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CIVIL ENGINEERING MAGAZINE
Rafael Viñoly Architects
Conceived to resemble a series of covered suspension bridges, Pittsburgh’s new $370-million David
L. Lawrence Convention Center boasts a cable-supported stainless steel roof that breaks the mold in
American convention center design by daylighting interior spaces. By James O’Callaghan, C.Eng
The major frames to the north and south of the building on each of the 15 framing lines are referred to
as the bow and stern frames, and this rendering shows why. With a design that pays tribute to
Pittsburgh’s industrial heritage, the new convention center also draws on the latest advances in
sustainable development
In 1998 the Sports and Exhibition Authority (SEA) of Pittsburgh and Allegheny County
initiated an architectural design competition for the proposed renovation and expansion of the
David L. Lawrence Convention Center. The 20-year-old center was located on a site adjacent
to the Allegheny River that is bounded by Penn Avenue, Tenth Street, and the railroad, and the
competition called for a proposal that would expand the existing facility beyond these site
boundaries toward Ninth Street—the total site area to encompass approximately 450,000 sq ft
(41,805 m2).
In January 1999 Rafael Viñoly Architects, of New York City, London, and Buenos Aires, was
selected as the winner of the design competition. Viñoly had engaged the international
structural design firm Dewhurst Macfarlane and Partners, in association with Goldreich
Engineering PC, of New York City, to provide structural design advice during the conceptual
competition phases, and it subsequently engaged the services of both firms as the structural
design team for the project.
One of the SEA’s objectives was that the convention center be accorded Leadership in Energy
and Environmental Design (LEED) status by the U.S. Green Building Council. Burt Hill Kosar
Rittelmann Associates, of Butler, Pennsylvania, provided the mechanical and electrical
engineering services that embodied the sustainable features of the building design. These
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include natural ventilation and daylighting for the main exhibit halls as well as the use of
recycled water to flush toilets. An application for LEED certification has been submitted, and on
the basis of very thorough preliminary assessments the project is expected to qualify for an
LEED gold rating, one of the highest. This would distinguish the convention center as the
largest LEED-approved building in the world and the only convention center in the United
States to possess LEED certification. Computer modeling has indicated that the convention
center will be approximately 35 percent more energy efficient than a similar center designed in
strict accordance with current codes and standards.
Viñoly’s vision was to relate the building to Pittsburgh’s urban topography and industrial history.
The site’s proximity to the Seventh Street and Ninth Street suspension bridges inspired Viñoly
to design a structure reflective of early-20th-century engineering technology. The Sixth Street,
Seventh Street, and Ninth Street bridges—the Three Sisters—link the north side of the city to
the Golden Triangle area and stand as the only example in the world of three identical bridges
positioned side by side.
Ultimately, the convention center will incorporate 1.5 million sq ft (139,350 m2) of space,
including 330,000 sq ft (30,657 m2) of exhibit space—250,000 sq ft (23,225 m2) of it
devoid of columns. The center includes a main hall, a secondary hall, meeting rooms, two
lecture halls, a 33,000 sq ft (3,066 m2) ballroom, and a 700-space garage.
Viñoly’s vision was to relate the building to Pittsburgh’s urban topography and industrial
history. The site’s proximity to the Seventh Street and Ninth Street suspension bridges
inspired Viñoly to design a structure reflective of early-20th-century engineering
technology. The Sixth Street, Seventh Street, and Ninth Street bridges, referred to
collectively as the Three Sisters, link the north side of the city to the Golden Triangle area
and stand as the only example in the world of three identical bridges positioned side by
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side. The design was also driven, however, by the physical features and limitations of the
site, which led to the evolution of a building that, in plan, tapers from east to west.
The engineers collaborated closely with Viñoly in determining methods of effecting a
clear span roof above the main exhibition space in a manner sympathetic to the ideals of
the city’s original suspension bridge technology. The result is a roof structure of primary
suspension cables over central masts anchored at the end by the main building structure.
But the design and construction of this roof structure presented very significant structural
challenges.
Uplift in the upper cables is prevented by the action of the lower damping cables. The arch of the
lower cable reflects that of the upper cable. The lower damping cables extend over the main
exhibition floor of the convention center and help to support the ventilation system.
One of the primary design dictates was that the David L. Lawrence Convention Center be
a convention facility encompassing the largest column-free space in the United States.
This led to an investigation of long-span structures; subsequently the idea of integrating
the principles of suspension bridge design into the building resulted in what was seen as
an ideal method for creating a clear span.
The structural design of the building was developed to minimize the need for the concrete
anchorages typically used in suspension bridges to contain the massive tension forces
developed in the supporting cables. The building’s design evolved in a way that would
efficiently accommodate not only the overall structural demands but also the major
internal loads developed by the tension cable roof structure. The anchorages at either end
of the cable are major steel frames that transfer the roof tension loads and form the
building’s floor and roof support. A key principle of the structural design is the resolution
of these high tension forces within the building’s framework, reducing the need to resolve
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the forces through costly foundation works. This resolution was achieved by using steel
trusses, floor-supporting beams, and a tension grade beam.
The lateral stability of the building is achieved by using the main concrete cores located
on either side of the main exhibition floor. Lateral loads imposed on the building are
transferred through the floor plates via diaphragm action to the main concrete cores.
Rafael Viñoly Architects,
all
The upper main cable supports lightweight steel trusses spanning perpendicularly to
the adjacent cable, the trusses being 10 ft (3 m) on center down the slope of the roof,
above top right. Gable end facade hanger cables are tensioned against the main roof
cables, above top left. Each upper main cable spans from the anchorage weldment on
the bow frame over a central mast (increasing in height from frames 1 to 15) and down
to an anchorage weldment at the third floor of the stern frame, bottom.
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Although the overall structure can be separated into distinct elements for the purpose of
discussion, it is important to emphasize that the structural interaction of all of the
elements is fundamental to the behavior of the structure as a whole. The main elements
are the foundations, the structural frame, and the roof structure.
The soil beneath the building is for the most part a mix of gravel and marl with fill in
areas to a depth of 60 ft (18.3 m). Because of its proximity to the river, the site had
historically been used for docks and railroads, resulting in the presence of many hidden
obstructions—large concrete foundations for the old elevated railway system, for
example—that required removal.
The ground investigation survey detailed the depth of rock strata as being between 50 and
70 ft (15.2 and 21.3 m), depending on location, and indicated that the strata were suitable
for piles or caissons. On the basis of the recommendations included in the ground
investigation report and the high column loads, a deep foundation system was developed.
An analysis was undertaken to decide between piles and caissons, and the latter were
chosen because the cost of the pile caps for large pile groups would have been
prohibitive.
The caissons primarily resolve the vertical gravitational loads generated from the
structure above. The caissons vary in diameter from 1 ft 6 in. (0.5 m) to 7 ft (2.1 m), the
larger caissons carrying up to 4,000 tons (3,629 Mg). Concrete grade beams spanning
between the caissons were used to accommodate external envelope conditions and
elevator pits.
The major frames to the north and south of the building on each of the 15 framing lines
are referred to respectively as bow and stern frames—so named because of their
resemblance to those parts of a ship. The configuration of this main frame is such that it
supports the main floors and serves as the anchorage mechanism for the main cable roof.
As a result of the loads induced by the roof structure, the members within these frames
are frequently beyond the capacity of domestically available rolled steel sections. This led
to the decision to detail plated W sections—often weighing in excess of 500 lb/ft (744
kg/m). The plating method was deemed preferable because the steel could be obtained
domestically, as opposed to using “jumbo” sections, which are available only overseas.
The total weight of steel used in the structure exceeds 18,000 tons (16,329.5 Mg). The
bow frames each weigh approximately 120 tons (108.9 Mg); the stern frames, 200 tons
(181.4 Mg).
A strut placed between the bow and stern frames is used to help resolve internal forces
developed by the roof structure. The steel strut is a fabricated plate box girder weighing
800 lb/ft (1,190 kg/m).
The framing between the bow and stern frames forming the floors generally takes the
form of deep rolled W sections, which in turn support concrete double tees on the stern
and the concrete and metal deck in the bow. Above the main stern frame the system
changes to a steel beam and post system—a more traditional approach. The floors at the
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fourth and fifth levels comprise metal decks on steel beams and concrete cast to a
thickness of 61/4 in. (159 mm).
The rhythm of the main structural frames at 60 ft (18.3 m) on center resulted in the need
for a floor structure that could efficiently span these distances. Moreover, the requirement
for the second-floor exhibition space is particularly demanding in terms of the 350 psf
(16.76 kPa) live-load criteria. The solution devised to meet these demands, as well as
those relating to cost, scheduling, and ease of construction, was the use of precast double
tee sections, the double tees designed for high loadings at a depth of 36 in. (914 mm).
The tees are supported on the steel structure at every frame line. Deflections of the
structure during roof tensioning had to be incorporated into the detailing of the precise
double tees. Each tee had to effectively transfer shear between itself and the adjacent tee
while facilitating the axial shortening of the supporting beam. A simple folded plate shear
connector was developed by the team that offered a highly cost-effective solution to a
complex problem. The tees are topped with 3 in. (76 mm) of concrete to furnish the
required diaphragm action across the floor and to provide the finished surface.
To maximize the economic benefits of using precast concrete for the main second-floor
exhibition space, the decision was made to use precast-concrete columns and structural
members to form the floors between the stern frames.
Column-Free Exhibition Floor
Rafael Viñoly Architects
The cable structure proved to be
a more efficient means of
effecting clear spans over the
second-floor exhibition space
than a long-spanning steel truss
structure.
The
economic
rationale was that over a
distance of 300 to 350 ft (91.4
to 106.7 m) cable roofs become
very competitive mechanisms
for achieving long spans. This
was a driving factor of the
structural design, as was the
intention to weave suspension
bridge technology into the
design.
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A main cable spans the distance between the bow and stern frames, with the frames
attached to the cable using large plate weldments. The main span of the roof varies
between 300 and 400 ft (90.9 and 121.2 m) along the length of the building. The cable
roof consists of an upper cable spanning from the anchorage weldment on the bow frame
over a central mast (increasing in height between frames 1 and 15) and down to an
anchorage weldment at the third floor of the stern frame. The upper main cable supports
lightweight steel trusses spanning perpendicularly to the adjacent cable, these trusses
being 10 ft (3 m) on center down the slope of the roof.
A standing seam stainless steel roof spans between the steel roof trusses to form the roof
surface. The upper cable is prevented from uplift by the action of the lower damping
cable. The lower cable is a reflected arch of the upper cable, each cable inducing tension
in the others by means of vertical “hanger” cables that initially serve as the mechanism by
which the main upper and lower cables are tensioned. The stiffness of the tensioned cable
truss limits the overall vertical deflections of the roof.
The gable ends of the building required a glass facade that would be able not only to
accommodate the large deflections experienced by the roof but also to deal with the
curving geometry between the building and the roof structure. The first of these
challenges was addressed by combining the mullions of the facade with the roof
structure. By dropping cables at every proposed mullion position and tensioning them
between the flexible structure and the rigid building structure, the live-load deflections of
the roof structure were reduced from 3 ft (0.9 m) to less than 6 in. (152 mm). Clearly this
was the major advantage of making the head gasket detailing significantly less complex.
The tensioned vertical hangers could then be used as the wind load support for the
facade’s glass panels. Since the facade panels are unitized, the detailing between adjacent
panels had to be such that the large out-of-plane deflections could be accommodated
without compromising the weather seal. This flexible cable wall, with its insulated glass
unitized panels, is a world first in that it offers a mullion-free glass wall spanning a large
distance.
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A joint venture composed of the
Pittsburgh offices of Turner
Construction Company, P.J. Dick,
Inc., and Advanced Technology
Systems, Inc., managed the
construction of the convention
center. The SEA had requested a fasttrack procurement process, and the
design team accommodated this
request through staged bid packages.
With respect to the structure, these
packages were for deep foundations,
foundation concrete (caisson caps),
structural steelwork, precast
concrete, cast-in-place concrete, and
the cable roof. The first of these
packages was put out for bid prior to
the completion of the design
development phase. The subsequent
letting of contracts for the structural
steelwork and roof structure prior to
the completion and coordination of
the structural documents led to
complex management and control of
the design evolution by both the
design and construction management
teams.
80
Rafael Viñoly Architects
The major frames to the north and south of the building
on each of the 15 framing lines—the bow and stern
frames—support the main floors and serve as the
anchorage mechanism for the main cable roof. Starting
from the bow frame, shown here, the elevation
increases.
The complexity of the cable roof and the interaction of the roof with the steel frame to
which it is anchored had to be overcome by erection engineering. A time history
computer analysis of the roof-tensioning procedure—including the deflections of the
anchorage frames—was set up by Philip Khalil, a project structural designer for
Dewhurst Macfarlane and Partners, in association with Goldreich Engineering PC. This
analysis tool allowed the structural designers to model each stage of the roof tensioning
and the associated frame deflections. By comparing the predicted deflections of the
anchorage frames at various points during the tensioning, it was possible to make
adjustments. This ability to make the required realignment adjustments was built into the
frame design. The analysis, review, and implementation of this process proved extremely
effective and accurate given the size of the roof structure and the loads being generated
through it.
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Despite the complexity of the structural erection, the project schedule—and budget—
were adhered to, and the convention center opened to great acclaim on September 20.
The landmark convention center gracing the city’s waterfront stands as an eloquent
testament to the city’s engineering legacy and sets new standards for convention center
design.
James O’Callaghan, CENG, MIStructE, a senior associate, served as the project design
manager for the New York offices of Dewhurst Macfarlane and Partners, in association
with Goldreich Engineering PC.
CE Magazine Table of Contents | ASCE Publications Home Page | ASCE Home Page
Copyright © 2003 ASCE. All rights reserved.
NOVEMBER 2003 CIVIL ENGINEERING MAGAZINE
A. READING & UNDERSTANDING
Please read the each paragraph of above READING first then try to understand
clearly, after that you may make a statement with your own words describing the
paragraph that you just read.
( The student could be divided into groups, each group may do the statement
differently, after they finished, the lecturer may asked each group of student to read in
order ).
B. TRANSLATION
Please translate your new statement ( from A ), into bahasa Indonesia.
C. GRAMMAR
This grammar is continuation of the former chapter.
Untuk menyatakan suatu perbuatan yang telah terjadi, dan hubungan dengan suatu
waktu tertentu ( Past, Present, atau Future ) kita pakai “perfect” tenses : Present
Perfect, Past Perfect dan Future Perfect.
a. Present Perfect tense dipakai untuk menyatakan perbuatan yang telah terjadi
dalam waktu lampau, dihubungkan dengan waktu sekarang; atau yang terjadi pada
waktu lampau dan berlaku sampai sekarang.
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Dibentuk dengan have/has + Past Participle ( Bagian Kata Kerja Ketiga ).
Example :
Where are Andy and Beth ?
They’ve gone to the movies.
What time did they go ?
They went about an hour ago.
Dimana Andy dan Beth ?
Mereka telah pergi ke bioskop.
Jam berapa mereka pergi ?
Mereka pergi kira-kira satu jam yang lalu.
I’ve cooked and cleaned and washed the dishes.
Saya sudah masak dan membersihkan rumah serta mencuci piring.
Mother has already cooked and cleaned and washed up.
Ibu telah selesai masak dan membersihkan rumah serta mencuci piring.
b. Untuk menyatakan suatu perbuatan yang telah selesai sebelum waktu tertentu
dalam waktu lampau, kita pakai bentuk Past Perfect Tense ( dibentuk dengan had
+ Bagian kata kerja ketiga ).
Example :
We had just gotten up when it began to rain.
Baru saja kita bangun disaat hari mulai hujan.
After the children had gone to the movies, I took a nap.
Sesudah anak-anak pergi ke bioskop, saya tidur sebentar.
c. Untuk menyatakan bahwa suatu perbuatan akan selesai ( terjadi ) pada suatu
waktu dalam waktu yang akan dating, kita pakai Future Perfect Tense. ( Dibentuk
dengan shall/will have + Kata Kerja Ketiga ).
Example :
Now they are still asleep, but by 7 o’clock they will gotten up.
Sekarang mereka masih tidur tetapi sebelum pukul 7 nanti, mereka akan bangun.
By the end of this month we will have gone to the movies four times.
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Pada akhir bulan ini kita jadi empat kali pergi ke bioskop.
D.
NUMBERS
One
Two
Three
Four
Five
Six
Seven
Eight
Nine
Ten
-
first
second
third
fourth
fifth
sixth
seventh
eighth
ninth
tenth
Please continue by yourself.
A hundred
A hundred and one
-
hundredth
hundred and first.
A thousand
A million
A billion
A trillion
-
thousandth
millionth
billionth ( British ) = sejuta juta
trillionth ( American ) = sejuta juta
E. FRACTIONS
A half
A third
Two-thirds
A quarter/a fourth
Three-fourths
A fifth
Four-fifth
A tenth
A sixteenth
A twentieth
A hundredth
A thousandth
A millionth
-
setengah, separuh
sepertiga
dua pertiga
seperempat
tiga perempat
seperlima
empat perlima
sepersepuluh
seperenam belas
seperdua puluh
seperseratus
seperseribu
sepersejuta