prefabrication 2011

8/14/2019 prefabrication 2011

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prefabrication

group members-

shashank srivastava

sumit tiwari

sonam sahu

vaibhav gupta

vaibhav jaiswal

vaibhav kulshreshtha

vijay kumar

vijay kumar vermavirat singh


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The concept of precast (also known as prefabricated)construction includes

those buildings where the majority of structural components are standardizedand produced in plants in a location away from the building, and then

transported to the site for assembly.

These components are manufactured by industrial methods based on mass

production in order to build a large number of buildings in a short time at low

cost.

The main features of this construction process are as follows:

a) The division and specialization of the human workforce

b) The use of tools, machinery, and other equipment, usually automated, in

the production of standard, interchangeable parts and products

This type of construction requires a restructuring of the entire conventional

construction process to enable interaction between the design phase and

production planning in order to improve and speed up the construction.One of the key premises for achieving that objective is to design buildings

with a regular configuration in plan and elevation.

prefabrication


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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 constructionsite 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 materials to the construction site where all assembly is

carried out.

In prefabricated construction, only the foundations are

constructed in the traditional way, while sections of walls, floors

and roof are prefabricated (assembled) in a factory (possibly with

window and door frames included), transported to the site, lifted

into place by a craneand boltedtogether.

The theory behind the method is that time and cost is greatly

reduced.

The method finds application particularly where the structure is

composed of repeating units or forms.
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Production of Precast ConcreteThe production of precast concrete elements takes place under controlled conditions in

enclosed factories.

Forms

Precast forms are normally made of either steel or plywood. A large number of castings informs is typical in the production of precast concrete elements.

Plywood form use is limited to about 20 to 50 castings depending upon the complexity,

maintenance and shape of the form.

A large number of castings can be made by precasting using steel forms.

Form OilForm oils have been developed ( in place of mineral oil) containing of a mix of marine

ester, medical white oil and vegetable oil. These oils are easily biodegradable and are non-

toxic. Approximately 0.5 kg form oil per m3 of concrete is used.

Silicone

Silicone is frequently used to seal joints in forms.

Admixtures

Admixtures can be divided into four main groups:

water-reducing, air-entraining, retarders and accelerators.

In addition, there are several other types of admixtures

For special applications


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Reinforcement

The process of preparing mild steel reinforcement may be

the same for a precaster as for a contractor.

Fibre reinforced polymer (FRP)

composite materials can be used to reinforce the sectionsto allow the infrastructure to achieve its full lifetime.

Other Materials

In precast concrete production, special materials are

occasionally needed such as epoxy, lacquer, varnish and

paint. These materials are slightly hazardous, they arenormally used in very small amounts and their effects can

be controlled during prefabrication.

Transportation and Erection

In precast construction, the rigging of scaffolding,

formwork, storage areas etc. is either not necessary ordone only once. Scaffolding is generally not required for

precast structures. Cranes are used to lift precast

components into their place in a structure.

An erection team consist of a crane and small crew.

Experienced team can erect a whole frame and the floors

and roof together with the walls of a building.


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Large Panel Prefabrication System

The designation large-panel system refers to multistory structures

composed of large wall and floor concrete panels connected in the vertical

and horizontal directions so that the wall panels enclose appropriate

spaces for the rooms within a building.

These panels form a box-like structure. Both vertical and horizontal panels

resist gravity load. Wall panels are usually one story high. Horizontal floor

and roof panels span either as one-way or two-way slabs.

Depending on the wall layout, there are three basic configurations of

large-panel buildings:

1) Cross-wall system. The main walls that resist gravity and lateral loads

are placed in the short direction of the building.

2) Longitudinal-wall system. The walls resisting gravity and lateral loadsare placed in the longitudinal direction; usually, there is only one

longitudinal wall, except for the system with two longitudinal walls

developed in Kazakhstan.

3) Two-way system. The walls are placed in both directions.


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Thickness of wall panels ranges from

120 mm for interior walls to 300 mm

for exterior walls. Floor panel

thickness is 60 mm. Wall panel

length is equal to the room length,typically on the order of 2.7m to 3.6

m. In some cases, there are no

exterior wall panels and the facade

walls are made of lightweight

concrete.
http://www.engpedia.com/index.php/Image:Large-panel-concrete-building.jpg


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methods of prefabrication

individual mould method

in this method each

components of building

made in individual mould.

like : wall, beam, roof, pile,

etc.

extrusion method

unlimited length.

used self consolidation.no vibrator.
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battery method

in this walls are made

and spaces used forcuring.

stack methodIn this horizontal module

are made. Like slab.

tilting method


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Steel reinforcedconcrete is concrete in which steelreinforcement bars,

plates or fibers have been incorporated to build up a material . In

industrialized countries, nearly all concrete used in construction isreinforcedconcrete. There are a number of building materials that have

been found to be exceptional when it used in the construction of

buildings

STEEL REINFORCEMENT

Structural steelis steelconstruction material, a profile, formed with a specific shape

or cross sectionand certain standards of chemical compositionand mechanical

properties. Structural steel shape, size, composition, strength, storage, etc., is

regulated in most industrialized countries.

Structural steel members, such as I-beams.

STRUCTURAL STEEL
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Fibre reinforced concrete(FRC) is concretecontaining fibrous material which increases its

structural integrity. It contains short discrete fibresthat are uniformly distributed and

randomly oriented. Fibres include steel fibres, glass fibres, synthetic fibresand natural

fibres. Within these different fibres that character of fibre reinforced concrete changes

with varying concretes, fibre materials, geometries, distribution, orientation and densities.

NON CEMENTITIOUS MATERIAL

Glass Fiber Reinforced Concrete(GFRC) is a type of fiber reinforced concrete. Glass

fiber concretes are mainly used in exterior building faade panels.
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Take advantage of the strength of Reid steel

structures with office, workshop, storagefloors. Thick galvanized composite style

decking on Reid joists at close centers allow

you to make safe, light concrete floors easily

and with no propping. We can design for any

loading and these floors are particularly good

for Earthquake and Hurricane areas.

Mezzanine with composite decking

and joists at close centres.

Mezzanine floor with precast concreteplanks on Reid Steel beams.

Where Precast Concrete Planks are

readily available Reid steel can be

designed to carry your floors.

Insitu concrete floors can be

supported on Reid Steel Beams.

Reid steel can support your

own insitu floors spanning one

way or two ways.

Flooring arrangements


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Metal Decking Floors (Durbar or Boot

scraper). Here with handrail.

Steel floors, steel walkways, cat ladders,

stairs can easily be added to Reid Steel

Framed Buildings. They can be in non skid

Durbar plate or in boot scraper grid. Theycan be designed for any load from light

maintenance to heavy trucks or plant.

Lightweight floors on cold

rolled joists.

light weight timber or tongue-and-

grooved chipboard floor on Reid steel

close spaced joists.

Mezzanines can be supported on

light braced trestles.

Temporary floors can easily be

built on light supports providing

the floor is strong enough.


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Available -A large stock of sizes in 50mm increments allows fast and efficient delivery times.

Affordable - Our highly efficient production technologies combined with our range of products and experience in design of precast

elements enables us to provide cost efficient solutions.

Reliable - Fitting of precast is a fast process and not subject to the same weather dependency as traditional construction methods with an

average house being covered within a few hours.

Hollow core Composite Floors

Hollow core Composite Floors combine the benefits of our standard Hollow core unit, with a Structural Topping, fixed on site,

to give a greater load bearing capacity.

Hollow Composite Floors use Hollow core units with a structural concrete topping that provides improved load capacity.Hollow core Composite Floor can be designed in the unwrapped or partially propped condition to suit the particular

requirements of construction. This makes the product well-suited to industrial developments, tall buildings, car parks, etc.

Suitable for use in all types of building these pre-stressed units feature a series of voids that run the length of each

section thus reducing weight and improving thermal performance.

Hollowcore Floors

Solid Composite Floors are a combination of solid prestressed concrete units with a structural concrete topping which is

placed after the solid slabs have been erected

Solid Composite Floors

Precast concrete floors

Precast concrete flooring options


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Prefabrication in slab columns and beam


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Prestressed rectangular beam

Variable width :from 15cm to 60cm,variable height from 15cmto 70 cm.

It is compatible with all slab including the

prestressed slab in the market , namely the hollow core slab,

the prestressed ribs and blocks , the predalle and the conventional insitu cast slabs.

Therefore , It is is provided with a double strip on top to

insure the proper level to the slab components.


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dvantages Large span up to 17.00m,higher

fire resistance up to 4 hours

A smooth finishing with chamfered angles

quick erection

Withstand higher load

it could be manufactured with high concrete resistance up to 50 MPa

Design code and quality control

The structural and seismic design are to French code BPEL 91.

The Fire resistance is also to French code DTU 1987.

The quality control is carried out in our factory material laboratory on daily basis .

The client will be provided with the test results on the ordered products.


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A structural member composed of two or more dissimilarmaterials joined together to act as a unit. An example in civil

structures is the steel-concrete composite beam in which a steel wide-flange shape (I or W shape) is attached to a

concrete floor slab(see illustration). The many other kinds of composite beam include steel-wood, wood-concrete, and

plastic-concrete or advanced composite materials

concrete. Composite beams as defined here are different from beamsmade from fiber-reinforcedpolymericmaterials.

PROPPED CONSTRUCTION
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There are two main benefits of composite action in structural members. First, by rigidly joining the two parts together,

the resulting system is stronger than the sum of its parts. Second, composite action can better utilize the properties of

each constituent material. In steel-concrete composite beams, for example, the concrete is assumed to take most or all of

the compression while the steel takes all the tension.

Design of Composite Beams

The design involves the following aspe

1. Moment capacity:

Design the section such that the mome

2. Shear capacity

To ensure adequate capacity; this ba

structural steel design.

3. Shear connector capacity

To enable full composite action to

adequate.


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4. Longitudinal shear capacity

Check to prevent possible splitting of t

5. Serviceability checks:

a. Deflection;

b. Elastic behaviour, and;

c. Vibration.


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The steel beam is supported at mid- or quarter-span until the concrete slab has

hardened sufficiently to allow composite action. Propping affects speed ofconstruction but allows smaller steel sections.

PROPPED CONSTRUCTION

UNPROPPED CONSTRUCTIONThe steel beams must carry the weight of the wet concrete on its own. By the time

construction loads can be applied to the slab, some composite behaviour can be used.


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Today, building structures have become so innovative that ordinary propping equipment can no longer support the

challenging techniques. If the architecture has become advanced, the propping equipment, shoring system and propping

accessories have also come up to the mark. To meet the new challenges, many inventive types of propping equipments

have surfaced lately.

Some of the advanced propping equipments are:

Tilt PropsFor the tilt up slab construction, tilt propping equipments are used. The push pull prop can be used for high load

applications. Both sections of the props are permanently tagged with model and working loads. Tilt up can be dangerous

as the heavy ton panels are lifted by cranes. Here the safety measures are very crucial. The Tilt Propping equipments are

used to support the whole process of the tilt up construction.crow PropsThe Acrow Props are very vital for any construction. Every building construction needs the Acrow Props for support. The

Acrow Props offers the simplest and quickest method of temporary support and that is why it is necessary in every

construction.
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Multi PropsMulti props post shores are usually made of aluminium. They are considerably very light. A Mega prop 350, which can be

extended from1.95m to 3.50m, can weigh only 18.8 kg. The Multi Props are high load-bearing capacity.Trishore PropsThe Trishore Props have many advantages. They are able to support heavy loads at considerable height, fine adjustment by

screw jacks, economical and great savings in labour and transport, Trishore Props in groups can support extremely heavy loads

and have interchangeable sections. The Trishore features intermediate sections available in three different lengths, domed

bearing plate for concentric loading, head adjustment that fits R.S.J bearers and quick action connector.Slim SoldierSlim Soldier is a heavy-duty support for vertical and raking shoring. It can be used for variety of civil engineering and building

works. The Slim Soldier can support both large walls and precast units. The Slim Soldiers can convert into effective push pullprop with the standard adjustable jack units to the ends linked with suitable end connections.
http://www.shorehire.com.au/http://www.shorehire.com.au/http://www.shorehire.com.au/http://www.shorehire.com.au/http://www.shorehire.com.au/http://www.shorehire.com.au/http://www.shorehire.com.au/http://www.shorehire.com.au/http://www.shorehire.com.au/http://www.shorehire.com.au/http://www.shorehire.com.au/http://www.shorehire.com.au/http://www.shorehire.com.au/


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Megashore PropsThe Megashore Props are ultra heavy-duty modular propping system, which has been designed for axial loads of up to 1,000 KN

(100 tonne). It is highly versatility and used in heavy lifting towers, bracing for excavations, support spines for tunnel formwork,

shoring andtrusses.Titan PropsA Titan Prop is capable of supporting eight times the load for the same weight of its steel counterpart. Titan Props can be easilyhandled in discomfited locations and is suitable for tight and difficult access applications.
http://www.shorehire.com.au/http://www.shorehire.com.au/http://www.shorehire.com.au/http://www.shorehire.com.au/http://www.shorehire.com.au/http://www.shorehire.com.au/http://www.shorehire.com.au/


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PRECAST CONCRETE

Precast Concreteis a construction product

produced by casting concrete in a

reusable moldor "form" which is then cured in a

controlled environment, transported to the

construction site and lifted into place.
http://en.wikipedia.org/wiki/Molding_(process)http://en.wikipedia.org/wiki/Molding_(process)


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COMPONENTS OF A PRECAST REINFORCED

CONCRETE FRAME SYSTEM


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PRECAST CONCRETE

COLUMN

The precast concrete column elements

are 1 to 3 stories high. The reinforced

concrete floor slabs fit the clear span

between columns. After erecting the slabs

and columns of a story, the columns and

floor slabs are prestressed by means of

prestressing tendons that pass through

ducts in the columns at the floor level and

along the gaps left between adjacent slabs.


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Precast concrete walls providean excellent envelope for lowrise

commercial and industrial buildings. They

are relatively easy to manufacture,

structurally efficient, durable, and

attractive.

Shear walls are the main vertical structural

elements with a dual role of resisting boththe gravity and lateral loads.

PRECAST CONCRETE

SHEAR WALL

A single-family detached homebeing built up from precast concrete parts
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PRECAST CONCRETE BOX

A reinforced concrete box, is a square orrectangular "pipe" made of concrete with

rebaror wire mesh fabric strewn throughout for

the addition of extra strength. Multiple such

boxes are arranged sideways to make a pipe or

tunnel like structure.

It is often used for sanitary sewer trunks, storm

drain spillways, pedestrian subways, utility

tunnels, catch basins, and other similar

underground passage ways. Due to the

enormous strength of reinforced concrete, it is

often used in sewers or tunnels that have little

cover above them which means they will be

subjected to the stress of the roadatop them. In

India, pre-cast concrete boxes known as "Magic

Boxes"" are used for the constructionof flyoversand underpasses

a reinforced concrete box being

used in a storm drain

RCC Magic Box, used to

build an underpass
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PRECAST DOUBLE-T SLAB


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Double Wall Precast -

Concrete Sandwich Panels

The walls consist of two wythesofconcrete separated by an insulated

void. The most commonly specified

thickness of the wall panels is

8 inches.

The two wythes of the interior and

exterior concrete layers are held

together with steel trusses. Concrete

sandwich panels held together with

steel trusses are inferior to those held

together with composite fibreglass

connectors. This is because the steel

creates a thermal bridge in the wall,

significantly reducing the insulative

performance and reducing the ability

of the building to utilise its thermalmass for energy efficiency.

ACTIONS
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EXAMPLES OF FORCE TRANSFER SYSTEMS

Encasing

Threaded

anchors,

ferrules

and bolts

Reinforcing in

bond


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OTHER EXAMPLES OF FORCE TRANSFER SYSTEMS

Welded

connections

CONNECTIONSTYPES

Compression actions (forces) such as

end bearing concrete to concrete

Proprietary bearings (not that common inbuildings but are used in flooring)

Connections for tensile and compression forces

Connections for shear forces


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EXAMPLES OF CONNECTIONS TYPES

Bearing TensionShear

PROPRIETARY CONNECTIONS

Cast in channel Shear connector

RESTRAINT CONNECTION


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RESTRAINT CONNECTION

Avoid the use drilled fixing into base of

beam/slab as drilled fixing is likely to clash

with reinforcing.

Use 200x150 or 200x 200 EA to give sufficientleg lengths


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DIFFERENT TYPES OF JOINTS


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Column and foundation connection


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Beam and column connection

Typical connection


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Typical connection


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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 anearlier 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 be generated and in a factory setting it may be easier to recycle

it back into the manufacturing process, for instance it is less costly to recycle

scrap metal generated in a metal fabrication shop than on the construction site.

Moulds can be used several times.


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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 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

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 are lost

prefabrication 2011

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