, of the oblique reaction C
supported by the shear keys and a horizontal reac­
tion N, which is responsible for securing the joint.
The axial stress distribution at the joint cross
section differs in this case from what would be ob­
--i­
+1.9
0
deflectiolls with proper' use of
tained by ordinary calculations. I t is obvious that N
is smaller than F (the sum of forces F 1 and F 2)' Let
Q' be the angle of the key support faces with respect
to the horizontal; then F
N == W tan Q', and for a
typical case of tan Q' = 0.50, F N == W 12. Consider
a segment weighing 50 tons (45 mt), temporarily
assembled by a prestress force of 100 tons (90 mt)
located in the top slab; the axial force reduction is
25 tons (23 mt)-that is, 25% of the total applied
prestress force.
If the rate of erection of the precast segments is
sufficient to ensure the positioning of four seg­
ments before the resin in the first joint has set, then
the reduction in the effective axial force in this
joint will be 100 tons (90 mt), which more or less
corresponds to one tendon of twelve! in. diameter
strands. The same conclusion would be valid when
the permanent prestressing was used to ensure the
temporary stability of the cantilever.
In conclusion, it is recommended that this re­
duction of the effective prestress force be taken
Characteristics of Precast Segments and Match-Cast Epoxy Joints
487
I!oIPROPI:R CAM9ER
SEGM£N'T
( -35)
--,--­
CAMBER
(
LOAD~
-1~
TOTAL
o
CAM8ER
UJAOS
(])
~
SEGMENT
CD
SEGMENl
(0
23)
+_.­
10TAL
0
CAMSER
--.----~
LOADS
5
TOTA ....
-8
CAM8ER
a
LOADS
6
rOTA i..
0
+
FIGURE 11.27. Follow-up of deflections with improper use of
camber diagram.
. TEMPORARY
SEGMENT
ASSEMBLY
JOINT
EOUILIBRIU~
N
(v)
F2
(b)
(a)
FIGURE 11.28. Temporary assemblv. (a) Elevation of temporary assembly. (b) Joint
equilibrium.
into· account while verifying the cantilever resis­
tance and stability. Failure to do so may result in
temporary joint opening. which is undesirable al­
though not dangerous for stability.
It is also preferable to choose the intensity and
the point of application of the forces F I and F 2 such
as to allow the axial force N to be as close as possi­
ble to the section centroidal axis, thus ensuring a
Technology and ConstructiQll of Segmental Bridges
488
nearly uniform axial stress distribution over the
total height and hence a resin film of constant
thickness.
be satisfied, however, in order that the resin cure
properk
1.
Permanent Assernbl,·; Structural Importance of Epoxy
Resins As regards 'the final prestress tendo.n pro­
files, it was shown in Chapter 4 how the resIstance
of the different cantilevers is ensured by a first
group of tendons, known as cantilever tendons,
which may be straight or curved in profile and an­
chored o~ the various segment faces. The stressing
operations remain in the critical path of construc­
tion because a new pair of segments cannot be
placed before the last pair has been stressed to the
existing cantilever, Figure 11.29.
The second grou p of tendons joins the different
cantilevers together and makes the structure CO~1tinuOllS. Thev are anchored either in block-outs m
the bottom slab or in the fillets at the junction be­
tween the top slab and the webs after upward de­
viation (0 (OP slab level.
. .
The service shear forces that act upon the Jomts
\ar" according to the type and characteristics .of
the structure. In variable-depth bridge decks WIth
draped prestressing tendons the shear stress across
the joints is usually low. In a long-span, constant­
depth bridge deck with straight tendons, howev.er,
the shear stresses at the joints can exceed 600 pSI (4
MPa), as was the case in several structures men­
tioned in Chapter 4. A bad choice, or improper
use, of the epoxy resin can be a critical factor con­
cerning the shear resistance of th~ joint:, and f.or
this reason joints of this type reqUire strIct quality
control.
In general, the different t}:pes of epoxy resins
available have final strengths substantially exceed­
ing that of concrete, so they do nOl c.o~stitute a
weak point in themselves. Several condItIons must
2.
3.
4.
Mixing the constituents III their correct· pro­
portions.
Eliminating any solvents that have a fatal effect
on the properties of the resin.
Avoiding any flexible additives, such as
thiokol, that greatly increase the deformabilitv
of the epoxy.
Mixing and applying carefully.
With respect to the last point, the surfaces to be
joined must be specially treated if the best results
are to be obtained. Comparative tests have shown
that sand blasting gives the most satisfactorv re­
sults, the surfaces being kept clean, dry, and free
from grease d Ul'ing placillg. I n damp or raim
weather alcohol is burnt on the joint surfaces t<l
eliminate surface moisture. The water present in
the concrete itself has no detrimental effect on the
performance of the resin.
It has also been established that rapid placing of
successive segments has a favorable effect on the
properties of the resin. The additional compres~i\'e
stress applied to an epoxy joint under polymerIza­
tion when the next segment is prestressed im­
proves the resin's ultimate mechanical properties.
Finally, note that in variable-height structures
the joint detailing is' such .that the joint plane is
not normal to the principal stress, especially at the
bottom slab level. The epoxy joint is then subjected
to shear forces that may be quite large and that can
cause failure of the bottom sbb in the event of
non polymerization of the epoxy resin.
In addition to the precautions taken to ensure
correct curing, one may provide against the risk of
bad results by including shear keys in the bottom
slab.
FINAL SEGMENT ASSEMBLY
J J.5.2
FIGURE 11.29.
Final segment assembly.
SECOXD-GEXERATIOX SEGMEXTS
Although the characteristics and performance of
the first structures built with match-cast joints are
not in doubt, it seems a good idea to investigate
new types of joints allowing the transmission of
shear forces without relying on the strength of
epoxy reslIls.
Second-generation segments do just this, being
equipped with interlocking keys in the top and
bottom slabs and in most of the height of the webs.
This configuration of shear keys at regular inter­
vals, which improves the behavior of joints by re­
lieving the epoxy of its structural role, has the
Characteristics of Precast Segments and Match-Cast Epoxy Joints
advantages of simplicity and safety. This type of
segment has been used with success in several
bridges, notably the Alpine Motorways, the Saint
Andre de Cubzac Bridge, and the Sallingsund
Bridge, and more recently in several structures
in the United States such as the Long Key and
Seven Mile bridges in Florida.
with properties that depend upon the type of resin
and hardener used. Three grades of epoxy resin
are commonly used, depending upon the ambient
temperature range under which the resin is to be
applied:
40 to 60°F (5 to 15°C)
60 to 75°F (15 to 25°C)
Ribs and Interior Anchorage Block, Anchorage
blocks (blisters) or stiffening ribs are currently
used inside the segments for the final longitudinal
prestress anchors. The tendons, ensuring the sta­
bility and resistance of the cantilever and placed
progressively as construction proceeds, can be an­
chored away from the joint faces, thereby render­
ing the stressing operations and the segment­
placing operations independent of one another.
The ribs and anchorage blocks are generally used
to house the temporary prestress that ensures the
provisional stability of the cantilever, thus leaving
the top slab completely free.
Bolted Ribs Despite the tensile strength of the
epoxy resin at a glued joint, no tensile resistance is
usually considered, as 'preca~t segmental structures
are nearly always totally prestressed and so no ten­
sile stresses can develop across the joint. However,
we can further improve epoxied match-cast joints
bv giving them a certain resistance to tension by
using bolted ribs, which ensure the continuity of
the longitudinal reinforcing steel, Figure 11.30.
11.5.]
EPOXY FOR JOINTS
The structural importance of the thill layer of
.epoxy resin forming the joint between two adjacent
precast segments was discussed in Section 11.5.1.
We now take a closer look at the physical and me­
chanical properties of these resins and the various
precautions to be taken to ensure satisfactory and
consistent results.
Epoxy Types Epoxy resin glues are made up
from two components: the epoxy resin and the
hardener. Mixing these two components in the
correct proportions gives a thermostable product
489
Fast-reacting epoxy
Medium-fast-reacting
epoxy
Slow-reacting epoxy
1. COLO'T The resin and the hardener must be
of clearly contrasting colors thus avoiding any con­
fusion. When properly mixed, the final product is
to be a homogeneous gray color similar to that of
concrete.
2. Shelf life of components Both components
may be stored for up to one year, provided that the
storage temperatur; is kept between 50 and 70°F
(10 and 20°C). After three months' storage it is
necessary to check that the epoxy resin shows no
sign of becoming crystalline. If it does, then special
treatment must be given to the resin, followed by
tests, before use.
3. Pot Life of the :Hixed Glue The pot life of an
epoxy resin is a measure of the time interval be­
tween the mixing of the components together and
the moment when the glue becomes no longer
workable. The workability of the glue is deter­
mined by its internal temperature, depending
upon the grade of epoxy resin employed. For a 10
Ib (5 kg) mix used on site, mixed under isothermic
conditions until an even color of mix is obtained,
the following results are required:
Workability
Limit
Temperature
Epoxy Grade
{oCe
5 to 15°C
c
(104°F)
e (104°F)
15 to 25°C
40
25 to clOoe
55 to 60°C
(131 to HO°F)
The pot life must be approximately:
Ambient Temperature
Epoxy Grade
5 to 15°C
15 to 25°C
25 to clODe
41°F
50°F
we)
( looq
40 min.
15 min.
59°F
( 15°C)
68°F
(20 o q
20 min.
15 min.
25 min.
18 min.
490
. Technology and Constructiop oj Segmental Bridges
BOLTED RIB JO INTS
FIGURE 11.30.
On site, each 10 Ib (5 kg) mix of epoxy resin must
be applied to the concrete surhlce within the pot­
life period as specified above.
f!l
the Applied Epoxy Glue The
open time of the glue is defined as the period be­
tween its application to the concrete surface and
the moment when it reaches its workability limit
temperature. Because of the much greater heat
dissipation from the thin layer [~ to ~ in. (l to 3
mm)] on the concrete surface, the applied glue
takes much longer to reach the workability limit
temperature than the mix in the pot.
4.
Opm Time
The open time must never be less than one
hour, regardless of the grade used. One measur­
ing device used to determine open time is the
Vicat's needle shown in Figure 11.31. A 1 mm layer
of epoxy glue is spread onto a steel plate. and the
stopwatch is started. The time lapsed before the
needle will penetrate only 0.5 mm into the glue
layer is defined as the open time.
5. Thixotropy This characteristic gives an in­
dication of the epoxy resin's ability to be applied to
vertical surfaces with relative ease and yet with sub­
sequent running. Thixotropy may be. measured
using Daniel's gauge, Figure 11.32. The gauge is
placed on a level surface with the gutter section
horizontal. The gutter is then filled with freshly
mixed resin and hardener and abruptly turned to
the upright position, as shown in the diagram. The
flow time relationship is recorded. The test should
be carried out at the maximum temperature for
which the resin is specified. A resin that flows less
than 30 mm in 10 minutes is suitable for applica­
tion to vertical concrete surfaces. Other testing
methods are available such as the sag flow ap­
paratus according to ASTM D2730-68.
Bolted rib joints.
Other characteristics of the epoX\' glue that may
be resred on sile are:
The angle ol internalfric/ion: The ease with which
the excess resin may be squeezed out of the joinl
when subject 10 uniform pressure.
..!'Iungf!r
300gr weight
Nf!l!'dll!' lmmt
~~
FIGURE 11.31. Open-time testing-Vicat's needle.
Characteristics of Precast Segments and Match-Cast Epoxy Joints
491
4 X 4cm
p
E
u
!£>
FIGURE 11.32. Thixotropv testing-Daniel's gauge.
Shri rz}wgl':
\1 ust be praltiLall \' nil.
Wilta absorption mtl' and solubility in water:
Maximum permissible true water absorption­
12%. Maximum permissible quantity of epoxy sol­
uble in water at 25°C (77°F)-4%.
FIGURE 11.33. Shear-resistance test.
ceptable ultimate shear stress at the interface is
1400 psi (10 MPa).
2. Shear i'vl()duhL~ The instantaneous shear
modulus (G i ) must be greater than 220,000 psi
(1500 MPa) at:
\Iinimum required value accord­
ing to :\fostells (Dl;\J 53458) on week-old 10 x 15
x 120 1ll!11 test rods is 50°C (122°F).
25°C (77°F) for grade 15 to 25°C
,\1 ahlt niw[ /Jrojil'l't iI'S
40°C (104°F) for grade 25 to 40°C
Heat resistance:
I. Shm r rf,li,I/(J1/('1' The shear resista nce of the
mixed epoxv glue is determined on rectangular
concrete test specimens with the following dimen­
sions: 1.6 x 1.6 x 6.3 in. (4 x 4 x 16 cm) with a
resin interface at 17° to the vertical, Figure 11.33.
The concrete test pieces are made from a high­
quality concrete comparable to that used in precast
segment manufaLture and are cured under water
seven days from time of casting.
After removal from the water the pieces are dab­
dried and the surfaces to be assembled are pre­
pared by shot blasting, wire b!'ushing, or other
similar methods to remove laitance. The test pieces
are then resubmerged in water for three hours,
after which they are removed and dabbed dry with
a clean cloth. The resin is then applied in a layer of
jj\ in. (2 mIll) on one surface and the test beam
clamped in an assembly that maintains a normal
pressure on the interface of 21 psi (0.15 .:vIPa). The
assembly is stored for seven days at a temperature
repre'sentative of the desired working conditions,
and then the test is carried out. The minimum ac-
15°C (59°F) for grade 5 to 15°C
The long-term shear modulus must be greater
than 14,500 psi (1000 .:vIPa) after 28 days at the
same temperatures as above. Solid cylindrical test
pieces are used for measuring these values in con­
junction with the easily made test apparatus shown
in Figure 11.34.
- Certain epoxy resins show an excessive sensitiv­
ity to high temperatures that makes them unac­
ceptable in warm climates. Figure 11.35 shows
comparative results of ten different resins tested
for the Rio Niteroi Bridge. It is obvious that a
produLt that becomes practically plastic with no
shear modulus at 60°C is completely unacceptable.
3. Tensile Bending Strength A three-point
bending test is carried out on a pair of glued con­
crete cubes with a compressive strength of 5700 psi
(400 kg/cm 2 ), Figure 11.36. The faces to be glued
are shot blasted, or bush hammered, so as to re­
move laitance. The cubes are then submerged in
water for 72 hours. When taken out of the water
the surfaces to be glued are dried simply by dab­
bing with a clean cloth. Immediately after the dab
Technology and Construction of Segmental Bridges
492
Dial
X....J
vi~
X-X
Vie-w from one- side-
FIGURE 11.34. Shear-modulus test.
2500
2000
1500
1000
500
o
~---------L--------~--------~------~~----~--~t('C)
20
30
FIGURE 11.35.
40
50
60
70
\'al-iatioll of shear l1]odulus G wit h tcmpcrature.
drying the glue is applied in a layer of II,; in. (1.5
mm) to one of the prepared faces. The corre­
sponding face of the other cure is placed against
the glue layer, and the two cubes are clamped to­
gether with a clamping force of 300 Ib (150 kg).
The assembly is then wrapped in a damp cloth,
which must be kept wet until the three-point
bending test is carried out.
4. Compressive
Strength The
compressive
strength is determined according to DIN I I 64 on 4
cm (H in.) cubes of cured epoxy glue. After 24
hours (from the time of preparing the samples) at
the maximum temperatures for each grade the
compressive strength must be not less than 12,000
psi (SO MPa). The loading rate is to be approxi­
mately 3600 psi (25 MPa) per minute.
5. Elastic modulus in compression The instan­
taneous modulus (E j ) is determined on cubes of
pure epoxy after curing for seven days at the
maximum group temperature. These cubes are the
same size as those used for the compressive·
strength determinations. The modulus must not be
less than 1,140,000 psi (7850 \IPa)
Prartical u.\(' of E/JOx)' ill Malch·Cast joillfl III
regard to the me of the resin, the two compo­
nents should be mixed carefully and quickly as
near as possible to the surfaces to be coated. Under
no circumstances should oil or grease be allowed to
come into contact with surfaces that are to be
glued. Most standard de molding agents are suita­
ble for use, but care should be taken to ensure that
no oil-based de molders are used. Exposure to
weather during the storage period is often
sufficient to remove the demolding agent. For best
results, surface laitance should be removed by shot
blasting or bush hammering. This treatment is
normally carried out in the storage yard. With the
use of multiple keys, the structural role of the
I
!
=
=
Manufacture of Precast Segments
Loa~ied
493
here
EPOXY JOINT
FIGURE 11.36.
Tensile bending-strength test.
epoxy is considerably reduced and a special prepa­
ration of the Sli rbce is' not a mandatory feature.
lmmediatelv before the glue is applied, the sur­
faces are to be cleaned to remove traces of dirt,
grease or oil. and dust.
C nder normal climatic conditions it will not al­
ways be possible to avoid dampness on the surfaces
to be glued. If the surf~lCes do show signs of mois­
tllre, the\' mllst be dab dried with a dean cloth. and
no gluing mav proceed until all free water has been
eliminated.
The thickness of the glue laver should be about
1.~ in. (1.5 mill). A.s soon as possible after the resin
has been applied, the surfaces must be brought to­
gether. Pressure must be applied before the open
time of the epoxy resin expires. The pressure
applied by either tern porarv or final prestress
should !lot be less than 30 psi (0.2 "'IPa).
11.6
2.
ing along the bed for the successive casting op­
erations.
Short-line casting (with either horizontal or
vertical casting), where segments are man­
ufactured in a step-by-step procedure with the
forms maintained at a stationary position.
For match-cast joint structures, the accuracy of
the segment geometrv is an absolute priority. Ade­
quate surveying methods and equipment must be
used to ensure an accurate foilow-u p of the
geometry and an independent verification of all
measurements and adjustments.
Immediately after the manu facture of a segment
the as-cast geometry should be controlled and
compared to the theoretical geometry to allow any
necessary adjustment to be incorporated in sub­
sequent casting operations. This aspect of match
casting is particularlv important for the short-line
method and will be covered later in this chapter.
Manufacture of Precast Segments
11.6.2
11.6.1
The various methods used until now for precasting
segments fall into two basic categories:
1.
LONG-aVE C-ISTING
INTRODL'CTlON
Long-line casting, where all segments to make
Lip either half or a full cantilever are manufac­
tured on a fixed bed with the form work mo\'­
In this method all the segments are cast, in their
correct relative position. on a casting bed that
exactly reproduces the profile of the structure with
allowance for camber. One or more formwork
units travel along this line and are guided by a
preadjusted soffit. With this method the joillt sur­
faces are invariablv cast in a vertical position.
·I.
,.
.'
l._:
Technology and Construction of Segmental Bridges
494
Figure 11.37 shows the casting sequence.:l The
pier segment (3) is cast first. then the segments on
either side of the pier segment (l) and (2). If a pair
of forms is llsed, then the symmetrical segments on
eacb side of the pier segment can be cast simul­
taueously, thus saving casting time. As segment
casting progresses, the initial segments may be re­
moved for storage, leaving the center portion of
tile casting bed free. If enough forms are available,
tben the casting of a second pair of cantilevers may
proceed even though the first pair is not com­
pleteh cast.
Figure 11.38 shows the typical cross section of a
long-line casting bed with the formwork in opera­
tion. The method was initially developed for
constant-depth box girders (Choisv-le-Roi and
C(lurbevoie Bridges). It was later extended to the
case of variable-depth decks such as the Oleron
Viaduct (the two sketches of Figures 11.37 and
11.38 refer to this structure) and also adopted in
other coul1tries (Hartel Bridge in Holland).
The importallt advantages of the long-line cast­
ing method are:
It is e;lsy to set out and cOlllrolthe deck geometry.
'After form stripping, it is not necessary to im­
mediatel\' transfer the segments to the storage area
in order to continue casting.
The disadvantages are:
Substantial space may be required. The minimum
length is usually slightly more than half the length
of the longest span of the structure, but it depends
upon the geometry and the symmetry of the
structure.
The casting bed must be built on a firm foundation
that will not settle or deflect under the weight of
the segments. If the structure is curved, the long
line must accommodate this curyature.
All equipment necessary for casting, curing, and so
on must be mobile.
11.6.3
SHORT-LISE HORIZO.\T·IL C"IST/.\'(;
The short -line casting method requires all seg­
ments to be cast in the same place, using stationan'
forms, and against the previously cast segment in
order to obtain a match-cast joint. After casting
and initial curing, the previously cast segment is
1:t!J=!
.~.
~II
,>¥!>)$)?e;
!:W:]
li~ll!
. .I Y'
~'
,5)P7999
I
Segments being cast
FIGURE 11.37.
r
I
Ii
Travelling
crane leg
I
•
knL~
•
l.J.v,L
r .!
.'
•
r]
'Ltpl)$~
Segments completed.
Typical long-line precasting bed.
Mobile outside
formwork
Telescopic inside
form work
FIGURE 11.38. Tvpical cross section of long-line casting bed with form work.
Manufacture of Precast Segments
removed f()r storage and the freshly cast segment is
moved into its place. The casting cycle is then re­
peated. This operation is illustrated in Figures
11.39 ami 11.40.~·4
TO STORAGE
BLANK END
,
t
FIGURE 11.39.
l\pictl ,llOrt-lille precaslillg opcra­
II Oil.
It is important that the reader fully comprehend
the principle of the method insofar as building a
deck of a given geometry is concerned. When a
straight box is desired, Figure 11.41, the match
marking mate segment (n - 1) is moved from the
casting position to the match-cast position along a
straight line, and this is usually verified by taking
measurements on four elevation bolts (a) em­
bedded in the concrete roadway slab and two
alignment stirrups (b) located along the box cen­
terline. A pure translation of each segmellt be­
tweell the cast and match-cast positions therefore
results in t.he construction or a perfectly straight
bridge (both in elevation and in plan view), within
the accuracy of the measurements made at the
casting site.
To obtain a bridge with a vertical curve, the
match-cast segment (1/ - 1) must first be translated
from its original position and then give a small ro­
tation in the vertical plane (angle a shown in Fig­
ure 11.42). Usuallv the bulkhead is left in a fixed
position, and all sef!;ments have ill devatjon the
shape of a rectangular trapezoid with the tapered
face along the match-catch sef!;llleni. It is thcl'efore
onlv necessarv to <l(ljust the soffit of the cast seg­
ment dUl-ing the a(ljustment operations.
A curve in the horizontal plane is obtained ill the
same fashion. Figure 11.43. by firsl moving the
malch-cast segment (n - 1) to its position by a pure
translation followed bv a rotation of a small angle f3
in plan to realize the desired curvature.
CONJUGATE UNIT
FIGCRE 11040.
495
Formwork used in casting scgmellls.
,
ELEVATION
TRANSVERSE
SECTION
STRAIGHT BRIDGE
PLAN VIEW
FIGURE 11041.
Straight bridge.
[ J
ELEVATION
TRANSVERSE SECTION
BRIDGE WITH
CURVE
VERTICAL
PLAN VIEW
FIGURE 11042.
496
Bridge with vertical curve.
497
Manufacture ofPrecast Segments
TRANSVERSE SECTION
ELEVATION
BRIDGE WITH
HORIZONTAL CURVE
PLAN
VIEW
FIGURE 11.43.
Bridge with horizontal curve.
Change in the superelevation of the bridge may
also be achieved with a short-line casting; however,
the principle is a little more difficult to properly
grasp. Figures 11.44 and 11.45. A constant trans­
verse fall of the bridge does not need to be re­
peated in the casting machine. Segments may be
cast with soffit and roadway slab both horizontal
and placed at their proper attitude in the bridge by
offsetting the bearing elevation under the webs to
obtain the desired cross fall. Only a variable
superelevation must be accounted for in the cast­
ing operation, and this is the normal case in
bridges with reverse curves and in transition areas
between curves and straight alignments. In such a
case match-cast segment (n - 1) needs to be ro­
tated by a small angle such as y around the bridge
centerline. Because the bridge geometry is usually
defined at roadway level and not at soffit level. the
rotation given to the match-cast segment results in
a slight horizontal displacement of the soffit in the
casting machine, which must be accounted for.
Also all surfaces of the box segment (top slab,
soffit. and webs) are no longer true planes but are
slightly warped. To allow the form work panels to
adjust to this change of shape, it is absolutely man­
datory to eliminate all restraints such as closed tor­
sionally stiff members.
The basic advantages of the short-line casting
method are therefore the relatively small space re­
quired and the fact that all equipment and
form work remain at a stationary position. The
mobility of equipment necessary for the long-line
method is no longer needed. Also, horizontal and
vertical curves as well as variable superelevation
are obtained with short-line casting without the
major change in soffit configuration that would be
required in the long-line casting method. How­
ever, success will depend upon the accuracy of ad­
justment of the match-rast segments, and precise
survey and control procedures must be initiated
(Section 11.6.5). This last aspect represents the
major potential disadvantage as a direct conse­
quence of the intrinsic potential of the method.
11.6.4
SHORT-LINE VERTICAL CASTING
Normally. for both the long- and short-line
methods, the segments are cast in a horizontal po­
sition. A variation in the short-line method is that
used for the Alpine Motorways near Lyons,
France, where the segments were cast in a vertical
position (cast on end) as shown in Figure 3.100.
The procedure is as follows: after the first segment
is cast, the forms are removed and moved upward
498
Technology and Constru:tion oj Segmental Bridges
TRANSVERSE
ELEVATION
SECTION
BRIDGE WITH VARIABLE
SUPER ELEVATION
PLAN VIEW
FIGURE 11.44.
Short-lille cast.illg-hridge with \';triable supcrelc\"atioll"
CONJUGATE UNIT
END BULKHEA:!
FIGVRE lI.45.
su perele\'a tioll.
Short-line casting-isometric view of segment casting with \"ariable
so that each succeeding segment can be cast above
the previous one. After a segment is cast and
cured, the segment beneath it is transferred to
storage and the one removed from the forms is
moved down, 10 rest on the floor. The advantages
claimed for vertical match casting include easier
placing and vibration of the concrete. However,
special handling equipment and procedures are
required to rolate the segment from the vertical to
its final horizontal position.
Manufacture of Precast Segments
11.6.5
499
GEQ,lMnRi' AND SURVEY CONTROL
Segment Precasting in a Casting lHachine
The principles described in this section apply to
short-line horizontal casting hut may be easily ex­
tended to vertical casting. The apparatus used to
form the concrete segment is usually referred to as
a casting machine and is made up essential! y of five
components:
'rhe bulkhead that forms the front section of
the segment.
2. The match-cast segment, properly coated at
the front end section with a suitable demolding
agent and used to form the back end section of
the newly cast segment.
3. The mold hottom (or soffit).
4. The side forms, properly hinged for stripping
and firmlv sealed to the bul khead and the
match-cast segment during casting. The inside
forms, which pivot and retract for stripping.
5. The imide forms, which pi\ot and retract I'or
stripping.
Joint A
1.
The relationship between ail individual segment
and the finished structure is established bv means
of three different svstems of reference:
1.
2.
3.
The final ,,),stnn of nferenre, which is the refer­
ence for the finished geometry of the struc­
ture. I n this s\'stem each segment is described
by its basic geometrY.
The auxiliary system of reference, which corre­
sponds to the precasting machine and is at­
tached thereto.
The elementary reference s)'.,tem, which is attached
to each segment and would be the equivalent
of intrinsic coordinates ill space geometry.
The principle of the precasting method is as
follows. During the casting of segment A (segment
B being in the match-cast position) the elementary
reference system of A is identical with the auxiliary
reference system, that of the casting machine.
To position B with respect to A becomes simply a
matter of positioning B with respect to the pre­
casting machine. It is the task of the design office to
provide the theoretical geometric information nec­
essary for positioning. The values are computed
from the basic geometry with the addition of the
relevant compensatory values for deflections. The
definitions of these reference systems are pre­
sented below.
FIGURE 11.46. Auxiliary I-eference system (casting­
IIlachine reference).
The auxiliary reference system refers to the
casting machine and is defined in Figure 11.46.
The plane of the bulkhead is perfectly venical.
The upper edge of the bulkhead is a horizontal in
this plane except when segments do not have pla­
nar top surfaces. The x, y and z axes refer to the
casting-machine reference system, whereas XA, y,!,
and Z,I refer to the elementary system of reference.
The elementary system of reference is materialized
on each segment in the following manner:
I.
2.
3.
The x" axis: This axis is represented by marks
(such as saw cuts) made on two steel stirrups
anchored in the top slab as near as possible to
the joints.
The origin 0,,: The origin 0" is located at the
point where the x" axis intersects the plane of
the joint at the bulkhead.
The plane x"' o",y,,: This plane may be defined
by three fixed leveling points, the position of
each point with respect to the plane x, 0, y being
arbitrary but invariable. For practical reasons,
four leveling points are used and materialized
by bolts anchored in the top surface of the
segment above the webs and as close as possible
to the joints.
Now that the elementary system of reference has
been established (all measurements and readings
being made while the segment is in the casting
machine before the forms are removed), the seg­
ment can be positioned with respect to the aux­
iliary reference system, so that it can be placed in
the correct countercasting position according to
the calculations supplied by the design office.
500
Technology and Construction of Segmental Bridges
In order to correctly position the countercasting
segment. information is needed about the final
geometry of the structure. The overall geometrv of
a bridge structure is lIormallv defined by thc
geometry of the roadway. From this roadway
geometry it is necessary to determine the geometry
of the concrete structure itself.
The longitudinal reference line to which all the
necessary parameters are related is known as the
/lox ,I.,rirdtr IiJl!' (BGL). This line may coincide with
the top concrete surface of the box girder. but it
IlJa\ also he a fictitious line of reference if the box
girder top slah shape is not regular.
The box girder line is ustlally described using
two ClInes, Figure 11.47:
zontal plane and follow the curvilinear abscissas.
The segment lengths chosen on this basis may be
retained, but in calculating the real lengths of
cast-in-place closure joints and t hree-dimel13iollal s
curve must be used.
Because of the way a casting machine works, the
segment joint at the bulkhead end is ill\'ariably
perpendicular to the axis of the segment. There­
fore, ill plan view, the segments are generally of
trapezoidal shape. except for segments over the
piers which are rectangular in order to provide a
constant starting- point for each cantilever, Figllre
1 1.48.
Olle curve (fT) ill a horizolltal plane, which gives}'
<l!-. a function of x for each point where the box
girder line intersects a joint planc between seg­
ments and also the center points of supports (abut­
ments or piers); this curve is simply the projection
of the true space box girder line onto a horizontal
plane and is sometimes referred to as the "hgl"
(small letters).
All measurements on a segment are made when
the segment is still in the casting machine.
Readings mllst be taken when the (,OIIOTtc has
hardened and hefore forlllwork st ripping, Figure
11.49. Horizontal alignment readings give t he dis­
tance of the segmellt axes as marked on the stir­
rups frolll the casting-machine reference line.
Longitlldinal profile le\·e1 readings are given In the
fOllr bolt elevations relative to the horilontal refer­
ellce plane.
Readings Illllst be taken Oil the segment jllst cast
and also on the match-cast segment. Correuiol1s
are applied \0 allow for the geollletric defects in
the preceding segl1lent, Figure 11.50, and are lIsed
as "theoretical yalues for adjustment."
Olle curve (s) in a developed vertical plane giving z
as a fUllction of (T for the same points mentioned
abo\'e. Thisl curve is the real box girder line. BGL.
To complete t he definition of the segment posi­
tion ill space-at each joint line and at support
centers-we must define the transverse slope of
the theoretical extrados line.
It is important for both the bgl and the BGL to
calculate the fT and .1 parameters, respectively, ill
order to obtain an accurate determination of pro­
jected and real span lengths.
The calculations and structural drawings refer to
Ilominal segment lengths and span lengths. Usu­
ally these lengths refer to the projection on a hori-
Pil!'f
3
I
SCfPlll'lI1 CaS/III/?: Parmlll'/cr.1
Surue'li Control During
1.
Theoretical basic data supplied In' tlte design
office, allowing the preparation of the hori­
100ltai alignment and the two parallel bolt
lines.
2.
Corrected values defined eit her graphically or
by computer.
Survey control readings_
Linear measurements on the segments.
Schematic representation of the segment to
rapidly verify the relative positions of the seg­
ment axes.
A level check to pick up any gross error in level
readings on the same segment­
3.
2
I
4.
5.
Cr'
lHorizontat proJPction
o! box 9trdeor
'Iobgt lf
FIGURE 11.47.
Box girder line cunes.
Operatum)
The surveyor in charge of the operations mllst
complete a data sheet for each segment containing
essentially:
line
Pjrt
Precastillt.;
6.
"Of'
7.
Comments on the casting operations.
1
I
lHanufacture of Precast Segments
501
(St'gmt'nt axis
,r-Segment
over pier
Pier
~
FIGURE 11.48.
'\
Box girder line "bg ,"
or c:r ( sigma) curve
Short-line casling-position of sel-{Illent joillls in plan \'iew.
I
i
,AN
i
!
I CASTING
MACUINE
, RUE. RENeE Ll NE
FIGCRE 11.49.
me;lsurcnleIHs.
Ca,ling-machine
As an example, Figure I L5I shows the typical
survey control made on the first four segments of a
tvpical cantilever. Control of alignment and. levels
rnav be followed graphicallv or numerically by
computer, using the basic geometric data obtained
in th~ casting machine and shown in Figure 11.52.
In order to avoid any significant deviation from
the theoretical geometry, it is necessary to provide
orientation
and
segmenl
for corrections when casting the next segment.
Figure 11.53 shows how this would be done for the
plan alignment. Similar corrections are made for
the longitudinal profile on the two parallel bolt
lines. It is essential not only to follow carefully the
trajectory of the two bolt lines separately but also to
check for each segment that the superelevation
(given by the crosswise difference in level between
502
Technology and Construction of Segmental Bridges
w~'
1£4'
-.
-~--+ ",--'IISTIA/!: I'1)1CffINE
R!'FER!'IYC{ iJ¥E
FIGURE 11.50. Plan yjew of casting operation­
readings using sunf)' instrumems.
i -LON
I
-~,
8otts­
Lf
CD
.'-zs~~.~~
FIGURE 11.51.
Casting operation-typical survey control.
the two boll lines) varies regularly according to the
theoretical geometry. Failure to do so has resulted
in important geometric imperfections on certain
projects.
Sun1ey Contml During Construction
The nature of match-cast segmental construction is
such that the structure is really "built" in the pre­
casting yard. Although corrections can be made in
the field, such corrections are undesirable and al­
ways a source of additional expense and delays.
Close control of precasting is far more efficient. It
is nevertheless important to check the evolution of
the structural geometry during segment placing:
1.
To compare actual deflections with computed
values,
2.
To ensure that no major errors have escaped
the control in the precast yard or factory.
Such checks at the site should include:
1.
2.
3.
4.
5.
Pier positions, height and in plan.
Bearing positions, level and orientation.
Pier segments, level and orientation.
Cantilevers proper, every third segment, in­
cluding levels, superelevation, and orientation.
Overall geometry of the structure after con­
tinuity is achieved between the individual can­
tilevers.
Conclusion
The principles of geometry and survey control are
more complicated to explain than to use, once the
Manufacture of Precast Segments
503
THEORfTICt1L1I)IIS Of 0
REIlL /lXIS
OF" 0
Se:GME.NT1
SeGMENTO
I<EIlL LEVf.LFOR 0
:nU:'ORE:TICAL LEVEL FOR 1
I
NWO"
I
-;--- _
NEOI
NWO
-L
--+---- _
HIEORETICAL
Lf:VE"L FORO
f
NE a"
- r
--
)
_.- I _ __,_ ___ __ __
NW11
r
--
+- .
.i:!J!&l.~...REFERENCE
L_--o"------~-r
:NE,1)
LE.VE.L·O.OOOO
C4STING MACI-IINE" BU!J(H~AD
5EGME:NT 0
FIGURE 11.52. Sliney control-horizontal alignment and longitudin;ll profile results.
(1/)
Horiwnt;tl alignment. (b) Longitudin;t1 profile.
FIGURE 11.53, Typical alignment corrections during casting operations.
basic principles of a casting machine are thor­
oughly understood. The short-line method has
great potential to construct segments for bridges,
cycn . those with very complicated trajectories,
rapidly and economically. Outstanding examples
are the Chillon and St. Cloud Viaducts in Europe
and Linn Cove Viaduct in the United States. At
Saint Cloud, 120- to 140-ton segments were cast
on a one-day cycle, and the final geometry of the
bridge was obtained with no on-site adjustment.
,['
ii
I
I
Technology and Construction oj Segmental Bridges
504
Oil the other hand, a loose approach to, In the case of wide decks or long spans, where the
segment length is reduced to reduce the unit
g('ometry control at the casting yard mav lead to
weight, the usual geometric proportions may vary
serious difficulties at the pn~ject site.
considerably; stich is t he case for two notable
structures:
11.6.6
PRECASTlNG fA/W AND FACTORIES
The precasting operations are usualJv carried out
in a vaHi or e\'en a facton if the size of the project
allows the corresponding im'estmenl. All opera­
tions, such as:
Preparation of the reinforcing steel cages and
ducts for post-tensioning tendons
l\lanufacture 01 concrete
!\1anufacture
or segmellts including heat curillg
Storage of segments including finishing and qual­
i1\ control are performed in a repetitive fashion
under facton conditions.
:\s all example or typical precasting-yard lay­
outs, Figures 11.54 and 11.55 show \'iews of:
The Saint Cloud Viaduct precasting :anl with
short-Ii lie casting
The Oleron Viaduct precasting yard with long-line
casting
The tvpical precasting c\'c1e (with either the
long-line or t lIe short-line met hod) is of one seg­
ment per fOrIllwork per day with a one-day work
shirt, COIHTele hardenillg laking place during the
night (at least 14 hours between the completion of
conuete plaeing ill the evening and the stripping
of forms the Ilexl morning), Shorter construction
cn:\cs may be obtained hy reducing the time of
concrete hardelling, but quality mav decline if all
the operatiollS are not kept under very strict COI1­
t rol.
Heat (urillg of the concrete 10 reduce the con­
struction cvcle and accelerate the rotation of the
casting machines is perfectly acceptable. Its im­
proper use, however, may alter the. accuracy of
joim !natching bet ween segments, as shown in Fig­
ure 11.56. This effect would be particularly
significant ror wide but short segments.
Typical segments usually have the following di­
mensIOns:
Width
Length
Ralio width/length
30 to 40 ft (9 to 12 m)
10 to 12 ft (3 to 3.6 m)
3 to 3.5
St. Cloud
St. Andre de Cubzac
width iO ft, length i It.
ratio 10
width 58 ft, length 5.8 ft,
ratio 10
For sllch segments, heat curing is more likely to
create smail changes in the segment shape, which
may build up progressi\ely and so alter the ef­
fectiveness of joint matching. This is due to the
development 01 a temperature gradient in the
match-cast segment, which is in contact on one
side with the newly cast heated segment and on
the other side with the lower uutside temperature,
The problem may be completely eliminated by
always heat curing both segmt'llts simultaneollsly
so as to avoid any temperature gradient. Experi­
ence has proved the method totally eHicient.
When the project lIl\'olving segment precasting
is of sufficient magnitude or \\'here climatic comii­
tions al'e adverse, precasting ElClOries are a logical
extrapolation from the short-line method per­
formed in an open precasting yard. Segment man­
ufacture takes place in a completely enclosed
building with a better use of personnel and a more
consistent quality of products.
An interesting e~ample is afforded by the B-3
South Viaducts. requiring production or 2200 pre­
cast segments weighing between 2H and 5H tons (25
to 53 mt). The precasting site was installed close to
the project and included four main areas:
1.
2.
3.
4.
An assembly workshop. where the reinforcing
steel cages were prepared and the prestressing
ducts positioned. The finished cages were
handled by a 5 ton tower crane,
A concrete mixing plant.
A precasting factory where the segments were
cast and cured.
A storage area where the finished segments
were left to cure adequately. These segments
were handled by a traveling portal crane.
The precasting factory was equipped with four
precasting machines, all of which were entirely
protected from the outside environment. Two
machines were reserved for the manufacture of 15
to 20 ft (4.5 to 6 m) segments and two for the 20 to
(,J,
<::>
I.>l
r:::
Q)
......
([l
~
.
3.
Pt'Pstl'f'SSlng st(>,,1 storac(f'
7, 1'.[,)ulo bottom
6. Travf'lling crall" tcal'\(
5. Segment storagf'.
Z\)fH~
Launching;5\ n.\P!' assl'!llbly
.\
t"
Loadin!,( po \ nt fo
:l
Sf'l!,lnpnr.s:
!\cr.f'SS
:2
l'amp
and tcolll'Y
1. Laurlchin.; tl'ack for ginlf'!"
Q)
;"'/' " B
.....,
-+-'
Pt".>{'ast plo:.>ll1 P !lts
C(>(~f·r3\
cps.
"~;f'C\:,Cf'S
al \ .'111\1('1\ I
(t'utucp (:~lrf>la~p'.vay
----
FIGURE 11.54. Sl. C10tld Viaducl, precislillg rani IalOtll. (I) I
ami trolle~·. (~) Access ramp. (3) Loadillg pOilll for segmellts. (-1)
assembly wile. (5) Segmellt storage. (6) Tral'dillg crane track. (7) :\(old bottom.
Presll'essillg Sled stor;lge, (9) rower (Jalle Irack. (10) Reiul()lu'1I1elll asselllbly. (II)
COliC rete plallt. (1~) Precast ('1('IIll'llIS. (I:~) Prestress (elldon mallufaCiure. (H) Of'fices.
(15) (;clleral ,ell ices. (Ifi) '1011 g:lIe pmilioll. (t7). hUlIll' clrri<lgell'<I\
\'7
Iii. Toll .;atp PUSIU\JII
I c)
11
f2ctur p
13. l'!'p>iII'PSS tf'IUI-H! mll!lU'
1'2
CASTING YARD
H"llIiul·,:f'!l1f'flt as,;pmbly.
rUWf'r crall" track
It. C\,I1<,<,,,tp plant
10
~J
Scale 1/500
p
6
~7
r
to Maren nes
"II
\
- ..•. --~.--,--;jj
506
Technology and Construction of Segmental Bridges
Staff quarters
:....- Duct storage area
FIGURE 11.55.
O]cron \'iaduCi. precasting
L
Office
~'anl ];l\OUI.
CONJUSt.TE
UNIT
g~~~~~~Tti
CNIT
AMBIANT
:EMPERATUqE
<-:2ic2dL----l
r
y
AO'F
R
.
EFFECT OF IMPROPER CURING OF SEGMENTS
IN SHORT LINE CASTING
FIGURE 11.56.
Effect of improper curing of segments in
31 ft. (6 to 9.5 m) segments, Figures 11.57 and 11.58.
Each casting machine was made up of a mobile
form, an end form or bulkhead, two hinged out­
side forms, and a telescopic inside form, Figure
11.59. Handling of concrete and reinforcing steel
inside the factory was performed by two 10 ton
travel cranes.
~hort-line
casting.
The production of the different segments
volved the following operations:
1.
2.
3.
111­
Assembly of the steel cages in a template.
Steel-cage storage.
Final steel-cage preparation and duct installa­
tion.
Handling and Temporary Assembly of Precast Segments
FIGURE 11.57.
B-3 South Viaducts, inside view of the precasting factory.
Casting machine
FIGURE 11.58.
507
Concrete Plant
Control System
B-:, Sou th Viaducls. pIa n \'iew of I he precasling
Inside formwork
facLOlV,
of the newly cast segment to the match-cast po­
sition by means of an independent motorized
trolley.
11.7 Handling and Temporary Assembly
of Precast Segments
Bottom formwork
FIGURE 11.59.
machine.
4.
5.
6.
7.
8.
B-3 Somh Viaducts, detail of a casting
Positioning of steel cage inside the formwork.
Adjustment of casting machine, including
alignment of match-cast segment and sealing
of all form panels.
Concrete casting and finishing.
Steam curing.
Fonnwork stripping, followed by transfer of
the match-cast segment to the storage yard and
In either long- or short-line casting, segments can­
not be handled before the concrete has reached a
sufficient strength to prevent:
Spalling of edges and keys
Cracking of the parts of the segment subjected to
appreciable bending stresses due to self-weight
Inelastic deformations that would ultimately Im­
pair proper matching of the segments
Critical sections in a typical single-cell box segment
are, Figure 11.60:
Technology and Construction of Segmental Bridges
508
FIGURE 11.60.
Critical ~ecljollS ill a t\'jlical seg-mellt at time of IOrlmmrk ~Iri]l]lillg.
Section A where the side calltilevers are attached to
the wehs
Sectiolls Band C at midspan oflhc top and bottom
slab
Sectioll A is allllost alw<lvs the lllost critical. Section
B is IlS11;tlh· suhjected ro moderate tensile stress he­
cause the top slab is huilt-ill Oil the weh when the
inner fOllllwork is stripped. Section C is critical
oIlh· oIlloIlg-lille casting when the casting bed docs
not have a continuous soffit and when the span of
the bottom slab is larger than 16 to ~() ft (5 to 6 m).
Experience has shown that at t he time of form
stripping and bef()re any handling of the segIllent
is allowed, the tensile cracking strength of the COll­
crete should be at least equal to the bending stress
due to the segment weight in the most critical sec­
tiolls (A, B, and C). Practically, the corresponding
compressive strength is:
j;i
= 30()O to 4000
psi (21 to 28 MPa)
In the casting yard, segme!1\s are usually handled
hv a portal crane traveliIlg on rails or on steeriIlg
wheels for added mobility. A typical portal crane in
the Olel'On Viaduct precasting yard is. shown in
Figure I 1 .61.
Proper handling of the segment requires proper
pick-up poillts to keep the stresses in the section
within the allowable limits. A typical example of
halJ(llillg three different shapes of box girders is
shown in Figure 11.62.
For the conventional single box, inserts or through
holes are provided near the web in the roadway
slab, allowing lifting to be accomplished by a simple
spreader beam.
FIGURE 11.61.
OlclOll \'iatiuct, portal cralle ill 1'1('­
casting \·anL
For the twill-box, three-web section, a four-point
pick-up is usually nccessarv to eliminate excessive
transverse bending of the top and bottom slab. A
triple spreader-beam arrangement allows the load
transfer from the four pick-up points to the single
lifting hook.
For a triple-box, four-web section (such as used ill
the Saint Cloud Bridge), temporary ties are pro­
vided in the outer cells to transfer the reaction of
the outside webs 10 the center webs. A simple
spreader beam is then sufficient to lift the segment.
Segments must be stored in a manner designed
to eliminate warping or secondary stresses. Con­
crete beams installed at ground level provide a
good bearing for the segments, which must be
supported under the web or very close thereto. If
stacking is required to save storage space, precau­
tions must be taken to transfer weight from the
=
Placing Precast Segments
FIGURE 11.62. H;tlldlil1~ prct,l~l segments.
Illellt. (i) Four-wcb ~l'gnlt'lll.
upper to tltc lov,.-er lavers of se~mellts without ex­
cessive bendin~ of th(' slab. _
11.8
Placing Precast Segments
Transportation and placement of segments may be
performed bv one of several methods. depending
Oil t he site location and the ~eneral characteristics
or the strllcture. These methods can be divided
illto three main categories:
1.
2.
3.
Transportation by bnd or water and place­
Illelll b~ an independent lifting apparatus.
Trall5porlation bv land or water and place­
ment with the help of a beam and winch carried
by the bridge deck itself.
Transportation b~ \;tnd. water, or along t!le
bridge deck alreadv constructed and place­
ment with the help of a launching girder.
There are methods that fall into none of these cat­
egories, such as the use of a cableway, but their use
is limited.
11.8.1
IXDEPEXDEXT LIFTING EQCIPJIENT
This method, where feasible, is the simplest and
least expensive. It W;IS llsed for the Choisy-le-Roi,
Courbevoie. Juvisy, and Conflans bridges, where
the navigable stretch of water lent itself to the use
(II)
509
T\\,()-\\Tb segmt'Tlt. (hl I"hrl't'-\\'ciJ s<'g­
of a barge-mounted crane, ensuring tile colleUiol1
of segments from the precasting site and their po­
sitioning in the final structure. A terrestrial crane
was employed for the Cardon, Bourg-Saint An­
<leol, and Bonpas Bridges. The same crane, ma­
neuvering either on land or over water (011 a
barge), assured the positioning of all the segments
used to construct the upstream and downstream
bridges of the Paris Ring Road.
'When site conditions are suitable, the same lift­
in~ crane may be lIsed both to serve the precasting
van\ and to transport the segments to their final
position in the structure (Hartel Bridge, Holland),
This principle was enlar~ed successfully durin~ the
construction of the bridges over the Loire River at
TOllrs ('.[otorwav Bridge and Mirabeau Bridge).
where the segments were placed with the aid of a
mobile portal frame. The portal frame is placed
astride the bridge deck and moves along a track
supported by two bailey bridges, one either side of
the structure. The track length is approximately
twice that of the typical span, and the track itself is
lTloved forward progressively as construction pro­
ceeds. The bailey bridges are supported on tempo­
rary piers driven into the river bed. The segments
are first brought to the bridge deck and then taken
by the mobile portal frame, which transports them
to their final position in the finished structure, Fig­
ure 1.47,
Where a mobile truck or crawler crane is used
for placement, there are often difficulties in the
510
Technology and Construction of Segmental Bridges
positioning of the key segments at midspan, be­
cause the finished structure on either side of the
key segment prevents the crane from maneuvering
properly and hinders the positioning of the seg­
ment, which may be carried out only from the side
of the structure. For the B-3 Motorway Bridges a
special apparatus was designed to place those seg­
ments in the cantilever arm to be constructed in the
direction of the completed structure, Figure 3.95.
Two longitudinal girders are braced together and
rested on the pier head of the cantilever to be con­
structed at the front, and on the existing structure
at the rear. The apparatus consists of a mobile
winch-trolley, ensuring the hoisting and position­
illg of the segments, and an advancing trolley
situated at the rear and equipped with a translation
lllotOr. The front and rear supports are conceived
in such a manner as to transmit the vertical loads
through the segment webs.
The segments 011 the other side of the cantilever
are easily placed by the mobile crane. This beam
lIlay easily be used to ensure cantilever stability
<lUI'iug cOllstruction when the piers are not
sufficiently rigid to support unsymmetrical load­
ing. The cantilever is rigidly fixed to the girders by
damping bars Lapable of resisting both tension and
compression, The crane and the girders, used to­
gether, will allow a 130 ft (40 m) span to be erected
in four working days.
Placement of segments with a mobile crane has
found another application in the construction of
small-span structures such as three-span motorway
overpasses (see the discussion of the Alpine
Motorway, Section 3.15, and Figure 3.103). The
segments are precast in a central factory, trans­
ported to the various sites bv road and positioned
by a mobile crane according to the erection
scheme, which consists essentially of the following:
Two temporar~' adjustable props, easily dismount­
able, placed at the one-fourth and three-fourths
points of the central span.
Temporary supports with jacks allowing cantilever
construction
Temporary prestress to tie the segments together
before stressing the final prestress
Elimination of the classic cast-in-place closure joint
by direct junction of the two cantilever arms face to
face.
Final prestress by continuous tendons instead of
can tilever-type layou t.
The total construction time for such an overpass,
including the piers, usually does not exceed two
weeks, of which less than one week is spent .on the
bridge supel'structure itself. This method has been
used with great success for the Rhone-Alps motor­
way o\'erpasses, with spans varying between 60 ft
(18 m) and 100 ft (30 m).
11.8.2
THE BEA,\1-AXD-Wll\'CH METHOD
The beam-and-winch method of placing precast
segments was conceived for the construction of the
Pierre-Benite Bridges over the Rhone River. This
construction method requires a fairly simple ap­
paratus rolling along the already constructed part
of the cantilever and ensuring the lifting, transla­
tion, and positioning of all the segmelits. The ap­
paratus is shown diagrammatically in Figure 11.63.
I t consists of the lifting gear B carried by the trolley
C rolling along the bridge deck on tracks D. The
segment A is brought, by land or water, beneath
the pier in question, where it is lifted by the
equipment. It is then transported to two laun~hing
beams E that cantilever out from the bridge deck,
upon which it contillues to advance until reaching
its final position, whereupon it is lifted to its final
level next to the previous segment, Figure 11.64.
This system can, of course, be simplified if the
segment can be brpught by some independent
means to a location vertically below its final posi­
tion in the structure.
As originally conceived, this system was not
completely independent; another construction
procedure was required to erect the pier segment.
The pier segment was cast in place in the Pierre­
Benite Bridges. It was precast and placed by a
crane for the Ampel Bridge in Holland and by a
floating barge crane for the Bayonne Bridge over
the river Adour. This weakness was eliminated in
the construction of the Saint-Andre-de-Cubzac
Bridge. For this structure, the pier segments,
which form the starting point for each cantilever,
were placed by the same equipment that placed the
typical span segments, Figure 3.72. The equipment
was hung, with the help of cables, to an auxiliary
mast fixed to a lateral pier face. The pier segment
was brought in from the opposite side, lifted and
placed by the mobile equipment's winches. In the
same position the following segment was located
and the auxiliary mast removed, Figure 3.73. At
this point it was a simple matter to reposition the
mobile lifting equipment in order to place the typi­
cal span segments, Figure 3.70.
Placing Precast Segments
511
PLACING SEGMENTS NEAR RIGHT BANK
LIFTING APPARATUS
I
rANTILEVER BEAM
LIFTING APPARATUS TRANSFER
TROLLEY
TRANSFER TROLL Y
SERVICE WALKWAY
PIER
BLOCK
SEGMENT BEING PLACED
FIGURE 11.63.
cn
Paris Downstream Bridge, placing apparatLls.
~------:--::-".
~'~:r'\'~)
evolved and how the original concept has been
modified.
,
•
Launching Girders Slightly Longer Than
the Span Length
FIGURE 11.64.
ing a segment.
11.8.3
Paris DO\\nstream Bridge, position­
LAU.vCHI,VG GIRDERS
This last method, by far the most elegant, uses a
launching girder above the bridge deck to bring
the segments to their position in the structure.
Employed for the first time during construction of
the Oleron Viaduct in France, this method has now
been successfully used for many different bridges
throughout the world. We shall now look at the
most important structures constructed by this
method to see how the launching girder has
We first consider the construction method of the
OIeron Viaduct Bridge superstructure, Figure
3.32. The segments were brought along the top
slab until they reached the launching girder, then
lifted by the latter, transported to their final posi­
tion, lowered so as to come into contact with the
previous segment erected, and prestressed to the
cantilever. The launching girder itself, slightly
longer than the span length, was made up of a steel
trellis beam with an entirely welded rectangular
section weighing 124 tons (l13 mt) and measuring
312 ft (95 m). The maximum span length of the
bridge was 260ft (79 m).
[he launching-girder system consists of two
fixed supports, called tunnel legs, allowing the
segments to pass between them, one at the rear of
the girder and the other at the center. At the front
end is a mobile prop enabling the girder to find
support on the next pier. The bottom chords of the
girder are used for the rolling track that supports
the segment trolley, which can move the segment
horizontally and vertically and rotate it a quar­
512
Technology and
COllstruct~on
Placing center segment
- - 1 1 8 ' --~-.-~ 141'~...............
- - - 259'-~·--·--
~- ---~-~-
Moving gantry to next pier
I~~~
f.,
I
i
I
II,I
i
~---141'
i
I
Placing segments '" daub:" cantilever
FIGURE 11.65.
Olewll
"l)('r;ttioll.,. tAl Rear
Viaduct,
bunciIing-girder
~UppOrl.
(H) cellter support. (e)
IClIlfJOlan from prop, (D) prop SlIp]>OI·t. (E) pier seg­
IllCIlt,
(I-')
tellljloran'
SlippOIi.
ttT-turn. Three phases <Ire clearly distinguishahle
in the COBstruction of a cantilever, Figure 11.65:
Plw.W' J: Placing tlie l)il'1' ,\egllll'lIt
The launching girder rests on three supports-the
rear SUppOI't, the center support near the end of
the newly constructed cantilever, and the front
prop, which is attached to the front of the next pier
with the help of a temporary prop support.
of Segmental Bridges
A wpport adjustment was carried out with the
help of hydraulic jacks when the girder was resting
on the rear and central supports and the te,mpo­
rary front prop, before installing the pier segment.
The purpose of this adjustment was to obtain the
optimal distribution of the launching girder self­
weight alllong the three supports. While the frollt
prop is being installed, the central support rests on
the end of the pre\'ious cantilever in the same po­
sition in which the rear support will be during the
erection of the t\'I?ical segments. In this phase tbe
launching girder rests on two supports and is
therefore staticall\' determinate: nothing call be
done (() change the rear-support reaction. While
the pier segment is being placed, howe\'er, the
girder is resting on three supports and is staticallv
indeterminate. It is therefore necessary to ensure
that the reaction at the central support is less than
or equal to that which will he produced 1)\ the rear
support during the next construction stage. in­
cluding the weight of the trollcy alld the tractor
placed ill the near \·ieinit\'. Se\'eral other strllctllres
have been built with launching girders of the same
generation (I, the one used for the Oleron Viaduc\.
The Chillol1 Viaduct, Figures :i.43, 1 1.66, and
11.6i, along the bank of Lake Leman used a 400 ft
(122 Ill) launching girder weighing 253 tons (230
mt). The maximulll span length was 341 it (104 111).
The launching p;irder, of constallt rectangular sec­
tion, was of the suspe.nsion type, being suspended
at the one-quarter points bY'cahle sta\'s anchored at
the central mast, which extended above the level of
the launching girder. The supports were h\­
draulicallv a(Uustable, allowing the girder to cope
with different angles of superclevation, Figure
Phase 2: [Hoving the launching girrll'T furward
The girder rolls along on the rear support and the
segment trolley, which is rigidly attached to a metal
framework known as the temporary translation
support, which is fixed to the pier segment. The
rear and central supports are equipped with bogies
and roll along a track fixed to the bridge deck while
the girder is being moved forward.
Phase 3: Placing typical segments
The launching girder rests on two supports, the
central support anchored to the pier segment and
the rear support tied with prestressing bars to the
end of the previously constructed cantilever.
FIGURE 11.66.
operatioll.
ChillOll Viaduct. laullching-girder in
Placing Precast Segments
513
zndSt,uge
PI;;.clil-3 p'¢r Sti:'3I"'t",~,at5
4th '5t.;;q~
Glr~<:i !dUC'Nlr'g
ur1""I.,"' '
FIGL'RE 11.67.
(:hill,,11 \'iadllCl. blltlchillh-ginkr
llH)\,('llIl'llls.
11.68. The laullching- girder included three means
of adjustlllent:
,!;\,
/
I
I
/
/
'
I
Ai/illstllll'lIt DI:
Lateral movement of the trollev in
order 10 place eccentric scg-mctlls
"'lriiustltll'llt D2: Lateral translation of the celltral
support ill order to cope with
horizontal curvature of the
structure
"1 diu.,tml'lIt D 3: Vcnical ,l(ljustlllem of bog-ies to
take up the slIperelevatioll and so
keep the central support vertical.
\
\
1\
/
\
\
\
Horizontal
chassis
FIGURE 11.68.
,ldjllstllll'llt s.
Chilloll
\'iadllcl.
lalillchillg-ginier
III order to follow the horizontal curves the
launching ginler rotated about the rear support
while llIo\'ing- sidew;:vs across the central support,
Fig-ure 11.69. The mobile temporary front prop
was conceived in the same way as the other sup­
ports so as to allow the passage of the first segments
to either side of the pier segment.
The Blois Bridge on the Loire River in France
had a 367 ft (112 Ill) long launching girder weigh­
ing 135 tons (123 mt). Figure I L70. The
maximum span length was 300 ft (91 m). The
launching girder. of constant triangular section.
could be dismantled and transported by road. All
of the girder components were assembled wilh
high-strength bolts. ensuring the transmission of
514
Technology and Construction of Segmental Bridges
CONSTRucnON
CONSTR.UCTION
OF
Of"
HQIl!I'ZONTIl.L..
~OR'Z:ONTAL
FIGURE 11.69.
struction.
eURvl:.
CURve
( STAGE 1. )
(STAGE 2 )
Chillon Viaduct, cun-ed span con­
ELEVATION
FIGURE 11.70.
I}~~I
Blois Bridge, launching girder.
SECTION A
forces by friction between adjoining plates, Figure
11.71.
The use of a very light structural steel
framework carried with it the risk of large deflec­
tions. These were reduced and controlled by two
sets of cable stavs, passive and prestressed, which
came successively into play during maneuvering of
a segment (upper passive stays) and during the
launching-girder advancement (lower prestressed
stays). This launching girder was later used for the
erection of two other structures: the Aramon
Bridge on the Rhone River, Figure 11.72, and the
2950 ft (900 m) long Seudre Viaduct.
The Saint Cloud Bridge on the Sei~e, Figure
3.78, is a recent example of the use of a large
launching girder. The girder could place segments
weighing up to 143 tons (130 mt) in spans of up to
335 ft (102 m) with a minimal radius of curvature
in plan of 1080 ft (330 m), Figure 3.79. The weight
of the launching girder was 260 tons (235 mt) and
its total length was equal to 400 ft (122 m).
The adjustments adopted were similar to those
used for the Oleron, Blois, and Chillon bridges.
The launching girder, which used upper passive
stays and lower prestressed stays, was constructed
FIGURE 11.71.
sClllhh delail.
Blois Bridge. launching-girder as­
FIGURE 11.72.
River.
Aramon
Bridge over the Rhone
with a constant triangular section made up of indi­
vidual elements assembled by prestressing. This
launching girder is notable, apart from its assembly
by prestress, for its ability to follow extremely tight
curves. The movements used for the Chillon Via­
Placing Precast Segments
duct were, of course, lIsed for this purpose. How­
ever, in the Saint Cloud Bridge it was necessary
also for the launching girder to take up several in­
termediate positions during the erection of a given
cantilever so as to bring each segment to its final
position in the structure. The total lateral transla­
tion reached 19.7 ft (6 Ill) at its maximum. Con­
struction speed of the bridge deck was 130 ft (40
m) per week, including all launching-girder ma­
neuvers. Two other structures erected with the
help of the Saint Cloud launching girder were the
Angers Bridge and the Sallingsund Viaduct.
The launching girder used for the Alpine
\lotorw;JV network was conceived for spans and
segment weights of more modest dimensions; it is
typical of lightweight universal equipment that can
be easily dismantled for reuse in another structure,
Figure 11.73. This girder allowed the h,mdling of
segments weighing lip to 55 toIlS (50 !lit) over
spans lip to 20() ft (00 m).
Reflecting on the launching girders mentioned
above, we note that their evolution centers on two
major characteristics: the structural conception or
the girder and the assembly method (collnection
types, number of elem~nts, and so on).
Launching girders tend lIlore and more to be of
the lightweight tvpe, relving on exterior forces to
cope wit h diflerenl loadings. rhese exterior forces
arc provided by the exterr1<l1 .)ctive cable stays,
which allow tlte structure 10 be placed in a condi­
tioll ensuring a favorable behavior unde\· a givell
loading. This approach to launching-girder design
provides more optimal lise of materials than did
the first-gelleration girders of variable cross sec­
tioll.
Another advantage of a constant cross section is
that it facilitates I he construction of standard sec­
FIGURE 11.73.
.-\[pine
:-"[OlOn\<!v
launching- girder.
515
tions that can be interchanged and assembled on
site. In this way the girder length can be varied ac­
cording to the span length and the weight of the
segments. Connectjons are made with tensioned
bolts, Figure 11.74, which reduce considerably the
number required and consequelltly the time
needed to assemble or dismantle the structure.
These connections have recentlv replaced those
made with high-strength bolts and fish plates, nota­
ble on such structures as the Deventer Bridge and
the B-3 Viaducts.
Means of erection adjustments also have im­
proved, tending to reduce the forces applied to the
deck itself by ensuring thal the girder supports are
located over the piers or at Icast in t he very near
vicinity.
This natural evolution leads liS toward a new
type of launching girder, one whose total length is
slightly greater than twice the typical span length,
allowing the simultaneous placing of the typical
segmellls of cantilever N and the picr segment of
cantilever N + I.
LIIUIIChilig Girr/('n Sligh/tv Lllllg!'r Thall Twice lhl'
'(VjJical Spa n
The tirst launching girders of this type were used
011 the following bridges: Rio ;\;iteroi ill Brazil; De­
venter ill Holland, Figu re 3.50; and B-3 South
Viaducts in the eastern subudlS of Paris. Figure
3.93.
The Rio \literoi Bridge (Section 3.8), linking the
city of Rio de Janeiro with \literoi, consists 01 10
miles (16 km) of bridge deck constructed by four
identicallaul1ching girders, Figures 3.55 and 3.51>.
Each 545 ft (160 111) long girder could be com­
pletel\' dismantled. The const;Jllt lI·ianglllar sec-
FIGURE 11.74.
Prestressed conneClions.
"I"
Technology and Construction of Segmental Bridges
516
tion, weighing 440 tons (400 mt), could cope with
spans of up to 260 ft (80111). The conncctions were
identical in principle to those used for the Blois
girder. Each installation was equipped wit h three
supports of nontullnel type, olle fixed and the
other two retractable.
The erection sequence was as follows, Figure
1.51 :
Phose 1: Se{;IIII'IIII)/aciug
The girder rests on three supports, each one O\'er a
pier. Two segmellts are erected sillluitaneously,
one on either side of the douhle cantilever under
COllst ructioll. Thc pier segment of the nex t GlII­
tilenT is also placed with the launching girder in
t his position.
It'
Phose 2: ,\J01'ill{; Ihe /mJl/cilin{; {;irrirr/imL'flrd
The girdcr rolls on two telllporan' translation sup­
ports, olle placed ahove t he pier of the finished
c<lntile\el' and the ot her above t he pier of t he can­
tilever to hc constructed. These teJ))porar~' sup­
ports arc attached 10 the trolleys; the laullching
girder is lilted, thus frceing the penll;}ncllt sup­
ports: and tlte tmlleys arc cllgaged, enabling the
translatiOlI of IIle launching girder to a positioll to
erect the next calltilever. The temporal'\' transla­
tion supports are equipped with a mechanislll al­
lowing transycrse ll1()VelllelltS, as the structure in­
cllldes a ccrtain amolillt of horizontal CUr\'ature.
Thc Rio :\iteroi girder was equipped with three
sets of active stays: lateral sta\'s, central staYs, and
I;ltlllchillg sta\'s. The lateral stays, positioned Oil
the ullderside of the two spans and constalltly
ullder tension, ellsure the resistallce of the girder
while the load (segmellt) passes near midspan. The
central stays strengthell the girder in the vicillity of
tlte central support. The laullching stays, under
tellsion while Ill;tncuvering t he girder, trallsfer the
110llt and rear reactiolls to the central support.
Owing to the Jengt h of t he bridge and t he pres­
ence of a large stretch of water beneath the struc­
ture, the segments were brought to the launching
girder Oil bargcs. The ca nt ilc\'cr stahilit y (.)1' the
bridge was assu red \)\ the launching girder itself,
and ties and props were positioned as construction
proceeded.
The launching girder used for the Devenler
Bridge in Holland, Figures 3.49 and 3.50, were
also capable of being entireh dismantled alld of
triangular seclion. Its total length was 512 ft (156
111) for a weight
19H tOilS (IHO 1111). The
maximulll span length was 243 ft (74 111),
Assembly of the launching-girder elements was
COllsllllllllated by prestress hars norlllal 10 the
joints. It was supported by the fixed supports, of
which the rear and the ccntl'al allowed the passage
of a segmcllt, and two sets of cable st;.IYS: celltral
sla\'s alld launching st<l\'S. The translatioll opera­
tiolls wcre identical to those of the Rio :\itcroi
Bridge, CYCII though ollly OIlC seglllcllt could be
lowered illto plaC<.~ at a tillie.
\\'ilat was peculiar about this laullching girder
was its ahilit~ to raise itsellto its working Icvdln its
OWIl llleans, alld this frolll the ground level where
it was ;lsselllbled. This was lllade possible bv the
central sllspension mast, which acted as a lifting
jack.
In the case of the B-3 South Viaducts, Figure
3.92, the cOllstantly varying structure supportcd \)\
200 piers, crossing five railw<I\ tracks, the Ourcll
Callal, alld several uri>all r~)adwa\s, was lllastered
In a highh mechanized launching girder. The
simultalleolls placillg of two seglllents of the same
calltilever, each weighillg between 33 and 55 tOilS
(:H) and 50 lilt) either side of the pier, is controlled
by a radio-controlled servo lllechanislli that S\'n­
chronizes the loading al each end of the girder.
Agaill the length of the launching girder was
slightly greater thall twice the typical span length,
or
'TYPICIl.L
CR055_.:5ECTIQN
t
L{t.ng tl'"OUflJ
(
J
l.Ifttng tmlk,!l
[
Cent.rat $uppor-t,
CanlA<tvef" sta b, II Z<2'I"
FIGURE 11.75,
~I
u
B-:1 Smull Viaduct Iaullching girder. gcneral layout.
517
Refere1lces
that IS, between four and SIX segments per day.
The average construction speed, including
launching-girder maneuvers, was therefore 200 ft
(60 Ill) per week.
The B-3 launching girder was recently reused
for the ,'.Iame-Ia-Vallee Viaduct, which carries
high-speed suburban rail for the Paris transport
authorit\',
References
FIGURE 11.76.
B-:) South \·iadllCl. segment t rallS­
I. Anon., ,\1111/1/(/1 jill' Quality CUll/ml/o,- PIIIII/.1 111111 Pro­
Iiflcliol/ Q/Premsi Pre,'Iressed COlladl' Pmliutls, .\I::\L­
Itti.70, Prestressed Concrete Institute, Chicago,
1970.
port (I'actor.
which varied between 100 and 164 ft (30 and 50
m). Figure 11,75. The ginler support reactions
were thus applied in the region of the piers, and
the cantilever stabilitv was ensllred bv the launch­
ing girder itself. This stabilizing device can be seen
to the left of the central support in Figure 1L75.
The segments were supplied 1)\ a special eight­
wheeled tractor Illoving along the top slab. Figure
11.76. :\ special de\'ice llsed to unload and store
the seglllents hrought ·bv the tractor freed the lat­
ter and remo\ed the suppl\' ()f segments from the
erection critical path. The c\cle of segment place­
ment and girder ;td\'ancelllent is represellted in
Figure :3.9~~. The next pier segmellt was placed
during the sallle phase as the tvpical segments.
About two spalls were cOllStl'llcted each week-
Anoll.,.{CI Jtw/l/aloj COl/tTell' i'raf'Iif'!', Part 1, Allleri­
can Concrete Institute, Detroit, 197~I,
:{, "Proposed Recolllmendatiolls for Se~lllelltal COll­
structioll ill Prestressed Concrete," Fl P COllllllis'
sioll-I'refabricuioll. 3d Orall, Scptclllher I(li7.
'l
4. "Recolllillenc!ed Practice for Se~lllelltal Const rlletioll
ill Prestressed Concrete," Report bv COJlllllinee 011
Se~Jllelltal COllstl'llLtioll. jOIlrt/([1 oj 1/[1' Prnlrt'lS/,d
Co/Ur!'ie 1lI"Iilllil'. Vol. :!O, ::\o.:!. ,\/arch-.\pril 197'i.
.'). Anoll .. PCI PO.l/-TfIlsifJllillg ,\1([1/11([1. Prestressed
crete Institute. Chicag-o. 1972.
fi.
:\!lOIl .•
COI1­
PTI PosI.Tensioning .\lfll/wd. Post-Tensioning
Phoenix. Arizolla. 1970.
r Ilslit ute.
7. T.
J
Ikzouska, Field III'I}('!'/ioll of Grollieli Po,II­
T!'IIt/olls.
Post-Tensioning- Illstitute.
Phoenix. :hizOIl;l, \fa rch 1977,
T!'IIsiouillg
'r'
I
12
Economics and Contractual A·spects
0,[ SegJnental Construction
12.1
iI
"
12.1
Bidding Procedures
A bridge design ~hould 011 principle be economical
awl as a practicalll1atter must fall within budgetary
rest nctiolls of a particular project. The economic
"moment of truth" for a given bridge design occurs
when hids are recei\'ed and evaluated,
III a hasicallv stable economy where material and
lahor costs are predictable within relativelv small
fluctuations, the selection of structure t\'pe and
materials is reiali\'Cly straightforward. This situa­
tion prevails when the time required fe)r the design
is relativelv. short and thus is not affected by eco­
Ilomic cycles, or, if the design time is relatively
long, the economic cycles are mild. In an inflation­
an ecollomy there is no economic stability, and de­
signers are hard put to make rational choices, as
they have no control over economic parameters
that can influence their design decisions. In short,
the problem is whether economic assumptions
made during the course of design are valid at the
time of bidding.
,
518
12.2.5
12.2.6
12.2.7
12.2.8
12.2.9
12.2.10
BIDDING PROCEDURES
12.1.1 Single Design
12.1.2 Design and Build
12.1.3 Value Engineering
12.1.4 Alternate Designs
12.1.5 Summary Remarks on Bidding Procedures
]2.2 EXAMPLES OF SOME INTERESTING BIDDINGS AND
COSTS
12.2.1 Pine Valley Creek Bridge, California
12.2.2 Vail Pass Bridges, Colorado
12.2.3 Long Key Bridge, Florida
12.2.4 Seven Mile Bridge, Florida
12.3
Zilwaukee Bridge, Michigan
aine Avenue Bridge, Indiana
Napa River Bridge, California
Red River Bridge, Arkansas
North Main Street Viaduct, Ohio
Summary of California's Experience
INCREASE IN EFFICIENCY IN CONCRETE BRIDGES
12.3.1
12.3.2
Redesign of Caracas Viaducts, Venezuela
Comparison between Tancarville and Brotonne Bridges,
France
REFERE.">lCES
Orn'ioLlsh, the design and the bidding (tender­
ing) of a project are closeh related. Contractual
bidding procedure!> \'ar~' from countn 10 countrv,
and current economic pressures are leading to
changes in these procedures. The various bidding
methods used in \'arious countries can be broadlv
categorized (with sOl11e possible variations) as fol­
lows: (I) single design. (2) design and build, (3)
\alue engineering. and (4) alternate designs.
12. Ll
S/.\'GLE DES/G.\'
Heretofore, single design was the major method
used in :\orth America and Great Britain. In this
method, in general, design drawings prepared for
bid are very detailed, to the extent that even the
length and other dimensions of every reinforcing
bar may be given. The bidding period is followed
by a tight construction schedule. The contractor
bids and executes the project in strict accordance
with the bidding documents, No variation from the
documents is allowed unless an error in design is
Bidding Procedures
discovered, or a specific detail proves impractical to
consummate, or geological perturbations are dis­
covered that differ from what was assumed in de­
sign and delineated in the contract documents.
These changes are authorized by a change order,
and if there is an increase in cost the contractor is
paid an "extra."
This system worked well for many years when
the economy was fairly stable and predictable and
when economic changes were gradual over an ex­
tended period. Its disadvantage is its lack of flexi­
bility to accommodate a n inflationary economy,
sudden price changes in materials, a rapidly ad­
vancing technology, and the current emergence of
specialty contractors with unique equipment or
skills, proprietary designs, and patented construc­
tion methods. Its biggest advantages are ease in
administering the contract and absolute control
over the final design.
12.1.2
DESIG,V A,VD BUILD
In some European countries. by contrast, bid
documents are prepa.red with the intention that
the contractor will prepare' and submit his own
detailed design for the project. Thus, bid plans will
be more general and, for a bridge, may show only
span lengths, profile, and typical sections. The
cnntractor may then refine the original design or
submit an alternate design of his own choice, the
responsibilitv for producing the final design and
details being his rather than the engineer's. This
procedure allows the contractor to use any special
equipment or technique he may have at his dis­
posal. For example, a cast-in-place concrete box
may be substituted for a steel superstructure where
the contractor has special know-how in concrete
construction, or the change may be less drastic and
involve onlv a reduction in the number of webs in a
box girder.
Verification of the adequacy of the contractor's
final design is generally carried out by a "proof en­
gineer" who is retained by the owner or is on the
owner's engineering staff. In 'order to minimize
disagreements between the contractor and the
proof engineer, European codes have been made
very specific. As a result, European contractors
usually maintain large in-house engineering staffs,
although they may also use outside consultants.
The outcome apparently is a savings in construc­
tion cost, achieved by the investment of more de­
sign' time and effort than in the single-design
method.
519
The advantage of the design-and-build method
is that in an atmosphere of engineering competi­
tion, innovative designs and construction practices
advance very rapidly. The state of the art of de­
signing and constructing bridges advances in re­
sponse to the need for greater productivity. The
disadvantage is the lack of control over the selec­
tion of the type of structu re and its design. There is
some concern, too, that quality of construction may
suffer as a consequence of overemphasis on pro­
ductivity and initial cost. However, the contractor
is usually required to produce a bond and guaran­
tee his work over some period of time, and anv de­
fects that surface during this period have to be re­
paired at his expense. Whether such a system could
be adopted in the United States is debatable.
12.1.3
VALUE ENGI,VEERING
Value engineering is defined by the Society of
American Value Engineering as "the systematic
application of recognized techniques which iden­
tify the function of a product or service, establish a
value for that function, and provide the necessary
function reliability at the lowest overall cost. In all
instances the required function should be achieved
at the lowest possible life-cycle cost consistent with
requirements for performance, maintainability,
safety, and esthetics."l
In 1962 the concept of value engineering be­
came mandatory in all U.S. Department of Defense
armed services procurement regulations (ASPR).
Before this time value engineering had been
applied to materials, equipment, and systems. The
advent of ASPR provisions introduced value en­
gineering concepts to two of the largest construc­
tion agencies in the United States-the U.S. Anny
Corps of Engineers and the U.S. ~avy Bureau of
Yards and Docks. Soon thereafter the U.S. Bureau
of Reclamation and the General Services Adminis­
tration (GSA) adopted and inserted value en­
gineering clauses in their construction contracts,
and the U.S. Department of Transportation estab­
lished a value engineering incentive clause to be
used by its agencies.
Several value engineering clauses (or incentive
clauses) are in use today by many agencies. In gen­
eral, they all have the following features l :
1.
,f
A paragraph that defines the requirements of
a proposal: (a) it must require a change to the
contract and (b) it must reduce the cost of the
contract without impairing essential functions.
I
I
520
2.
:\.
4.
!),
Economics and Contractual Aspects of Segmental Construction
.~ hdocllIIlenlalion'1 paragraph that ilelnizes
the information the contractor should furnish
with each proposal. It should be comprehen­
sive enough to ensure quick and accurate
evaluations, detailed enough to reflect the
contractor's confidence in its practicabilitv, and
refined to the point where implementation will
not cause undue delay in construction opera­
tions. Careful de\'e\opment of this paragraph
and meticulous adherence to its requirements
will preclurle scatter-shot proposals bv the
contractor and burdensome review bv the
agencv.
:\ paragraph on "submission." This paragraph
details the procedure for submiual.
A paragraph on "acceptallce," which outlines
the right of the agency to accept or reject all
proposals, the notification a contraClor may
expect to receive, and appropriate reference to
proprietary rights of accepted proposals.
paragraph on "sharing," which cOlltaills the
forl1lula ror determining the contract price
a!ijustlllent if the propo.sal is accepted alld sets
forth the percentage of sayings a contractor
lIlay expect to receive.
:\
As generally practiced by highway agencies III
the United States, a value engineering proposal
lIlllst indicate a "substantial" cost savings. This is to
pn>clude minor changes such that the cost of pro­
cessing offsets the savings to be gained. SOll1e other
reasons for which a value engineerillg proposal
llla\' be dellied are as follows:
Technical 11OlIcOllIpliance.
Delay ill construction such that the cost saYlllgs
would be subst alllialiv nullified.
Proposed change would require resubmission of
tlIe pn~jeCl for any number of \'arious permits,
slIch as environmental impact statement, wetlands
permit, and navigation requirements. Resubmis­
sion would in all probability delay construction anrl
II ulli fy any cost savings.
Savings resulting from a value engineering pro­
posal are generally shared equally by the agency
and the contractor, after an allowance for the con­
tractor's development cost, the agency's cost in
processing the proposal, or both. As practiced in
the United States, all cOntractors must bid on the
design contained in the bid documents, and only
the low bidder on the base bid is allowed to submit
a \'alue engineering proposal. This is, of course,
value engineering's biggest disadvantage. Ally
!lumber of contractors rnav have more cost­
effective proposals that they' are not allow'ed to
submit because they were not low bidder on the
base bid, Its advantage is that to some degree it aI­
lo\\'s contractor inno\,<ttioll to be introduced.
12,1.4
ALTER.\'ATF /)ES/(;\'S
Alternate designs, as it is developing ill the United
States, basically is an attempt to produce a hybrid
sYstem cOllsisting of the besl elements of the
single-design and the design-and-build methods. It
attempts to accomplish the following:
Retain for the authorizing agency cOlltrol over the
"t\Ve selection" of the structure and it~ design
Provide increased competition bet ween lIIaterials
(structural steel versus concrete or prestressillg
5t ralld verSll s hal'S) or const ruet ion proced 1I res
(cast-in-place VerSlIS precast segmental or halallced
cantilever versus increlllelltal launchillg-, and so
OIl )
Pn)"i de COlI t raet or fkxi bi Ii t y (const ruct ion proce­
dures, methods, and/or expertise)
This met hod has de\'eloped, wit h encouragement
from the Federal H)gh way Ad millist ration, as an
<lIlti-inflationarv measure iO COl II Ilat dramatic in­
creases in highway construction costs. A technical
Aclyisorv Z published by the Federal Flighway Ad­
ministration stales:
Balw..'>!' offluc/ualillg I'col/ollli( (of/diIIOIlS, II Isfdl Ihlll
mulliplp rr/Jl'litizll' SflaW, IOllg .1/11/11\ or ml1jor hndg!'s,
or where Ihere is 1111 ('xlnuled /)aiod of design from (011­
(1'/lllOn of IiiI' /lmjerl 10 (J ),I'I('(J,\CfOT hids, Ihere CI1II he I/O
(LISUrIJllC(,
/lri«(' slabilily /1)1' (l parlilll/aJ' malnial or
(ollslruc/ioll mel/wr/olof-',," Wilh allerllal!' des ig 11.1, no
Il/al/a how lite ('COllOm), rhallges, lfIore del'lgns 111'1' m'oi/­
aille at IiiI' lime of fn'r/ding thai are tike/,,' 10 lie SlIill'd 10 Ihe
ml
or
/)revailing ('col/Olnir (ollditiolls.
General recommendations regarding alternate
designs from the same document2 are as follows:
1.
To receive the most economical construction
between basic structural materials, consistent
with geographic, environmental, ecological
or other site restrictions, there should be
maximum opportunity for competition he­
tween structural steel and concrete.
Bidding Procedures
2.
\Vithin environmental, aesthetic, site, and
other constraints. the plans and bid docu­
ments should show or otherwise indicate what
alternative types of structures will be allowed
or considered. The contractor should be al­
lowed the option to bid any designated alter­
native design that is consistent with the con­
tractor's expertise, available equipment, and
so on.
3. Bid documents and the contract plans should
clearly indicate the design criteria and what
type of alternative designs andlor con tractor
options will be acceptable. Determination of
practical and economical alternatives and/or
contractor options should be developed in the
preliminarv design.
4. Bid documents should be considered as
"open" documents in regard to construction
method, erection systems, and prestressing
systems.
5. Consistent design criteria should be used for
alternatives; for example, if load factor de­
sign is llsed, it shollid be used for all alterna­
tives.
6. Span lengths should be identifled on the
contract plans. However, other than where
pier locations are constrained by physical and
geological conditions at the site, consideration
should be given to allowing a tolerance in pier
location lo avoid placing a particular alterna­
ti\'e at an economic disadvantage. For exam­
ple, in a typical three-span structure, the side
span should be approximately HO percent of
the center span for structural steel, 70 per­
(ellt for conventioll;;! cast-in-place concrete
011 falsework, and 65 to 70 percent in seg­
lllellt~ll balanced cantilever cOllstruction.
7. 'To avoid an economic disadvantage lO a par­
ticular Sli perstructure alternative. alternative
substructure designs mav be required. Limi­
tations Oil the substructure, such as allowable
axial load and moment, should be clem'lv
identified on the contract plans.
'
8. Where specific design requirements are not
covered by the ;\merican Association of State
Highwav and Transportation
Officials
(AASHTO) Bridge Specifications, the con­
tractor should be allowed to use other recog­
nized codes and standards where applicable.
However, the alternative design should
document where these provisions are to be
'used, why the AASHTO requirements do not
9.
10.
11.
521
apply, and which articles of the substituted
code or standard are to be used. Such provi­
sions should be subject to approval by the en­
gineer and appropriate agencies.
Prebid conferences are to be encouraged as a
means of communication between the en­
gineer, high way agencies, and contractors.
In order to allow a contractor adequate time
to investigate the various alternatives and
prepare plans, it is recommended that the
advertising time be commensurate with the
size and complexity of the project with a
minim.um of 60 days.
In order to allow adequate review and
checking of the low bidder's proposal, award
of contract should be extended commensu­
rate with the size of project.
Specific recom mendatiom/ regarding prestressed
concrete alternates are as follows:
To increase the competition in post-tensioned
concrete construction, it is recommended that
plans and other bid documents allow cOllven­
tional cast-in-place Oil falsework, precast pre­
stressed span units, and segmental construc­
tiOll or combinations thereof.
2. Segmental construction should· allow the fol­
lowing at the contractor's option:
a. Precast or cast-in-place segmental COll­
struction.
b. An\' of the post-tensioning ,>vstems-that
is, strand, WIre, or bars or combinations
thereof.
c. :\nv of the following construction
methods: balanced cantilever, span-bv­
span, progressive placing, incremental
launching, or combinations thereof.
d. Exterior dimensiolls 0(' the cross section
should be fixed, At the cOlltractor's option,
the thickness of wehs and Hanges 111;1\' be
\'aried to accommodate proposed con­
struction and erection methods a nel
post-tensioning systems, provicl ing that
any changes in the dead weight, shear, and
so on are accommodated in the design.
3. The contract plans should indicate the
maximum and minimun final prestressing force
(Pf ) and moment (Pf X e) required, after all
losses, for the final condition of the structure
-that is, dead, live, impact, and all superim­
posed loads. Any increase in prestressing force
1.
522
4.
5.
G.
Economics and Contractual Aspects of Segmental Construction
requirements as a result of the method of con­
struction, election, or type of tendon system
should be evaluated at the shop drawing stage.
Changes in eccentricity of prestress should be
accompanied with appropriate changes in pre­
stress force to produce the same minimum
compressive stress due to prestress.
The minimum prestress force should be such
that under any loading condition, both during
and after construction, stresses will be within
allowable limits. Consideration should be given
to secondary moments due to prestress, redis­
tributed moments due to creep, and stresses
resulting from thermal gradient (between the
top and bottom of the girder and between the
inside and outside of webs).
Contractor revisions to contract plans, with
supporting calculations, should be submitted
to the ellgineer for apprO\·al.
12.1.5
SU,HMARY REMARKS ON BID])].\'(;
P1WCEDURES
All or the bidding procedures described above
have one thing in common: they all attempt to
produce the lowest initial cost by competition in
construction and/or design. All of the last three
approaches (design-and-build, value engineering,
and alternate designs) require decisions based on
comparisons or basic structural materials, structure
types, construction methods, and so on. This im­
plies that the basic premise in the selection process
is equivalency-comparable service, performance,
and life-cycle cost of the facility.
Life-cycle costs refer not only to initial cost, but
also to maintenance and any rehabilitation costs
during the life of the structure. True cost of the
project must be considered. What may be initially
least expensive may in the long run, when future
costs are accounted for, be actually most expensive.
Some newer structure types and designs are at the
fringe of the state of the art and have only been
used in the United States within the last decade or
less. Thus, an adequate background of experience
is unavailable to evaluate life-cycle costs. The esti­
mation of life-cycle costs may be difficult in many
cases, such as for new and progressive bridge de­
signs. Functionally, alternative structures are de­
signed to the same criteria. Only years of opera­
tjonal experience can provide the data base for
reasonably estimating life-cycle costs and thereby
true equivalency in design insofar as cost is in­
volved. However, the problem of adequacy of data
does not diminish the importance of the question
and the need to attempt to answer it.
Allother anti-inflationary measure lIsed in l't:cent
years is that of stage construction. This concept
may take one of two forms .. Major structures, be­
cause of their size, lend themselves to stage
construction-that is, separate substructure and
superstructure contracts. Usually several years will
elapse between bidding and awarding of the sub­
structure contract and the superstructure contract.
The economic superstructure span range for dif­
ferent alternative types and materials is a variable.
In this form of stage construction the substructure
is let first; thus the spans for the superstructure de­
sign become fixed. This mayor may not impose an
economic disadvantage to specific superstructure
alternates. The substructure must be designed for
the largest self-weight superstructure alternati\·e,
which mayor may not be the successful super­
structure alternative. It appears that this form
of stage construClion maybe to some extent self­
canceling or counterproductive to cost savings.
\Vith a total alternative design package, the sub­
structure (foundation, piers, span arrangement)
can also have alternatives commensurate with the
superstructure alternatives.
The other form of stage construction concerns a
large project. containing many bridges, that is sub­
divided for bidding purposes into a number of
smaller prqjects. Its f>rimaq,' purpose is to encour­
age small contractors by pn)\iding pn~jects of
manageable size, thus increasing competition.
However, certain construction techniques, by vir­
t ue of the investment in sophisticated casting or
erection equipment, require a certain volume of
work to amortize the equipment and be competi­
tive. Depending upon the size of the subdivided
contract, this form of stage construction in some
instances may also become counterproductive.
The value engineering concept can be divided
into two major areas of application: during design
and during construction. Value engineering pro­
cedures in the design stage may result in very
specific recommendations based on a certain set of
assumptions at a particular point in time for the
design. If conditions change during the interval
between the design decision and the actual con­
struction, which can be several years, conditions on
which the assumptions were based may have
changed. Such changes could make the original
value engineering decision incorrect. The alterna­
tive design concept, on the other hand, does not
make all such specific design decisions at an early
Examples of Some Interesting Biddings and Costs
stage but retains some options in order to allow a
later response to changed conditions. Therefore,
there is an apparent incompatibility between the
application of value engineering principles in the
design stage and the concept of alternative designs
for bidding purposes. However, the concept of
value engineering is a powerful tool and can be
made compatible with the concept of alternative
designs if its principles are used to determine
whether a given project should require alternative
designs and, if so, what structure types should be
considered as equivalent alternates.
12.2
12.2.1
Examples of Some Interesting
Biddings and Costs
PISE VALLEY CREEl\. BRIDGE, CAUFORSIA
The Pine Valley Creek Bridge (Section 2.7) was the
first segmental bridge in the United States to in­
corporate the concept of value engineering (cost­
reduction incentive proposal) in the bidding
docu mellts. The origi nal design assu med cast-in­
place balanced cantilever construction with the
prestressing force (P f ) ;ind nHllllent (Pf X e) based
on strand capabilities.
Project plans developed by CALTRA:--JS re­
quired construction of the cantilever~d sections at
piers 3 and 4 before those at piers 2 and 5 (refer to
Figure 2.40). Because of rigid specification re­
quirements for the protection of the valley slopes,
TABLE 12.1.
the contractor was faced with a difficult and costly
erection procedure. At least one cable way span­
ning the entire valley would have been required to
transport men and material to appropriate loca­
tions during the construction procedure. Complete
site installations on both sides of the valley would
have been required, which were accessible only
with a great deal of difficulty.
The superstructure design alternative submitted
under this proposal employed the Dywidag system,
which included the following: (1) use of the
threaded-bar system especially suited to segmental
construction, (2) increased prestress-force eccen­
tricities, since most longitudinal prestressing bars
could be placed and anchored in the slab, (3)
diagonal prestressing in the webs to cater to the
shear stresses, and (4) a modification in construc­
tion sequence so as to work from piers 5, 4, 3, anci
2, Figure 2.44.
Changes proposed under the value engineering
clause are summarizied in Table 12.1. Total sav­
ings as a consequence amounted to $382,000.:1
12.2.2
Structural
svstem
Concrete stresses:
Construction
Tension
Concrete shear
VAIL PASS BRIDGES, COLORADO
The Vail Pass structures are part of Interstate 1-70
near Vail, Colorado, in an environmentally sensi­
tive area. Environmental considerations played a
dominant role in the selection of the bridge types
and the design thereof. Another factor considered
was the relatively short construction season at the
high elevations of the sites.
L
Pine Valley Creek Bridge, Value Engineering Proposal
Original
Construction
sequence
523
CRIP
Long cantilevers before
shorr to minimize
creep ..ls
Cantilever for D.L.,
continuous for L.L.
+ added D.L.
:\0 Redistribution
Reverse to facilitate
constr. from abutment
0.-1f;.
3vr:.
o
"63" .\CI, mild steel
Slab designs
.\.\SHTO loads, method
and distribution reinf.
Hinge
Two diaphragms
Savings
estimated
$ 88,0()()
Conti n uous for
all loads
Full redistribution
0.55/;.
Pri nci pal stresses
diagonal prestress
A.\SHTO loads with
"Hornberg" graphs, no
distri bution rei nf.
No diaphragms
$228.000
22,000
22,000
22,000
$382,000
r
~
Economics and Contractual Aspects of Segmental Construction
524
Of the 21 bridge structu res in this project, 17
were designed and bid on the basis of alternative
designs. One alternative design considered
trapezoidal steel hox girders composite with a con­
crete roadway flange. The other alternative design
was for precast concrete segmental box girder de­
sign, with the Federal Highwa\ Administration re­
quiring that the contractor be given the option of
cast-in-place segmental construction.
At two locations, the site constraints were such
that thev were bid without alternatives as steel box
girders. Two other locations required 80 ft (24 m)
long simple-span underpass structures to provide
lor wildlife migration. These structures were built
of cast-in-place concrete box ~irder construction.
The remaining 17 structures were completelv de­
signed and detailed for the two alternatives, one in
structural steel and the other in precast concrete
segmental (with a coni ractor option of providing a
cast-in-place segmental design). Spans varied in
nUIIIber from t\\"o 10 five and ill length frolll 30 to
:260 ft (9 to 79 111).
Table 12.2 tabulates the five contracts that in­
volved the 17 hridges hid 011 the basis of alternative
designs and lists them in the order in \\'hich the}
were hid. 4 Approximately a year elapsed between
the lettillg of the first and last COlllracts. Although
considerable differences in bid prices are shown in
individual projects, for the lotal pn~ject there is less
than $80,000 difference oul of an approximate
total cost
$17 million, or less than 0.5% dif­
or
TABLE 12.2.
ference in bid prices for the alternatives. Precast
segmental was the low bid on project I and cast­
in-place segmental was the low bid on project 4.
Based upon length (width was constant), the seg­
mental concept was successful in approximately
60o/c of the total project.
The consultants, I nternational Engineering
CompanY, Inc., estimated that the additional cost
10 produce alternative designs \vas about 2.So/c of
construction cost. It is difficult to estimate what
savings were achieved by bidding alternative de­
signs rather than· a single design; however, overall
sa\'jngs of 7 to 10% of Ihe construction costs ale
not unreasonable. 4
12.2.3
LOXG;..,:n BRlJ)(;E. FlDUlJ)A
The Long Kev Bridge in the Florida ~eys was hid
lit ilizi ng t he concept 01' alternate designs. Fou r
complete sets of contract plans were prepared for
the alternative construction schemes indicated in
Table 12.3. Plans for the AASHTO precast, pre­
tensioned I girders were prepared by the Florida
Department of Transportation. Plans for the three
basic precast segmental schemes were prepared by
the state's consultant, Figg and \luller Engineers,
Inc.
III the prciiminan design stage three methods
or segmental COllst ructioll were considered lor
this pn~ject: balanced cantile\er, span-by-span,
and pl'Ogressi\e plat-ing. The progressi\e placing
Results of Alternative Bids, Vail Pass Bridges
TOlal
Proj.
Hridge
:":0.
:":0.
4
5
Totals
F-II-AX
F-I I·:HV
F·II-A\,
F-II-.\C
F-12·AK
F-12-A\1
F-12-:\:":
F-12-AO
F-12-AI'
F-II-AP
F-II-AO
F-II-A:\'
F-II-A:>'1
F-II-AL
F-II·AK
F-12-AT
F·12-AS
:..: o.
Spa I1S
4
5
4
4
3
2
3
~-I
:-i
3
2
4
4
4
3
4
4
Length
(It )
Length
(it )
Low
Steel
Hid
Cost IF!".
Steel
Low Connete
Bid
Cost/Ft 2 ,
COllcrele
7'27
880
6YO
668
220
240
350
368
600
2965
S5,992.155
$48.12
1778
$3,777,549
$50.59
$4.111,170
$55.05
$994.347
$44.50
$1,053,364
$47.14
2448
$4,257,771
$41.41
$4,108,057
$39.96
1452
9175
$2,29S,409
$17,320,231
$37.69
$44.95
$2,598,938
$17 ,39S,84 7
$42.62
$45.15
$44.39
310
222
740
744
514
450
726
726
Examples of Some Interesting Biddings and Costs
TABLE 12.3.
525
Long Key Bridge, Alternatives
Substructure
Su pers t rucw re
Precast Piles
Drilled Shalts
A
B
C
D
F
H
Precast I!;irders, .\,\SHTO
Segllle n tal:
Span bv span, V piers
Span by span, vertical piers
Cantilever, \'ertical piers
First option. slab reinforcing
E
G
RIC epoxy coated
Pretensioning
Cast.-in-place conventional
Precast (never integral)
Second option, barrier curbs
method was discarded because it was felt to be (at
the lime) too new for acceptance in L' .S. practice. It
was later introduced on the Linn Cove Bridge in
:--Jorth Carolina. The basic difference in the two
span-by-span alternatives for the Long Key Bridge
is in the pier configuration: V piers or vertical
piers,
Aside from the const ructioll alternatives and
pier t.-pes, the contractor was offered the option
Oil all segmemal alternatives of transversely rein­
forcing the top flange' either~ with epoxy-coated
conventional reinforcing steel or by transversely
pretensioning with ~ ill. (1~.7 mm) diameter
strand. Further, he had the option on all segmental
alternatives of either precasting or casting in place
the traffic barriers.
The contractor also had the option of casting the
segments rightside lip or upside down. Casting the
segments upside down was intended to facilitate
transversely pretensiol1ing the top Bange. How­
ever, since no waterproof membrane or wearing
surface was specified, the top flange surface of the
deck was required to have a grooved or tined sur­
face for sUd resistance. If the segment v.rere cast
upside down, then, the form would be required to
produce the desired texture. Specifications were
left open such that strand or bar prestressing ten­
dons could be bid. All conventional steel rell1­
forcement was required to be epoxy coated in all
alternatives.
The eight basic alternatives for this project pro­
duced bids from eight contractors, as indicated in
Table 12.4. :--Jote that there were six bids for the
span-by-span method, one for the balanced can­
tilever method, and one for the precast preten­
sioned AASHTO I girders.
The low bid in precast segmental was $2.6 mil­
lion less than the AASHTO I-girder bid. Low bid
was for the span-by-span alternative with precast V
TABLE 12.4.
Bid Rank
Long Key Bridge, Bid Tabulation
A!ternati\'e Chosen
Relative Bid
D
F
F
F
B
F
F
H
1.0000
1.0225
1.0539
I .0911:)
1. I 7:11
1.1HH
1.2557
1.306:)
2
:)
-t
:i
()
7
H
piers and drilled shaft foundations. The contractor
elected to precast the segments near the project site
and cast the segments rightside up, using trans­
verse prestressing in the top flange. He slip­
formed the cast-in-place barriers after segment
erection. Further, he elected to move the scaffold­
ing trusswork from span to span by using a
barge-mounted crane as opposed to having the
falsework trusses mOllnted on barges.
Table 12.5 presents a cost analvsis of the low bid
as compared with the AASHTO pretensionecl 1­
girder alternative."
TABLE 12.5. Long Key Bridge. Cost Analysis of the
Low Bid and the AASHTO I-Girder Bid
Sp<ln-bv-Span
Segmental
Precast AASHTO
I Girder
TOl,d cost"
$26.63/h~
Su perstructure
cost
Substrnctllre cost
Segments erected
Total bid
Total area
:$2 I. 43 1ft2
$30.95Iftl
:$23.59/ft2
:$ 5.20/ft2
$19.16Ift 2
515.307,375.91
468,30 I ft2
$17.956,538.75
470,277 ft Z
"The mobilization bid items were proportioned to the structural
items in all cases. The Florida Department of Transportation
estimate was $14,550,000.
Economics and Contractual Aspects of Segmental Construction
526
TABLE 12.6.
Seven Mire Bridge, Alternatives
Substruct ure
SuperstrucLUre
Precast Piles
Drilled SlJafts
A
B
C
E
D
F
Precast AASHTO I-girders
Segmental:
Span-by-span, vertical piers
Cantilever, vertical piers
First option, slab reinforcing
RIC epoxy coated
Pretensioning
Cast-in-place conventional
Precast (n~ver integral)
Cast-in-place conventional
Precast
Second option, barrier curbs
Third option, box piers
12.2.4
SEVEN MILE BRim;};, FLORIDA
Seven Mile Bridge in the Florida Keys had the
same basic alternatives as Long Key Bridge, except
that the span-by-span with V piers was eliminated
and the contractor had the further option for the
vertical piers of casting in place conventionally or
precasting, Table 12,6.
Six bids were received, with all bidders se­
lecting alternative D, Table 12.7. Low bid was
$44,986,942.31. There were no bids for the
AASHTO I-girders. The low bidder optioned to
reinforce the top slab with conventional reinforce­
ment, epoxy coated; to cast the barrier curb in
place; and to precast segmental box piers. The low
bid included $5,128,600 for waterline, roadway
approaches, and navigational requirements. Anal­
ysis of the bid items revealed a superstructure cost
of $23.22/ft2 and a substructure cost of $5.68/ft2 ,
resulting in a $28.90/ft 2 total cost. The Florida
Department of Transportation estimate was $52
million ($7 million higher than the low bid).
12.2.5
ZILH'AUKEE BRIDGE, ,\1/CHIG,4N
This structure was designed with ailernatives of
steel plate girders and precast segmental concrete
box girder. Bids were first taken in November
] 978, Table 12.8. The engineer's estimate for the
concrete alternative was $60,609,614.30 and for
the steel alternative $71,3] 6,854.90. On the basis
that the low bid of $80,999,445.50 was 33% higher
than the estimate, the bids were rejected.
The design underwent revision, and the bid
documents allowed tbe contractor to make design
and prestressing system changes under a "cost re­
duction incentive," and an escalation clause was
introduced. The pr~ject was rebid in August] 979
(nine months later), Table 12.9. The engineer's es­
ti mate was $71,645,661.50 for the concrete alter­
native and $71,965,516.70 for the steel alternative.
The low bid of $76,787,252.65 was 7% over the
estimate-5% below the previous low bid. By re­
bidding the pi oject (after nine months of inflation)
a savings of $4.2 million was achieved.
TABLE 12.8.
TABLE 12.7.
Bid Rank
2
3
4
5
6
Seven Mile Bridge, Bid Tabulation
Alternative Chosen
Relative Bid
D
D
D
D
D
1.0000
1.0214
1.0768
L1404
1.2297
1,2556
D
Bid Rank
I
2
3
4
5
6
Zilwaukee Bridge, Ranking of
First Bids
Relative Bid
Alternative
1.0000
1.0115
1.0562
1.0816
1.1 071
1.1375
Concrete
Concrete
Steel
Concrete
Steel
Steel
527
Examples of Some Interesting Biddings and Costs
TABLE 12.9.
Bid Rank
2
3
4
:)
12.2.6
Zilwaukee Bridge, Ranking of
Second Bids
Relative Bid
Alternative
I.(JOOO
1.0798
1.0829
1.1231
1.1501
Concrete
Concrete
Concrete
Sleel
Steel
CUSi:' .4VEXUE BRIDGE, ISDIANA
The Cline Avenue bid documents were very liberal
towarcl redesign, with the bidder only having to in­
form the state of the intention to redesign at bid
opening. As designed, the plans and specifications
provided the option of a steel plate girder or pre­
cast segmental box girder structure. The structure
was redesigned as cast-in-place on falsework, pre­
stressed concrete box girder, except for the main
channel spans which are cast-in-place segmental.
rhe steel option was a composite load factor de­
sign. The low concrete bid was for $53,545,770.55
with the engineer's estimate being $53,560,259.78.
Relative bids are listed in Table 12.10.
12.2.7
SA.P..!. RIVER BRIDGE, CAUFOR.Vl.4
The Napa River Bridge (Section 2~ 11) is another
example of the lise of alternative designs. For this
prc~ject. because the lower structure height made
falsework feasible, bid documents were prepared
for three alternati\'e schemes:
Alternative C used a transverse prestressed deck in
order to reduce the number of girders. Strong
competition was expected from the steel industry,
as this site is readily accessible by water from the
yards of two major fabricators. However, the low
bidder, G. F. Atkinson Company, selected alterna­
tive C and cast the bridge generally in half-span
segments on falsework to the ground as a series of
balanced T's. About 60 ft (18 m) of the 250 ft (76
m) span over the navigation channel was con­
structed in three segments on falsework suspended
from the cantilevered boxes on each side."
There were six other bidders, of which only one
bid the steel alternative and none bid alternative A.
Relative bids are listed in Table 12.11. The first six
bids were for alternative C, and the last and highest
was for alternative B.
12.2.8
This is a seven-span structure with five imerior
spans of 210ft (64 m), end spans of 135 It (41 m),
and a roadway width of 32 ft (9.75 m). Estimated
cost was $3.3 million. Eight bids were received, six
in structural steel and Iwo for concrete segmental.
Bids ranged from $3.22 to $4.89 million. The con­
crete segmental was completelv open as to the
method of construction (both concrete bids were
based on the incremental launching method). Rel­
ative bids are listed in Table 12.12.
TABLE 12.11.
!\.
Conventional continuous cast-in-place box
girder bridge
Bid Rank
B:
Trapezoidal continuous structural steel box
girder bridge
2
3
4
C:
Cantilever prestressed segmental concrete
bridge with either precast or cast-in-place
segments, and erection either bv the balanced
cantilever method or on falsework
Because of poor fOll ndation material and a
readily available aggregate su pply, all alternatives
used lightweight concrete in their superstructures.
TABLE 12.10.
Bid Rank
2
3
~
Cline Avenue Bridge, Ranking
of Bids
RED RIVER BRlDGE, A.RI\.ANSAS
Napa River Bridge, Ranking of Bids
Relative Bid
1.0000
1.00~H
I. I ~ !i'l
I. I H:I 7
:)
1.~7h5
6
7
1.-{:lll5
1.5:!IO
TABLE 12.12.
Bid Rank
Relative Bid
Alternative
2
3
4
1.0000
1.0252
1.0596
Concrete
Steel
Steel
6
7
8
5
Red River Bridge. Ranking of Bids
Relative Bid
Alternative
LOOOO
1.1437
1.2685
1.2800
1.3099
1.3229
1.4267
Steel
Steel
Steel
Steel
Concrete
Concrete
Steel
Steel
1.5175
Economics and Contractual Aspects of Segmental Construction
528
Structural steel prices \'aried from a low of
$O.65/Ib to a high of $O.9:1/Ib \\'ith an a\'erage of
$0.78/lh. Structural steel prices in Arkansas for this
t \'pe of const ruction had pre\'iOllsly been i 11 the
range of $0.80 to $O.85I1b. The low bid price of
$O.6S/lb represents a reduction of approximateh­
19 to 2:17£-. All steel prices were for domestic steeL
Note that the bid prices included the demolition
of the existing bridge. If this item were deleted, the
bidding would be rearranged as illciicated in Table
12.1 :1.
The IUIllp-sum price for the concrete super­
structure was, for the low cOllcrete bicider, $~H.3i/
hZ. which cOlllpares fan)rabl\' with the Keys
bridges ill Florida. However. this price was 110t
cOl1lpetitive. Cndoubtedl\, there are numerous
reasolls why. One m;1\' he that there was no pre­
castillg plant within sufficient distance of the site,
and thus the (ost of shipping the seglllellts ma\'
ha\'e beell prohihitive. The project was not large
ClloUgiJ to attract contractors with the expertise to
set up a precaslillg operation at the site. The two
cOllcrete seglllelllal hids recei\'ed were based 011 ill­
crclllcl1tallaunching, and evideIIlI\' the proiect was
Ilot large ellough to a<iequateh' amortize t he cost of
the casting hed aud launching equipmellt on this
project to make the method cOlllpetitive.
12.2. 'J
.VOFOII .HAI:\, STRFl':T
~submilled, three optional concrete redesi~ns were
bid.
As designed, the plans and specifications pro­
vided the option of a steel plate girder or precast
segmental box girder structure. Rici documents
were quite liberal for redesign but requireci quite a
hit of cietail with the hid docillnents. The winning
bid was steel girders, as desiglleci, priced at about
$R7!fi2 without one abutment, which was to be con­
structeci under another contract.
The steel girders were a noncomposite,
working-stress design. The approximatelv 15 mil­
lion pounds of A5RH structural steel was bid at
SO. 7 5!1b. It shoulci be noted that aciditional sa d ngs
in steel could have been accolllplished ,,·ith a com­
posite design. Tahle 12.14 is a reiatiH' summarv of
the eight bids.
Note that the low concrete hid was ollh· 3.7(lc
abo\'e the low bid, which indicates the co'mpetiti\,e­
ness.
12.2.10
SC.\1.HAR}' OF C.,/UFO!?X!A·5., 1-:XPfJUF,XCE
California\ experience with a cost reduction in­
cewive proposal (CRIP) (\';!luc el1~illeerilJg) and
alternative designs for projects in\'olving segmen­
tal construction is sUll1marized in Table 12.15. 6
,'",mucr, ON f()
12.3
The low hid 011 this project was $25,715,733.00,
as compared with the ellgineer's estimate of
$2~,2()O,OOO. Probahly a llIajor reason why the 1m\'
hid was 127r under t he en gi neer's estimate was the
cOlllpetition offered In the two plan alternative de­
signs ill concrete and structural steel, resulting in a
minimulll savings of at least $3,500,000. The com­
petitive situation was further enhanced by allowing
bidders to propose additional optional designs.
Alt hough no additional steel optional ciesigns were
Increase in Efficiency in Concrete Bridges
As stated ill previous charitCl's, prestressed con­
crete segmental bridges ha\c extended the prac­
tical and competitive economic span range of
concrete bridges. An interesting comparati\'e
exercise is to look back at bridges built in the
past anc! evaluate them in the light of presenl­
ciaI' de\'elopments.
TABLE 12.14.
TABLE 12.13.
Bid Rank"
4
:!
H
:~
:'>
6
7
Red River Bridge, RerankingofBids
Relative Bid
Alternative
1.0000
1.1147
Steel
Steel
Steel
Steel
Steel
Concrete
Concrete
Steel
1.l6:!O
1.2841
1.3379
1.3919
1.40:'>4
1.:'>276
"Ranking corresponds with lhal presented in Table 12.12.
Bid
Rallk
2
3
4
Relative
Bid
1.0000
1.0370
:>
1,()40 I
1.0579
1.0884
6
1.1128
7
8
1.1508
1.4099
North Main Street Viaduct,
Ranking of Bids
Alternative
Sleel alternative as per plan
Redesign concrete alternative
Steel alternative as per plan
Concrete alternative as per plan
Steel alternative as per plan
Steel alternative as per plan
Redesign concrete alternative
Redesign concrete alternative
TABLE 12.15.
Length!:'I!ax.
Spall (ft)
Date
Bid
Summary of California's Segmental Prestressed Bridge Experience
Bridge
Design AlterllatiH:'
Provided
Cost-Hndge
Work Olll)"
Remarks
------~--------------------~.
21i2
Pine \. alley
Creek
I iOO/-I:JO
S H.2 \\
= S69/1t2
A.
Camilel'er prestressed
concrete scgrnenlal
nox girder with
either:
I, Prestressed rock
anchor I()()tings"
2. :'v!ined rock shaft
CR I P hy contractor re­
I'ised superstnldllre de­
sign and cOllstruct;oll Se­
quence. Savings to slale,
Sl9I,OOO,
foundatioll
'1172
SI27 1111 (ind,
S]2,0 :'II
prol'. lor future widelling)
Stanislaus
River at ~e\\'
'(clones
A.
Cantilever prestressed
t:oncrelC segrnenlal
B.
box girder
Sth'Clllral steel box
g-inlcr(J
Both with either:
I, Prestressed rock
Seven contractors bid steel
and t\\'o hid concrele \.1>'..1
separated lo\\' sleel and
low concrete.
anchor footiugs
:).:"i:\
h'l Riln BL
;llld Overhead
1:IK71:\ 10
S;i.O :'1
= S:I'i lit"
,.\,
2, :'v(illed shaft
f'H1mlatiolls <I
Colll'emiollal t\\'in
t \\'o-cel] cast-ill-place
preslressed concrete
hox girdep;
I Ie 71
:\"I'a RiltT
:\;'1"1
.li
.\.
COil vel1l iOllal si x -celi
cast-ill-place pre­
stressed box girder
I'.,
Struclli ral steel bo:.,
girder
Cantilever prestressed
C.
CRll' lllodilied design to
single-cell
hoxl's. 'ttx. f:d"'I\'ork
height 92 i't ::. Salings to
statc', S I l2,M2 L
Sj" 01 ,el'('!] h"lders chos('
C. Fal.s<,work heights lar­
ied Irom ti! 10 1:12 IL
se;~me11lal
COJJcrete se)..{lllL'lltal
\117;-)
Colorado
River
;1[
7.1 \1
S:I lilt'
.\.
Y1I1ll;1
two-cd I box ginkr"
Segmental pre­
'it
rc'O,'icd concrete
sin:-\Ie cell h"" wilh
criteria pro"ided to
COllven to cantilever
12:7(;
S2.1; \1
Cu"dalupe
S2Kilt'
A.
COlll'emi()llal sel'Cll­
I'.,
cell prest ressed con­
tTCle hox II
.\ four-cell pre­
Riler at S;lll
JOS('
stressed box dcsig-tH2d
I'DI' segmclItal Cllll­
<:alltilel'er cOllslructioll
('oll,icie!'ed I,,' lOllt rannr
bUI Hot lIs('d
bccau,,<,
cot)­
tfado!' 0\\ lled ade'lU<lll'
"'1)plv
['a"ework, \l;lX.
falst'work height 70 It ~
or
\(axilllllm lalsework
height ,HJ l't ()\ er a ,,'aSOl!­
alII, dry ril'er. COlltr;Wl()r
lnexpl:'rlt'tlccd iIi '\('f{Illt"ll­
Lal ('()t1strllctioll,
SIl"llClion
3,76
S;m .Jo;''luiu
'HO Id(j()
STU \1
,\.
Pn:strl'ssed Cllnerele
with three main ,'pallS
designed t(lI' call­
tilel'er seg'lllemal COll­
struction and 20 300
I't ~,pproach spallS de­
signed ['or segmelllal
construction with
provisions to modify
B.
Structll ral steel
welded plate girders
(unpainted A-588)
wi th 29 200 It ap­
proach spans"
Same as :\ with 200 ft
approach spans
River ;u ,\llti­
oell
.-\I1I;\'e bidders ,ito,,' 'IVl'l.
L()wer-thalhllltilil"lte,1
(rorl'i~J)1 .,tel'l prices pre­
I';liled.
to cantilel'cr
C,
529
530
Economics and Contractual A.fpects of Segmental Construction
TABLE 12.15.
Date
Bid
Bridge
II7K
San Francisco
Bay al Dumbarton (ap­
proach spans)
Length/Max.
Span (n)
Cmt-BJ-idge
Wmk Only
46501150
$24.3 M = $59/ft2
(Cimillillni)
Design Allel'nalin~s
Pnwided
A.
B.
C.
"Select('d by
123.1
Im\
I\luch bidder interest in all
choices during prebid
stage. Final results: ,e\en
chose A. one chose C.
Some uncertainties about
nileria provided in B.
1)I(lder.
/a,f)J,.'iIGS OF C·IR.4CAS VIADUCTS,
l'ESEZl.TLA
Tlte Caracas Viaducts in Venezuela (Chapter 8)
were completed in )952, approximately thirt~
rears ago. If these viaducts were built today, the
chosen strtlclure would probably be very differ­
ent from that chosen at the time after exhaustive
feasibility studies. III 1973 these structllres were
ree\'alua;ed ill terms of the more conventional
halanced cantilever method of girder construc­
tion. Figures it~~O and 8.31 compare the actual
project COllst rutted in 1952 with possible alter­
native designs in 1973 and 1975. The three-arch­
rib and eight-beam superstructure would be re­
pl;tced by a variable-depth twin box section
(cantilever construction using precast segments)
Sllppol'\C'd 011 slip-formed piers.
Today, with the same span arrangement consid­
ered in '1973, possible alternatives might be a single
two-cell box similar to that used in the Kipapa
Stream Bridge, or a ribbed single-cell box as in the
V(~jle I-Jord Bridge, Figures 4.24 and 4.22, respec­
tively. This approach would require only single
shaft piers.
123.2
Precast delw girders"
Twin single-cell pre­
stressed box gJrders
designed for seg­
mental constructJon
with criteria for rede­
sign for canlileH'ring
or launching
Structural steel hox
girder
R('mark~
Tancan'ille Bridge designed in ) 956 incorporating
a 2000 it (6 10m) span steel suspension bridge
Brotonne Bridge designed in 1973 incorporating a
1050 ft (320 Ill) span concrete stayed "bridge
These two structures are oilly 20 miles (32 km)
apart and are located in very similar surroundings
topographically and geotechnicalh (see Figures
12.1 and 12.2).
On the left bank, a flat expanse of meadows and
fields requires a long approach viaduct to reach the
desired altitude of the main crossing above the
navigation channel, while a deep formation of soft
soil overlying the load-bearing strata requires deep
pile foundations. On the right bank, the limestone
cliff extends close w the river bank and calls for
only a short transition bet\.\'een the main river span
and the approach highway. The comparison pre­
sented here pertains only to the left-bank approach
viaduct of each structure, although interesting
comments could be made also on the relative char­
acteristics of their other parts.
The Tancarville approach viaduct has eight 164
ft (50 m) spans, having five 140 ton (127 mt), 10 ft
CO.HPARISO!\' BETH'EEI\' TA,VC4RVILLE
AND IWOTOY\'F, BRIDGES, FRANCE
Progress is made slowly through accumulated ex­
perience, and it is worthwhile to look back pe­
riodicallv and try to measure such progress. With
this in rr;ind, and as a conclusion to this chapter, a
comparison is offered between two similar con­
crete 5t ructures separated in time by seventeen
vears.
, As mentioned in Section 9.8, the Seine River
between the maritime inland harbor of Rouen and
the English Channel is now crossed twice by two
outstanding structures:
FIGURE 12.1. Tancarville Bridge, aerial \'iew
the south\\'est showing left bank approach viaduct.
531
Increase in Efficiency in Concrete Bridges
FIGURE 12.2.
Bmlollne
Ihidt-;c. aerial vicw from the southwest sh(m ing left bank ap­
proach viadlH \.
deep precast ginlers in each span, Figures
I :l.:> and I :lA. Piers are fOllfHthl on precast con­
crete piles and were cast ill place with a box section.
When the design was prepared. it represented the
most advanced technolog\' ill terms of lise of matc­
rials. rhe elastic stabilit v of these very long, slender
precast ginlers was even the occasion of interesting
illllO\'at ive st tidies. COllst ruct iOll methods were also
far from conventional.
.\11 gi rders were prefabricated in a vanl located
at the original ground level. ~I()\illg and lifting op­
eratiotls for one girder (see Figure 12.5) included:
(3 m)
Placing hrirdt;'r 011 dollies, lIlo\'ing in two perpell­
dicular directiolls to bring it at the foot of the sup­
porti ng piers
FIGURE 12.3.
Hoisting girder along the piers with special steel
rigs, Figure 12.6
Placing girder on top of the pier with the rotating
arm of the special rig, Figure 12.7
Transverse displacement of girder
tion
to
its final posi­
Suspension of the girder at both ends was achieved
by the means of special cantilevers to provide the
highest safety against lateral buckling during lift­
ing operations of such slender girders, Figure 12.8.
The project was carried out smoothly and com­
pleted successfully a long time ahead of the other
contracts for the entire crossing.
Fifteen years later. the same problem of safelv
and economically building an aesthetically pleasing
Tancaryille Bridge, elevation of approach spans.
532
Economics and Contractual Aspects of Segmental Construction
43'-10"
40'-10"
4'-0"
i·
'.
l..k;W
-.. 9)'
.... 1
~i
4'-0"
'I',"
.....
.,
-.,
7'-5"
..
.1,
i
.
.~
'-1
r
I
I
I
P
.
,
..
It ~
V'L.-": ~'\
~y
11'-4'
11'-4"
4'-0"
,.
~ ~
:
4'-0"
::-:-::-::
W~,
L:.o:l~
P
11'-4'
.1
I
.1
11'-4'
FIGURE 12.4. Tancan'ille Bridge, typical cross section of approach spans.
FIGURE 12.5. Tancarville Bridge, lifting one precast
girder for the approach spans.
TABLE 12.16.
approach viaduct for the Brotonne crossing was
solved with very different methods, both of design
and construction. The light single box section se­
lected for the stayed structure was also used for the
approach spans. Precast piles were replaced in the
foundations by cast-in-place slurry load-bearing
walls. Box piers were slip-formed instead of incre­
mentally cast in successive lifts. The superstructure
was cast in place in balanced cantilever with travel­
ers, Figure 12.9. Today precast segments would
probably be preferred, although the characteristics
of the deck would remain substantially unchanged.
A comparison between quantities of materials
per square foot of deck appears in Table 12.16.
The savings in concrete volume of Brotonne over
Cost Comparison Between Tancarville and Brotonne Approach Viaducts
Tancarville, 1956
(Adjusted 1973)
1.
2.
3.
Quantities (per ft2)
(super- and substructure)
Concrete (yd 3 )
Reinforcing steel (Ib)
Prestressing steel (I b)
Labor (hr/ft 2)
Cost ($/ft2 )
Labor
Materials
Equipment, plant, and job overhead
Su bcontracts
Design, overhead and fee
4. Tolal
0.14
Brotonne, 1973
6.4
4.1
0.11
14
3.1
1.6
14.20
6.90
15.70
3.70
12.90
5.60
6.30
5.00
4.20
4.20
11
$53.40
--
$25.30
Increase in Efficiency in Concrete Bridges
533
0' P'ltt~
jTop
-----­
..._ _
~.~~v
~
~ -r­
LOW1!:R
~L.OCl<$
;---~-
,
I
~-
bi
.'1
"I
I
--t
FIGURE 12.6.
spans.
fancarville Bridge. equipment for lifting precast girders in approach
Tancarville is justified only by the fact that
minimum weight was vital for the concrete stayed
bridge and was maintained in the approach spans.
Weight of prestressing steel is approximately half
because the deck is continuous at Brotonne and the
box section is more efficient than the I-girder sec­
tion.
More important, however, is the comparison of
costs and the components thereof, Table 12.16 and
Figure 12.10. One is struck by the total labor re­
quirements for both sub- and superstructure:
Tancarville
Brotonne
~---.----.------.----~.----.
PLACinG GIRDE.R on PIER
FIGURE 12.7.
Placing precast girder over pier cap.
4.1 hr/ft 2
1.6 hr/ft 2
In the 15 years that elapsed between the two proj­
ects, the combination of design improvements and
more efficient construction methods allowed the
labor to be divided by 2.5.
A similar trend has been observed in other fields.
For example, a complete survey of all hydroelectric
534
Economics and Contractual Aspects of Segmental Construction
60
$53.40
50
CAMTIL.f:VER
12,90
.t:: 40
3.70
II
Q;
C.
<f>
30
15.70
.E
..,
$25.30
~
u
I
\r+-:::~
20
4.20
4.20
6.90
5.00
10
6.30
14.20
5.60
0
I,.A"~t::I"'L. 5ADQ..L.~~.-t'+....~...
Tancarville
Brotonne
(readjusted 19731
(1973)
FIGURE 12.10. Cost comparison bet \\'een rancanille
and Brolonn<:' approach yiaduCls. (:'» Desigh o\crhead
and fee. (4) subcontracts. C1) equipmcnt. plallt. and site
O\'crhead. (;!) materials. (I) labor.
DOLLI~&
Df!:TAIL Of" GIRDER SUSPEHS10H
FIGURE 12.8.
Lifting de\'ice at precast girde,- ends.
0::
<1
LLl
>­
50 o:x;­
(
,
,
~.-'*
,
-i(: l,
'. -:
I
"~",'
YEAR
FIGURE 12.9. Brotonne Bridge. cantilever construc­
tion of superstructure of approach spans.
FIGURE 12.11. Increase of productiyil\ on power
projects in France,
projects carried out by French Electricity between
1950 and 1970 showed that the annual value of in­
vestment for each worker was multiplied by 2
without allowance for inflation and by 3 including
inflation, Figure 12.11. Cost wise the true gain
would be somewhat less significant, because labor
rates have constantly increased faster than material
rates.
The comparison between other items of the cost
breakdown of Tancarville and Brotonne is equally
instructive. Material costs are almost equal, in­
cluding the value of subcontracts (pile foundations
References
and roadway work in both projects). The essential
differences are seen in the two following areas:
Equipment, plant, and job overheads: reduced
from $15.70 at Tancarville to $5 at Brotonne. This
difference is due essentially to increased efficiency
in management but also to a climate of fierce com­
petition.
Design, overheads and fees: reduced from $12.90
for Tancarville to $4.20 for Brotonne. The same
two reasons explain this drastic reduction, which
also reflects the change in the overall operation of
large construction companies during the last
twenty years from family-owned or controlled
craftsmen such as building contractors to modern
management industrial companies.
When Eugene Freyssinet designed his Plougastel
Bridge masterpiece (see Chapter 8), he was per­
sonally involved in the project for more than
three years and probably involved in little else. One
generation later, an experienced engineer would
have to control or at least participate in many dif­
ferent projects during the same period.
In summary, the c6mpari~~on of costs between
Tancarville and Brotonne approach viaducts with
prices of both projects reduced to 1973 levels is:
Tancarville
Brotonne
$53.-tO!rt 2
$2S.30/fr 2
Both projects were bid completely on a design­
and-build basis and awarded to the lowest bidder.
The above costs are a true picture of the technol­
535
ogy and of the level of prices for the two respective
periods.
To estimate both projects at the level of today's
prices (1980) it would be necessary to multiply the
labor rates by 2.3 and the materials and equipment
rates by 1.7.
References
1. "Guidelines for Value Engineering (VE)," prepared
by Task Force 19, Subcommittee on New Highway
Materials, AASHTO-AGC-ARTBA Joint Coopera­
tive Committee.
2. "Alternate Bridge Designs," FHWA Technical Advi­
sorv T5140.12, December 4, 1979, Federal Highway
Administration, Washington, D.C.
3. Richard A. Dokken, "CALTRANS Experience in
Segmental Bridge Design," Bridge Noies, Division of
Structures, Department of Transportation, State of
California, Vol. XVII, No.1, :Yfarch 1975.
4. A. B. Milhollin, and C. L. Benson, "Structure Design
and Construction on the Vail Pass Pnuect," Trans­
portation Research Record 717, Transportation Re­
search Board, :-Iational Academy of Sciences,
Washington, D.C., 1979.
5. James M. Barker, "North American State of the Art
Current Practices," Prestressed Concrete Segmental
Bridges, Structural Engineering Series No.6, Fed­
eral High\\"ay Administration, Washington, D.C.,
August 1979.
6. Donald W. Alden, "California's Experience with Cost
Saving Contracting Techniques," Prestressed Concrete
Segmental Bridges, Structural Engineering Series No.
6, Federal Highway Administration, Washington,
D.C., August 1979.
13
Future Trends and Developments
INTRODUCfION
MATERIALS
13.2.1 Prestressing Tendons
13.2.2 High Strength Concrete
13.2.3 Fiber Reinforced Concrete
13.2.4 Polvrner Concrete
13.2.5 Co~posite Concrete Materials
13.2.6 Material Limitations
13.3 SEGMENTAL APPUCATION TO BRIDGE DECKS
13.4 SEGMENTAL BRIDGE PIERS AND SUBSTRUCTURES
13.1
13.2
13.1
1ntroduction
As observed in previous chapters, prestressed con­
crete segmental bridges have extended the practi­
cal and competitive economic span range of con­
crete bridges. The Bendorf Bridge in Germany
(Section 2.2) constructed in 1964 with a navigation
span of 682 ft (208 m) was a monumental achieve­
ment. Because of economic differences bf'tween
Europe and the Cnited States (primarily the ratio
of labor cost to material cost) it was not until the
early 19705 with the JFK Memorial Causeway
(Section 3.10) with a span of 200 ft (61 m) and
shortly therafter the Pine Valley Creek Bridge
(Section 2.7) with a span of 450 ft (137 m) that
segmental construction was introduced in the
Lnited States. Today these spans are somewhat
commonplace when one considers the Three Sis­
ters Bridge (Section 1.10). the Koror-Babelth uap
Bridge (Section 2.12), and the Houston Ship
Channel Bridge (Section 2.14), with spans of750 ft
(229 m), 790 ft (241 m), and 750 ft (229 m), re­
spectively. When combined with the cable-stay
concept, spans increase to 981 ft (299 m) for the
Pasco-Kennewick Bridge. 1050 ft (320 m) for the
Brotonne Bridge. and 1300 ft (396 m) for the
Dame Point and Ruck-A-Chucky Bridges.
536
13.5
APPUCATION TO EXISTING OR NEW BRIDGE
TYPES
13.5.1 Overpass Structures
13.5.2 Arches, Trusses, Rigid Frames
13.5.3 Wichert Truss
13.5.4 Stress Ribbon Bridges
13.5.5 Space Frame Bridges
13.6 SL'MMARY
REFERENCES
In earlier years these spans for concrete bridges
would have been considered incomprehensible and
certainly not economical. The fact that they have
become achievable. -only within the last decade.
stands as a testimonial to 'rapid technological ad­
vances and to the courage and vision of those engi­
neers who participated in this development.
In the United States as of November 1980, 19
segmental bridges had been completed and there
were 16 under construction. 22 in design, and 29
under slUdy-a total of 86 bridges. We may con­
clude that segmental prestressed concrete con­
struction is a viable concept for highway bridges
and that there are no known major problems to
inhibit its use. \Vhat, then, is the potential for seg­
mental bridge construction in the 1980s? This
chapter will look at this potential in terms of new or
improved materials, potential application in bridge
decks, piers, and substructure, and application to
existing or new bridge superstructure types.
13.2
Materials
During the nineteenth century timber, stone, and
masonry were the common materials for bridge
construction. Then iron, steel, concrete, and rein­
Materials
forced concrele emerged successively as favorite
materials. culminating in the twentieth century
with prestressed concrete. The present materials
used in bridge construction have some or all of the
following disadvantages: weight. cost. or inherent
weaknesses in one form or another. In the recent
past. development of improved bridge systems has
evolved primarily by more exact methods of cal­
culation made feasible by the electronic computer
or by innovative bridge systems such as the cable­
stayed and segmental types of bridges. Intensive
development of the materials themselves has
barely begun.
13.2.1
PRESTRESSI,Vc TE.VDO.VS
Until recently. corrosion of prestressing tendons
has caused few problems and little concern. How­
ever, with the advent of segmental construction
and transverse prestressing on the top flange, an
increasing concern has been expressed about the
potential deterioration of the tendons resulting
from their closeness to the deck surface and expo­
sure to the action of de-icing chemicals. Current
methods of alleviating this concern are the use of
polyethylene ducts or the pOssibility of epoxy coat­
ing the duct, epoxy coating post-tensioning bar
tendons, alld possibly epoxy coating the prestress­
ing strand. A research effort is required to deter­
mine the production feasibility and cost; the effect,
if any, that nonmetallic coatings might have on the
bond of strand to concrete; and the compatibility
of strains between the coating and the tendon. An­
other potential method uses individual unbonded
strands with successive coatings of teflon, a corro­
sion inhibitor, and polypropylene, Figure 13.1.
An old idea that may need to be resurrected is
that of using glass fibers for prestressing. This
material was being investigated in the I950s, I but
for either technical or economic reasons it never
reached fruition. There were problems of chemical
reaction of the glass fibers with the cement; how-
"'7'
537
ever, Owens-Corning Fiberglass Corp. has de­
veloped a coating for glass fibers for fiber­
reinforced concrete. Perhaps this coating could be
used for a glass fiber prestressing strand. An ulti­
mate strength of 400 ksi (2758 MPa) and a low
modulus of elasticity ranging from 6000 to 10,000
psi (41 to 69 MPa) might be expected. The high
strength and low modulus would indicate a low
percentage of prestress losses-a decided advan­
tage. The high strength would produce, for a given
required prestress force, fewer or smaller tendons.
th us reducing congestion. Smaller tendon sizes
would reduce web thickness, thus reducing dead
weight an'd prestress force requirements, and so
on. Obviously. suirable end anchorages would have
to be developed.
13.2.2
HIGH-STRENGTH CONCRETE
Early prestressed concrete designs were based on
3000 psi (20.7 MPa) strength concrete. As knowl­
edge of concrete properties and quality control in­
creased, it became more feasible to use a 6000 psi
(41.4 ~[Pa) strength concrete for man y prestressed
concrete structures. In the Pacific Northwest an
8000 psi (55.2 ~IPa) strength is readily and
routinely available. Use of such concrete has per­
mitted the design of longer-span, lighter-weight
concrete structures.
Within the past few years it has been found that
strengths of 10,000 psi (68.9 MPa) and higher can
be obtained where special attention is given to (I)
selecting the constituent materials, (2) propor­
tioning the concrete mix, and (3) handling, plac­
ing, and curing the concrete.
It has recently been demonstrated that the appli­
cation of ultrahigh-strength concrete is not on Iv
practical but also economically feasible. High­
strength concrete, 9000 to 11,000 psi (62 to 75.8
MPa), has been used in the columns of five high­
rise buildings in Chicago. The concrete was pro­
duced in a local ready-mix plant and trucked to the
Bonded low friction
7 Wire prestressing
Slra
'T'''oo)
Polyproplylene
covering
FIGURE 13.1. Corrosion-resistant strand tendon.
538
Future Trends
project site. An economic study for a short tied
column indicated that the cost per foot varied with
the concrete strength and steel percentage as fol­
lows: $15.50 for 9000 psi (62 MPa) concrete and
1% steel compared to $39 for 4000 psi (27.6 MPa)
concrete and 8% steel.
Over the past five to ten years considerable re­
search has been conducted on high-strength con­
crete, dealing primarily with selecting materials,
developing concrete mix design criteria, and de­
termining basic physical properties of the con­
cretes. Very little, if anything, has been done
regarding the implementation of high-strength
concretes, especially in bridge structures.
In an interim report,2 "Applications of High
Strength Concrete for Highway Bridges," pre­
pared by Concrete Technology Corporation for
the Federal Highway Administration, a segmental
bridge segment at a pier was redesigned with
high-strength concrete. The purpose was to de­
termine to what extent the thickness of the lower
flange could be reduced, and in turn what effect
this reduction would have on the overall moments.
For purposes of this study, the Shubenacadie
Bridge in Nova Scotia (Section 2.15.4) was selected
as a design example. Overall dimensions of the
bridge are shown in Figure 13.2. It has a 700 ft
{r
A
r
..l
an~
Developments
(213.4 m) main span and 372 (l13.4 m) side spans.
The bridge was constructed with a 5000 psi (34.5
MPa) concrete strength and used It in. (32 mm)
diameter Dywidag bars for post-tensioning." For
the analysis, the top flange was assumed to be uni­
form and I Ii in. (292 mm) thick. The bottom
flange was assumed to taper uniformly from its
thickest point at the su pport piers to 6 in. (152 mm)
at midspan. The centroid of the prestressing force
r4a.' assumed to be located 5/ in. (146 mm) below
the top of the section-that is, centered in the top
flange. AASHTO Bs 20-44 was used for loading,
as in the actual bridge.
Prestress force was provided by It in. (32 mm)
diameter Dywidag bars with a minimum yield
stress of 150 ksi (1034 ,MPa). These bars were as­
sumed to provide 104 kips (0.46 MN) of final pre­
stress force each. This assumes a jacking force of
70% of the minimum yield strength and 20 ksi
(137.9 'MPa) losses. Maximum allowable compres­
sive stress in the concrete was assumed to be O.4f~,
and an allowable tensile stress was assumed to be
zero.
Significant benefits were found in the use of
high-strength concrete to reduce the thickness of
the lower flange. As shown in Figure 13.3, the total
flexural prestress demand is reduced by approxi­
ELEVATION
=t=
35'.
35'· 6"
I
L..
6~
ll'lillhv
I
I'· 2"
1'.2"
I
I
I
20'·0"
..,
~
SECTION B-B
M
I
I
,
•
1/
20'.0"
.1 ~ ,
I 6"
SECTION A-A
FIGURE 13.2. Shubenacadie Bridge.
B
Materials
539
36,000
B
35,000
-0
.9:
""
':":
"'
o
...J
34,000
.2
~
'"
.t
33,000
2'-6"
Deflection
1'-6"
32.000
FIGURE 13.4.
31,000
5
6
8
9
10
Concrete strength SKI
FIGURE 13.3. Variation of prestress force with con­
crete strength-Shubenacadie Bridge.
mately 10% as a result of the red uced dead load,
The optimum lower flange thickness is about 1 ft 8
in. (508 mm), obtained at 8 ksi (55 MPa) concrete
strength,
13.2.3
FlBER-RFLVFORCED CONCRETE
A relatively new material that has not yet seen
much application in structures is fiber-reinforced
concrete. Fibers have been used to reinforce brittle
materials since ancient times; straws were used to
reinforce sun-baked bricks, horsehair was used to
reinforce plaster, and more recently various fiber:>
have been used to reinforce Portland cement. 3 A
state-of-the-art report 1 prepared by ACI Commit­
tee 544 defined fiber-reinforced concrete as "con­
crete made of hydraulic cements containing fine or
fine and coarse aggregates and discontinuous dis­
crete fibers."
Schematic load-deAection diagram.
Several types of fibers along with several of their
properties are listed in Table 13.1.3,1 As can be
seen, fibers have been produced from steel, plastic,
glass, and natural materials in various shapes and
sizes.
Two stages of behavior in the load-deformation
curve have been generally observed when fiber­
reinforced concrete specimens are loaded in
flexure. The load-deformation curve may be con­
sidered as approximately linear up to point A in
Figure 13.4. Beyond this point the curve is
significantly nonlinear, reaching a maximum at
point B, The load or stress corresponding to point
A has been called first-crack strength, elastic limit, or
proportional limit, while the stress corresponding to
point B has been termed the ultimate strength.
Two theories have been suggested for predicting
the first-crack strength of fiber-reinforced con­
crete: the spacing concept and the composite-materials
concept. The spacing concept attempts to explain or
determine the first-crack strength by a crack-arrest
mechanism derived from the field of fracture
mechanics. The basic mechanism that controls the
TABLE 13.1. Typical Properties of Fibers
Young's
Modulus
( 103 ksi)
Cltimate
Elongation
Type of Fiber
Tensile
Strength
(ksi)
Acrylic
Asbestos
Cotton
Glass
Nylon (high tenacitv)
Polyester (high tenacity)
Polyethylene
Ra yon (high tenacity)
Rock wool (Scandinavian)
Steel
30-60
80-140
60-100
150-550
110-120
105-125
100
60-90
70-110
40-600
0,3
12-20
0.7
10
0.6
1.2
0.02-0.06
1.0
10-17
29
25-45
0.6
3-10
1.5-3.5
16-20
II 13
10
10-25
0.6
0.5-35
Specific
Gravity
l.l
3.2
1.5
2.5
1.1
1.4
0,95
1.5
2.7
7.8
540
Future Trends
an~
Developments
WITHOUT FIBERS
•WITH FlBERS
Section A-A
FIGURE 13.5.
Schematic
or arrest mechanism.
first-crack strength depends primarily on the
spacing of the fibers."
The crack-arrest mechanism for fiber-reinforced
concrete, as presented by Romualdi and Batson,6
can best be described with the aid of Figure 13.5,
which represents a mass of concrete in tension.
The reinforcement consists of a rectangular array
of rods at a spacing 'A and located parallel to the
direction of tension stress. At some interior loca­
tion an internal flaw exists in the form of a flat
disk-shaped crack.
The basic rationale is illustrated by section A-A,
which is a side view of an internal crack between
two fibers. I n the presence of a gross stress the ex­
tensional strains in the vicinity of the crack tip, by
virtue of the stress concentration, are larger than
the average strains. These strains, however, are re­
sisted by the stiffer fiber, and there is created a set
of bond forces (assuming that the bond between
the mortar and the steel is intact) that act to reduce
the magnitude of stresses at the crack tip. Under
proper conditions of fiber spacing and diameter,
an internal flaw could be prevented from prop­
agating tojoin up with other flaws into microcracks
which then join with other microcracks to form
macrocracks. The basic philosophy is that if the
internal flaws can be locally restrained or retarded
from extending into adjacent material, thereby re­
straining crack propagation, the tensile-strength
characteristic of the concrete is improved.
The crack-arrest mechanism in bending may be
idealized as indicated in Figure 13.6. When a criti­
cal strain is reached, the beam cracks; unlike the
nonreinforced beam, however, the cracks do not
propagate through the beam but are arrested by
the fibers that span the cracks.
FIGURE 13.6.
bending.
Idealized crack-arrest mechanism
III
The composite-materials concept hypothesizes
that the properties of fiber-reinforced concrete, in·
eluding the first-crack strength, can be. predicted
from the individual properties of matrix and
fibers. It assumes that fiber-reinforced concrete
can be analyzed as conventional reinforced con­
crete, the main difference being that the rein­
forcement is shorter, thinner, and randomly dis­
tributed.
Table 13.2 summarizes the improvement of the
properties of a steel-fiber-reinforced concrete as
compared to plain concrete. 3
13.2.4
POLYMER CONCRETE
Concrete produced with Portland cement and air­
entraining agents can contain approximately 13%
voids, which are interconnected and distributed
throughout the mass. When this concrete is heated
to drive out the chemically unbonded moisture and
TABLE 13.2.
Concrete Reinforced with U.S.S.
Fibercon Steel Fiber
Properties
Compression
Flexural modulus of rupture
Tensile strength
I mpact strength
Crack and spall resistance
Fatigue strength to 2 million
cycles
Abrasion
Shear and torsional strength
Corrosion resistance
Freeze-thaw
Conductivity (thermal and
electrical)
Approx.
I mprovement over
Plain Concrete
10-30%
70-300%
50-300%
150-1000%
70-300%
100%
30%
50-300%
Good as or better
Good as or better
Conducts both
Materials
541
TABLE 13.3. Summary of Properties of Concrete-Polymer Material
Property
Compressive strength (psi)
Tensile strength (psi)
Modulus of elasticity (psi)
Modulus of rupture (psi)
Flexural modulus of elasticity (psi)
Coefficient of expamion (in.!in. OF)
Thermal conductivity at 73°F (23°C)
(BTu/ft-hr-OF)
Water permeability (ft/yr)
Water absorption (%)
Freeze-thaw durability:
Number of cycles
Percent weight loss
Hardness-impact ("L" hammer)
Corrosion by 15% HCI (84-dav exposure),
% weight loss
Corrosion by sulphates (300-day exposure),
% expansion
Corrosion by distilled wa~er
then impregnated with a chemical monomer, such
as methyl methacrylate CM~lA), and irradiated
with gamma rays, some startling changes in its
properties are produced, Table 13.3. 7 Tensile and
compressive strength are almost quadrupled.
Modulus of elasticity is increased by a factor of 1.8
and modulus of rupture by more than 3.5. A com­
pressive stress-strain curve for this material shows
complete linearity up to more than 75% of failure
load, Figure 13.7. 7
Thus far, research with this material has aimed
toward its application in bridge decks. Problems in
polymerizing large units such as bridge segments
have yet to be solved. Practical resolution of these
problems could offer a tremendous advantage for
concrete structures.
Concrete
Control Specimen
(Type II Cement)
Concrete with up to 6.7
Weight % Loading of
Polymeth yl Methacrylate,
Co-60 Gamma Radiation
Polymerized
5,267
416
3.5 x 10 6
739
4.3 x H)6
4.02 X 10- 6
1.332
20,255
1,627
6.3 x 10 6
2,637
6.2 x 106
5.36 X 10-6
1.306
6.2
X
o
10-4
5.3
0.29
590
26.5
32.0
10.4
2,420
0.5
55.3
3.6
o
0.144
Severe attack
No attack
18
16
Impregnated CP
concrete 5.4 wt
%MMA
14
12
E = 5.5
;;;
X
106
Cl.
o 10
0
0
~
~
8
Unimpregnated
CP concrete
Ul
6
4
13.2.5 COAIPOSITE CONCRETE MATERIALS
2
Assuming that the materials previously discussed
can be developed to a point of practical usage, what
improvement in properties might be expected if
these materials were combined? Sukiewicz and Vir­
0la8 have presented flexural-load-versus-deflection
data for concrete and composite materials, Table
0
1000
2000
3000
4000
Compressive strain (m,croinchesiinch)
FIGURE 13.7. Compressive stress-strain .curve for
MMA-impregnated concrete.
542
Future Trends and Developments
TABLE 13.4.
Relative Load Versus Relative
Deflection
Approx.
Relative
Max. Load
Plain concrete
Steel-fiber reinforced
Polymer impregnated
Pohmer impregnated and
steel-fiber reinforced
Approx.
Relative
Midspan
Deflection
at Max.
Load
5
18
20
100
5
20
13
105
13.4. It is obvious that a vast improvement in be­
havior and toughness can be expected.
13.2.6
MATERIAL LIMITATIONS
With improved material properties, not only would
structures become lighter but also the depth of
superstructure and thickness of individual ele­
ments would be reduced. There are some practical
limitations, however, as to how much the thickness
of a web, for example, may be reduced. The prac­
tical limitations of placing the concrete in the forms
and of congestion of supplemental reinforcement
and prestressing tendons must still be considered.
To some extent this could be alleviated by the use
of external tendons, as implemented in the Long
Key Bridge in Florida, Figure 6.53. This also has
the advantage of reducing the complexity of fabri­
cation for precast segments.
Perhaps a more important limitation in using
materials with improved properties is that at some
point in the design, stress no longer becomes the
controlling criterion. Deformations, both global
and local, may govern. Because of the reduced
section required from a strength point of view,
there may be more concern not only with flexibility
of the structure in a global sense but also with the
possibility of web buckling and limberness of the
deck slab.
13.3
Segmental Application to Bridge Decks
-prestressing has been used to a greater extent in
the construction of segmental bridges-to provide
greater load capacity and load distribution for
large overhanging flanges and between adjacent
single-cell box girders.
Although a few bridge designs have included
transverse prestressing, much greater use could be
made of it for more economical bridge structures.
For replacement of the decks on existing bridges,
precast prestressed concrete segmental construc­
tion offers great advantages, only some of which
can be associated with identifiable costs.
As with the segmental box girder, a full-depth
segmental panel bridge deck may be precast in
short segment lengths longitudinally and may be
full deck width or partial deck width, Figure 13.8,
depending on the width of deck required for a
particular application. Also, in addition to the
transverse prestressing, segmental bridge decks
may be conceived as having expoxied transverse
joints and longitudinal prestressing.
A transversely prestressed segmental fuil-depth
panel bridge deck, Figure 13.9, has been proposed
by T. Y. Lin International as an alternative design
for SR 182, Columbia River Replacement Bridge,
in the state of Washington. This proposal has the
following features:
1.
2.
3.
I\
Pru:ast full-depth panels of lightweight con­
crete to reduce dead load.
Transverse prestressing to achieve large can­
tilever overhangs and ·thus economies in the
superstructure.
Attachment of the panels to the superstructure
with shear studs in block-outs of the panel to
achieve composite action with the superstruc­
ture.
\_---1
t
J
f
)J
1\
\ ...... ,..T
a
[
1\
To date, there has been very little use of precast­
ing, prestressing, and segmental construction for
bridge decks. Transverse prestressing has been
used in the top flange of large, Gist-in-place on
falsework, concrete box girders. Lately, transverse
]
I I I I
FIGURE 13.8.
Deck configurations.
a
4
Segmental Bridge Piers and Substructures
62'· O'
18',6"
18' 6'"
]
~!
~
::
543
made to act compositely by means of shear-transfer
devices placed at regular intervals through block­
outs cast into the deck.
To date, the incremental launching method has
been implemented for the construction of ten
bridge decks in Switzerland. IO • 11
~
~
---~
13.4
Segmental Bridge Piers and Substructures
FIGURE 13.9. SR-182 Columbia River Bridge.
--t.
Longitudinal prestressing of the deck to
maintain a compression across the transverse
joints.
Another segmental method of constructing a
bridge deck is a transfer of technologv from the
incremental launching of segmental box-girder
bridges. H• w. 11 This methodology, as applied to
bridge decks, has been pioneered in Switzerland
alld consists of the following operations:
1.
2.
:~.
--t.
The casting of a convenient segment lengt h of
bridge deck behind an abutment, Figure
I:LIO, or at midlength,of the bridge, Figure
13.11, whichever is more convenient. Segmet.t
length is normallv 65 to 80 ft (20 to 25 m).
The jacking forward of the segment, Figure
L}.12, onto the flanges of the steel super­
structure, Figure 13.13, thus freeing the cast­
ing bed.
Preparing the casting bed for concreting the
next segment.
Repeating the c'ide until completion of the
bridge cleek.
The finished deck, therefore, consists of seg­
ments that have been incrementall\' cast and lon­
gitudinallv launched. As in conventional structures
the deck is attached to the SlI perstructure and
Piers do not have to be massive solid cross sections;
a tubular cross section may be more effective and
more economical. In the U nitecl States it is gener­
ally felt to be more economical to cast a solid pier.
However, for tall piers the economics of solid-pier
casting should be evaluated against the cost of the
additional de