Prefabrication involves assembling components of a structure in a factory and transporting them to the construction site. It has advantages like reduced cost, material, and time compared to traditional construction. Precast concrete components like walls, beams, slabs are produced in a controlled factory environment and assembled on-site. Prefabrication requires planning for transportation, lifting equipment, installation, and connections between components. While it offers benefits, it also has challenges like handling of large precast units and achieving monolithic joint connections.

2. WHAT IS PREFABRICATION?
 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.
 It is combination of good design with modern high performance components and quality controlled
manufacturing procedures
 This work is carried out in two stages, manufacturing of components in a place other than final location
and their erection in position.
PREFAB CONCEPT
 Prefabricated sections are produced in large quantities in a factory and then shipped to various
construction sites.
 This procedure may allow work to continue despite poor weather conditions and should reduce any
waste in time and material at the site.
 Precast concrete units are cast and hardened before being used for construction
 Sometimes builders cast components at the building site and hoist them into place after they harden.
 This technique permits the speedy erection of structures.

3. DESIGN CONCEPT FOR PRECAST
CONCRETE BUILDINGS
The design concept of the precast
buildings is based on
1.build ability.
2.economy
3.standardization of precast components.

5. PREFAB BUILDING COMPONENTS
 Beams can vary in their complexity of design and
reinforcement from the very simple beam formed
over an isolated opening to the more common
encountered in frames where the beams transfer
their loadings to the column.
Precast Walls
Precast SLABS
Precast BEAM & GIRDERS
A hollow core slab, also known as
a voided slab or hollow core plank, is
a precast slab of prestressed
concrete typically used in the
construction of floors in multi-
story apartment buildings. The slab has
been especially popular in countries
where the emphasis of home
construction has been on precast
concrete, including Northern Europe.
Precast concrete popularity is linked
with economical constructions because
of fast building assembly, lower self
weight (less material), etc.

6. PREFAB BUILDING COMPONENTS
 A column is a vertical member carrying
the beam and floor loadings to the
foundation.
 It is a compression member and therefore
the column connection is required to be
proper.
 The main principle involved in making
column connections is to ensure continuity
and this can be achieved by a variety of
methods.
Column to Column Connection Precast Columns
Precast columns
Precast concrete Stairs Steel plates supported
on 2 steel beams
Precast stairs

7. PREFAB BUILDING COMPONENTS
METHODS OF CONNECTING BEAMS AND COLUMNS ARE
 A pre-casting concrete haunch is cast on to the column with a
locating dowel or stud bolt to fix the beam.
 A projecting metal corbel is fixed to the column and the beam is
bolted to the corbel.
 Column and beam reinforcement, generally in the form of hooks,
are left exposed. The two members are hooked together and
covered with concrete to complete the joint.
 This is as shown in the figure.

8. PREFAB BUILDING COMPONENTS
WAFFLE UNIT FOR FLOORING /
ROOFING:
 These are suitable for roofs / floors
spanning in two directions.
 They are laid in a grid pattern.
 These units are cast in moulds.
 The saving achieved is not much. Also
Shuttering are complicated and costly.
 Time consumption for construction is less
SLAB TO BEAM CONNECTION
 Precast concrete
structure consisting of
solid wall panels and
hollow core slabs.
WALL TO SLAB CONNECTION

9. DESIGN CONSIDERATIONS
 final position and loads
 transportation requirements – self load and position during transportation
 storing requirements – self load and position during storing – (avoid or store in the same
position as it transported / built in)
 lifting loads – distribution of lifting points – optimal way of lifting (selection of lifting and
rigging tools)
 vulnerable points (e.g. edges) – reduction of risk (e.g. rounded edges)
TYPES OF PRE CAST SYSTEM
1. Large-panel systems
2. Frame systems
3. Slab-column systems with walls
4. Mixed systems

10. TYPES
 Box-like structure.
 Both vertical and horizontal
elements are load-bearing.
 One-story high wall panels
(cross-wall system /
longitudinal wall system /
two way system).
 One-way or two way slabs.
 Components are usually
linear elements.
 The beams are seated on
corbels of the pillars usually
with hinged-joints (rigid
connection is also an option).
 Joints are filled with
concrete at the site.
2. FRAME SYSTEMS1.LARGE-PANEL SYSTEMS

11. 3.Lift-slab systems
 partially
precast in
plant (pillars)
/ partially
precast on-
site (slabs).
 one or more storey high pillars (max 5).
 up to 30 storey high constructions.
 special designed joints and temporary
joints.
 slabs are casted on the ground (one on
top of the other) – then lifted with crane
or special elevators.

12. PLANNING TRAFFIC ROUTE
 How long transporter vehicle is required?
 What is the required load capacity of the
transporter vehicle?
 What is the maximum vertical extension
of the shipment
 Routs on the site
 Is route permission required?
EQUIPMENTS
cranes:
mobile crane
tower crane (above 3stories)
lifting tools:
spreader beams
wire rope slings
rigging tools:
eye bolt
shakles
hooks

13. PRE FABRICATION
 The Prefabrication as defined will be done in two stages Manufacturing at factory condition and
erection of components at the required location.
 This requires certain stages of preparation. They are
Casting
Curing
Transportation and erection
 CASTING: Precast components are casted
with controlled cement concrete in moulds of
required shape and sizes. The vibrator is
used to vibrate concrete and this removes
any honeycombing inside the components.

14. PRE FABRICATION
 CURING: After 24 hours of casting, the casted
components are released from the mould and
transported to curing tanks. Certain special
components like railway sleepers where high
strength is required are steam cured.
 TRANSPORTATION AND ERECTION: After
complete curing is done the components are
transported to the site with heavy trucks and
erection will be done using cranes with skilled
labour force.

16. EXAMPLES….
The hospital will
feature multi-trade
prefabricated racks in
the corridors, an
approach that is still
new in the U.S.

17. ADVANTAGES AND DISADVANTAGES
Advantages:
 Saving in cost, material, time & manpower.
 Shuttering and scaffolding is not necessary.
 Installation of building services and finishes can be done immediately.
 Independent of weather condition.
 Components produced at close supervision .so quality is good.
 Clean and dry work at site.
 Possibility of alterations and reuse
 Correct shape and dimensions and sharp edges are maintained.
 Very thin sections can be entirely precast with precision.

18. LIMITATIONS
 size of the units.
 location of window openings has a limited variety.
 joint details are predefined.
 site access and storage capacity.
 require high quality control.
 enable interaction between design phase and
production planning.
 difficult to handling & transporting.
 SCHEDULING
some approximate data for installation
 emplacement of hollow core floor slabs - 300 m2/day
 erection of pillars/columns - 8 pieces/day
 emplacement of beams - 15 pieces/day
 emplacement of double tee slabs - 25 pieces/day
 emplacement of walls - 15 pieces/day
 construction of stair and elevator shafts - 2
floors/day

19. Miami Valley Hospital
Dayton,OH
EXAMPLES….

20. ADVANTAGES AND DISADVANTAGES
Disadvantages:
 Handling and transportation may cause breakages of members during the
transit and extra provision is to be made.
 Difficulty in connecting precast units so as to produce same effect as
monolithic. This leads to non-monolithic construction.
 They are to be exactly placed in position, otherwise the loads coming on
them are likely to get changed and the member may be affected.
 High transport cost.
 Need of erection equipment.

 Skilled labour and supervision is required.

21. CONCLUSION
 The prefab components and prefab structures eliminate space and time over conventional
constructions.
 Although prefabrication is employed to a large extent in a wide variety of countries, in
India, construction industry, in spite of its expansion continues to adopt same conventional
methods.
 The root of the economic problem is the fact that the majority of the households do not
have the confidence needed to construct prefab houses.
 These structures are easy to erect as it is light material. This type of prefab buildings were
constructed in earthquake prone areas of Lature and Gujarat.