prefabrication used in building construction

1. PREFABRICATION
Open Prefab System, Large Panel Prefab System, Joints, Pre-casting Methods,
Materials, On-site And Off-site Prefabrication, Components.
Presented by : Shubham jain

2. FABRICATION: The action or process of manufacturing or inventing something.
What is PREFABRICATION ?
Prefabrication is the practice of assembling components of a structure or building 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.
PREFABRICATION IN GENERAL PRACTICE
BRICKS
Railings, GrillsUPVC Door, Windows
Door, WindowsBricks Toilet fixture

3. Scale Of Prefabrication:
It is the classification according to the degree or extent of precast elements using in the construction.
1. Small prefabrication
For e.g. brick is a small unit pre-casted and used in buildings. This is called as small prefabrication. That the
degree of precast element is very low.
2. Medium prefabrication
Suppose the roofing systems and horizontal member are provided with precast elements. These constructions
are known as medium prefabricated construction. Here the degree of precast elements are moderate.
3. Large prefabrication
In large prefabrication most of the members like wall panels, roofing/flooring systems, beams and columns are
prefabricated. Here degree of precast elements are high.

4. Prefabrication construction system
1. Open system:
By means of standardization of dimension and details, the components produced by different companies in
construction industry can be used together to design and construct the building. The component can be
selected from the catalogues.
On basis of dimension or size compatibility prefabricated system can be categorized as:
The standard prefabricated concrete components which can be used are,
1. Reinforced concrete channel units
2. Hollow core slabs
3. Hollow blocks and battens
4. Precast plank and battens
5. Precast joists and tiles
6. Cellular concrete slabs
7. Pre-stressed / reinforced concrete slabs
8. Reinforced / pre-stressed concrete slabs
9. Reinforced / pre-stressed concrete columns
10. Precast lintels and sunshades
11. Reinforced concrete waffle slabs / shells
12. Room size reinforced / pre-stressed concrete panels
13. Reinforced / pre-stressed concrete walling elements
14. Reinforced / pre-stressed concrete trusses
The elements may be cast at the site or off the site.

5. 2. Close system:
The components are not interchangeable with the components of another system. The components are
produced as the certain parts of a package and can not be replaced with other companies components.
1. Skeleton systems:
prefabricated systems that comprise structural, load-bearing elements such as columns, beams, and slab
elements.
On basis of structure prefabricated system can be categorized as:
2. Panel system:
Prefabricated systems that comprises structural, load-bearing elements such as walls and slab elements.
Large panel system: panel are greater than 2 m2 . The components used are precast concrete large panels for
walls, floor roofs, balconies, stair cases etc
Small panel system : panel are smaller than 2 m2
Heavy panel system: Lifting equipment are required
Light weight panel system: Panel can be lifted without equipment
3. Cellular systems: prefabricated systems that comprises three-dimensional cellular units.
4. Combined systems: prefabricated systems that use different types of elements stated above together.
On basis of the extent of prefabrication used in the construction
1. Partial prefabrication open system:
The system basically emphasizes the use of precast roofing and flooring components and other minor elements
like lintels, sunshades, kitchen sills in conventional building construction. The structural system could be in the
form of in-situ frame work or load bearing walls.
2. Full prefabrication open system:
In this system, almost all the structural components are prefabricated.

6. The Prefabrication will be done in two stages:
1. Manufacturing at factory condition
2. erection of components at the required location.
This requires certain stages of preparation. They are
1. CASTING.
2. CURING
3. 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.
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 labor force.

7. Pre-casting method:
The various processes involved in the manufacture of precast elements are as follows:
1. Mixing or manufacture of fresh concrete (done in a mixing station or by a mixing plant).
2. Prefabrication of reinforcement cage (done in a steel yard of workshop)
3. Manufacture of inserts and other finishing items (conduits, electrical box etc) to be incorporated in the
main precast products.
4. Providing and assembling the moulds and lubrication of mould.
5. placing reinforcement cage in position for reinforced concrete work.
6. Fixing of inserts and tubes or conduits where necessary.
7. Depositing the concrete in to the moulds.
8. Vibrating the deposited concrete into the moulds to remove honey combing.
9. De-moulding the forms.
10. Curing (steam curing if necessary)
11. Finishing the precast products.
12. Testing the precast products.
13. Stacking the precast products

8. Factory prefabrication (off site prefabrication):
Factory prefabrication is restored in a centrally located plant for manufacture of standardized components on a
long term basis.
It is a capital intensive production where work is done throughout the year preferably under a covered shed to
avoid the effects of seasonal variations. High level of mechanization and quality control can always be
introduced in this system where the work can be organized in a factory like manner with the help of constant
team of workmen.
The basic disadvantage in factory prefabricated, is the extra cost in occurred in transportation of elements from
plant to site of work sometimes the shape and size of prefabricated components are to be limited due to lack
of suitable transportation equipment roads controls etc.
Production:
The location of pre-casting yards consist of storage facilities suitable for transporting and erection equipments
and availability of raw materials are the critical factors which should be carefully planned and provided for
effective and economic use of prefabricated components in construction.
The manufacturing of the components can be done in a centrally located factory or on site where pre-casting
yards set-up at or near the site of construction.
Site prefabrication (on site prefabrication):
In this scheme, the components are manufactured at site or near the site of work as possible. This system is
normally adopted for a specific job order for a short period. The work is normally carried out in open space
with locally a valuable labour force. The equipment machinery and moulds are of mobile nature.
Therefore there is a definite economy with respect to cost of transportation. This system suffers from basic
drawback of its non-suitability to any high degree of mechanization. It has no elaborate arrangements for
quality control.

9. ADVANTAGE OF PREFABRICATION
1. Self supporting readymade components are used so the need for formwork shuttering and scaffolding is
greatly reduced.
2. Construction time is reduced and buildings are completed sooner allowing on earlier return of the capital
invested.
3. On-site construction and congestion is minimized.
4. Quality control can be easier in a factory assembly line setting than a construction site setting.
5. Prefabrication can be located where skilled labour, power materials space and overheads are lower.
6. Time spent in bad weather or hazardous environments at the construction site is minimized
7. Materials for scaffolding is stored partly or in full and used
8. Availability of precise structure and expect workmanship.
9. Work time is reduced.
10. Fewer expansion joints are required.
11. Interruptions in connecting can be omitted.
12. Work is done with a better technology.
13. Less workers are needed.
14. Members can be used again.
The main reasons to choose precast construction method over conventional cast-in-situ method
1. Economy in large scale project with high degree of repetition in work execution.
2. Special architectural requirement in finishing
3. Consistency in structural quality control
4. Fast speed of construction
5. Constraints in availability of site resources (e.g. materials & labour etc.)
6. Other space & environmental constraints
7. Overall assessment of some or all of the above factors which points to the superiority of adopting precast
construction over conventional method.

10. DISADVANTAGES OF PREFABRICATION
1. Careful handling of prefabricated components such as concrete panels or steel and glass panels is required.
2. Attention has to be paid to the strength and corrosion-resistance of the joining of prefabricated sections to
avoid failure of the joint.
3. Similarly leaks can form at joints in prefabricated components.
4. Transportation costs may be higher for voluminous prefabricated sections than for the materials of which
they are made which can often be packed more efficiently.
5. Large prefabricated structures require heavy-duty cranes & precision measurement and handling to place
in position.
6. Large groups of buildings from the same type of prefabricated elements tend to look drab and
monotonous.
7. Local Jobs are lost.
MATERIALS USED FOR PREFABRICATION AND THEIR PROPERTY:
There are many materials used in the prefabricated components. The modern trend is to use concrete steel,
treated wood, aluminium cellular concrete, light weight concrete, ceramic products etc. While choosing the
materials for prefabrication the following special properties are to be considered.
1. Light weight for easy handling and transport and to economic an sections and sizes of foundations.
2. Thermal insulation property .
3. Easy workability.
4. durability in all weather conditions.
5. Non combustibility.
6. Economy in cost.
7. Sound insulation

11. PREFAB BUILDING COMPONENTS AND CONNECTION: FOUNDATION TO COLUMN JOINT
CAST-IN-SITU CONCRETE FOUNDATION

12. PREFAB BUILDING COMPONENTS AND CONNECTION: FOUNDATION TO COLUMN JOINT

13. PREFAB BUILDING COMPONENTS AND CONNECTION: COLUMN TO COLUMN JOINT
Exposed reinforcement connection

14. PREFAB BUILDING COMPONENTS AND CONNECTION: COLUMN TO COLUMN JOINT
Plate and stud connection

15. PREFAB BUILDING COMPONENTS AND CONNECTION: COLUMN TO BEAM JOINT

16. PREFAB BUILDING COMPONENTS AND CONNECTION: BEAM TO SLAB JOINT