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sr. no. Particulars Pg no.

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Introduction to precast concrete

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Types and procedure of precast concrete construction

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Precast technology in residential building

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Case study on the precast technology in Bandra worli

sea link (BWSL)

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Research paper study on the future of precast

technology in law rise building

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Precast technology

Subject: Advanced construction practice

Topic: Precast technology

Prepared by: Hardik Patel (PT101214)

Guided by: Prof. Jyoti Trivedi

Dr. Ganesh Devkar

Date: 7th oct. 2014

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Precast Concrete

Introduction to precast concrete

Types and procedure of precast concrete construction

Precast technology in residential building

Case study on the precast technology in Bandra worli

sea link (BWSL)

Research paper study on the future of precast

technology in law rise building

Video on manufacturing of precast wall

Video on installation of precast modular pavement

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Precast Concrete

Precast concrete is a construction

product produced by casting concrete in

a reusable mould or "form" which is then

cured in a controlled environment,

transported to the construction site and

lifted into place. In contrast, standard

concrete is poured into site-specific

forms and cured on site.

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History

precast paneled buildings were pioneered

in Liverpool England, in 1905

A process was invented by city engineer John

Alexander Brodie.

Between 1917 and 1932, they erected 145

such buildings

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Why Precast???

Speed to market

Strong image

High quality

Low maintenance

Effective pricing

Safety

Early input

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Why precast ?? As a

Project Manager Elimination of needs for supports / scaffolding

Elimination of temporary structures

Reduced health and safety risks

Reduction in lorry traffic and traffic management

Easier management of steel procurement

Elimination for long and continuous pouring operations

Significant reduction/elimination of temporary shuttering

Controlled curing of concrete

Improved quality controls performed at the factory

Process not subjected to weather conditions

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Precast concrete Products

Agricultural Products

Building and Site Amenities

Retaining Walls

Sanitary and Storm water

Utility Structures

Water and Wastewater Products

Transportation and Traffic Related Products

Modular Paving

Marine Products

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Raw Materials

Portland cement

water

Sand

Gravel

admixtures

For light weight

clay, shale, or slate

pumice and scoria blast furnace

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Design

The shapes and sizes of most common concrete blocks have been standardized to ensure uniform building construction.

block design, called a split-faced block, includes a rough, stone-like texture on one face of the block instead of a smooth face

we must consider not only the desired shape, but also the manufacturing process required to make that shape

We must consider the utility facility requirements in building during design

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Procedure for

precast

manufacturing

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Procedure for precast construction

Production of reinforced cages and main connections

Assembly of moulds

Mix being poured

Compaction of concrete using poker vibrator

Precast concrete being moved to the storage area

Storage of high-quality units in storage area

Transport to site

Erection at site

Finished building

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Production of reinforced cages and

main connections

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Assembly of moulds

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Mix being poured

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Compaction of concrete using poker

vibrator

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Precast concrete being moved to the

storage area

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Storage of high-quality units in

storage area

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Transport to site

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Erection at site

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Types of precast construction

Large-panel systems

Frame systems

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Large-Panel Systems

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

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Large panel

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Frame Systems

Precast frames can be constructed using either linear

Elements or spatial beam-column sub assemblages.

Precast beam-column sub assemblages have the advantage that the connecting faces between the sub assemblages can be placed away from the critical frame regions; however, linear elements are generally preferred because of the difficulties associated with forming, handling, and erecting spatial elements.

The use of linear elements generally means placing the connecting faces at

the beam-column junctions.

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Installation CONSIDERATIONS

All safety issues on site when handling precast elements,

especially so when working within a tight site

The lifting capacity of the crane used

The working boom-radius of the crane

The suitability of construction materials for the purpose of use,

i.e. sealant, grouting, shim plate, propping etc

Co-ordination with the precaster and specialist supplier to achieve the best performance and working method - precaster often provide relevant technical requirements to the contractor during the design development phase to avoid discrepancy

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Crane Position

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Setting Out

1. Surveyor to set cross reference.

2. Transfer grid and mark wall position on slab.

3. Mark 100mm offset line from rear building

edge.

4. Offset wall position by 200 mm.

5. Secure 2x2 timber to the floor at wall edge to guide wall.

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Setting Out

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Wall Positioning

1. The first wall in place has to be the partition wall

at the rear.

2. Mark a line parallel to and 100mm from the

external edge of the wall.

3. Place shim plate @~500 c/c on the floor and

level to wall soffit. Shim plate may also be

placed on Non-shrink mortar bed and allow to

set.

4. Adjust position of the dowel bar.

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Setting Out

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Wall Adjustment

1. Position adjacent walls and plumb wall corners

at 200 mm offset

2. Adjust verticality until within +2 or 2 mm

3. Ensure the four faces of every walls are

adjusted

4. Position string 250 mm from face of walls

5. Walls within the same line are to be adjusted

within same tolerance

6. Ensure air-pocket is fully grouted

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Wall Adjustment

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Beam Setting Out

1. Cast wall joint.

2. Mark 1 m reference line.

3. Confirm pocket level. Position shim plate to

correct beam soffit level if required.

4. Mark position of beam on floor.

5. Hoist beam in place and check top level.

6. Plumb beam to verify position on floor below.

7. Ensure beam verticality with a spirit level.

8. Wedge beam against pocket and grout the

gap between the beam and the wall.

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Beam Setting Out

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Slab Setting Out

1. Position the slab temporary supports and

adjust the slab soffit level approximately.

2. Raise the height of the supports about 5 mmabove slab

soffit level

3.Hoist slab in place on top of beam and support.

4.Verify level of every plank soffit at four corners

and center.

5. Adjust level of temporary support accordingly

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Slab Setting Out

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Staircase

1. Position landing or slab and verify soffit

level at four corners.

2. Adjust level to within tolerance.

3. Position shim plates at staircase support

location to correct level.

4. Verify level difference between pegs on

top and below.

5. Hoist staircase in place.

6. 10mm gap between precast plank andstaircase

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Staircase

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Installation Requirements

Elements of control

Alignment, Verticality and Levels

Tolerance level

1. For Wall

Vertical deviation +2 mm, -2 mm

Horizontal deviation 0 mm

2. For Beam & Slab

Departure from intended horizontal position, +2 mm or 2 mm

Departure from intended vertical position, +2 mm or 2 mm

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Connection types

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Columns Connection

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Beam-column connection

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Slab-Beam Connection

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CONSTRAINTS SOLUTIONS

! Small road in front of site may not !

allow crane and delivery trailers up to 3.Sm wide to

park.

Use smaller crane and trailers to deliver and

install small

components.

! Crane and trailer are unable negotiate small

turning radius junctions of small roads.

to ! Study the locality and look for at available space

for turning. Have one worker direct traffic while crane

and trailer is turning.

! Diversion of existing services such ! as

lamp-posts, fire hydrants and overhead electrical

cables may be necessary.

! Existing trees and shrubs in front ! of

site require National Parks Board

approval before they can

be removed and later reinstated.

Diversion must be done before installation of precast

components begins.

The consultants must write in to National Parks

Board for approval much earlier before construction

begins.

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Cost saving

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Time saving

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Time comparision

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Material saving

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Limitations

Each panel variation (especially openings, bracing inserts and lifting inserts) calls for complex, specialized

engineering design.

It is often more expensive than alternatives (can be offset by reduced construction times, earlier access by following

trades, and simplified finishing and services installation).

Building services (power, water and gas outlets; conduits and pipes) must be accurately cast in and are difficult to add or alter later. This requires detailed planning and layout at design stage when plumbing and electrical trades are not usually involved.

Erection requires specialized equipment and trades.

High level site access required

Panel connection and layout for lateral bracing requires detailed design.

Temporary bracing requires floor and wall inserts that have to be repaired

later.

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Research paper study

The Future for Precast Concrete in Low-Rise Housing

by. Dr Jacqueline Glass (BA (Hons), Dip Arch, Dip BRS, Phd, CertHE.)

Dr Jacqueline Glass is the British Cement Association Senior Lecturer in the School of Architecture at Oxford Brookes University where she has been carrying out research in concrete construction since 1994. Dr Glass is currently Project Manager of an EPSRC funded research project in innovation in reinforced concrete and has previously contributed to Partners in Technology projects on tilt-up and hybrid concrete construction. Dr Glass is Architectural Consultant to the British Cement Association and the Reinforced Concrete Council and is an active participant on several concrete industry trade associations. She has published widely in both trade journals and scholarly publications and has lectured in the UK and USA on a broad range of concrete related topics.

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The Future for Precast Concrete in

Low-Rise Housing

This report is about the future use of precast concrete in low-rise housing in the UK. It has been produced in response to a growing level of interest in prefabrication.

focuses on the use of precast concrete, and considers the history of precast concrete in housing

examines the key features of concrete in general, and precast concrete specifically. Fire resistance, thermal mass, acoustic insulation and durability are included together with a discussion of cost and value issues

considerations such as services integration and adaptability are related to the future needs of occupants, and procurement strategies are noted.

Report also contains an account of the current market success of

other materials in the prefabricated housing sector

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Conclusions and recommendations

1. The problems of the past can be avoided

2. Low-rise is not high rise

3. Cultural and perceptual views are critical

4. The market potential for precast concrete exists

5. The balance of cost and value needs to be clear

6. Precast means innovation in delivery

7. People need to be convinced

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Case study on

Precast deck of

BWSL

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Why precast segmental deck????

Total length : 5.6 kilometres

Width : 2 x 20 meters (66 ft)

Height :126 meters (413 ft)

Longest span :2 x 250 meters (820 ft)

Clearance below :20 meters (66 ft)

The Maritime Board does not allow marine traffic in monsoon

season.

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Decision for precast segmental

construction

800m long Precast Segmental Approach Bridge on

Bandra Side.

200m long Precast Segmental Approach Bridge between Bandra Cable Stayed Bridge and Worli Cable Stayed Bridge.

1400m Precast Segmental Approach Bridge on Worli

Side.

811m long link to Khan Abdul Ghaffar Khan Road

comprising 510m Precast Segmental Bridge and

310m Cast-in-Situ Bridge.

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SAGMENT PARAMETERS

a hollow concrete box section with 3 cores

Length:1.5m to 3.1m.

post tensioned

slender and lightweight deck is to reduce the longitudinal

stiffness

pre-casting yard using short line method

A typical 50m span comprises of 15 numbers of precast

segments, a Pier segment and 200mm (nominal) in-situ wet

joints

8 cells to makes all the different types of segments.

centralized pre-casting yard using short line method of casting

Sophisticated software for correct casting curves

A complete construction of a segment takes about a month (20

to 30 days)

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Segment Construction Procedure

survey team sets the bulkhead, the rebar setup

takes place

After rebar setup is done, the concrete is poured in the

formwork

initial tensioning about 30% of its maximum capacity

After strength of about 40Mpa final testing with rest of

the 70% load

Shifted to store at yard

Transported by trailer truck to site

Transported by barge in the sea

Erection by gantry

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Connection of male-female segment with wet concrete

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equipments which deployed in

the pre-casting yard

1) Hydraulic Jacks of different capacities

2) Turn Buckles

3) Gantry, for lifting segments

4) Tower Crain

5) Concrete Pumps

6) Cutting and bending machines for rebar of

segments.

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Formwork and rebar setup

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A segment being cast and its conjugate

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Casting Yard

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Erection of segment

The precast concrete sections of the deck were launched incrementally between the pillars using a truss system, known as the balanced cantilever method

The two segments are being linked through a male-female joint, in the meanwhile the casted segment is allowed to gain strength and also its curing is done side by side.

The precast sections were then epoxied together and given a certain degree of pre-stress to hold them in place

Once each span had completed and geometrical adjustments made the primary continuous tendons were stressed to the required level.

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Equipments which deployed in the

erection

Launching Truss: Weighing 1250 tonnes and measuring 112 m in length, it was used for lifting segments each weighing 130 tonnes. This has been fabricated in India.

Flat barge: Size 30x12x2m. Like motor boats, they are driven inside the sea for material transportation.

Self-propelled barge: It is a barge with a machine component and is

used for concrete transportation.

Crawler crane: Capacity ranges from 75-150 tons. It is used for material and heavy lifting activities. 13 barges for concrete

eight steel boats

three tug boats

six smaller passenger boats.

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The Erection Gantry

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Erection of segment

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Challenge of Ground Stabilisation for Pre-Cast Yard

located on reclaimed land

yard caters to casting, storing and handling of pre-

cast Segments

numbers of segments 2342

The storage capacity of yard 470nos.

Area is limited, the segments stored in three layers.

The bearing capacity of the ground was was very

poor to less than2 T/Sqm.

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Solution

Excavation of the ground to a depth of ~

2.5Mtrs.

Strengthening the ground using rubble soling

and filling the voids with sand.

The soling thus done was compacted layer by

layer using vibratory rollers.

Total area of the Pre-cast Yard was covered with

a layer of PCC.

RCC Footing done to facilitate storing of

segments.

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Challenges for project manager

The superstructure of the approach bridges was the heaviest spans in the country to be built with span-by-span method using overhead gantry through a series of vertical and horizontal curves.

Erection of 20000 MT Bandra cable-stayed deck supported on stay cables within a very close tolerance of deviations in plan and elevation.

Navigation and transporting 19 precast segments in 24

hours at different open sea locations was a challenge.

How to move the large truss from the Bandra end of the bridge to the Worli end without having to dismantle the truss which would be too time consuming on such a high profile structure with a strict timescale.