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PREFABRICATIONAnd its

techniquesSUBMITTED TO: SUBMITTED BY:

AR.NIPPY GARG NARENDER KONDLAS

SYED SUHAIB

KHAMANSHU BANSAL

SATINDER KAUR

SILVEY DEAN

SANDRA BERNARD

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INTRODUCTION Prefabrication is the practice of assembling components of a structure in a factory or

other manufacturingsite, and transportingcomplete assemblies or sub-assemblies to theconstructionsite where the structure is to be located.

The term is used to distinguish this process from the more conventional construction

practice of transporting the basic materialsto the construction site where all assembly is

carried out.

It is frequently used when fabricationof a section of a machine or any movable structure

is shifted from the main manufacturing site to another location, and the section issupplied assembled and ready to fit.

An example from house-building illustrates the process of prefabrication. The

conventional method of building a house is to transport bricks, timber, cement, sand,

steeland construction aggregate, etc. to the site, and to construct the house on site from

these materials.

In prefabricated construction, only the foundations are constructed in this way, whilesections of walls, floors and roofare prefabricated (assembled) in a factory (possibly with

window and door frames included), transported to the site, lifted into place by a crane

and boltedtogether.

http://en.wikipedia.org/wiki/Structurehttp://en.wikipedia.org/wiki/Factoryhttp://en.wikipedia.org/wiki/Manufacturinghttp://en.wikipedia.org/wiki/Transporthttp://en.wikipedia.org/wiki/Constructionhttp://en.wikipedia.org/wiki/Materialhttp://en.wikipedia.org/wiki/Fabrication_(metal)http://en.wikipedia.org/wiki/Brickhttp://en.wikipedia.org/wiki/Timberhttp://en.wikipedia.org/wiki/Cementhttp://en.wikipedia.org/wiki/Sandhttp://en.wikipedia.org/wiki/Steelhttp://en.wikipedia.org/wiki/Construction_aggregatehttp://en.wikipedia.org/wiki/Prefabricated_buildingshttp://en.wikipedia.org/wiki/Foundation_(architecture)http://en.wikipedia.org/wiki/Wallhttp://en.wikipedia.org/wiki/Roofhttp://en.wikipedia.org/wiki/Crane_(machine)http://en.wikipedia.org/wiki/Screwhttp://en.wikipedia.org/wiki/Screwhttp://en.wikipedia.org/wiki/Crane_(machine)http://en.wikipedia.org/wiki/Roofhttp://en.wikipedia.org/wiki/Wallhttp://en.wikipedia.org/wiki/Foundation_(architecture)http://en.wikipedia.org/wiki/Prefabricated_buildingshttp://en.wikipedia.org/wiki/Prefabricated_buildingshttp://en.wikipedia.org/wiki/Prefabricated_buildingshttp://en.wikipedia.org/wiki/Construction_aggregatehttp://en.wikipedia.org/wiki/Construction_aggregatehttp://en.wikipedia.org/wiki/Construction_aggregatehttp://en.wikipedia.org/wiki/Steelhttp://en.wikipedia.org/wiki/Sandhttp://en.wikipedia.org/wiki/Cementhttp://en.wikipedia.org/wiki/Timberhttp://en.wikipedia.org/wiki/Brickhttp://en.wikipedia.org/wiki/Fabrication_(metal)http://en.wikipedia.org/wiki/Materialhttp://en.wikipedia.org/wiki/Constructionhttp://en.wikipedia.org/wiki/Transporthttp://en.wikipedia.org/wiki/Manufacturinghttp://en.wikipedia.org/wiki/Factoryhttp://en.wikipedia.org/wiki/Structure

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THE PROCESS THEORY OF PREFABRICATION The theory behind the method is that time and cost is saved if similar construction tasks can

be grouped, and assembly linetechniques can be employed in prefabrication at a location

where skilled labour is available, while congestion at the assembly site, which wastes time,

can be reduced.

The method finds application particularly where the structure is composed of repeating

units or forms, or where multiple copies of the same basic structure are being constructed.

Prefabrication avoids the need to transport so many skilled workers to the construction site,

and other restricting conditions such as a lack of power, lack of water, exposure to harsh

weather or a hazardous environment are avoided.

Against these advantages must be weighed the cost of transporting prefabricated sections

and lifting them into position as they will usually be larger, more fragile and more difficult to

handle than the materials and components of which they are made.

http://en.wikipedia.org/wiki/Assembly_linehttp://en.wikipedia.org/wiki/Assembly_line

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Current uses:

The most widely-used form of prefabrication in building and civil engineeringis the use of

prefabricated concreteand prefabricated steelsections in structures where a particular part

or form is repeated many times.

It can be difficult to construct the formworkrequired to mouldconcrete components on site,

and delivering wet concrete to the site before it starts to set requires precise time

management.

Pouring concrete sections in a factory brings the advantages of being able to re-use moulds

and the concrete can be mixed on the spot without having to be transported to and pumped

wet on a congested construction site.

Prefabricating steel sections reduces on-site cutting and weldingcosts as well as the

associated hazards.

Prefabrication techniques are used in the construction of apartmentblocks, and housing

developments with repeated housing units.

The quality of prefabricated housing units had increased to the point that they may not be

distinguishable from traditionally-built units to those that live in them.

http://en.wikipedia.org/wiki/Civil_engineeringhttp://en.wikipedia.org/wiki/Concretehttp://en.wikipedia.org/wiki/Steelhttp://en.wikipedia.org/wiki/Formworkhttp://en.wikipedia.org/wiki/Mouldhttp://en.wikipedia.org/wiki/Weldinghttp://en.wikipedia.org/wiki/Apartmenthttp://en.wikipedia.org/wiki/Apartmenthttp://en.wikipedia.org/wiki/Weldinghttp://en.wikipedia.org/wiki/Mouldhttp://en.wikipedia.org/wiki/Formworkhttp://en.wikipedia.org/wiki/Steelhttp://en.wikipedia.org/wiki/Concretehttp://en.wikipedia.org/wiki/Civil_engineering

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The technique is also used in office blocks, warehouses and factory buildings.

Prefabricated steel and glass sections are widely used for the exterior of large buildings.

Detached houses, cottages, log cabin, saunas, etc. are also sold with prefabricated

elements.

Prefabrication of modular wall elements allows building of complex thermal insulation,

window frame components, etc. on an assembly line, which tends to improve quality

over on-site construction of each individual wall or frame.

However, tradition often favors building by hand in many countries, and the image of

prefab as a "cheap" method only slows its adoption.

http://en.wikipedia.org/wiki/Thermal_insulationhttp://en.wikipedia.org/wiki/Assembly_linehttp://en.wikipedia.org/wiki/Assembly_linehttp://en.wikipedia.org/wiki/Thermal_insulation

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Advantages of prefabrication Self-supporting ready-made components are used, so the need for formwork, shuttering and

scaffolding is greatly reduced.

Construction time is reduced and buildings are completed sooner, allowing an earlier return of the

capital invested.

On-site construction and congestion is minimized.

Quality control can be easier in a factory assembly line setting than a construction site setting.

Prefabrication can be located where skilled labour is more readily available and costs of labour, power,

materials, space and overheads are lower.

Time spent in bad weather or hazardous environments at the construction site is minimized.

Less waste may occur

Advanced materials such as sandwich-structured compositecan be easily used, improving thermal and

sound insulation and airtightness

http://en.wikipedia.org/wiki/Sandwich-structured_compositehttp://en.wikipedia.org/wiki/Sandwich-structured_compositehttp://en.wikipedia.org/wiki/Sandwich-structured_compositehttp://en.wikipedia.org/wiki/Sandwich-structured_composite

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DISADVANTAGES 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 efficiently.

Large prefabricated sections require heavy-duty cranes and precision measurement and

handling to place in position.

Larger groups of buildings from the same type of prefabricated elements tend to look drab

and monotonous.

Local jobs may be lost, if the work done to fabricate the components being located in a

place far away from the place of construction.

This means that there are less locals working on any construction project at any time,

because fabrication is outsourced.

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Prefabrication in India Prefabrication in India began with the emergence of the Hindustan Housing Factory.

The company was developed by the first Prime Minister of India, Pandit Jawaharlal Nehru, as

asolution to the housing crisis that resulted from the influx of refugees from West Pakistan in the

1950s. The Hindustan Housing Factory pioneered the production of pre-stressed concrete railway

sleepers to replace dilapidated wooden sleepers on Indian Railways.

The company changed its name shortly there after to reflect the diversity of its operations. It is now

known as the Hindustan Prefab Limited or HPL.

Located in Delhi, today the government run company prefabricates primarily precast concrete for

architectural and civil projects throughout greater India.

When HPL began it was intended to produce low-income housing solutions for the deficit in India.

Precast wall panels and frame members such as beams and columns provided a much needed set of

tools to erect quick structures for mass housing.

The most difficult technology transfer obstacle for the HPL has been the cost of machinery and

materials for production. Since the government could not recoup the return on investment for the

factory through housing production, prefabrication from HPL.

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Components are manufactured units, made to pre-determined sizes, to be used in building.

Dimensional co-ordination governs their design and use and forms the necessary disciplinefor industrialized, "system" or "component" building.

For example a prefabricated standard staircase component to rise 2660 mm will govern the

floor to floor height of the building in which it is to be fixed.

COMPONENTS AND JOINTING

Pqefabqicaved uvaiqcaue uvaiqcaue

Prefabricated wall cladding panels will closely govern the storey heights and the

length of the building, or part of a building where they are used.

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The structural frame is usually erected by site work methods, e.g. insitu reinforced concrete,

and the prefabricated units, whether mass produced to standard sizes or specially made for

the particular building project, are fitted to it.

An accurate tie-up between the respective dimensions of structure and cladding units is

essential, and only a certain degree of tolerance my subsequently be allowed for either.

Standardized components are joined together to form building elements.The dimensional co-ordination between all the components concerned is

essential, and for this method of building it is necessary that this co-ordination

shall be based upon a suitable module.

That is a certain unit length which shall form the increment of change of size, and

so the overall dimensions of the building will be a multiple of these modules or

units of length

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Acvtal mantfacvtqed componenvu sill aqyulighvly shen made fqom vhe upecifieddimenuionu and may be utbjecv vo ftqvheqmoemenv

Bovh aqiavion in uize and uhape aqe vobe allosed sivhin accepvable limivu.

ComponenvMax.uize limiv

Min. uize limiv

The diffeqence bevseen vheue vso limivuqepqeuenvu vhe voleqance allosed.

-The aqiavionu in uize and uhape, andupace neceuuaqy vo moe vhe componenv invo

pouivion and fix iv, aqe allosed foq in vhesidvh of vhe joinv bevseen componenvu.

-The joinv sidvh sill aqy sivh vhesoqk uize (uize upecified foq ivu mantfacvtqe)+ deiavion (aqiavion in uize and uhape) foqeach componenv.

THE JOINT:-The gqeaveq vhe acctqacy ofvhe componenvu vo be joined, vhe leuu sidvh

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In oqdeq vo qemain avvached vo vhe vsofaceu of a joinv, vhe uealanv hau vo beable vo accommodave moemenv dte vovheqmal oq ovheq facvoqu.moemenv accommodavion facvoq (MAF)

(aqieu bevseen diffeqenv uealanvmaveqialu. )

Long expeqience hau uhosn vhav a goodeuvimave can be made fqom vhe follosing:Joinv sidvh in mm) = voval lengvh of vheadjacenv panelu in m)Thtu foq a joinv bevseen vso panelu of lengvh7m and 8m, vhe voval iu 15m, giing a joinvsidvh of 15mm.

The uimpleuvpqofileiu auvqaighv urtaqejoinv. Thiu hauueeqaladanvageu:

iv iu eauieq vocauv; iv gieu

ftll upace foqvhe uealanvu;i allosu

'joggle' joinv:In pqacviceiv uhotld beaoided au :

Iv iu moqediffictlv vocauv; iv doeunov pqoideenotgh upacefoq a dotbleueal; iv

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PREFABRICATED PANELS tued foq exveqioq sallu fqamed sivh sood oq lighv seighv uveelfqaming clad in exveqioq oq inveqioqfiniuheu.

convainu inutlavion , siqing, oq pqe-ctvopening foq sindosu and dooqu conuvqtcvion of panelized homeu incltdeushole sallu sivh sindosu , dooqu, siqeu oqotvuide uiding pqepaqed in facvoqyand eqecved on uive.

Pqecauv concqeve cladding Pqecauv concqeve panelu aqe qeinfoqcedconcqeve tnivu aailable in a side qange ofmixeu, colotqu and finiuheu.

Finiuheu can incltde acid-evched, umoovh oqcoaque gqotnd, gqiv oq uand-blauved, qtbbedoq poliuhed. Mixeu deuigned vo qeuemblenavtqal uvone can aluo be pqodtced . Highly aqvictlaved deuignu can beaccommodaved by vhe moldable concqeve mix.

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PREFAB CONCRETE PANEL SYSTEM Theqe aqe aqeau sheqe good rtalivy bqicku aqenov aailable foq qoofing. The pqefab concqeve panel uyuvem pqoideu vheadanvage of pqefabqicavion foq incqeauingupeed in conuvqtcvion and in uivt concqeve vodeelop monolivhically uvqtcvtqe. In vhiu concqeve 3.5cm vhk and paqviallypqecauv concqeve joiuvu of lengvh aqepqefabqicaved on vhe gqotnd sivh pqopeqqeinfoqcemenv. vhe concqeve panelu aqeutppoqved on vhe joiuv and 3cm vhk cemenvconcqeve iu laid oeq vhe qoof.

The qoof iu economical and sivhin vhecapabilivieu of vhe local ukilled and tnukilledlabotq.

Pqecauv concqeve panelu aqe cauv face-dosnsaqdu in ptqpoue-btilv motldu, tutally madeof eivheq vimbeq oq fibqe glauu.

A uveel qeinfoqcemenv cage iu placed in vhemotld pqioq vo vhe concqeve being potqed.

Timbeq motldu can be eauily adjtuved uo vhavmaximtm tue can be made of each bauic motld,ftqvheq convqibtving vo couv efficiencieu.

By inueqving mavu oq qodu in vhe baue of vhemotld diffeqenv deuignu and effecvu can beq a d - fqom falu oin u o in qi a l af

Pqoceuu

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TECHNIQUES

PRECAST RC PLANK SYSTEM

PRECAST BRICK PANEL ROOFING PRECAST RC CHANNEL

PRECAST CONCRETE PANELS ROOFING

THIN PRECAST RC LINTEL

PRECAST RC PLANK ROOFING SYSTEM

This system consist of precast RC planks supported over partially precast joist. The

completely finished slab can be used as intermediate floor for living also. The total

thickness of slab is 6 cm . The planks are made in module width of 30 cm with

maximum length of 150 cm and the maximum weight of the dry panel is 50 kg . The

scheme is ideally suited for spans up to 4.2 m , but can be used for large spans, by

providing secondary beams.

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PRECAST BRICK PANEL ROOFING

This system comprises of prefab brick based component and

partially precast Rc joists panels are laid over partially precast

joist the typical size of panel is 1040mm X 640mm in which 16

bricks 2 bars of 6mm dia. And m-15 conc. are used .

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PRECAST RC CHANNEL ROOFING

Precast channels are trough shaped with the

outer sides corrugated and grooved at the

ends to provide shear key action and totransfer moments between adjacent units.

Nominal width of units are 300 mm or 600 mm

with overall depths of 130 mm to 200 mm .

The lengths of the units are adjusted to suit

the span.

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PRECAST CONCRETE PANELS ROOFING

The system comprise of precast panels 600 mm 600 mm and

only 30 mm thick . The reinforcement consists of 2 mm dia MS wire or equivalent

welded mesh. The panels are placed over fully precast RCC beams of 75 mm width and

125mm to 150 mm depth depending on the span. The ends of panels are tapered so

as to form a V-groove when placed over beams. This groove is filled with cement

mortar. The beams are designed as simple supported.

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THIN PRECAST RC LINTEL

Lintels can be as well designed as composite member consisting of 75mm

Thick rc lintel with the masonry on top the precast lintel 75mm X230mm with

(3)numbers of MS dia bars.

LINTEL WITH CHAJJA