Prestressed concrete pretensioned concrete post tensioned concrete prefabricated buildings

1. Precast
Construction
G 06: 202132031, 202132012, 202132024, 202032012

2. Precast
Concrete

3. ● Precast concrete is a form of concrete that is prepared, cast and cured off-site,
usually in a controlled factory environment, using reusable moulds.
● Precast concrete elements can be joined to other elements to form a complete
structure.
● Products include buildings, wall or panel systems, support slabs, columns, etc.
What is Precast Concrete?

4. Precast Concrete Manufacturing
1. Poured into a wooden or steel mold .
2. It is cured in a controlled environment - usually at a plant.
3. Once finished, the precast concrete is transported to a construction site and put into place.

5. History
● Believed to be first used in Rome
● But first documented use: Walnut Lane Bridge,
USA

6. Precast Elements
● Precast Concrete Slabs
● Precast Concrete Beams
● Precast Concrete Wall
● Precast Concrete Columns
● Precast Concrete Staircase

7. Precast Concrete Slabs
1. SOLID FLAT SLABS:
○ Huge self weight
○ Prone to cracking quicker
○ Spans from 12’-24’
○ Depth: span/40
2. HOLLOW CORE SLABS:
○ Reduced self weight
○ Spans from 12’-24’
○ Depth: span/40

8. 2. Single T Slab
○ Spans from 30’-120’
○ Depth: span/30
○ Used in bridges and flyovers
2. Double T Slab
○ Spans from 30’-100’
○ Clean Solid Appearance
○ Depth: span/28
○ Common Uses:
i. Sewage and Water Treatment Plants
ii. Parking Structures
iii. Food Processing Facilities
iv. High Moisture Structures

9. Precast Concrete Beams
○ Depth: span/15
○ The dimensions vary depending on the manufacturer and availability

10. ● Can be designed according to preferences
● Can be modular with corbel (A and B) or
linear (C)
Precast concrete columns span ratio:
● 10" x10" (255 x 255) column will support
approximately 2000 sf (185 m2).
● 12X12" (305 x 505) column will support
approximately 2750 sf (255 m2).
● 16" x 16" (405 x 405) column will support
approximately 4500 sf (418 m2)).
Precast Concrete Columns
A B C

11. Precast Concrete Walls
Precast walls are of mainly three types:
a. Solid panels
b. Composite / Sandwich panels
c. Ribbed/ Load bearing panels

13. Precast Concrete Stairs

14. Precast Concrete Connections:
BOLTED CONNECTIONS
● The simplest and quickest
● Last-minute alignment and correction can be done
afterward without using valuable crane time.
● Costly and prone to quicker damage
WELDED CONNECTIONS
● The most frequent and usual connection
● These connections adapt readily to changing field
conditions and are architecturally effective.
● A loose plate is often sandwiched between two structural
steel plates immersed in the cast-in-place or precast
concrete panel and then joined by welding.
DOWEL/ANCHOR BOLT CONNECTIONS
● With a dowel connection, the bond formed, embedding
length, and dowel diameter all affect how strong the
dowels are under tension or shear.
● The foundation's exposed threaded anchor bolts and
rebar anchor dowels form the crucial initial connection to
the precast components.

15. Columns To Foundation Joining
Beam Column Joining

16. Precast Slabs Joining:

17. Advantages
● Construction period can be reduced .
● High-level performance in thermal
comfort, durability, acoustic separation,
and resistance to fire and flood .
● Inherent strength and structural capacity
able to meet standards for housing.
● Ability to incorporate service
● Low wastage occurs on site .
● Adding fly ash into the cement increases
the strength and durability of cement.
● Scope of deconstruction, reuse or
recycling of any materials that is being
used.
● Earthquake resilient
● For predesigned outcome from industry,
each panel variation needs specialized
engineering
● It is often more expensive for shorter
spans.
● Building services (power, water and gas
outlets; conduits and pipes) must be
accurately cast in and are difficult to add
or alter later.
● Requires specialised equipment
● Cast-in services are inaccessible and
more difficult to upgrade
● It has high embodied energy.
● Details at the joint become very critical
and needs careful attention.
Disadvantages

18. Sydney Opera House, Australia
Ar. Jørn Utzon
The Sydney Opera House is a modern expressionist
design, with a series of large precast concrete "shells",
each composed of sections of a sphere, forming the
roofs of the structure, set on a monumental podium.
After the 2,194th precast shell segment was installed in
1967 the second stage of the project was finished.
Examples

19. Examples
The Pierre, Washington
Ar. Olson Kundig
As a stunning example of how precast concrete
embraces nature, The Pierre is a private residence that
was built atop a natural stone deposit on the owner’s
property in Washington State.

20. Examples
Jubilee Church, Rome
Richard Meier & Partners
Made to resemble the sails of a ship, the arcs are
made from precast concrete.
Titanium dioxide was added to keep the church white
and designed in such a way to make the building itself
more energy efficient.
It also provides a way to clean the air that comes into
contact with the structure: when ultraviolet rays
interact with the titanium dioxide, a reaction occurs
that breaks down pollution in the air.

21. The Precast and the Cast-in-situ Concrete
Ease on
Casting
Is comparatively easy to manufacturing
by controlling the temperature, mixing
ratio.
Weather condition has no effect on
casting.
Has the difficulty on those aspects-
elements casting in advance, control
over the mixing
Delay on casting due to the weather
condition.
Maintaining of
the quality
Quality can be controlled and maintained
easily.
Not as simple in the maintenance
and quality control.
Precast and cast-in-situ concrete both are the product produced by casting concrete in a mould
or formwork cured to get the strength of RCC elements. But there are some
differences between them-
PRECAST CAST-IN-SITU
Definition
Cast into a specific shape at a location
other than building site like factories.
Casting into forms on the building
site.

22. PRECAST CAST-IN-SITU
Cost
Cheaper if large structures are to be
constructed.
It is cheaper for small structures.
The Precast and the Cast-in-situ Concrete
Requirement
of worker &
machinery
less labours but skilled and technical
contractor is required on the construction
site.
It requires heavy machinery and cranes
for installation.
More labours are required. Local
contractor can also build and no
requirements of such handling
equipment.
Considering
Strength
Becomes quick comparatively to get
installed and there is no waiting to gain
strength on the site.
Also high strength concrete can be
produced in industry.
Here the strength is depended on the
site condition, how much time is
being needed to make the perfect
concrete mixing.

23. Prestressed
Concrete

24. PRESTRESSED CONCRETE
● High tensile stress-induced artificially on the
reinforcement bars of concrete before the
placement is called prestressed concrete.
● After completion of structure work, It helps
the concrete to detain the shrinkage crack
formation.
● A steel reinforcement is given tension upto
70% of its ultimate strength.
PRESTRESSED CONCRETE is of two types
mainly:
1. PRETENSION PRESTRESS
2. POST TENSION PRESTRESS
AFTER LOADING AND DEFLECTION

25. 1. PRETENSIONED PRECAST CONCRETE
● Concretes are casted on a steel strand that is
already applied tension to.
● Is done in factory: precasted hence should be
transported to the site.
● More reliable and durable compared to the cost
because requires no sheathing
● Minimum grade of concrete M30

26. ● Concretes are casted with a duct in between
through which steel strands are passed.
Tensioning is done later on.
● Can be done on site allowing much flexibility in
designing.
● Minimum grade of concrete used M40
2. POST TENSIONED PRECAST
CONCRETE

27. WHY PRESTRESSED CONCRETES ARE USED?
● Prestressing minimises the effect of cracks in
concrete elements by holding the concrete in
compression: if the member is subject to
overload, cracks, which may develop, will close
up on removal of the overload.
● The entire concrete cross-section of prestressed
concrete resists applied load. This is because the
concrete in tension zone does not suffer cracking
and hence it would take part in carrying loads.
● Prestressed concrete allows reduced beam depth
to span ratio
● Reduced self weight to strength ratio.
● Prestressed concrete is more economical when
spans are over 9 m (10 to 18m)
● The use of curved tendons and the pre-
compression of concrete helps to resist shear.
● Sizable liquid-retaining structure

28. DISADVANTAGES:
1. Prestressed concrete requires high-quality
dense concrete of high strength. Perfect quality
concrete in production, placement and
compaction is required.
2. It requires high tensile steel, which is 2.5 to 3.5
times costlier than mild steel.
3. Prestressing process requires complicated
tensioning equipment and anchoring devices.
4. Construction requires perfect supervision at all
stages of construction.
5. Prestressed concrete needs skilled labors.

29. ● First prestressed concrete beam used to built
3 span bridge
● Thirteen 160’ long girder beams of I cross
sections placed side by side
● These girder arrangements allowed for the 44
ft (13.4 m) wide roadway and two 9ft 3 in. (2.8
m) wide sidewalks making the bridge a total
of 63 ft 9.5 in
● These girders were prestressed by post-
tensioning four wire cables embedded in the
concrete (1951)
● Later on in 1990, reconstruction of the bridge
was done with using pretensioned girder
beams in the same alignment.
● Using precast system costed $700,000, 30
percent cheaper than a regular concrete arch
design.
Walnut Lane Memorial Bridge,
Philadelphia, Pennsylvania, USA
F-WalnutLane-Nasser-Oct081.pdf (structuremag.org)

30. ● The girder beams have a
thickness of 30” at the
base but 51” at the slab
end.
● The depth of the beams
are 79” making the ratio of
span to depth almost 1/12

31. PREFABRICATED
BUILDINGS

32. What is Prefabricated Construction?
● Prefabricated buildings, or prefabs, are buildings with components (walls, roof, and floor) that
are manufactured in a factory or manufacturing plant. These components can be fully or partially
assembled in a factory, then transferred to the site.
● Prefabrication is more efficient than conventional on-site
construction since manufacturing through a production line
is more controlled.
● Prefabricated buildings can be classified according to the
degree of construction. The different types of
constructions are component, panel, module, hybrid,
and complete buildings

33. Manufacturing and installation of Prefabricated Buildings
Design and Engineering:
The design of the building is created using Computer-
Aided Design (CAD) software, and then engineered to
ensure that the structure is stable and meets the
required safety standards.
Material Procurement:
Materials such as steel, wood, concrete, and
insulation are purchased and delivered to the factory
where the prefabricated building will be constructed.
Fabrication:
The building components are fabricated in a
controlled factory setting using specialized machinery
and tools. The process involves cutting, shaping, and
assembling the materials to form the various parts of
the building, such as walls, floors, and roofs.

34. Quality Control:
Quality checks are performed throughout the
manufacturing process to ensure that each
component meets the required standards for strength,
durability, and safety.
Transportation:
Once the components are complete, they are
transported to the final site for assembly. This is
typically done using trucks or shipping containers.
Assembly:
The prefabricated building is assembled on-site using
cranes and other heavy equipment. The components
are connected together using bolts and other
fasteners, and the building is then secured to the
foundation.

35. Components of Prefabricated Buildings
The various components of prefabricated buildings are engineered at a factory and delivered
to a location where they are assembled. Prefabricated buildings are a viable and reliable
alternative for creating work space, storage area, and flexible manufacturing facilities. The
components of prefabricated buildings include framing, secondary supports, wall and roof
panels, door and window frames, fasteners, and sheeting and insulation.

36. Prefabricated Panels
Structural Insulated Panels (SIPs):
This type of panel consists of two structural facings with a layer of insulating
material sandwiched in-between.
Insulated Precast Concrete Panels:
The construction of insulated precast concrete panels is similar to SIPs, where
two structural facings bound an insulating material. In this type, the facings are
concrete layers, called wythes,
Insulated Concrete Forms (ICFs):
This type of panel uses rigid insulating materials as permanent formworks for
creating reinforced concrete walls.
Timber Frame Panels:
These types of prefabricated panels are timber stud walls with plywood or
proprietary facings attached to either side of the walls. Insulating materials are
then fitted with insulation.
Lightweight Steel Frame Panels:
The main load-bearing members' studs are made of cold-formed steel, usually
C-sections. They are assembled by welding, bolting, or other fastening
methods. Facings and insulation materials such as gypsum board, stone wool,
oriented strand brands (OSB), and expanded polystyrene foams (EPS) are
added.

37. Four-sided Modules:
This type of module is manufactured with four closed sides creating a
cellular space. The panel frames are load-bearing can transfer both
vertical and lateral loads. The maximum height for this form is typically
6 to 10 stories,
Partially Open-sided Modules:
This module consists of one or more walls made up of an assembly of
panels that do not completely span the entirety of the wall. The
partitions are open, serving as accessways or corridors connecting
adjacent modules.
Open-sided Modules:
This module consists of one or two sides that are designed to be fully
open. The long sides are usually removed so that a larger space can be
created by attaching to other adjacent open-sided modules.
.
Prefabricated Modules
Prefabricated modules are three-dimensional in construction. Several modules are
placed adjacent or on top of each other, forming the whole building.

38. Modules Supported by Primary Structure:
In this type of module, an external steel structural
frame is added to support and transfer loads. The
external structure can provide open spaces at or
below ground levels while the modules are stacked
above
Hybrid Prefab Systems
Hybrid prefab systems utilize both three- and two-
dimensional components from modular and panel
systems to create a whole or a part of a building. This
type can also be referred to as mixed modular and
panel systems
Complete Buildings
These types are stand-alone modules or buildings.
Complete buildings are delivered and installed at the
site with prepared foundations

39. Unique Types of Prefabricated Buildings
Quonset Huts
Quonset huts are made from steel alloys and are known as arch steel
buildings because of their dome shape. Of the many varieties of
prefabricated buildings, Quonset huts are affordable, have low maintenance,
and can withstand all types of weather conditions and earthquakes,
Fiberglass Prefabricated Buildings
Fiberglass is used as a building material for prefabricated buildings due to its
lightweight and durability. It is a mold-free and rust-free material that can
be used for outdoor structures without being damaged by water or the build-
up of moisture due to its tightly sealed structure.
Temporary Prefabricated Buildings
Prefabricated buildings can be used as temporary relocatable buildings that
are used indoors or outdoors. They have a panel-type construction with a
frame made of steel or aluminum with a roof. The walls of shelters can be
made of several types of materials, including fiberglass, glass, and polyvinyl
chloride (PVC).

40. Prefabricated Buildings in Context of Present and Future Architecture
● Prefabs are suited Advanced construction systems
and ROD(Robot Oriented Design) and automated
Construction Factories like kajima(AMURAD),
oBAYASHI all use prefabricated elements
● Economic , Time efficient construction is a vital
side of prefabrication Temporary construction
is economic and profitable due the recycling
factor of prefabs
● Reconstruction of partially or fully damaged
buildings are possible in short period of time

41. WZMH Develops Modular System to Save Partially or Fully
Destroyed Structures
WZMH Architects developed a prefabricated- modular system for
salvaging thousands of structures across Ukraine that have been
partially or fully destroyed during the war. This system aims to
integrate building technology into new buildings to create more
sustainable communities.

42. The ZHA-EAA tents are designed to take advantage of natural daylight and protect
against the weather. The structures are modular, and easy to transport, assemble and
disassemble in various locations. They also contain upcycled and recycled elements.

43. These houses can be purchased in kits of parts at markets in
Bangladesh (Haimchar and Char Bhairabi) are easy to assemble
and disassemble, making them ideal for building on areas that
are likely to be flooded.
In the research, three vernacular houses that we made in Dohar
as flat pack system and shipped to Sharjah. Three architects
from Bangladesh went there with a carpenter and assembled
three houses in 15 days.
https://www.dezeen.com/2019/11/14/marina-tabassum-prefabricated-bangladeshi-home-sharjah-architecture-triennial/

44. Benefits of Using Prefabricated Buildings
● Faster On-site Construction
● Resistance to Uncontrollable Factors
● Higher Quality and Consistency
● Time and Efficiency
● Reusability and Disassembly
● Environmentally Friendly Materials
● Improved Worker Safety
● Performance and Lifespan Inspection