In these slides detail procedure of precast and prefab construction have been discussed in a student friendly way.

1. PREFABRICATED ONSTRUCTION
Prepared By
Gourhari Biswas

2. PREFABRICATED CONSTRUCTION
• Prefabrication is the practice of assembling components of
a structure in a factory or other manufacturing site,
and transporting complete assemblies or sub-assemblies to
the construction site where the structure is to be located.
• Prefabricated structures are structures that are built-in
pieces at the factory and assembled on the construction
site, prefabricated structures can be portable or non-
portable (permanently fixed to the foundation).

3. PREFAB INTRODUCTION
• Prefabricated units may
include doors, wall panels,
floor panels, stairs, window,
walls, roof trusses, room-
sized components, and
sometimes even entire
buildings.
• This technique controls
construction costs by
economizing time, wages,
and materials.
• This building method has been
gaining a lot of popularity and
builders across the world are
using factory precision and
efficiencies to construct quality
structures.

4. Advantages of Prefabrication :
• Self supporting readymade components are used. So.
The need for work shuttering and scaffolding is greatly
reduced.
• Construction time is reduced and buildings are
completed sooner allowing an earlier return of the capital
invested.
• On site construction and congestion is mini mixed.
• Quality control can be easier in a factory assembly line
setting than a construction site setting.
• Prefabrication can be located where skilled labour is
more readily available and costs of labour, power,
materials, space and overheads are lower.
• Time spend in bad weather or hazardous environments
at the construction site is minimized.

5. Disadvantages of Prefabrication :
• Careful handling of Prefabricated components such as
concrete panels or steel and glass panels is required.
• Attention has to be paid to the strength and corrosion-
resistance of the joining of prefabricated sections to avoid
failure of the joint.
• Similarly, leaks can form at joints in prefabricated
components.
• Transportation costs may be higher for Voluminow.
Prefabricated sections than for the materials of which they
are made, which can often be packed more efficiently.
• Large Prefabricated Structures require heavy-duty cranes
& Precision measurement and handling to place in
position.
• Large group of buildings from the same type of
Prefabricated elements tend to look drab and monotonous.
• Local jobs are lost.

6. METHODS OF PREFABRICATION
• Plant/Factory prefabrication- large
scale production
• Site prefabrication- for large
prefabricates

7. FACTORY PREFABRICATION
• The prefabrication of the factory is restored in a central plant
for the manufacture of standardized products.
• Plant prefabrication is done under permanent plant or
factories. It is done under the covered roof so the effect of
weather does not affect the work. So the quality and
strength of the members can be improved considerably.
Plant prefabrication reduces the cost of prefabrication if the
number of prefabricate needed is more.
• Further, there should be some room for the possibility of
introducing enhanced technology. To ensure continuous
production, work has to be organized in a factory-like
manner with support from a team of workmen.

8. Disadvantages of Plant Prefabrication :
• It is a capital intensive production where the work is
carried out throughout the year, preferably under a
covered shed to avoid the effects of seasonal variations,
the high level of mechanization can it will always be
introduced in this system where work can be organized
similarly to a factory with help from the constant team of
workers.
• The basic disadvantage in the prefabricated factory is
the additional cost in the transportation of elements from
the plant to the workplace, sometimes the shape and
size of the prefabricated must be limited due to lack of
adequate transport equipment road controls, etc. The
members produced are to be transported t the place of
construction this accounts for about 10-15% of the cost
of production and assembling.

9. contd...
• Prefabrication is appropriate for mass
production for manufacture of
standardized members.
• Needs costly materials for batching and
production.
• This method is most suited in the case of
small prefabricates which are to be
prefabricated in very large number.
• Employment of organized labor and their
service benefits cause a huge
establishment.

10. Site Prefabrication:
• In this scheme, the components are manufactured at the
site near the worksite as possible. It is usually adopted
for a specific work order for a short period. The work is
usually done in open space with a valuable local
workforce.
• The locally available labor force is, as for as possible,
used, and the equipment and molds are rented.
Generally, the work is carried out in open space.
• There is a defined economy with respect to the cost of
transportation. This system suffers from the basic
inconvenience of its failure to adapt to any high degree
of mechanization. It has no elaborate Quality control
arrangements.

11. Although this has some economic benefits,
there are a few disadvantages:
• The RC members are produced at the site in the open air or in the
temporary she
• The difficulties in construction in general are felt in this mechanization
can case.
• Mechanization can not be of such high degree as site PF is done for
smaller duration of time.
• When the prefabricates are of large size it is difficult to transport the pre
fabricates to the site.
• In comparison with plant prefabrication transportation of the members
are not needed. As large members are not transported the design and
weight of the prefabricates are not limited.
• There are no elaborate arrangements for quality control.
• Work may be disrupted due to weather conditions.
• A high degree of mechanization can not be adopted.

12. Elements in Precast Concrete Building Systems
Structural elements
used in the
construction of precast
concrete buildings
include:
1.Precast concrete wall
(Panels)
2.Precast Slabs
3.Precast Beam and
Girders
4.Precast Columns
5.Precast Stairs
6. Precast Lintel &
Sunshade

14. • Precast concrete wall panels can be used for
both exterior and interior surfaces.
• They provide strength and lateral stability and
when assembled can form a shear wall
• They have been used in building projects as
high as 30 stories but are more commonly seen
in lower level constructions.
• Precast concrete walls serve two functions:
1. Stability
2. As walls or boxes surrounding staircases and
lift shafts.

15. Walls may be classified as
• Infill walls rely on
contiguous
composite action
with the beam
and column
frame.
• Cantilever walls
or boxes act as
deep beams to
which the frame
is attached.

16. PRECAST WALL PANELS

17. The precast walls can be load bearing or only partition
walls. The surface of the elements is smooth on both sides
& ready for painting or wallpapering.
Precast walls offer the advantage of speed of construction,
smooth surface finishing, acoustic insulation & fire
resistance.

18. Partition Walls
Partition walls made from
precast concrete can be lifted
into position or the panels
cemented together on site to
provide a wall to ceiling
partition wall solution. This
type of assembly can be as
much as six times quicker
than alternative brick work.
Panels are particularly suited
to sound insulation, so are
suitable for use in hotels,
kitchens, hospitals, schools
and apartments.

19. Precast floor slabs:
The main types of
slabs are used in the
precast frames are:
Hollow core floors
Ribbed floors
Concrete roof
elements
Massive slab floors

20. Precast floor slabs:

21. Hollow Precast Concrete Floor

22. Advantages of Precast Floors
The principle
advantages of
precast floors are
speed of
construction,
absence of
scaffolding, large
variety of types,
large span
capacity, &
economy.

23. PRECAST BEAMS
• A precast beam is a type of construction element
that is made by casting concrete into a mold and
then curing it in a controlled environment. These
beams are then transported to the construction
site and installed in place as part of a building
structure. They can be used for both load-bearing
and non-load bearing applications, and can be
made in a variety of shapes and sizes.
• The cross-sections of a precast concrete beam
will depend on its location within a structure, its
purpose and how it is connected to other
members. The simplest will be rectangular,
probably with reinforcement links projecting out of
the top around which in situ concrete can be cast.

24. Precast Beams:
There are two main categories of beams:
1.Internal beams – where floor loading is approximately
symmetrical
2.External beams – where floor loading is
predominantly non-symmetrical.
Precast concrete beams are an integral feature of many
buildings today. They are particularly suited to floor
construction in houses, flats and commercial buildings and
provide a low-cost flooring solution. Edge and spandrel
beams which have a sill, go around the edge of the
construction adding strength and with the sill providing the
base from which floor slating can start. Spine beams are
like spandrel beams but have two sills. Suspended beam
and block floor systems utilising precast concrete minimise
excavation requirements.

25. Beams
Fig: Internal beams Fig: External beams

26. PRECAST BEAMS

27. Precast Columns:
• With both strength and flexibility, precast
concrete columns add strength and flexibility
and increase the life of any building.
• Columns can be made to the architect’s design
and incorporate any special features or fittings.
• These columns can be erected as much as five
times faster than in-situ methods of concrete
production, so are labour saving.
• For structures of five storeys or less, each
column will normally be continuous to the full
height of the building. For structures greater
than five storeys two or more columns are
spliced together.

28. The main types of precast columns
are:
1.Edge columns –
symmetrical in one
direction.
2.Internal columns –
symmetrical in all
directions.
3.Corner columns –
not symmetrical at all.

29. PRECAST COLUMNS
• Precast columns are vertical load-bearing components
with hauches or corbels used to transfer horizontal loads
to the foundations. Columns can be fabricated in various
shapes, sizes and colors. Various architectural finishes
can be applied to the surface as well as brick or stone
veneer products, to enhance a building’s design. Precast
columns can be designed to transfer even the heaviest
of building loads.
• Combined with precast beams, they can be used to
create the entire framing system for the shell of a
building. A precast concrete structural system can
provide a number of benefits, including speed of erection,
single-source provider for all framing needs, consistent
high quality, durable structural support, fire resistance
and others.

30. PRECAST COLUMNS

31. Precast staircases:

32. PRECAST STAIRCASES
Precast concrete stairs are
cost-efficient and quality
products that are easy and
quick to install on the
construction site. The precast
staircase removes the need
for any temporary metal or
wooden stair solution and
eliminates the need for
complicated formwork and
propping of the casted
structure if made cast-in-situ.

33. A precast staircase is a cost-efficient and safe
• It is a safe and fire-
resistant solution.
• Precast stairs range from
individual steps to straight
monobloc units with
landings. Flights and
landings of the straight
stair can be cast as
separate elements or
combined in one piece.
There may be differential
levels at floors and half-
landings in the latter
solution, requiring a
finishing screed or other
solution.

34. Precast Staircase Application & Advantages
 Application
The precast stair is an
excellent choice for any multi-
storey buildings.
 Advantages of precast
stairs

35. Precast Footings
Precast footings are
foundations that are
easy to install and
used as soon as they
arrive on site. They
are extremely strong
and provide a stable
and level base from
which to build.
Footings

36. Precast Lintel & Sunshade Unit:
Lintels function as beams to support the wall
weight and other loads over an opening, and
to transfer these loads to the adjacent
masonry. Because of their rigidity, strength,
durability, fire resistance and aesthetics, the
most common types of lintels for concrete
masonry construction are those
manufactured of precast reinforced concrete
or reinforced concrete masonry units (ref. 3).
The color and surface texture of these lintels
can be used as an accent or to duplicate the
surrounding masonry.

37. Precast Lintel & Sunshade Unit:

38. PRESTRESSED CONCRETE LINTELS
• Prestressed concrete lintels play a pivotal role in
any building’s structural integrity typically used
for window and door openings. They can accept
a wide range of surface finishes without special
preparation and come in a variety sizes and
loadings.
• Prestressed concrete is one of the most reliable,
durable and widely used in the construction
industry, it boasts a number of benefits including
lower construction cost, fewer joints and a high
strength to section ratio.

39. Components of Pre-cast Door and Window frames
 Pre-cast concrete Door & Window frames (IS code 6523-
1983) are available in a knock-down state with three and
four pieces respectively. For Doors, two vertical Posts,
one lintel member are fixed in a proper position through
interlocking grooves.
 For the window frame, an additional horizontal element is
provided at its base. With a cross-section of 4 x 2.5 inch;
varied length between 5 – 7.5 feet can be manufactured.
The frame uses nominal MS reinforcement, typically 4 mm
bar and concrete of grade M- 15 and provided with locking
holes and hinge screw area casted within the frames. The
Technology provides uniform shape and size, which is at
par with the wooden alternative.

40. Applicability of Door & Window Frames
Precast reinforced concrete door
window frames are feasible in any
weather conditions and any building
typology. This easy to install technology
is even applicable for multi storey
buildings. However, the technology is
best suited to attain for longevity and
high durability of door window frames.
RCC frames are best suited in regions
with high rainfall – they doesn’t
require anti termite treatment as
required in wood or corrode as in case
of metal frames. Since frames are made
of RCC, they also provide structural
support to the building

41. PRE FABRICATION PROCESS
The various processes involved in the
manufacture of prefabricated elements are
classified as follows:
• Main process
• Secondary process
• Subsidiary process

42. MAIN PROCESS:
• It involves the following steps,
• Provide and assemble the molds, placing the
reinforcement cage in position for reinforced
concrete works
• Fixation of inserts and tubes when necessary.
• Deposit the concrete in the molds.
• Vibrate the concrete deposited in the molds.
• Moldings of the forms.
• Healing
• Stacking of prefabricated products.

43. SECONDARY PROCESS:
• This process is necessary to successfully
complete the process covered by the main
process.
• Mixing or manufacturing fresh concrete.
• Prefabrication of reinforcement cage
• Manufacture of inserts and other finishing
elements to incorporate in the main
prefabricated products.
• Finishing of prefabricated products.
• Test prefabricated products.

44. TRANSPORT
• The transport of the prefabrication elements must be
carried out and with extreme care to avoid any flock and
anguish in the elements and handled as much as
possible to place it in the final portion.
• The transport of prefabricated elements within the
factory depends on the production method selected for
manufacturing.
• The transport of prefabricated elements from the factory
to the place of action must be planned in accordance
with the traffic rules and regulations stipulated by the
authority, the size of the elements is often restricted by
the availability of appropriate transport equipment, such
as the tractor -am- tailored, to adapt to the load and
dimension of the member, in addition

45. Transportation and Hosting of
Prefabricates:
For Transporting Prefabricate elements
following Cranes are used :
• Truck cranes
• Gantry cranes
• Mast cranes
• Derrick cranes
• Twinned mast cranes

46. Prefabrication Elements Installation
Installation of vertical components
• Verification of delivered panels Verifies that the delivered panels have the
correct lifting hook and position, etc.
• Surface finish condition, Prefabricated Dimension Compliance, Reinforcement
position compliance with architectural details, Setting Check, the panels
delivered by markings, lifting hook and condition.
• Set the reference lines and the grid check the starter bars for vertical
components before lifting for installation Establishment of the quality control
point secure the correct scroll line Verify plate level and sign rubber gasket
property secured external wall and backrest column Lifting and rigging and
installation while leaning, provide a rubber pad to avoid splinters.
• Lift and place the panel in the designated location . Adjust the panel in position
and secure elevation of space by adding elements with a balanced center of
gravity.
• Ensure correct horizontal alignment Secure
• The panels vertically to correct the plumb line to check the consistency of the
space between panels checks the stability of the strut before releasing the lifting
cable.

47. IMAGES OF PRECAST CONSTRUCTION

48. Prefabrication Elements Installation contd..
• Groundwork
• Apply mortars without shrinkage to seal Patented grouts in pipe
slabs. Keep the panels installed without discomfort for 24 hours.
• Verify that joint widths are consistent before grouting grout used
must be of the same degree of components and self-compacting to
avoid cracksCollect a sample of test cube to test critical elements or
load-bearing elements that join joints on-site cast joints install
reinforcing bars as necessary configure shapes to melt together
make concrete remove shapes after sufficient resistance external
connections sealant will be user panel with welded connections
welding as the required installation process.
• Installation of horizontal elements.settings the reference
line/compensation line at the required alignment and slab/beam
level during installation put temporary support to support the precast
slab/beam elements before lifting quim.
• Dimensions Check the level and stability of the wedgeVerify that the
protruding/initial bars are within the specified tolerance to avoid any
observation during the assembly process

49. Lifting and installation
• Temporary accessories to support the
slab/beamLift and mount the items at the
designated location align and verify the
level before placement teams must prop
up at least two locations.
• Balcony planter and more than two
locations will be supported based on
design considerations. Check the level of
prefabricated elements

50. Joining Elements
• Prefabricated with cast iron joints in situ position
reinforcement bars as necessary establish a way
of working to melt together remove formwork
after achieving concrete strength.
• The support beams will be designed to be part
of the work joints.
• The connection/lapping bars tied and secured
the same grade of concrete 10 that will be used
as the panel.
• Installation using a Big canopyHigh-rise
prefabricated concrete construction system with
large canopy is used for a faster and more
efficient process.

51. Precast Prefabricated Concrete
Construction Procedure
1. After the completion
of construction
preparations, the layout
of the structure is set.
2. Then, the foundation
of the columns are
constructed
Foundation for Precast
Concrete Columns

52. contd...
After that, the columns
are placed using suitable
machines (Fig. 11), and
continuously checked by
surveyor for alignment
(Fig. 12). In the case of
Frame system and slab-
column system with
shear wall. Alternatively,
precast panels are
installed inthe case of
large panel system(Fig.
13).
Fig. 11: Final Adjustment and Installation
of Columns

53. IMAGES OF PRECAST CONSTRUCTIONS
Fig. 12: Install Precast
Concrete Columns
Fig. 13: Large Panel Precast Concrete
System Construction

54. Precast Beam Erection
4. Beams for precast
frames (Fig. 14), and
precast floors in the
case of large panel
systems (Fig. 15)
and column-slab
systems are placed.
Fig. 14: Precast Beam Erection

55. IMAGES OF PRECAST CONSTRUCTIONS
Fig. 15: Placement of Hollow Core Precast
Concrete Slab on Walls

56. Precast Concrete Slab Placement
5.For precast
frames, after the
installation of
precast concrete
beams, precast
concrete floors are
erected.
Fig. 16: Precast Concrete Slab Placement

57. PRECAST CONSTRUCTION

58. Joints of different structural connections:-

59. Cleated Connector
Fig. 17: Expensive but Safe Cleated
Connector

60. CONNECTIONS
Fig. 18: Sliding Plate Connections

61. BEAM TO COLUMN CONNECTION
Fig. 19: Beam to Column Seated
Connection

62. Seated Connection
Fig. 20: Seated Connection

63. WALL CONNECTIONS
Fig. 21: Deep Nib Connection Between Walls
Provide Large Complimentary Shear Stiffness
and Strength

64. VERTICAL JOINT
Fig. 22: Vertical Joint Using Deep
Nib

65. Structural Stability
The stability of
precast concrete
structural systems
are provided through
bracing. There are
number of
techniques through
which structures are
braced, as illustrated
in the following figure.

66. Erection of Prefabrication in Prefabricated
Building
What is the erection and prefabrication item
of works?
It is the process of assembling the
prefabrication element according to the
drawing. The following tasks must be carried
out in the construction of prefabricated
elements.

67. Equipment required for erection
• The equipment required for prefabrication elements in the industry can
be classified as,
• Machinery necessary for extraction, of course, and fine aggregates.
• Transport equipment, such as conveyors, chain conveyors, etc.
• Concrete mixers
• Vibrators
• Assembly equipment such as cranes, cranes, pulleys, etc.
• Transport machines
• Workshop of machinery for the manufacture and repair of steel.
• Machines for stretching, bending and welding bars
• Tools and smaller sockets, such as wheel bars, concrete hubs, etc.
• Steam Generation a plant for accelerated curing
• Planning Coordination
• It is important that the installer/installer and the precaster builder work
together to achieve the best performance.

68. Site access and storage

69. CONTD...
• Plan another team
• Boom lift and scissor lift to unhook installed panels.
• Lifting gears
• Qualified staff
• Competent crane operators
• Rigging equipment
• Signal equipment
• General considerations for crane selection
• Total lifting weight
• Crane model
• The safe work load for crane
• Lifting capacity must be 1.5 times the total weight
• Lifting and balancing radius
• Crane counterweight
• The length of the crane boom is related to the vertical and horizontal
separation of the building.