Prefabrication construction

 INTRODUCTION.
 PREFABRIC CONCEPT.
 PREFABRICATION.
 PREFABRIC COMPONENTS.
 ADVANTAGES AND DISADVANTAGES.
 CONCLUSIONS.
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.
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 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.
5

 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.
6

 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.
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 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.
10

For Indian conditions partial prefabrication is well
suited.
12

Some of the prefabricated components are as explained
below
 Columns: - 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.
14

15
Column to Column Connection

 Beams: - 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.
Methods of connecting beams and columns are
A precasting 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 insitu concrete to
complete the joint.
This is as shown in the figure.
16

 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
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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
23

Advantages:
 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.
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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.
25

Disadvantages:
 High transport cost
 Need of erection equipment
 Skilled labour and supervision is required.
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 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.
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 Google.com
 Britanica.com
 www.dictionaryofconstruction.com
 bkaviani.wordpress.com
 www.concrete.org.uk
 IE (I) Journal—AR
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