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PRECAST CONCRETEARUSHI BANDHUSECOND YEAR AROLL NO. 5

INDEXS.NO. CONTENTSPAGE NO.1.INTRODUCTION 12.PROCESS OF CONSTRUCTION PRECAST 23.PRECAST STRUCTURAL SYSTEM34.ILLUSTRATIONS-FRAME SYSTEM4-75.PRECAST LOAD BEARING WALL8-96.PRECAST STRUCTURAL ELEMENTS10-137.STRUCTURAL CONCEPT14-168.ILLUSTRATIONS179.ADVANTAGES AND BENEFITS18-1910.PRODUCTS AND SERVICES2011.EXAMPLES OF PRECAST BUILDINGS IN INDIA21.12.BIBLIOGRPHY22.

The concept of precast (also known as prefabricated) construction includes those buildings, where the majority of structural components are standardized and 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:

The division and specialization of the human workforceNo space needed on site for storing moulds an reinforcement. The use of tools, machinery, and other equipment, usually automated, in theproduction of standard, interchangeable parts and productsCompared to site-cast concrete, precast concrete erection is faster and lessaffected by adverse weather conditions. Plant casting allows increased efficiency, high quality control and greater controlon finishes.

UNLOADING STRAIGHT ONTO BUILDINGMOVING INTO POSITIONFINAL PLACINGPRECAST COMPONENTS ARE MADE IN A FACTORY AND DELIVERED TO SITE WHERE THEY ARE LIFTED STRAIGHT FROM THE LORRY ONTO THE BUILDING.BETTER FINISHES CAN BE OBTAINED WITH PRECASTCONCRETEBECAUSE THE INSIDE SURFACE OF THE MOULD IS KEPT IN GOOD CONDITION.INTRODUCTION ARUSHI BANDHUSECOND YEAR AROLL NO. 51.

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PRODUCTION OF REINFORCED CAGES AND MAIN CONNECTIONS: The precast factory often has specialist workshops for the manufacture and maintenance of moulds, and for the production of jig-built reinforcing cages and connections.2. ASSEMBLY OF MOULDS: The reinforced cage is positioned in the partly assembled mould, then the remaining mould section is completed.3. MIX BEING POURED: Carefully specifiedconcreteis placed into the mould. Many precast works now employ computer controlled batching plants.4. COMPACTION OF CONCRETE USING POKER VIBRATOR: To ensure that optimum density is obtained and that specified strengths are achieved,concreteis placed and compacted using high-frequency external vibrators or pokers.5. PRECAST CONCRETE BEING MOVED TO THE STORAGE AREA: Once an appropriate strength has been reached, the precast units are moved to the storage area. Units are usually handled within hours of casting as part of the rapid production cycle.6. STORAGE OF HIGH-QUALITY UNITS IN WORKS AREA: The finished precast components are stacked on clean battens or plastic pads positioned to suit thedesignof the component. Care is taken to keep the stacks vertical and to ensure that battens are placed directly above one another within the stack.7. TRANSPORT TO SITE:PRECAST CONCRETE PROCESSARUSHI BANDHUSECOND YEAR AROLL NO. 52.

PRECAST BUILDING SYSTEMDepending on the load bearing structures, the most common precast structural systems are-1.FRAME SYSTEMSFrame structures are suitable for buildings which need a high degree of flexibility. Large spans and open spaces can be achieved without interfering walls.This system is particularly suitable for shopping malls, multistory car parks, sports facilities, office buildings and industrial buildings.2. LOAD BEARING WALLS AND FLOORS Precast load bearing walls can appear as walls in shafts and cores, cross-walls and load bearing external walls.Precast wall systems have been used in residential projects. they provide advantages of fast construction ,ready to paint surface finish, acoustic insulation and fire resistance. The slabs between walls can either be precast or in-situ flat plate structure.The aim is to build free open spaces between the load bearing walls and to use partition walls for the internal layout.3. CELL SYSTEMSCell units are feasible for specific uses of a building, for instance, bathrooms and kitchens.The advantage of the system lies in the speed of construction and high productivity in manufacturing since finishing's and fittings of the cells are completely done at the factory.ARUSHI BANDHUSECOND YEAR AROLL NO. 53.

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Structurally continuous beamcolumn connection may be created by passing a tendon from a pocket in the top of one beam, through the column, to a pocket in the top of the other beam. The tendon is anchored to a plate in one pocket as it is tensioned by a jack in the other pocket.

BEAM TO COLUMN CONNECTION DETAIL

ILLUSTRATIONS-FRAME SYSTEMARUSHI BANDHUSECOND YEAR AROLL NO. 54.

Topped hollow-core roof slabs supported on beams are joined to a column with vertical rods. A similar connection can be used for floor beams resting on corbels.

DETAIL AT A.(SECTIONAL VIEW)AILLUSTRATION 2ARUSHI BANDHUSECOND YEAR AROLL NO. 55.

The beams in this system of framing rest on concrete corbels that are integrally cast with the column. The smooth-topped hollow-core slabs are detailed for use without topping. (a) Weld plates are cast into the column. (b) Beams are placed on bearing pads on the corbels. There is a weld plate cast into the top of each beam at the end. (c) Short pieces of steel angle are welded to the plates to join the beams to the columns. Smooth-top hollow-core precast concrete planks are placed on bearing pads on top of each beam. Grout is poured into the gap between the ends of the planks to unite loops of reinforcing that project from the tops of the beams, reinforcing bars that are inserted through the loops, and lateral pieces of reinforcing bar that are grouted into the keys between planks. The end result is a tightly connected assembly that supports an untopped precast concrete floor or roof.ILLUSTRATION 3ARUSHI BANDHUSECOND YEAR AROLL NO. 56.

This column-to-column connection uses proprietary sleevesthat are cast into the lower end of the upper column section.Before the sections are assembled (upper left), the lowerends of the vertical bars from the upper column section,which reach down to the midheight of each sleeve, are theonly contents of the sleeves. Assembly of the column sections starts with the placement of a stack of steel shims in the center of the top of the lower section. These shims serve to adjust the height of the column and to maintain a space for grouting between the two sections.ILLUSTRATION 4ARUSHI BANDHUSECOND YEAR AROLL NO. 57.

Precast concrete walls provide an excellent envelope for low rise commercial and industrial buildings. They are relatively easy to manufacture, structurally efficient and durable.Precast walls have been used for seismic load resistance by designing them to emulate cast-in place shear walls.This is typically accomplished using ductile vertical reinforcing coupled with splice sleeves to create continuity across horizontal wall joints.In adopting the wall thickness, structural adequacy is not the sole consideration. Other factors to be considered include: Connection details for supported beams and slabs.Sound transmission and fire rating. Joint details at panel-to-panel connections. Possible future embedded services, which could reduce the concrete areaavailable.Based on typical layouts and building configurations, a thickness of 180mm is recommended for the precast panels.

PRECAST LOAD BEARING WALLARUSHI BANDHUSECOND YEAR AROLL NO. 58.

PRECAST NON-LOAD BEARING FACADE PANELS Typically, the wall panels for the front and rear elevations are non-load bearing facade elements. Support of these panels is achieved by any of the following methods: The facade panel is connected to main load bearing walls and is designed to carry its own weight between supports. The facade panel is connected to the floor slab or beam, which is then designed to provide support to the wall. These panels will typically be designed for vertical loads due to self weight and anallowance for floor loads, if applicable, in addition to horizontal loads due to externalwind pressures. A typical panel thickness of 120mm is proposed on the basis ofstrength considerations and to accommodate window fixings and profiles around thewindow perimeter.

PRECAST NON LOAD BEARING WALLARUSHI BANDHUSECOND YEAR AROLL NO. 59.

PRECAST CONCRETE SLABSThe most fully standardized precastconcrete elements are those used formaking floor and roof slabs.These may be supported bybearing walls of precast concrete ormasonry or by frames of steel, site castconcrete, or precast concrete.

TYPES OF PRECAST SLAB ELEMENTSFOR SHORT SPANSAND MINIMUM SLAB DEPTHS, SOLID SLABSARE APPROPRIATE.IN HOLLOW-CORE SLABS, PRECAST ELEMENTS SUITABLE FOR INTERMEDIATE SPANS, INTERNAL LONGITUDINAL VOIDS REPLACE MUCH OF THE NONWORKING CONCRETE.FOR THE LONGEST SPANS, STILL DEEPER ELEMENTS ARE REQUIRED, AND DOUBLE TEES AND SINGLE TEES ELIMINATE STILL MORE NONWORKING CONCRETE.PRECAST STRUCTURAL ELEMENTSESTIMATE SIZEPRECAST SOLID SLABDEPTH-90mm to 200mmPRECAST HOLLOW-CORE SLABDEPTH SPAN200mm 7.6m250mm 9.8m300mm 12mPRECAST CONCRETE DOUBLE TEESCOMMON DEPTHS-300.350,400,460mmPRECAST CONCRETE SINGLE TEEDEPTH-915mmSPAN-2.5mPRECAST CONCRETE COLUMN250mm,300mm,,400mm,600mm

STANDARD PRECAST CONCRETE BEAM AND GIRDER SHAPES.PRECAST STRUCTURAL ELEMENTSARUSHI BANDHUSECOND YEAR AROLL NO. 510.

PRECAST REINFORCED CONCRETE FLOOR SYSTEMS:The precast reinforced concrete floor beams, planks, tee beams or beam and infill blocks that require little or no temporary support and on which a screed or structural concrete topping is spread are commonly used with structural steel frames and may be used for in situ cast floors.Precast beams and plank floors that require no temporary support in the for of centering are sometimes referred to as self-centering floor.The advantage of these precast floor systems is that there is a saving in site labor.

The two most common types are:PRECAST CONCRETE PLANK FLOOR UNIT:These comparatively thin, prestressed solid plank, concrete floor units are designed as permanent shuttering and for composite action with structural reinforced concrete topping. The units are 400 or 1200 wide,65,75 or 100 thick and up to 9 and half meters long for floors and 10 meters long for roofs.PRECAST HOLLOW FLOOR UNITS:Theses precast hollow floor units are generally 400-12200 wide,110,150,200,250 or 300 thick and up to 10 meters long for floors and thirteen and a half meter long for roofs. The purpose of voids or hollows in the floor unit is to reduce dead weight without affecting strength. The reinforcement is cast into webs between hollows.

PRECAST STRUCTURAL ELEMENTSARUSHI BANDHUSECOND YEAR AROLL NO. 511.

HOLLOW CLAY AND CONCRETE FLOOR: A floor system of hollow clay blocks and in situ cast reinforced concrete beams between the blocks and concrete topping cast on centering and falsework, resisting properties of the blocks. This floor system is much less used because of the very considerable labor in laying the floor.PRECAST BEAM AND FILLER BLOCK FLOOR:This floor system consists of precast reinforced concrete planks or beams that support precast hollow concrete filler blocks. The planks or beams are laid between them and a concrete topping is spread over the planks and filler blocks. The reinforcement protruding from the top of the plank acts with the concrete topping to form reinforced concrete beam.The advantage of this system is that the lightweight planks or beams and filler blocks can be lifted much more easily and placed in position than the much larger hollow concrete floor units.

PRECAST CONCRETE TEE BEAMS: Precast prestressed concrete tee beam floors are mostly used for long span floors in such buildings as stores, supermarkets, swimming pools and multi-storey car parks where there is a need for wide span floors and the depth of this type of floor is not a disadvantage. The floor units are cast in the form a double tee.

PRECAST STRUCTURAL ELEMENTSARUSHI BANDHUSECOND YEAR AROLL NO. 512.

PRECAST WALLSGROUTGROUND BEAM AND SLABFOOTINGThe foundation loads for the precast structural system will be similar to those for conventional design. The arrangement of the foundations below the load bearing walls will be different to those normally adopted for a column and beam structural system. The desirable arrangement should provide a relatively uniform support along the length of the wall and minimize the eccentricity effectsdue to any possible misalignment of the walls relative to the foundations. In the case of a footing foundationsystem, the recommended solution is acontinuous strip footing below the loadbearing walls, as shown in Figure.

FOOTING BELOW PRECAST LOAD BEARING WALLS

Similarly, a raft foundation system, as shown in Figure I. will provide a uniform support to the load bearing walls and excellent resistance to eccentricity effects.

For a piled foundation, uniform support along the full length of the wall can be provided by adopting piles at closer spacing with a first storey capping beam. This solution is unlikely to be economical. The recommended approach is shown in Figure II. which is based on the following structural concept: Within the precast concrete wall, zones are designated as load bearing and no-load bearing. Piles are located below the load bearing zones only. The piles are preferably provided in groups of two or more, located on each side of the wall centerline. If single piles are necessary, first storey beams are required in the transverse direction to accommodate any possible eccentricity effects.I. PRECAST LOAD BEARING WALL ON STRIP FOOTING OR RAFT FOUNDATIONII. PRECAST LOAD BEARING WALL ON PILED FOUNDATIONPRECAST FOUNDATIONARUSHI BANDHUSECOND YEAR AROLL NO. 513.

Based on considerations of buildability, economy and standardization of precast components, the structural concept developed consists of: Conventional foundations comprising footings, raft slab or piles and pile caps. Cast in-situ first storey, typically reinforced concrete beam and slab system. Precast concrete load bearing walls. Precast concrete non-load bearing faade panels. Precast concrete floor system, either:- Precast concrete beams and precast slabs (reinforced concrete orprestressed) with a composite in-situ toppingor Precast concrete walls with precast concrete slab systemPRECAST PRESTRESSED SLABS SPANNING BETWEEN WALLS WITH COMPOSITE IN-SITU TOPPING FOR 1ST STOREY

STRUCTURAL CONCEPTARUSHI BANDHUSECOND YEAR AROLL NO. 514.

PRECAST PRESTRESSED SLABS SPANNING BETWEEN WALLS WITH COMPOSITE IN-SITUTOPPING FOR 2ND STOREYPRECAST PRESTRESSED SLABS SPANNING BETWEEN WALLS WITH COMPOSITE IN-SITUTOPPING FOR ROOFSTRUCTURAL CONCEPTARUSHI BANDHUSECOND YEAR AROLL NO. 515.

A FULLY PRECAST BUILDING FRAME UNDERCONSTRUCTION. A POURED CONCRETE TOPPINGWILL COVER THE HOLLOW-CORE SLABS AND THEBEAMS TO CREATE A SMOOTH FL OOR AND TIETHE PRECAST ELEMENTS TOGETHER.WORKERS GUIDE TWO HOLLOW-CORE SLABS,LOWERED BY A CRANE IN WIRE ROPE SLINGS,ONTO THE PRECAST CONCRETE BEAMS THAT WILLSUPPORT THEM.ARUSHI BANDHUSECOND YEAR AROLL NO. 516.

DOUBLE-TEE SLAB ELEMENTSSUPPORTED ON A FRAME OF PRECASTCOLUMNS AND L-SHAPED GIRDERS

HOLLOW-CORE SLAB ELEMENTSSUPPORTED ONPRECAST CONCRETE LOADBEARING WALL PANELS.DOUBLE-TEE SLAB ELEMENTS SUPPORTED ON A PERIMETER OF PRECAST CONCRETE LOADBEARING WALL PANELS AND AN INTERIORSTRUCTURE OF PRECAST COLUMNS AND INVERTED TEE BEAMS.ILLUSTRATIONSARUSHI BANDHUSECOND YEAR AROLL NO. 517.

FLEXIBILITY OF SHAPE AND FORM: Concrete can be molded into any shape, hence it is used to provide custom made design solutions. STRENGTH: precast exterior cladding can be easily designed to handle structural building loads. DURABILITY: Studies have shown that concrete products can provide a service life in excess of 100 years.

BENEFITS AND ADVANTAGESARUSHI BANDHUSECOND YEAR AROLL NO. 518.

DESIGN-BUILD EFFICIENCY:Precast concrete provides an efficient delivery model for your project; allowing building construction to proceed while the design is developed.ESTHETICS:An unlimited array of colorings, textures and patterns can be added to the concrete mix, or textured paints of any color may be used, for exceptional effects.ENVIRONMENTALLY FRIENDLY:An inherent characteristic of precast concrete is its natural resistance to mold, greatly reducing health concerns from VOCs and off gassing. With these environmentally friendly advantages, precast concrete satisfies a growing demand for sustainable design and construction. Additionally, precast concrete structures are completely recyclable making their impact on the environment minimal.ENERGY EFFICIENCY:The thermal mass inherent to precast concrete lends itself to energy efficiency and reduces the heating and cooling peaks and loads; often necessitating less costly mechanical systems.

BENEFITS AND ADVANTAGESARUSHI BANDHUSECOND YEAR AROLL NO. 519.

PRODUCTS AND SERVICESARUSHI BANDHUSECOND YEAR AROLL NO. 520.

SANTUSHTI HOMES AT BHIWADI

250 affordable homesG+3 Storied 3 BlocksLoad bearing Precast wallsPrecast Solid Slabs (room size)Site Based Precast PlantDesign Approved by IIT Delhi

LAKESIDE AT CHENNAI

300 apartment schemeStilt + 4 Storied 6 BlocksLoad bearing Precast wallsPrecast Hollow-core slabsDedicated Precast PlantDesign Approved by IIT Delhi

COMMUNE-1 AT BANGALORE

550 apartment schemeBasement +G+13Load bearing Precast wallsPrecast Solid slabsSite based Precast Plant

MARVEL SANGRIA AT PUNECommercial Building of 250,000 sqftShops at Ground & Mezzanine floorB+G+3 Storied 3 BlocksLoad bearing Precast wallsPrecast hollow-core slabsPrecast Portal Frames at all floorsPrecast Retaining Walls at BasementPrecast Plant located at Pune

EXAMPLES OF SOME PRECAST BUILDINGS IN INDIAARUSHI BANDHUSECOND YEAR AROLL NO. 521.

ARUSHI BANDHUSECOND YEAR AROLL NO. 522.ebooks.narotama.ac.idMcKay www.bca.gov.sgwww.fpcaweb.orgwww.researchgate.netprecast.org