NOVEMBER 2012

CASE STUDY OF BRIDGE FORMWORK

IntroductionFORMWORKIt is a structure which is usually temporary but can be whole or part permanent, it is used to contain poured concrete and other such materials to mould in into required dimensions and support until it is able to support itself.

Requirements of formwork

Strength

Rigidity

Less leakage

True to size

Smooth surface

Easy removal

Supports

ECONOMY IN FORMWORK

Forms of regular sizes and shapes

Allow reuse

Design structural components to allow use of commercially available forms

Clean and oil forms after use

Pre-fabricate the forms on the ground

MATERIALS FOR FORMWORK

Steel

Timber

Plywood

FORCES ON FORMWORK

Dead load

Live load

Vertical loads

Lateral pressure

Lateral loads

Special equipment loads

Other loads

CASE STUDY ON GOTA FLYOVER

DETAILS OF FORMWORK

LAYOUT OF MIDDLE SPAN PEIR

FORMWORK ON MIDDLE SPAN

J4 J3 J2 J1

J4 J3 J2 J1

25M

50M

ARRANGEMENT OF PRIMARY BEAMS

ARRANGEMENT OF TIE ROD

TRUSSEL

PRIMARY ISMB

SECONDARY ISMB

OVERLAPPING OF ISMB

Tie rod are used to hold shuttering so that is does not collapse during concreting. It has two wooden blocks connected with a rod for tightening arrangement.

JACK

Jacks are used to provide flexible arrangement over the trussels so that it can be easily removed during de-shuttering. During construction of pier wooden blocks are kept so that after concrete sets up, the wooden block is burnt so that formwork can be removed easily.

Jacks should be strong enough to withstand the dead load of concrete so they are made of steel,

Formwork for RE-Walls

Precast RE-walls were constructed on site with the help of above formwork. Here mild steel formwork is used for construction.

Both the approach roads were constructed using precast RE-walls.

SHUTTERING ON RE-WALLS

After erecting RE-walls cress barrier is constructed using ply shuttering and held with the help of tirods.

SHUTTERING

CASE STUDY ON FLYOVER NEAR ELLIS BRIDGEThe floyover starts from ellis bridge crossroads and extends up to Gujarat college road. Due to heavy congestion of traffic at ellis bridge crossroads, need was felt to build a flyover that would help in reducing the traffic congestion and travel time which in turn would reduce traffic accidents.

We observed mainly formwork erection of pier cap and bridge slab. During the visit at site, construction of pier was going on. The following are the main components of formwork for flyover

1. Steel Truss The most used component in formwork. It is made up using steel panels. Dimension of each panel are 1.5’x1.5’ It is responsible for transferring the entire load to foundation.

2. CLAMPING OF STEEL SUPPORT USING I-SECTION AND BOLT

Diameter of bolt is 12mm .

3. ERECTION OF STEEL SHUTTERS FOR PIER CAP Steel Shutters are erected on the edge of pier. The shutter assembly has holes on the edge which are to be fixed using bolts.

4. Connection between pier and steel shutter using bolts

5. SUPPORTING MECHANISM Steel truss props are laid. Over them, I sections are placed. Adjustable rods are placed between I-sections and Steel Shutters

Formwork for Bridge Slab

1. Inverted N-TYPE truss used above the steel supporting member

N-TYPE truss is placed above the supporting member.

2. I sections placed over N-TYPE I sections transfer the load to N-type truss. Over the I sections STEEL SHUTTERS are erected Steel shutters have box sections behind them for support. The final view after erection of steel shutters from below the bridge is as shown

in picture.

In case of curved portion of pier, above the I-section

BOTTOM VIEW OF CURVED SURFACE

ULTIMATE VIEW OF BRIDGE SLAB