PRE-FABRICATED
STRUCTURES
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Types of Prefabricated Structures:
1. Panelized Wood Framing
Used typically for roofs, these are long pieces of frames
built from laminated timber, covered either by a
plywood or some board roof deck. Panelized frames can
be up to 72 feet long, these roof panels can save
construction time and make roof construction a much
safer activity.
2. Sandwich Panels
Made from 2 thin facings of materials like concrete,
plywood, or stainless steel. The facings are then stuck to
an insulating core, made typically of materials like foam,
paper, cloth or rubber.
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3. Steel Framing
For ages, steel has been one popular and trusted
building material for commercial and residential
construction. Steel framing uses this strong and
durable material to create prefab panels which can
be used to construct buildings.
4. Timber Framing
Not very common in India, timber framing panels are
quite popular in other countries where timber homes
are common. These framings are built in factories and
then used in erecting timber homes.
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5. Concrete Systems
Having concrete fragments of a prefabricated building cast in the
factory provides more versatility and also saves time. Even though
architectural elements like concrete panels are heavier than other
building components, they are typically sturdier and can improve
a building’s aesthetics.
6. Modular Systems
These systems use all prefab styles and create a whole building
structure typically made from factory-constructed units. The
buildings are transported to the final construction site and then
simply connected to a prepared foundation.
Prefabrication demands the cooperation of architects, builders,
and suppliers, regarding the size and specification of basic
modular units.
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INTRODUCTION.
PREFAB CONCEPT.
PREFABRICATION.
PREFAB COMPONENTS.
ADVANTAGES AND DISADVANTAGES.
CONCLUSIONS.
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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.
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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.
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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.
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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.
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Column to Column Connection 66
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.
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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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SLAB TO BEAM CONNECTION
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GLANCE AT BUILDING PROCESS
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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
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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.
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Disadvantages:
High transport cost
Need of erection equipment
Skilled labour and supervision is required.
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IS 15916: Building Design and Erection Using
Prefabricated Concrete - Code of Practice
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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 79
Google.com
Wikipedia.org
Britanica.com
www.dictionaryofconstruction.com
bkaviani.wordpress.com
www.concrete.org.uk
IE (I) Journal—
AR
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