NEW APPLICATIONS OF HOLLOW-CORE COMPONENTS
IN HOUSING, ADMINISTRATIVE, AND PUBLIC BUILDINGS
by
FARNAZ A. BEROUKHIM
Bachelor of Art in Architecture
Southern California Institute of Architecture
Santa Monica, California
1982
SUBMITTED TO THE DEPARTMENT OF ARCHITECTURE
IN PARTIAL FULFILMENT OF THE REQUIREMENTS OF THE DEGREE
MASTER OF SCIENCE IN ARCHITECTURE STUDIES AT THE
MASSACHUSETTS INSTITUTE OF TECHNOLOGY
JUNE, 1985
O
Farnaz A. Beroukhim 1985
The Author hereby grants to M.I.T.
permission to reproduce and to distribute publicly copies
of this thesis document in whole or in part.
Signature of the author
~v
U,
~
UV
Certified by
-
wy"rV
Farnaz A. Beroukhim
Department of Architecture
k_
-/: C
Waclaw P. Zalewski
Professor of Structures
Thesis Supervisor
Accepted by
Departmental
Julian Beinart
Chairman
Committee for'Graduate Students
ROW-1
IN5INTE
OF TECHNOLOGY
MA SSA CHUSETI S
JUN 0 3 1985
L!BP.AIS
New Applications of Hollow-Core Components
in Housing, Administrative, and Public Buildings
by
Farnaz A. Beroukhim
Submitted to the Department of Architecture May 8, 1985
in partial fulfilment of the requirements for the Degree of
Master of Science in Architecture Studies.
ABSTRACT
Standard prestressed hollow-core slabs have many advantages
as construction members while being relatively very low in cost.
The principal advantages include the ease of mass production,
a small cross-sectional area, light weight, and flat surfaces.
In addition, the slabs have the advantages of concrete,
precasting and prestressing.
The only specifications which make hollow-core components
unsuitable for wall members are their lack of weight and mass,
their inability to be used as long members because of the
limited distance between the floor-to-floor height, and, in some
cases, insufficient insulating qualities.
This thesis recommends a practical and economical system
for the structural use of hollow-core components which have been
modified with two other additional structural members - a
This
continuous precast "L" beam and a precast support panel.
system will allow a high degree of standardization and an
additional saving in the total cost of the equipment and
Most of all, the wall members have the advantages of
formworks.
precast prestressed hollow-core slabs and their low cost.
The new system's applications are mainly directed towards
housing, administrative and public buildings.
A design example is also introduced and analyzed in terms
of possible variations in area of the individual units and the
The latter case shows that the
total cost of the building.
for the recommended
square-foot
per
total cost of structure
construction types.
other
the
than
lower
system is considerably
Thesis Supervisor:
Title:
Waclaw P. Zalewski
Professor of Structures
ACKNOWLEDGEMENT
I am grateful for the insightful advice and criticism of my
advisor, Professor Waclaw P. Zalweski of Massachusetts Institute
of Technology.
I appreciate the valuable comments and suggestions of my dear
husband, Professor Menashi D. Cohen of Northeastern University.
I also very much appreciate his full support, patience and
understanding.
I wish to thank people at Lonestar/San-Vel
information throughout the thesis.
for providing
I am also thankful to Professor Leon Groisser of M.I.T. and Mrs.
Janet Polansky of Jewish Vocational Service for providing
financial support.
In addition, I thank the Women's Scholarship Organization for
their scholarship award in 1985.
Most of all, I am grateful to my parents, brother,
for their support and encouragement.
and sisters
I also wish good luck to my dear friend, Kai-ie Lie,
graduate of Architecture Department, at M.I.T..
iii
1984
TABLE OF CONTENTS
ABSTRACT.
PAGE
....................
ACKNOWLEDGEMENTS..............
TABLE OF CONTENTS.............
LIST OF FIGURES AND TABLES....
.iv
.vi
1.0
INTRODUCTION AND OVERVIEW............................
2.0
CONCRETE.000000000000000000000
2.1
2.2
2.3
0.4
Concrete Block*.............
Cast-In-Place Concrete...
Precast Concrete.........
Connections......
2.3.1
2.3.2
2.4
2.7
3.0
.16
.16
.16
1
=
d
S
t
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0 0
i
Post-Tensioning the Steel..............
Prestressing types-Circular and Linear.
Partial Prestress Reinforcements .......
Prestres sed Standard Types.....................
Double Tee...........
2.5.1
Single Tee.............
2.5.2
Solid Flat Components.................
2.5.3
Hollow-Core Components.................
2.5.4
Other
.......................
Components
Cost for Common Types of Structural Constructio
Material
Prestressed Standard Types ............
2.6.1
Cast-In-Place Concrete................
2.6.2
Brick Veneer/Wood Stud Backup..........
2.6.3
Concrete Block Wall....................
2.6.4
...................
Concludi rg Discussion
0......
PRESENT APPLICATIONS OF STANDARD PRECAST PRESTRESSED
COMPONENTS
HOLLOW-CORE
3.1
3.2
3.3
4.0
.15
Reinforced Precast Types.
Reinforced.......
2.4.1
Prestressing the Co ncre te Pre2.4.2
2.5.5
2.6
.10
.11
.12
Finishes.........
nIs Z
2.5
a.....
1
..................................
Slab.................................
..........
Typical Connections....... ..
3.1.1
3.1.2
Coordination with Electrical, Mechanical,
Plumbing, Services and other Sub-Systems.
.
..
.. .........
Hollow-Core Wall.......... ..
Corewall Insulated Wall Panel....................
Hollow-Core
NEW APPLICATIONS OF STANDARD PRECAST PRESTRESSED HOLLOWCORE COMPONENTS.
Components .......
System 1 - Required Structural
4.1
0........................
Slab
Hollow-Core
4.1.1
Hollow-Core Wall Panel..................
4.1.2
00.00..000.00..00000.000..000000.000000.
4.1.3
Precast
"L"
Beam
.......
0000.0000000..00
PAGE
4.2
4.3
5.0
Precast Support Panel.....................52
4.1.5
Sequence of
Erection......................053
System 2 - Required Structural Components.........55
Advantages and Disadvantages......................56
EFFECTS OF THE NEW SYSTEMS ON HOUSING, ADMINISTRATIVE AND
PUBLIC
BUILDINGS...........................58
.............
..............
00...
.59
5.1
Housing
5.2
Administrative and Public Buildings...............60
5.3
Design
5.4
6.0
4.1.4
CONCLUDING
REFERENCES.....................
0
.................................
Example
..
61
5.3.1
Variations in Unit Dimensions.............62
5.3.2
Cost
Variations
Estimate ..........
of
DISCUSSION.
.......
.....
..
Planning ............................
..............................
64
66
68
......
0000...
70
PAGE
LIST OF FIGURES AND TABLES
Table
2-1
The strength of concrete decreases as the w/c
ratio increases..............
..
Table
2-2
Approximate relative strength of concrete as
.. . . . .. . . .
affected by type of ce ne nt.
Figure
2-1
Deformed reinforcing b
Figure
2-2
Manufacturing process for precast concre te
conponents............ ............
6
. 7
..12
.13
Figure
2-3
Channels for post-tens ioning tendo ns....
Figure
2-4
Double Tee............ ...........
Figure
2-5
Single Tee............
Figure
2-6
Solid flat slab....... ...........
.......
24
Figure
2-7
Hollow-core slab ......
.......
24
Table
2-3
Precast double "T"
.......
26
Table
2-4
Precast single Tees... wall
.......
926
Table
2-5
Precast planks........
.......
&27
Tab 1 e
2-6
Flat precast concrete.
.......
27
18
.
. 22
23
bea
. .
. .
.. o..........
Table
2-7
Cast-in-place flat pla
.......
28
Table
2-8
Cast-in-place concrete wall.......
.......
28
Table
2-9
Brick veneer/wood stud backup .....
.......
029
Tab 1e
2-10
Concrete block wall...
.......
30
Figure
3-1
Dy-core...............
*......34
......
Figure
Figure
3-2
3-3
Dynaspan..... .........
..
&
..
..
0
..
Flexicore.............
Figure
3-4
Spancrete ......
Figure
3-5
Span-deck ..........
Figure
3-6
Spiroll, corefloor....
.......
vi
.......
34
.......
35
......
35
.....
36
PAGE
Figure
3-7
Typical connection details of hollow-core slab
to structural wall-Exterior joints..............37
Figure
3-8
Typical connection details of hollow-core slab
to structural wall - Interior joints............37
Figure
3-9
Typical connection details of hollow-core slab
tobeal..................s.......low-core..la...3
Figure 3-10
Typical connection details of hollow-core slab to
shear wall ...............................
38
.......
Figure 3-11
Typical connection details of hollow-core slabs to
each ot e . . . . . . . . . . . . . . . . . . . 3
Figure 3-12
Underfloor electrical ducts can be embedded within
a concrete topping..............................39
Figure 3-13
Large openings in floors and roofs are made during
manufacture of the units ................. e.. .. 40
Figure 3-14
Kitchen/bathroom modules can be pre-assembled on
precast prestressed slab ready for installation in
buildings.............................
system
Figure 3-15
Prefabricated wet-wall plumbing systems incorporate
pre-assembled
42
piping.... .....................
Figure 3-16
Methods of attaching suspended ceilings, crane
.43
rails, and other sub-systems..........
Figure 3-17
Sections through vertical joints................44
Figure 3-18
Typical
Figure 3-19
Typical top connection.........................
Figure 4-la
Three degrees of diversity for prefabricates....48
Figure 4-lb
The new degree of diversity for prefabricates...48
corner
detail......
45
.....................
.45
Figure
4-2
Hollow-core
Figure
4-3
Hollow-core slab with post-tensioning conduits..49
Figure
4-4
Hollow-core wall panel - Section................50
Figure
4-5
Wall panels have equal heights at each
level
of
slab.......................
erection.....................
vii
.........
49
.
.51
PAGE
Figure
4-6
The height of every other wall panel vary in
one
story
increments
.................................
Figure
4-7
Precast "L"
Figure
4-8
Precast
Figure
4-9
Floor to bearing wall connection-Detail A......
Figure 4-10
Figure 4-11
Typical
..
51
beam................................ 52
support element .........................
53
54
section................................
55
Typical connection of floor slabs to load-bearin g
56
panel ...................................
wall
Figure 4-12
Section through load-bearing wall panels........ 56
Figure 4-13
Optional exterior finish-Detail B
Figure
5-1
Design example
Figure
5-2
Design example - Section ........................ 61
Figure
5-3
Considering the width between two structural
-
Plan.
5-4
....
5-5
*.
..
57
61
62
000000
Considering the width between three structural
walls ........
Figure
......
....................
walls...........................
Figure
..............
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
62
Considering the width between four structural
63
Figure
5-6
Variations
of planning..............
viii
...........
66
1.0
Introduction and Overview
-1-
1.0
INTRODUCTION AND OVERVIEW
The primary goal of the construction industry today is to
incorporate
the advantages of prefabrication,
while achieving
the architectural requirements of a space in a practical and
economical way.
one of the most important factors affecting a
Cost is
decision on the choice of materials and the nature of
construction.
Precast concrete products are usually used only
when rapid construction is more important than cost.
On the other hand,
when analyzing the costs,
manufacturing means of precasting,
we notice that precasting,
while being an expensive way of construction,
least expensive way as well.
types, and
For example,
can also be the
the reinforced
precast panels are now produced for about $18 to $20 per S.F.,
while standard hollow-core slabs are produced for about $3.50
per S.F.
Therefore,
it
is
not the precasting which is expensive,
but the method of precasting which makes the difference.
The main advantages of standard hollow-core slabs,
in
comparison with all other types of flooring and roofing
systems, are their very low cost, small thickness, light
weight, and flat surfaces.
They also have all the advantages
of prestressing, precasting and concrete.
While these specifications make concrete an ideal material
for slab, other characteristics make it less practical and
economical
for wall members:
its lack of weight, mass, and in
some cases insufficient insulating qualities, in addition to
-2-
its not being suitable for use as long members.
The goal of this thesis is to introduce a system in which
standard hollow-core components and/or their modifications can
be used practically and economically as structural floor and
wall panels while maintaining
the advantages of hollow-core
slabs and satisfying the architectural requirements of a space.
The principal advantages of using homogeneous floor and
wall members will be:
The manufacturing time is minimized through mass
a.
production of a simple cross-sectional shape.
b.
A standard method and technique can be used for
ma nufacturi ng.
c.
A significant saving in cost of equipment and
formworks will be achieved.
d.
Machines and equipment will mainly be used for
manufacturing.
Therefore, all of these will result in a significant
saving in
the total cost of the components.
-3-
2.0
CONCRETE
-4-
2.0
CONCRETE
that make it
Concrete has many characteristics
one of the
Concrete products
most widely used construction materials.
account for more than $250 billion dollars per year.
characteristics
of this material are its
Tha main
availability,
low
formability, and the relative ease with which its
price,
properties can be modified.
strength,
durability,
The main properties include
and fire resistancy; concrete
economy,
is
also a good sound insulator.
Concrete is
water and portland
a mixture of aggregates,
The active ingredients are water and cement which
cement.
combine chemically to form a paste that binds the aggregates
together.
This process is called hydration.
AGGREGATES
The major function of aggregates
economical.
place,
is
to make concrete more
In a mass, as hydration and evaporation take
the aggregates keep the concrete from shrinking and
cracking.
Therefore,
the number and sizes of the aggregates
can be adjusted for the strength and workability of the mix.
Fine aggregate can be either sand or rock screenings,
the particles range from very fine sand to 1/4 inch in
and
size.
Course aggregate is either gravel or crushed stone 1/4
inch to 1-1/2 inch in diameter.
Light-weight aggregates of various types may also be used
to control the weight,
thermal insulating,
characteristics of concrete.
Also,
-5-
and nailing
depending on the type of
the shrinkage,
light-weight aggregate,
strength and insulating
properties of the mix will vary.
WATER
For mixing concrete,
drink.
best to use water that is
it's
at a specific job site potable water is
If
fit
to
not
available, tests on samples must show that the compressive
strength of the mix at 7 and 28 days is at least equal to 90%
of the concrete made with potable water.
The common testing age for compressive strength of
concrete,
both normal and high-strength,
The more water added,
amount of cement,
is
7 and 28 days.
above a certain amount,
to a given
the weaker the concrete will ultimately be.
This relationship of water and cement is
known as the water
Table 2-1 shows that the strength of
cement ratio or W/C.
concrete decreases as the W/C ration increases.
Table 2-1
W/C
(weight)
Gallon&
per beg
.45
.49
.53
.57
.62
5.0
5.5
6.0
6.5
7.0
Approx.
28-day
atWe;th
5,000
4,500
4,000
3,500
3.000
The strength of concrete decreases as the W/C ratio
increase.
PORTLAND CEMENT
The manufacturing
of portland cement requires raw
materials which are mainly lime,
silica,
alumina,
and iron.
There are five types of portland cement based on ASTM
standards.
Each is
intended for a specific purpose although
they all achieve about the same strength after curing for three
months.
-6-
ASTM TYPE I (Normal)
This is the most common type of general purpose cement,
It is
and is used when a specific type is not required.
generally not used in large masses because of the generated
heat from hydration.
constructions,
pavements,
Its uses include most residential
bridges, railway structures,
sidewalks,
tanks,
water pipes,
and masonary units.
ASTM TYPE II (Moderate Heat or Modified)
cement is
Type II
used where low heat generation during
hydration or resistance to moderate sulfate attack is
It has been used in warm climates and structures of
important.
mass,
and retaining walls.
such as piers, abutments,
ASTM TYPE III (High Early Strength)
Type III cement is used when an early strength gain is
important and heat generation is
not a critical
factor.
For
example, it can be used when forms have to be removed for reuse
and/or the member will be put under full load within a few
days.
Table 2-2 shows the approximate relative strength of
concrete as affected by the type of cement and days of curing.
ASTM
I
II
III
IV
V
Table 2-2
Type of
Portland Cement
CSA
Normal
High-Early-Strenkth
Sulfate-Resisting
Compressive Strength (Percent
of Strength of Type I or Normal
Portland Cement Concrete)
3 mos.
28 days
7 days
I day
100
75
190
55
65
100
85
120
55
75
100
90
110
75
85
100
100
100
100
100
Approximate relative strength of concrete as
affected by type of cement.
-7-
ASTM TYPE IV (Low Heat)
Type IV cement is used where the rate and amount of heat
The strength development for type
generated must be minimized.
IV is slower than for type I.
Type IV
is primarily used in
large mass placements such as dams.
ASTM TYPE V (Sulfate-Resisting)
Type V is primarily used where the soil or ground water
contains high sulfate concentrations and the structure would be
exposed to severe sulfate attack.
Type V gains strength much
more slowly than type I.
Approximate amounts of heat generation during the first
days of curing,
using type I cement as the base,
7
are as
follows:
Type I
100%
Type II
80-85%
Type III
150%
Type IV
40-60%
Type V
60-75%
ADMIXTURES
Admixtures can be classified into two groups:
chemical admixtures,
and (2)
(1)
mineral admixtures.
Chemical admixtures are:
1.
Air-entraining
This admixture stabilizes bubbles formed by air
incorporated in the concrete during the mixing process.
The
bubbles create tiny voids which allow the concrete
to withstand the freeze-and-thaw cycle.
-8-
2.
Retarders
These admixtures are frequently used in high-strength
concretes to control the rate of hydration.
They can
be used on hot days to prolong the setting time from 30
to 60 percent.
retarders often provide an
In addition,
increase in compressive strength.
3.
Water Reducer
This admixture allows as much as 15 percent reduction
of water in a mix.
Therefore, it helps to minimize
problems relating to an excess of water (which causes
cracking in the concrete).
The admixture also
increases the concrete's strength and its bond to
steel.
4.
Accelerators
These admixtures are not normally used in high-strength
concrete.
They are counterproductive and lead to
long-term strength reduction.
Accelerators can be used
to get an early set in freezing weather.
Mineral Admixtures are:
1.
Fly Ash
A replacement of 10 to 30 percent by weight of cement
with fly ash will increase the compressive strength.
2.
Silica Fume
Using silica fume as partial replacement of or an
addition to cement will increase the compressive
strength.
-9-
Admixture Combination
The combination of superplasticizers with water reducers
or retarders has become common in order to achieve optimum
In certain circumstances,
performance at the lowest cost.
combinations of water-reducers or retarders plus an accelerator
have been proven to be useful.
CURING
Proper curing is
concrete.
essential
in achieving high-strength
The compressive strength and durability of concrete
will be fully developed only if it
is
properly cured for an
adequate period prior to being placed in service.
It
is
best
to keep the concrete moist and warm,
above 80 percent relative
humidity and 70 F for about 3 days.
If the humidity drops
below 80 percent,
the surface of the concrete shrinks,
resulting in a soft, dusty skin which is less resistant.
CONCRETE IN CONSTRUCTION
Concrete can be used in construction either plain or with
reinforcements.
In general,
concrete without reinforcements
are precast in the form of blocks; with reinforcements, it can
be precast or cast-in-place
2.1
in any desired form.
CONCRETE BLOCK
Concrete masonry building units, solid or hollow, are
widely used.
They are made from both light-weight and
normal-weight concrete in a great variety of sizes and shapes.
The properties of concrete blocks are made to comply with
certain requirements, such as compressive strength, rate of
-10-
moisture content,
absorption,
and thermal expansion.
weight,
Applications of concrete masonry building units include
exterior and interior load-bearing
curtain walls,
walls,
panel walls,
walls,
fire walls,
party
and partitions.
CAST-IN-PLACE CONCRETE
2.2
Concrete has great compressive strength but lacks tensile
whereas steel has great tensile strength.
strength,
cast-in-place
Reinforced
concrete is a combination of concrete and steel
that uses to best advantage the compressive strength of the
concrete and the tensile strength of the steel.
In this method
the reinforcements are placed in position, then the desired
form is
located before pouring the concrete mix.
Reinforced concrete
architectural
floors,
roofs,
is very widely used in
structural
field for foundations,
walls,
etc.
the
framing,
Reinforcements can generally be
grouped into two major categories:
1.
Steel Wires,
Strands and Bars
Steel wires can be welded to form wire mesh or grouped
in
parallel to form cable.
together.
Fig.
Strands are wires twisted
Bars are made either plain or deformed.
2-1 shows deformed reinforcing bars.
Deformed
bars create a better bond between concrete and steel.
Steel bars of high strength have also been successfully
applied to prestressing concrete.
Steel bars are
designated by the number of eights of an inch in their
-11-
diameter and are available in sizes from number 2 (1/4
inch diameter) to number 18 (2-1/4
Deformed reinforcing bars.
Figure 2-1
2.
inch diameter).
Fibers
Fibers which are typically used for the reinforcement
of concrete include steel,
glass,
and synthetic.
The
advantage of fibers, as opposed to continuous strands
or bars,
is
that they can be included during mixing,
therefore eliminating the labor associated with the
fabrication and placement of reinforcements.
2.3
PRECAST CONCRETE
Precast concrete products are construction items usually
manufactured
in a factory,
off site or on site, and delivered
for installation into the structure.
serve structural,
architectural,
The precast members can
or a combination of both
structural and architectural purposes.
In the two latter
cases, the members are normally called ARCHITECTURAL PRECAST
CONCRETE components.
The standard precast components include pipes,
catch
basins, and a variety of structural elements such as beam,
column,
wall,
floor and roof units.
Fig. 2-2 shows a chart describing the manufacturing
process for precast concrete components.
-12-
Figure 2-2
Manufacturing process for precast concrete
components.
ADVANTAGES OF PRECASTING
a.
The use of the most appropriate methods and equipment
in the factory result in consistently high quality
products and in an increase in productivity.
b.
Close supervision, control of materials, and a
specialized work force in a centralized plant produce a
high quality product in a shorter period of time.
c.
High quality products reduce the maintenance costs.
d.
The need for trained and specialized labor on site is
minimized since the work is
restricted to erecting and
jointing.
e.
Structural members can be mass produced in a plant
while excavation and foundation works are taking place
at the site.
Therefore, precasting considerably
reduces the time of construction.
f.
Economy in the amount of equipment and formworks
needed.
-13-
g.
Finishing work on concrete surfaces can be done in
various varieties and with better quality while being
easier and more efficient.
h.
In most cases the need for scaffolding, shuttering and
other temporary supports will be minimized.
i.
The production proceeds independent of weather
conditions.
All the above advantages result in a significant saving in
time and cost.
project,
Moreover, it is evident that the larger the
the more economical and suitable it
prefabrication.
therefore,
is
for
The number of identical units increases;
the cost of erection formworks,
and designs
decreases.
CONSIDERATIONS AND LIMITATIONS OF PRECASTING
a.
The structure should be composed of a small number of
different types of components.
b.
The manufacturing should require little time.
c.
The units should be so designed that variants of basic
types can be produced in the same mold.
d.
The engineeral design,
weight,
size and shape of units
should allow an economical and practical handling,
transportation,
e.
and erection.
The components should be compatible in weight in order
to use the full potential of the cranes.
f.
The connections should be simple and quick to
construct,
in order to obtain speedy and continuous
erection.
-14-
g.
The system should be able to limit the use of
scaffolding and other temporary supports.
h.
The height of the structure should be within the
reaching limit of the available cranes.
i.
The location of the precasting yard or factory should
be close to the construction site.
DISADVANTAGES
a.
OF PRECASTING
Often the units must be made larger or more heavily
reinforced than the cast-in-place equivalent because of
the free-ended condition.
b.
Adequate provision must be made for the stresses which
precast units may face in demolding,
transportation,
c.
handling,
and erection.
Camponents may be damaged or broken during handling and
erection.
d.
The joints between members can pose the greatest
problem.
e.
Precasting tends to be less suitable for small projects
or buildings with irregular features.
f.
The size and weight of precast members must be
restricted.
g.
2.3.1
Lack of monolithic continuity.
CONNECTIONS
The connections between precast members should be capable
of withstanding tension,
compression,
bending,
combination of any of the four without failure,
deformation,
or rotation.
-15-
shearing,
excessive
or a
Tension Connections can be made by one of the following:
a.
Welding the projecting reinforcing bars.
b.
Projecting of a reinforcing bar from one member into a
cast-in-place concrete section or a grout sleeve in an
adjacent member.
c.
Bolting.
d.
Post-tensioning.
Shear Connections between precast members can be made by
casting concrete against previously hardened concrete and tied
with steel projecting across the interface.
Compression
Connections between precast members can be
made by filling the joint with concrete or grout.
2.3.2
FINISHES
Surface finishes can be formed mechanically,
by the pattern or texture of the mold,
chemically,
or by coating and
painting.
REINFORCED PRECAST TYPES
2.4
Reinforced precast components belong to three categories:
reinforced,
pre-tensioned,
and post-tensioned.
REINFORCED
2.4.1
There are two ways of reinforcing precast reinforced
concrete products:
1.
Fiber reinforced.
synthetic.
Typical fibers are steel,
glass, and
In this method any type of fiber is mixed
-16-
with concrete before being placed in the forms.
2.
Normally reinforced.
In this method the steel is
the form and the concrete is
positioned in
the materials
When the concrete has cured,
around it.
placed
(concrete and steel) will be bonded together and will
act as one.
At least a major part of the
reinforcements in
same way as it
this type of unit is
placed in the
might be in cast-in-place concrete
members.
2.4.2
PRESTRESSING THE CONCRETE-PRE-TENSIONED STEEL
In this method a certain tensile force is applied to the
the direction of spanning with
high-grade continuous steels in
hydraulic jacks,
form.
before high-strength concrete
is
placed in
the
When the concrete has cured and has reached a specified
strength,
the tensile force is
removed from the steel and
therefore the stress is transferred to the concrete through the
bond between them, and this causes the concrete to be
compressed.
As a result, the prestressed concrete is able to
more load,
resist some tension; therefore,
longer span, or a
thinner cross-section can be achieved.
2.4.3
POST-TENSIONING THE STEEL
This method involves placing and curing a precast member
which is normally reinforced or prestressed and which also has
a number of ducts or conduits through which post-tensioning
-17-
strands or bars will be passed (Fig.
has reached a specified strength,
2-3).
After the concrete
the post-tensioning tendons
are inserted into the channels and anchored at one end and
stressed from the opposite end by a portable hydraulic jack.
After the member has gained the specified stress, the tendons
are anchored by a automatic gripping device.
Thus, the steel
remains in tension and the concrete in compression.
Noncontinuous
bearn
Channels for posttensioning tendons
Continuous beam
Figure 2-3
Channels for post-tensioning tendons.
Pre-tensioned or post-tensioned concrete has extended the
usefulness of reinforced concrete by making it more adaptable
The main advantage of pre-tensioning or
to various needs.
post-tensioning
is
the elimination or reduction of the tensile
These
stresses in
the concrete member by pre-compression.
components,
then, are by far more practical and economical than
normal reinforced concrete when they are used for bridges,
spans,
long
extending longer cantilevers, and controling
objectionable deflections while the cracks are eliminated.
Pre-tensioning has also suitable applications when
combined with precasting or semi-precasting such as composite
or lift-slab constructions.
-18-
ADVANTAGES OF PRE-TENSIONING
In prestressed concrete the employment of higher strength
materials and the applied stress load result in a smaller
cross-section for an applied load and the elimination of
cracks.
The smaller cross-section for members allows:
a.
Saving in
and floor-to-floor
columns,
foundations,
height.
b.
Considerable reduction in the use of materials and thus
the reduction of weight, or dead load.
This reduction
in
the weight of the units mainly results in a saving
in
time and in the costs of handling,
transportation
and erection.
From the aesthetic point of view,
the density of the
material causes a better surface finish for components.
Also,
the smaller cross-section for members gives the structure a
lighter appearance.
DISADVANTAGES OF PRE-TENSIONING
The disadvantages of pre-tensioning
a.
include:
By its own nature the prestressed units have less
weight and mass.
In situations where weight and mass
are required instead of strength, plain or reinforced
concrete could serve at a lower cost.
b.
Prestressed units require more care in design,
construction and erection because of the higher
strength materials and smaller cross-section members.
-19-
PRE-TENSIONING OR POST-TENSIONING
The pre-tensioning
technique is
usually employed in a
reqardless
plant where mass production of a particular shape,
In this system, the long
of its longation, is required.
members can be produced without difficulty and without the
necessity of precise measurements of the elongation of the
tendons during stressing; the members can then be sawcut to the
desired length.
In this method,
a high initial investment cost
is required for purchasing the plant and required equipments.
On the other hand,
the post-tensioning
usually employed for long members.
expensive than pre-tensioning.
of labor required in placing,
technique is
Post-tensioning
is more
This is due to the large amount
stressing and grouting the
tendons and cost of the conduits and anchorage devices.
Sometimes,
with age,
post-tensioning members tend to maintain
their properties better than do pre-tensioning.
Furthermore,
the post-tensioning method can be applied to smooth curves.
2.4.4
PRESTRESSING TYPES - CIRCULAR AND LINEAR
Circular prestressing is a term applied to prestressed
circular structures,
such as round tanks and pipes,
in
which the prestressing wires are wound around in circles.
In
contrast to circular prestressing, linear prestressing is used
to include all other types of prestressing, when the cables are
either straight or curved, but not wound in circles around a
circular structure.
-20-
PARTIAL PRESTRESS REINFORCEMENTS
2.4.5
In contrast to the criterion of no tensile stress in the
member,
which may be called "full prestressing,"
design allowing some tension is
prestressing."
Mainly,
the method of
often termed "partial
no basic difference between
there is
the two because while a structure may be designed for no
tension under working loads,
it
will be subjected to tension
under overloads.
Partial prestressing may be obtained by any of the
following methods:
1.
Using the same amount of steel, but tensioning it
lower level,
to a
will give effects similar to those of
method 2 but no end anchorage is
saved.
Hence the
method is seldom used.
2.
Using less prestressed steel and adding some mild steel
for reinforcing will give the desired ultimate strength
and will result in greater resilience at the expense of
earlier cracking.
-21-
PRESTRESSED STANDARD TYPES
2.5
Since prestressed components are being economically
manufactured and used, many standard types have been developed
to provide a greater saving in cost.
DOUBLE TEE
2.5.1
Double tees are used extensively for both roof and floor
constructions.
wall panels.
depths.
2-4.
In some applications they may also be used as
Double tees are made in a variety of widths and
A typical section of double tee slab is
shown in
Double tee slabs are structurally efficient,
in the case of long spans.
Fig.
especially
Large openings can be provided
within the width of flange between stems.
2"
8'0"
5 3/4"
2
20" (varies)
4'1-0"
L3
Figure 2-4
2.5.2
314
Double Tee.
SINGLE TEE
Single tees are used for heavy loading requirements and/or
long spans,
ranging up to 120 feet or more.
These units are
popular for exposed ceilings and where mechanical services are
-22-
channeled between stems for easy access.
single tee slab is shown in Fig. 2-5.
A typical section of
The section is
one of
high structural efficiency and has been used extensively in
many areas of the country.
1 112"
2-18-0
36-'
(varies)
Figure 2-5
2.5.3
Single Tee
SOLID FLAT COMPONENTS
Solid flat
components include solid flat wall panels and
slabs in a variety of widths and thicknesses.
Wall panels are
mainly used for partial, full-story, or multi-story heights for
either curtain wall or load-bearing use.
Solid flat slabs do not have an extensive use in
country.
Instead,
this
hollow slabs and solid post-tensioned slabs
have been used to a very significant degree.
of solid flat slab is
Fig.
shown in
2-6.
A typical section
The principal
advantages of prestressed solid slabs are the low cost, better
quality,
and more availability.
The principal disadvantages of
prestressed solid slabs are the limitation in
standardized elements.
-23-
number of
Width varies
2N
1 1/2"
Figure 2-6
2.5.4
8" (varies)
Solid flat slab.
HOLLOW-CORE COMPONENTS
The primary physical difference between this type of
element and solid flat components is
the voids.
Hollow-core
slabs are lighter and structurally more economical and
efficient.
They can carry more load and/or span a longer
distance while having a small cross-section.
is
shown in
2-7.
Fig.
Due to their low cost,
have a major application in housing,
A typical section
these members
administrative,
and public
buildings where flat ceilings and long spans are required.
While these specifications make it
an ideal material for
slab, the lack of weight, mass, and the limited distance
between the floor-to-floor height (which prevents it
less practical and economical
used as a long member) make it
for wall members.
4'-0"
112O
Figure 2-7
from being
..O....
Hollow-core slab.
-24-
2"
8"
(varies)
OTHER COMPONENTS
2.5.5
The other standard types of prestressed components are
girders,
beams,
columns,
and piles.
The standard beams include rectangular beams,
and inverted tee beams.
beams,
2.6
L-shaped
COST OF COMMON TYPES OF STRUCTURAL CONSTRUCTION MATERIALS
To make a better comparison between the cost of structural
construction materials, the costs of prestressed standard types
and of other common types (such as cast-in-place concrete,
brick veneer with wood stud backup,
and concrete block wall are
included.
The following prices are the cost estimates based on Means
Systems Costs,
1985 edition.
PRESTRESSED STANDARD TYPES
2.6.1
The following prices are based upon a 10,000 to 20,000
S.F.
project and include the transportation cost for 50 to 100
miles.
Concrete is
reinforcement
normal-weight and f'c = 5 ksi and for
Fy = 250 or 300 ksi,
-25-
Tables 2-3 to 2-6.
Precast Double ""' Beems - No Topping
3.5-230
1500
1600
SPAN
(FT.)
OBLE."T" SIZE
D (IN.) W (FT.)
30
18x8
18x8
700
18x8
112
5.92
18x8
188
20x8
20x8
20x8
20x8
137
162
87
97
107
132
5.97
5.97
4.37
4.65
4.65
4.78
40
20x8
157
5.18
24x8
24x8
103
113
4.38
4.66
2700
24x8
123
476
2800
24x8
148
478
24x8
173
5.19
24x8
32x10
32x10
32x10
32x10
32x10
32x10
32x10
32x10
32x10
82
104
114
139
164
94
104
114
139
164
4.78
5.32
5.14
5.24
5.58
5.22
5.24
5.58
5.88
6.53
2500
2600
50
2900
3000
3100
3150
3200
3250
3300
3350
3400
3450
3500
60
70
Precast double "T" beams.
3.5-220
Precast Single Tees No Topping
SPAN
(FT.)
60
1950
2000
2100
2200
'1
"T" SIZE
SINGLE
D (IN.) W (FT.)
36:8
36x8
368
36x8
70
2400
2450
2500
2550
2600
2650
2700
2800
2850
80
3000
3100
3150
3200
3300
3350
3400
3450
3500
3525
3550
Precast single Tees.
-26-
90
:00'
COST
LOAD
TOTAL
, PERS.F.
(P S.F.)
104
6.25
114
6.25
124
6.25
149
6.40
174
7.05
36x8
36x8
36x8
36x8
36x8
48x10
48x10
48x10
48x10
104
114
124
149
174
111
121
131
156
6.50
6.50
6.55
715
7.20
7.75
7.85
0.20
8.30
36x8
2300
Table 2-4
COST
PERS.F
5.42
5.92
1800
1900
2000
2100
2200
2300
2400
Table 2-3
TOTALLOAD
(P.S.F
92
102
48x10
181
8.30
48x10
48x10
48x10
48x10
48x10
48x10
48x10
48x10
4810
111
121
131
156
8.55
8.75
8.85
8.90
9.00
48x10
181
il
8.90
121
131
156
8.95
9.10
9.15
101
9.25
3.5-210
Precast Plank With No Topping
SPAN
FT
.0
0720
2750
'770
J800
5
TOTAL
DEPTH
(IN.)
4
6
6
6
TOTAL
LOAD
(P.S.F.)
90
6
6
6
6
6
6
8
8
125
150
90
125
150
90
130
155
8
130
-820
0850
0875
0900
0920
0950
0970
000
20
25
:200
20995
:300
400
.500
:600
40
45
_700
Table 2-5
125
150
90
COST
PERS.F.
3.30
3.29
3.29
3.29
3.29
3.29
3.29
3.29
3.29
3.29
3.40
3.40
3.40
3.40
10
170
3.58
10
12
110
145
3.58
3.94
12
110
3.94
Precast plank.
Fat Pr mt Concrete
4.1-1401
3200
3250
3300
3350
3400
3450
3500
(IN.)
THICKNESS
6
8
9.12
8.69
7.97
lowrise
15.05
11.42
10.04
2
low
rise
16.15
12.57
11.19
whiteface
none
lowrise
1540
11.82
10.61
whiteface
2
lowrise
16.50
12.97
11,71
1084
1574
12.11
10.90
10.04
16.89
13.26
12.05
6.59
7.31
6
4x8
8x8
10x10
whiteface
none
_0xI
_
4x8
8xe
10x10
9.69
20x10
7
8
8
4x8
8x8
10x10
20x10
4x8
0x8
10x10
20x10
4W8
8W8
10x10
whiteface
wniteface
none
rise
low
2
iowrise
1119
20x10
5150
9.3
9.23
20x10
7
4550
4600
4650
4700
4750
4800
4850
4900
4950
5000
5050
5100
lowrise
white
face
4150
4400
4450
4500
8.41
7.20
719
4x8
8x8
10x10
4350
COST
PERS.F.
ow rise
6
4100
4200
4250
4300
TYPE
12x20
3550
4000
4050
RIGID
PANEL
(IN.)
SIZE(FT.) FINISHES INSULATION
2
5:18
smoothgray
6:18
0x20
12x20
5x18 smooth
gray
2
6:18
0x20
Table 2-6 Flat precast concrete wall.
The costs of "T"
beam and "L" beam are as
follows:
Beam,
20' span is
$2.82 per L.F.
12" x 20" precast "L" Beam,
20' span is
$1.76 per L.F.
12" x 20"
precast "T"
-27-
2.6.2
CAST-IN-PLACE CONCRETE
The concete is
normal weight and f'c = 4 ksi and for
re inforceme nts F'y = 60 ksi.
Forms are for use,
the finish
steel trowel, and curing is based on spraying on the membrane.
Tables 2-7 and 2-8.
aw-1so
Ft
C..
2000
2200
2400
2600
3000
3400
3600
3800
4200
4400
4600
5000
5600
6000
6400
6600
7000
7400
7600
8000
Table 2-7 cast-in-place
4.1-110
Ph"t_
BAYSIZE
(FT.)
15x 15
SLAB
(IN.)
THICKNESS
5-1/2
5-1/2
5-1/2
22
5-1/2
244
5.76
14
16
22
24
16
20
24
24
18
20
26
30
20
24
30
7
7-1/2
8-1/2
8-1/2
7
7-1/2
8-1/2
8-1/2
8-1/2
9
9-1/2
10
9
9-1/2
10
127
169
231
281
127
175
231
281
146
188
244
300
152
194
250
5.91
6.17
6.52
6.54
5.91
6.17
6.51
6.55
6.49
6.62
6.99
7.17
6.61
6.90
7.17
1
15x 20
20x 20
20 x25
25 x 25
_
1
5.56
5.57
5.70
1
flat plate.
COSTPERS.F.
t In Place Concret
MAT.
INST.
5400
4000PS1
2.80
6.75
6.75
6.75
8
8
8
7 05
7.05
7,05
7 35
7.35
735
8.55
8.55
8.55
8.30
8.30
8.30
6.95
6.95
6.95
8.20
8.20
8.20
7.25
7.25
7.25
7 55
755
755
8 75
8 75
7075
850
8.50
5500
5000 P'S 1
2.87
850
8' high.6" thick.plainfmish,3000PSI
2100 Concwallreintorced.
4000P S.I.
2200
5000PSI.
2300
RubconcreteI side.3.000P.SA
2400
4000P.S.I.
2500
5000PSi
2600
Agedwoodliner.3000PSI
2700
4000PSI
2800
5000PS.I
2900
Sandblastlight I side. 3000P.S.I
3000
4000PSI
3100
5000PS.I
3300
heavyI side.3000PSI
Sandblast
3400
4000PS.I
3500
5000PSI
3600
strip.3000PS.I
3/4" bevelrustication
3700
4000PSt
3800
5000PS.I.
3900
8" thick.piaintinisn.3000PSI
4000
4100
4000PS.1
5000PS.1
4200
4300
Rubconcrete
i sine.3000P.SI.
4400
4000PSA
5000PS1
4500
4550
8" thick,agedwoodliner.3000PS.I
4000 P.S.I
4600
4700
5000 P.S.I
4750
Sandblasthiht I side.3000P.SI
4800
4000PS 1
5000 P.SI
4900
SandblastheavyI side.3000PS 1
5000
5100
4000P.S.1
5000P.S1
5200
5300
Table 2-8
COST
PERS.F.
TOTAL
LOAD(P.S.F.)
109
144
194
MINIMUM
SIZE(IN.)
COLUMN
12
14
20
3/4" bevel rustication strip. 3000 P.S1
cast-in-place concrete wall.
-28-
2.26
2.31
2.37
2.30
2.35
2.41
3.38
3.43
3.49
2.35
2.40
2.46
2.59
2.64
2.70
2.34
2.39
2.45
2.64
2.72
2.79
2.68
2.76
283
3 76
3.84
391
2 73
281
2,88
2.97
3.05
3 12
272
TOTAL
9.01
9.06
9.12
10.30
10.35
10.41
10.43
10.48
10.54
9.70
9.75
9.81
11.14
11.19
11.25
10.64
10.69
10.75
9.59
9.67
9.74
10.88
10.961
11.031
11.01
11.09
11.16
10.28
10.36
1043
11.72
11.80
11.87
11.37
11.22
11.3V
2.6.3
BRICK VENEER/WOOD STUD BACKUP
Exterior brick veneer/stud backup walls are defined in the
following terms: type of brick and studs,
bond.
stud spacing and
All systems include a brick shelf, ties to the backup,
and all necessary dampproofing and insulation.
Brick Veneer/Wood Stud Backup
4.1-22
100
1120
1140
FACEBRICK
Stanaard
STUD
BACKUP
2x4-wood
STUD
SPACING
(IN.)
16
English
14.82
2x6-wood
16
running
common
Flemish
11.14
12.09
13.65
English
15.01
24
running
common
Flemish
10.88
11.83
13.44
English
14.80
1160
1400
1420
1440
1460
1500
1520
1540
1560
Table 2-9
2.6.4
Table 2-9.
BOND
running
common
Flemish
COST
PERS.F.
10.95
11.90
13.46
Brick veneer/wood stud backup.
CONCRETE BLOCK WALL
The following prices include horizontal joints
reinforcing,
alternate courses,
in cases of hollow units.
control joints,
Table 2-10.
-29-
and insulation
Concrete Block Wall - Regular Weight
4.1-211
1200
1250
1300
1310
1340
1350
1360
1390
1400
1410
1440
1450
1460
TYPE
Hollow
SIZE
(I N.)
4x8x16
6x8x16
STRENGTH
(P.S.I.)
2.000
4500
2.000
4,500
8x8x16
2.000
4.500
12x8x16
Solid
4x8x16
6x8x16
2600
2650
2700
2750
2800
8x8x16
12x8x16
2350
2.7
2.000
4,500
2550
Table 2-10
COST
PERS.F
3.55
3.92
4.70
4.59
3.90
5.11
6.43
4.31
5.41
5
4.31
6.11
5.70
none
1490
1500
1510
1540
1550
1560
1590
2500
COREFILL
none
none
perlite
styrofoam
none
perhte
styrotoam
none
perite
styrotoam
none
perlite
styrotoam
2.000
perite
styrotoam
none
peride
styrotoam
none
none
5.01
7.49
6.62
5.78
8.14
7.27
6.43
3.81
4.500
none
415
2.000
4,500
2.000
4,500
2.000
none
none
none
none
none
4.32
4.77
4.87
5.45
6.68
4.500
none
7.53
Concrete block wall.
CONCLUDING DISCUSSION
In comparing the common types of structural materials, we
conclude that hollow-core slabs have the highest economical
advantages.
While having the advantage of prestressing,
precasting and concrete,
have smooth surfaces.
manufactured
these slabs are light in weight and
In addition, hollow-core slabs can be
in a standard fashion and used as long members.
From the point of view of cost, hollow-core slabs are the
least expensive type of flooring and roofing material.
because of their ease of manufacture,
handling,
efficiency in use of construction materials.
-30-
This is
erection and
In addition, the
manufacturing
requires the least amount of labor and time in
comparison to other types of structural construction materials.
While these specifications make hollow-core components an
ideal material
for slabs,
the fact that they cannot be used as
long members make them less practical for wall members.
Therefore,
this thesis presents ways in
deficiencies can be minimized and it's
panels be made more practical.
-31-
which these
use for wall
3.0
PRESENT APPLICATIONS OF STANDARD PRECAST
PRESTRESSED HOLLOW-CORE COMPONENTS
-32-
3.0
PRESENT APPLICATIONS OF STANDARD PRECAST PRESTRESSED
HOLLOW-CORE COMPONENTS
Hollow-core is a standard type of precast prestressed
concrete components.
Hollow-core components have an economical
and speedy manufacturing procedure based on the use of machines
and equipment rather than labor.
The members are produced in
long beds and sawcut to the desired length after they have
gained a sufficient strength.
members,
Normally for hollow-core
3 men are required to produce 4 lines of 500'
x 5',
while for other precast types 7 to 10 men are required to
produce 5 panels of 6'
x 30'.
In addition, hollow-core components have small depth to
length and/or weight ratio when they are positioned under
tension.
This mainly results from the use of high-strength
materials, the voids, and the applied stress.
3.1
HOLLOW-CORE SLAB
In comparison to all other types of flooring and roofing
systems (including prestressed standard types), the main
advantages of standard hollow-core slabs are the low cost,
surfaces, small thickness, and light weight.
flat
They also have
all the advantages of prestressing, precasting and concrete.
Typical voids in the slab may be of circular, oval, or,
sometimes, rectangular cross-section.
The various
cross-sections are shown in Fig. 3-1 to 3-6.
voids run in the direction of the span.
As a rule, the
The ribs between the
ducts are sufficiently stiffed by the top and bottom plates to
make cross ribs superfluous.
-33-
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3.1.1
TYPICAL CONNECTIONS
During the lifetime of prestressed concrete hollow-core
slabs, many types of connections have been developed.
common type includes its connection to walls,
The most
beams,
nonstructural elements and to each other. See Fig. 3-7 to 3-11.
T_
d
a
tgt
tg
Premt wall panel
2 Rrbws between gaps
from wail into topping
illow-core floor slab
Figure 3-7
Typical connection details of hollow-core slab to
structural wall-Exterior joints.
d
Figure 3-8
Typical connection details of hollow-core slab to
structural wall-Interior joints.
-37-
Typical connection details of hollow-core slab to
beam.
Figure 3-9
Precast wall panel
Rebars from
walls into topping
Welded wire fabric
iTop ping
r
Figure 3-10
Typical connection details of hollow-core slab to
shear wall.
Grouted key
Hollow-core
Welded wire fabric
kO~
Figure 3-11
~
oooOO
. 0OO
Hollow-core slabs---
-/
Typical connection details of hollow-core slabs to
each other.
-38-
3.1.2
COORDINATION WITH ELECTRICAL, MECHANICAL, PLUMBING,
SERVICES AND OTHER SUB-SYSTEMS
Prestressed hollow-core slabs are used in a wide variety
of building types.
Therefore, it is important to have
economical and practical ways to integrate them with
electrical,
mechanical,
plumbing,
services and other
sub-systems.
ELECTRICAL
Since a cast-in-place topping is usually placed on
prestressed floor members, conduit runs and floor outlets can
be readily buried within the topping (Fig. 3-12).
The other
options are to run them along the beams or at the intersection
wall and floor.
In the latter option the conduit runs and
outlets are positioned on the wall.
Figure 3-12
Under floor electrical ducts can be embedded
within a concrete topping.
-39-
MECHANICAL
There are two common ways of incorporating the duct work
within a hollow-core slab system:
1.
Using the voids inside the slab.
Additional openings
can be drilled in the field to allow the continuity of
the system.
2.
Using a suspended ceiling.
Large openings through the
floor and roof members are provided by block-outs in
the forms during the manufacture,
Figure 3-13
Fig.
3-13:
floors and roofs are made during
Large openings in
manufacture of the units.
PLUMBING SERVICE
To reduce the on-site time and labor,
prefabricated
bathroom units or combinations of bathroom and kitchen modules
have been developed (Fig.
3-14).
Such units can include
bathroom fixtures, kitchen cabinets and sinks,
ceiling and floor surfaces.
as well as wall,
To eliminate a double floor,
module can be plant built on the structural members,
-40-
the
with the
option of incorporating the prefabricated wet-wall plumbing
systems (Fig. 3-15).
It
is more practical and economical
in
precast multi-story construction to locate the service units in
a stack fashion with one type of service directly over the one
below.
Figure 3-14
Kitchen/bathroom modules can be pre-assembled on
precast prestressed slab ready for installation
in systems buildings.
-41-
Figure 3-15
Prefabricated wet-wall plumbing systems
incorporate pre-assembled piping.
Some core modules not only feature bath and kitchen
components, but also HVAC components all packaged in one unit.
These modules can also be easily accommodated in prestressed
structural systems by placing them directly on the prestressed
members with shimming and grouting as required.
OTHER SUB-SYSTEMS
Suspended ceilings, crane rails, and other sub-systems can
be easily accommodated with standard manufactured hardware
items and embedded plates as shown in Fig. 3-16.
-42-
#
0
0
Figure 3-16
Methods of attaching suspended ceilings, crane
rails, and other sub-systems.
3.2
HOLLOW-CORE WALL
Even though precast prestressed hollow-core slabs are
widely used in
they do not have many
the construction industry,
This is mainly because
applications as structural wall panels.
of the diversity in requirements of a floor and wall member.
The main disadvantages of hollow-core components as a wall
member include their lack of weight, mass and, in some cases,
their insufficient insulating qualities.
They are also not
able to be used as long members in structure.
Hollow-core wall panels have been used in
in 8' to 9' long members.
Dy-core,
some structures
The typical section includes
Dynaspan and Span-Deck,
Fig.
3-1,
3-2 and 3-5
respectively.
3.3
COREWALL INSULATED WALL PANEL
Many attempts were made to standardize
the manufacturing
of a practical and economical load bearing and non-load bearing
wall panels.
As a result of these attempts,
-43-
corewall insulated
wall panels were introduced in
1981 (Fig.
3-17).
G.E. SILPRUF SEALANT FOR 4 HOUR RATING,
TREMCO DYMERIC SEALANT FOR 3 HOUR RATING
POLYETHYLENE FOAMED ROD BACK-UP
EXTERIOR
8" COREWALL PRESTRESSED
CONCRETE PANEL WITH
2" POLYSTYRENE INSULATION,
1 LBiCU FT DENSITY
TREMCO CERA BLANKET.
1/" MINIMUM DEPTH
INTERIOR
TREMCO MONO SEALANT
Figure 3-17
Section through vertical joints.
The advantages of corewall panels are the fact that the
members can be mass produced in a standard fashion and can be
used in long members, while achieving high insulating
qualities.
The main disadvantages of the corewall insulated panels
include the following:
a.
The height of the building is limited.
The maximum
practical lengths for 8" and 10" thick corewall panels
are 26' and 32' respectively.
Therefore, the building
can be only about two to three stories height.
b.
Most of the roof and intermediate floor loads are
transferred to the "I" shape steel columns through the
steel "I" beams, instead of the structural wall panels.
Fig. 3-18 and 3-19.
In addition, the steel members
have to be fireproofed.
-44-
Corewall panel
Insulation
6" slotted insert
8"
/
Strap anchor
welded to beam
Erection "10"
clip (tenporary)
-
Rib
-' *
1 Min.
Alternate location
-D
connection
Rof
STANDARD RIB
Figure 3-18
Figure 3-19
Typical corner
connection.
detail.
The production of a panel is
C.
Typical top
done in
three steps and
all the connections have to be inserted into the wall
panel .
d.
Limited flexibility exists in the location of openings
since the panels come in
8' wide modules and special
panels should be designed individually for each
opening which varies in dimension.
Corewall panels are not suggested for load bearing or a
shear wall.
They are best used for curtain wall applications
or to carry light roof loads under certain conditions.
-45-
4.0
NEW APPLICATIONS OF STANDARD PRECAST
PRESTRESSED HOLLOW-CORE COMPONENTS
-46-
NEW APPLICATIONS OF STANDARD PRECAST PRESTRESSED HOLLOW-
4.0
CORE COMPONENTS
In general,
structural prefabricated
floor and wall
panels can be classified in three degrees of diversity (Fig. 4-la):
1.
The floor and wall panels differ from each other in
basic shape, cross-section, and in their production
demands,
and they require separate formwork and
different technology.
The floor and wall panels each have variations
2.
in
length or width, but their variations can be cast by
the same method and using the same formwork.
3.
The floor and wall panels each have variations in the
internal details,
but their variations do not affect
the basic sizes or production methods (incorporating
window openings,
surface treatment,
etc.).
This thesis presents another degree of diversity, for
structural prefabricated
-The
panel units (Fig.
floor and wall panels do vary in
4-lb) which is:
length or width
(4' or 8' modulars) but they can be cast by the same
method and using the same formwork.
The first
degree of diversity essentially affects the
capital expenditure while the second and third degree dictate
the organization of production, storing and erection. In
addition, the third degree affects the capital expenditure as
well.
-47-
The new degree of diversity will minimize the capital
expenditure,
but it
will require some degree of organization in
storinq and erection.
Figure 4-la
Three degrees of diversity for prefabricates.
Figure 4-lb
The new degree of diversity for prefabricates.
In the earlier chapters the advantages of standard precast
prestressed concrete hollow-core slabs were analyzed.
This
chapter introduces two systems in which this component and its
-48-
modification can be used practically and economically as
structural floor and wall panels while maintaining those
advantages.
4.1
SYSTEM 1 - REQUIRED STRUCTURAL COMPONENTS
The essential components of this system include the
following:
4.1.1 HOLLOW-CORE SLAB
Two types of hollow-core slabs are required.
1.
Standard prestressed hollow-core slab, Fig. 4-2.
voids
prestressed bar
.0.0.
.0.0.00.0L
.0.0
8'-0''
Figure 4-2
2.
Hollow-core slab.
Partially prestressed hollow-core slab with
post-tensioning conduits,
Post-tensioning conduit
Fig.
4-3.
Prestressed bars
0o nd uit s.
The manufacture of this component can be done using the
same method and equipment as the standard prestressed
hollow-core slab in Fig. 4-2.
The only differences in the
-49-
members are the replacement of four prestressing
two voids with two post-tensioning conduits.
strands and
The applied force
-which may be partial- to the prestressing strands should be
capable of handling the weight of the unit,
and hence the
cracks are eliminated during the handling and erection of the
component.
4.1.2 HOLLOW-CORE WALL PANEL
The wall panels can be made in the same form and by a
manufacturing method similar to that used for standard
However, three modifications
prestressed hollow-core slabs.
are required in
order to be able to use hollow-core slabs
practically and economically as wall panels (Fig.
holes for post-tensioning
to pass through
/rods
:00:
ino:oo:
4-4):
prestressed bars
:oo.il o0
8'-0"
Figure 4-4
1.
Hollow-core wall panel-Section.
Prestressed tendons should be added at the top of the
slab and some being eliminated at bottom during
manufacturing in order to secure symmetrical forces in
the cross-section of the unit.
2.
Some or all voids should be eliminated in order to
achieve
a more solid section for compressive
Two of the eliminated voids in
forces.
the wall panel should be
perpendicular to the post-tensioning conduits in
floor panel.
-50-
the
3.
Holes should be provided to enable the slab's
post-tensioning rods to pass through.
The holes can be
drilled in the factory after manufacturing.
The walls can be put beside each other, vertically, in two
basic patterns:
a.
The height of wall panels should be equal at each level
of erection (Fig.
b.
4-5).
The height of every other panel should vary in one
story increments.
This method adds support and
rigidity when construction continues in height.
Fig.
4-6.
CN'
'-4
0
CN
0
.4-J
V)
Figure 4-5
Wall panels have equal
Figure 4-6
The height of
heights at each
every other wall
level of erection.
panel vary in one
story increments.
4.1.3 PRECAST "L" BEAM
A vital component of this system is
(Fig. 4-7).
1.
the precast "L" Beam
The function of these beams are as follows:
Provide a temporary bracing for prestressed concrete
wall panels at different stages of erection.
2.
Align prestressed concrete wall panels when positioned
in place.
3.
Provide a bearing support for prestressed floor slabs.
-51-
4.
Allow openings between wall panels.
5.
Increase the overall lateral rigidity.
hole ispre-drilled
in the factory
Figure 4-7
Precast "L" beam.
Because the precast "L" beams are connected by the
post-tensioning rods to the wall panels,
provided through the beam.
holes should be
Moreover the holes have to be
aligned with holes in prestressed wall panels and thus with the
placement of post-tensioning conduits.
4.1.4 PRECAST SUPPORT ELEMENTS
The function of support elements is to support the
continuous precast concrete beams both during erection and
permanently.
Fig. 4-8 shows a typical precast support element.
These elements are placed perpendicular to the wall panels and
"L" beams.
-52-
-Dowel for aligment &
placement of upper panel
Holes for bolting the concrete
during erection
4
U
00
-Width of adjacent wall panel
4
Width of concrete beam
-4
U
0
-)For
.
connecting the
panel below
-support
\-Width of adjacent member
Figure 4-8
Precast support element.
SEQUENCE OF ERECTION
4.1.5
It
is
assumed that the foundation walls,
or the footings
have been casted and have reached
of the foundations,
sufficient strength:
1.
The prefabricated concrete support elements are placed on
top of the foundation walls and grouted.
The elements
are placed perpendicular at both ends of the forthcoming
beams and load-bearing wall panels.
2.
The prefabricated concrete beam is hoisted on the
designed ledges of the support panels and bolted.
3.
The prestressed concrete wall panels are placed in a
sequential order on top of the foundation walls and then
grouted.
The concrete beam acts as a lateral support for
the panels.
The lengths of the panels can vary in
one-story increments that are staggered at the top ends
of the panels to add support and rigidity when
-53-
construction continues in height.
4.
The temporary supports are connected for the erection
of the slabs to the wall (See
4-9).
Fig.
Drypack or epoxy grout
Prestressed hollow-core slab
Post-tensioning rod
Post-tensioning conduit
4. .For
- a*
I
-
erection only
Prestressed
IL
" I" bea m
Figure 4-9
5.
Floor to bearing wall connection-
o
bar
Detail A.
After the partially prestressed concrete floor slabs
have been placed on the temporary supports, the rods
are inserted into the two post-tensioning conduits
within the slab and is
4-9).
tensioned against the beam (Fig.
The cross-section area of each post-tensioning
rod is equal to the total cross-section area of the two
eliminated prestressing bars.
In addition,
the
reinforcing steel bars should be inserted between every
keyway and grouted.
6.
The standard prestressed concrete floor slabs should be
placed on the "L"
beams (Fig . 4-10).
Reinforcing steel
bars should be inserted between every keyway and
grouted.
-54-
Prestressed wall panel
Prestressed Hollow-core
floor panel w/ posttensioning conduits.
Standard prestressed
hollow-core slab
Precast continuous
"L" beam
Figure 4-10
Typical section.
The procedure of erection can continue in the same
fashion.
4.2
SYSTEM 2 - REQUIRED STRUCTURAL COMPONENTS
In this system the floor slabs are standard prestressed
hollow-core.
The wall panels are typically manufactured by the
same method as introduced in 4.1.2.
The major differences are
the placement of infilled voids and drilled holes.
and 4-12.
Fig. 4-11
The holes are drilled perpendicular to the center of
infilled voids.
The holes are used to boltthe precast beams to
the wall panels and therefore provide a support (the beam) for
the floor slabs.
The precast beams are rectangular.
Furthermore, in this method reinforced concrete support panels
are also used to support the beams during erection.
The
support beams have two ledges on the sides for supporting a
precast beam on each side.
-55-
Grouted Vert.
Keyway
Prestress ed Conc.
Wall Pane I
Prestress ed Tendon
Grouted Joint
IV.
.----------------]|- - ---"-- " " ''''
f
#3 Rebar Grouted
nto Keyw ay
-
Figure 4-11
Typical connection of
Figure 4-12
floor slabs to load-
H igh-S treength
S teel Bo l
Section through loadbearing wall panels.
bearing wall panel.
4.3
ADVANTAGES AND DISADVANTAGES
The principal advantages of using homogeneous components
for floor and wall units are that one standard method and
technique can be used for manufacturing and that there is
a
significant saving in the cost of equipment and formworks.
The principal advantage of the new systems is that the
wall members can have all the advantages of standard precast
prestressed concrete hollow-core slabs --
advantages of standardization,
precasting,
-56-
including the
prestressing,
concrete and hollow-core slabs --
requirements of a wall member.
while meeting the
In addition, the wall panels
can be used as long members, up to 3 or 4 stories in height,
and the need for bracing and scaffolding
is
minimized.
A major disadvantage of hollow-core components is
the lack
of high insulating qualities for exterior wall members.
problem can be solved in the new system as shown in
Prestressed
hollow-core slab
Fig.
This
4-13.
Face brick
--
Rigid insulation
1A
lb
Continuous conicrete beam
--
For post-tensioning rods
Prestressed wall panel
....... Prestressed bar
Rebar grouted into keyway
Figure 4-13
Optional exterior finish-Detail B.
In case of openings in system 1 an additional member
should be placed in the cavity between the cross-section of the
floor panels and the continuous beam.
-57-
5.0
EFFECTS OF THE NEW SYSTEMS ON HOUSING,
ADMINISTRATIVE AND PUBLIC BUILDINGS
-58-
EFFECTS OF THE NEW SYSTEMS ON HOUSING, ADMINISTRATIVE,
5.0
AND PUBLIC BUILDINGS
HOUSING
5.1
In no other sector of the building industry has
industrialization became so urgently necessary as in
residential building contruction.
The reasons for
industrialization are both economical and social.
The
economical reasons include the following present conditions:
a.
Small productivity per man-hour and high wages;
b.
The man-power shortage;
c.
The shortage of housing accommodation.
As in many
countries, the output of housing is not keeping pace
with the increase of population.
The social reasons include the following:
a.
The need to provide better working conditions;
b.
The permanent place of work which is sheltered from the
weather and unaffected by the seasonal variations.
The major concern about using prefabricated components has
always been to avoid rigidity in
variety and flexibility.
variety in
planning and to provide
In cases where some flexibility and
the plan were accomplished,
the system failed to be
economical.
The new system's incorporation of large members produces
large volumes and a high degree of flexibility in space for
planning while remaining economical.
-59-
Since the system is based
on an open-plan space in a variety of dimensions,
the
interiors, except the location of services, can be custom made
in order to satisfy a variety of plans and wishes.
5.2
ADMINISTRATIVE AND PUBLIC BUILDINGS
Multi-story buildings used for industrial purposes present
a very wide range of variety.
Because live loads,
spans and
story heights vary considerably, different structural solutions
may be applied.
It is possible, however, to establish some
basic principles.
Multi-story industrial buildings are characterized by
heavy live loads,
large story heights and,
relatively small number of stories.
in
general,
On the other hand,
a
in
administrative buildings (office buildings) the live loads
seldom exceed 75 lb/SF,
the story heights are not more than 12
ft., and there are often a large number of stories.
Public
buildings, particularly school and university buildings, have
generally the same live loads and story heights as
but seldom have a large number of
administrative buildings,
stories.
Thus,
public buildings occupy an intermediate position
between industrial buildings and residential buildings as far
as their structural solution with prefabricated components is
concerned.
On the other hand,
it
should be noted that public buldings
are often very large projects and that developments in
-60-
for such buildings are
prefabricated construction techniques
extremely rapid and economical.
The new system,
which can provide relatively large areas
without intermediate columns or walls, allows a fair degree of
versatility in the manner in which the space is utilized.
For
example, thus it permits a layout as open-plan offices of
single-zone type (offices on one side of a corridor) or of the
double-zone type (offices on both sides of a central corridor).
5.3
DESIGN EXAMPLE
Fig.
The following plan and section,
analyzed
in terms of variations in
5-1 and 5-2,
are
the dimension of the units
The building is based on
and the total cost of the building.
4' or 8' x 34' slab modulars and 24' depth of a typical living
unit.
C
34'-''
lyp.
Typ.
Typ.
-
-4'-'I
170'-0"
Figure 5-1
Design example - Plan.
Prestressed hollow-core
slab w/ p.t. conduits
Standard prestressed
hollow-core slab
Detail A
Detail B
$-4
0
4--j
Cn
U-)
Figure 5-2
Design example - Section.
-61-
5.3.1 VARIATIONS IN UNIT DIMENSIONS
1.
Considering the width between two structural walls or
(Fig. 5-3).
34' width of the slabs
24'
Depth x 34' Width = 816 S.F.
Area
34'-0"
Figure 5-3
Considering the width between two structural
walls.
2.
Considering the width between three structuarl walls,
or 2 x 34' width of the slabs (Fig.
a)
5-4a and 5-4b).
24' Depth x 68' Width = 1632 S.F. Area
I
.
34'-"
34'-0'
68'-0"
Figure 5-4a
Considering the width between three structural
walls.
b)
24' Depth x 20' Width and 24'
to
24' Depth x 25' Width and 24'
Depth x 48' Width
Depth x 43' Width
which is:
480 S.F. Area and 1152 S.F. Area
to
600 S.F. Area and 1032 S.F. Area
-62-
Therefore the area of units range from 480 S.F. to 600
S.F. and 1152 S.F. to 1032 S.F.
34'-9"
.20'-0"1. 5' 9'-Q"
43' to 48'
2F'to 25'e
Figure
the width between three
Considering
5-4b
34'-O'
structural
walls.
3.
Considering
the width between four structural
3 x 34' width of the slabs (Fig.
walls,
or
5-5).
24' Depth x 43' Width and 24' Depth x 39' Width
to
24'
Depth x 39' Width and 24'
Depth x 43' Width
which is:
Area and 1416 S.F. Area
to
1416 S.F. Area and 1032 S.F. Area
1032 S.F.
Therefore the area of the units range from 1032 S.F. to
1416 S.F.
34'-0"
,
34'-0"
,
16'
. 9',
34'-0"
II
43' to 59'
43' to 59'
Figure 5-5
Considering
the width between four structural
walls.
-63-
Based on 4' or 8' x 34' slab modulars and 24' depth of the
then,
units,
the following sizes and ranges can be achieved:
480 S.F. to 600 S.F., 816 S.F.,
1032 S.F. to 1416 S.F.,
and 1632 S.F.
It
should be also mentioned that the location of
partitions between units can vary on each floor; therefore,
different sized units can be achieved at each floor.
5.3.2 COST ESTIMATE
The assumptions for calculating the cost of a typical
building based on system 1 and Fig.
5-1 and 5-2 are as follows:
Building type = Residential
Building height = 5 stories
Cost of hollow core components (from table 2-6) = $3.50 /S.P.
Cost of precast "L"
beam = $1.80 /L.F.
Cost of support panels for 2' x 9' @ 3.75 S/S.F. = $67 /each
It
should be mentioned that the cost of the components
includes transportation and erection costs.
Total floor area = 56' width x (34'
x 5)
length x 5 no.
of stories = 47,600 S.F.
Total wall area
(1)
= 56' width x (9' x 5) height x 6 no.
of walls -
(8' width x (9' x 5)
height x 7 no. of omitted walls)=
15,120 S.F. -
2,520 S.F. = 12,600 S.F.
(2)
Total floor and wall area = Total area of hollow-core components required = 47,600 S.F. + 12,600 S.F. = 60,200 S.F.
-64-
(3)
therefore:
Total cost of hollow-core components=60,220 S.F.x $3.5 /S.F.=
(4)
$210,700
Total cost of precast "L" beams = 56'
each floor x 5 stories x
length x 6 no. at
1.80 $/L.F.= $
3,024
T
$
(5)
3,000
Total cost of support panels = 24 no. at each floor x
5 stories x
67
(6)
$/each = $8,040 * $8,000
Total cost for post-tensioning the tendons = (72 at each
floor x $11 a piece for reuseable grip devices x 1/2 since
it is reusable) + $595 hydraulic RAM = $991
m
(7)
$1000
Therefore, the total cost for structure, not including the
foundation and slab on grade cost, of a 5 stories and 47,600
S.F. is:
(4) + (5) + (6) + (7) = $210,700 + $3,000 + $8,000 + $1,000 =
$222,700
(8)
Consequently the cost of the structure per square foot is:
(8)
: (1) = $222,700
: 47,600 S.F. = $4.67 /S.F.
The cost for the usual reinforced precastpanel is
$18 per S.F.
and
for the cast-in-place concrete floor or wall is about $8 per S.F.
-65-
5.4
VARIATIONS OF PLANNING
Several variations
of planning with this system are schem-
atically shown in this section.
Direction of spaning
I
I
.
I
Direction of spaning
-66-
I
I
Ia
'a
a
a
-1~I
a
a
I
*
a
a
a
I
a--i
S
I
I
a
I
---. 5
a
a
*
a
I
L
-67-
6.0
CONCLUDING DISCUSSION
-68-
6.0
CONCLUDING DISCUSSION
The recommended systems makes it possible to incorporate
large members horizontally (floors) as well as vertically
Therefore,
(walls).
large areas or volumes can be provided
with a high degree of flexibility in space for planning.
In
addition, using the same method of manufacturing for
both floor and wall members will minimize the capital
expenditure mainly by saving in
equipment.
the cost of formworks and
Moreover, by developing an appropriate floor-to-
bearing wall detail connection,
wall components can be
manufactured and erected in long members.
This will increase
the level of productivity in the plant and the speed of
erection at the site.
wall)
Further,
are compatible in weight,
since the components (floor and
the cranes are used to their
full potential.
Above all, the recommended structural systems are is
considerably lower in cost.
-69-
REFERENCES
-70-
REFERENCES
Committee 506. "State-of-the-Art Report on Fiber
Reinforced." Concrete International (December,
1984), pp. 15-27.
1.
ACI
2.
Cornell University, Center for Housing and Environmental
Cornell
The New Building Block.
Studies.
University, 1968.
3.
Glover, C.W.
Limited,
4.
Hartland, .A.
1975.
5.
Basic Construction
Herubin, C.A. and Marotta, T.W.
Materials. Reston Publishing Company 1981.
6.
Hornbostel, C. Materials for Architecture.
Publishing.
7.
Klitsikas, M. State-of-the-Art Report on High-Strength
Department of Civil
Master's Thesis.
Concrete.
Engineering, Northeastern University, 1985.
8.
Koncz,
9.
Lewicki, B. Building with Large Prefabricates. Elsevier
Publishing Company, 1966.
C.R. Books
Structural Precast Concrete.
1965.
Halsted Press,
Design of Precast Concrete.
Reinhold
T.
Manual of Precast Concrete Construction Vol.
2, and 3. Bauverlag GmbH, 1971.
1,
Van Nostrand
10.
Libby, J.R. Modern Prestressed Concrete.
Reinhold Company, 1977.
11.
Lin, T.Y. Design of Prestressed Concrete Structures.
John Wiley and Sons, Inc., 1955.
12.
Lin, T.Y. and Kelly, J.W. Prestressed Concrete Buildings.
Gordon and Breach, 1962.
13.
Lonestar/San-Vel. Corewall Insulated Wall Panel Catalog.
Lonestar/san-vel, 1981.
14.
Lay, T.
15.
Means, R.S. Means System Costs.
Company, 1985.
16.
Morris, A.E.J. Precast Concrete in Architecture.
Whitney, 1978.
"Concrete."
Fine Homebuilding,
-71-
1943.
Means Publishing
Prestressed
17.
PCI.
Architectural Precast Concrete.
Concrete Institute, 1973.
18.
PCI.
Manual on Design of Connections for Precast
Prestressed Concrete. Prestressed Concrete Institute,
1978.
19.
PCI.
Manual for Quality Control.
Institute, 1968.
20.
PCI.
Manual for Structural Design of Architectural
Precast Concrete. Prestressed Concrete Institute,
1977.
21.
PCI.
PCI Design Handbook.
Institute, 1978.
22.
Design Philosophy and
Proceedings of May 1967 Symposium.
its Applications to Precast Concrete Structures.
Cement and Concrete Association, 1968.
23.
The Development of an Alternative Building
Simonic, L.
System. Master's Thesis, Department of Architecture,
MIT, 1984.
24.
Smith, R.C. Materials of Construction.
Company, 1979.
25.
Society for Studies on the Use of Precast Concrete.
Precast Concrete Connection Details Structural Design
Beton-Vertage GmbH, 1978.
Manual.
Prestressed Concrete
Prestressed Concrete
-72-
McGraw-Hill Book