Definition :Definition :
Prefabrication is the practice of assembling components of a structurep g p
in a factory or other manufacturing site, and transporting complete
assemblies or sub-assemblies to the construction site where the
structure is to be locatedstructure is to be located.
Meaning :Meaning :
The assembly of buildings or their components at a location otherThe assembly of buildings or their components at a location other
than the building site.
The method controls construction costs by economizing on time,
d i lwages, and materials.
Prefabricated units may include doors, stairs, window, walls, wall
panels, floor panels, roof trusses, room-sized components, andpanels, floor panels, roof trusses, room sized components, and
even entire buildings.
The term is used to distinguish this process from the more
l f h bconventional construction practice of transporting the basic
material to the construction site where all assembly is carried out.
Prefabricated building is the completely assembled and
erected building of which is the structural parts consist oferected building, of which is the structural parts consist of
prefabricated individual units or assemblies using ordinary
or controlled materials.
Prefabricated construction is a new technique and is desirable for
large scale housing programmes, yet this has to take a firm hold in
the countrythe country.
AIMS OF PREFABRICATION
Prefabrication is used to effect economy in
Components manufactured under controlled
The speed of construction is increased since
no curing period is necessary.
Prefabrication helps in the use of locally
available materials with required
h i i lik li h i hcharacteristics like light-weight; easy
workability, thermal insulation, non-
combustibility etccombustibility, etc.
ADVANTAGES OF PREFABRICATIONADVANTAGES OF PREFABRICATION
• High quality product
L b l t d i• Labor related savings
• Savings in time
• Overall efficiency is greatly increased• Overall efficiency is greatly increased
• Mass production is easier and quick
• Protected and controlled production environmentProtected and controlled production environment
• Potential for lower production costs and other cost
• Independence of climatic conditions
• The disruption of traffic is avoided
E hi h d f S f• Ensures high degree of Safety
CHARACTERISTICS ARETO BECHARACTERISTICS ARETO BE
Li h i h f h dli dLight weight for easy handling and transport,
and to economies on sections and sizes of
Thermal insulation property;
E k bilitEasy workability;
Durability in all weather conditions;
N b ibiliNon-combustibility;
Economy in cost, and
Disadvantages :Disadvantages :
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 theAttention 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 voluminous prefabricated
sections than for the materials of which they are made, which can often
be packed more compactlybe packed more compactly.
Large prefabricated sections require heavy-duty cranes and precision
measurement and handling to place in position.g p p
MATERIALSTO BE USED INMATERIALSTO BE USED IN
PREFABRICATION SYSTEMPREFABRICATION SYSTEMPREFABRICATION SYSTEMPREFABRICATION SYSTEM
Light weight concrete elements,
Ceramic products, etcp
COMPONENTS OF PREFABCOMPONENTS OF PREFAB
Flooring and Roofing Scheme
Sunshade/Chajja Projectionsjj j
PREFABRICATION SYSTEMSPREFABRICATION SYSTEMS
The system of prefabricated construction depends on the extent of the
use of prefab components, their materials sizes and the technique adopted
f h i f d i b ildifor their manufacture and use in building.
VARIOUS PREFABRICATION SYSTEMSVARIOUS PREFABRICATION SYSTEMS
OPEN PREFAB SYSTEM
This system is based on the use of the basic structural elements to formy
whole or part of a building.The standard prefab concrete components
which can be used are:-
Reinforced concrete channel units,
Hollow core slabs,
Hollow blocks and battens,
Precast planks and battens,
Precast joists and tilesPrecast joists and tiles,
Cellular concrete slabs,
Prestressed/reinforced concrete slabs,
Reinforced/prestressed concrete beams,
Reinforced/prestressed concrete columns,
Precast lintels and chajjas,
Reinforced concrete waffle slabs/shells,
Room size reinforced/prestressed concrete panels,Room size reinforced/prestressed concrete panels,
Reinforced/prestressed concrete walling elements, and
Reinforced/prestressed concrete trusses
CATEGORIES OF OPEN PREFABCATEGORIES OF OPEN PREFAB
There are two categories of open prefab systems
d di h f f b i i d i hdepending on the extent of prefabrication used in the
construction as given below:
Partial prefab open systemPartial prefab open system
Full prefab open system
PARTIAL PREFAB OPENPARTIAL PREFAB OPEN
This system basically emphasizes the use of precast roofing
and flooring components and other minor elements likeand flooring components and other minor elements like
lintels, chajjas, kitchen sills in conventional building
construction.The structural system could be in the form of
f k l d b llin-situ framework or load bearing walls.
FULL PREFAB OPEN SYSTEMFULL PREFAB OPEN SYSTEMFULL PREFAB OPEN SYSTEMFULL PREFAB OPEN SYSTEM
In this system almost all the structural components are
P f b i d Th fill ll b f b i k hPrefabricated.The filler walls may be of bricks or any other
LARGE PANEL PREFAB SYSTEM
This system is based on the use of large prefab components.
The components such as Precast concrete large panels for wallsThe components such as Precast concrete large panels for walls,
floors, roofs, balconies, staircase, etc. The casting of the
components could be at the site or off the site.
CLASSIFICATION OF STRUCTURALCLASSIFICATION OF STRUCTURAL
SCHEMEWITH PRECAST LARGE PANELSCHEMEWITH PRECAST LARGE PANELSCHEMEWITH PRECAST LARGE PANELSCHEMEWITH PRECAST LARGE PANEL
CrossWall System - In this scheme, the cross wall
are load bearing walls whereas the facadeWalls are
non load bearing this system is suitable for high risenon-load bearing this system is suitable for high rise
Longitudinal Wall System - In this scheme the cross
walls are non-load bearing whereas Longitudinal walls
are load bearing walls.This system is suitable for low
rise buildings.rise buildings.
A combination of the above system with all load bearing
walls can also be adopted.
precast flooring units could be homogeneous or non
Homogeneous floors :- could be solid slabs, cored slabs, ribbed
or waffle slabs.
N h fl ld b l l d hNon-homogeneous floors :- could be multi-layered ones with
combinations of light weight Concrete or reinforced/prestressed
concrete, with filler blocks
Staircase system could consist of single flights with in-built
risers and treads in the element only.The flights are normally
unidirectional transferring the loads to supporting landingg pp g g
slabs or load bearing walls.
In this system, room size units are prefabricated and erected
at site Toilets and kitchen blocks also be similarlyat site.Toilets and kitchen blocks also be similarly
prefabricated and erected at site.
This system derives its stability and stiffness from the box unit
which are formed by the four adjacent walls.Walls are jointed
to make rigid connections among themselves.The box unit
rests on the plinth foundation which may be of conventionalrests on the plinth foundation which may be of conventional
type or precast type.
The joints should be provided in the light of their assessment with respect
to the following considerations:
Feasibility -The feasibility of joint shall be determined by its loads-
carrying capacity in the particular situation in which the joints is to
Practicability -Practicability of joint shall be determined by the
amount and type of Material, fabrication and erection and the time for
fabrication and erectionfabrication and erection.
Serviceability - Serviceability shall be determined by the
joints/expected behavior to Repeated or possible overloading and
li i h i l di iexposure to climatic or chemical conditions.
JOINTTECHNIQUES/MATERIALS NORMALLYJOINTTECHNIQUES/MATERIALS NORMALLY
EMPLOYED ARE:EMPLOYED ARE:
Welding if cleats or projecting steel.
Overlapping reinforcement loops and linking steelOverlapping reinforcement, loops and linking steel
grouted by concrete.
Reinforced concrete ties all round a slabReinforced concrete ties all round a slab.
Epoxy groutingEpoxy grouting.
Bolts and nuts connection, and
A combination of the aboveA combination of the above.
Components Fixing and Jointing :Components Fixing and Jointing :
A h b i b ilt ithA house being built with
prefabricated concrete panels
The steel formwork for the
core wall construction.
Prefabricated wall panels being
installed in public housing
Installing and fixing the precast facades
into positioninto position
PRECASTING METHODPRECASTING METHODPRECASTING METHODPRECASTING METHOD
INDIVIDUAL MOULD METHOD
U i ld hi h b il bl d f b dUsing mould which may be easily assembled out of bottom and
sides, transportable , if necessary this may be either in timber or in
steel using needle or mould vibrations and capable of taking
prestressing forcesprestressing forces.
Used in – Rib Slab, beams, Girders window panels, box type
units and special elements.
BATTERY FORM METHODBATTERY FORM METHODBATTERY FORM METHODBATTERY FORM METHOD
BATTERY FORM METHOD
B f h d h i l b dj d i hBattery form method shuttering panels may be adjusted in the
form of a battery at the required distances equal to the thickness
if the concrete members.
U d i I W ll ( P l Sh ll l f dUsed in – InteriorWalls ( Panels, Shell elements, reinforced
concrete, battens, rafters , purlines, roof and floor slabs.
STACK METHODSTACK METHODSTACK METHODSTACK METHOD
BATTERY FORM METHOD
U d i Fl d R f l b lUsed in – Floor and Roof slabs panels.
TILTING METHODTILTING METHODTILTING METHODTILTING METHOD
BATTERY FORM METHOD
U d i M ld i W llUsed in – Mould exteriorWalls.
LONG LINE PRESTRESSING BEDLONG LINE PRESTRESSING BED
METHODMETHOD METHODMETHODMETHODMETHOD METHODMETHOD
BATTERY FORM METHOD
U d i D bl ib l b li d bUsed in – Double tees, rib slabs, purlines and beams.
EXTRUSION METHODEXTRUSION METHOD
BATTERY FORM METHOD - Long concrete mould with
constant cross section and vibration will be done automatically justconstant cross section and vibration will be done automatically just
as in concrete roads.
Used in – roof slabs, concrete walls, panels and beams.
LimitationsLimitations of Prefabricationof Prefabrication
1. Small number of units required may prove to be
2. Special connections, such as special bearings to
t it th ti l d h i t l l d ddtransmit the vertical and horizontal loads, can add
cost to the system.
3 Waterproofing at joints3. Waterproofing at joints.
4. Transportation difficulties.
5. Need for cranes.5. Need for cranes.