A SITE VISIT REPORT ON FLYOVER

FLYOVER

Site details:

Name of work: - Construction of 6 Lane Flyover bridge at k.m. 30/650 at Gota

Junction of N.H. - 8C in the state of Gujarat

Name of Agency: - M.S. Khurana Engineering Ltd.

Sanctioned Amount: - ₹ 22,04,90,906

Date of Starting: - 21-10-10

Date of Completion: - 20-01-12

Specification: - Bridge Work : 3 Span

Centre Span: - 50 m.

End Span: - 25 m.

Approaches: - G.L with R.E. Wall

Slip Roads: - 7.5 m. wide

Site Visit Purpose:

To study the Post tensioning method of prestressing adopted on the site.

Post Tensioning:

Bonded type Post tensioning system was adopted

M-50 Grade Concrete was used

The prestressing was carried out in two stages:-

o 1st stage:- After the concrete has gained 70% of the designed compressive

strength

o 2nd

stage:- After the concrete has gained 90% of the designed compressive

strength

19DP13 Prestressing system was adopted and multi-pull hydraulic type jack was used

for prestressing.

The prestressing cables adopted were 7 ply uncoated stress relieved low relaxation

strands with nominal diameter - 12.83 mm.

FORMWORK

It 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

DETAILS OF FORMWORK

LAYOUT OF MIDDLE SPAN PEIR

J1 J2 J3 J4

J4 J3 J2 J1

25M

50M

FORMWORK ON MIDDLE SPAN

ARRANGEMENT OF PRIMARY BEAMS

TRUSSEL

SECONDARY ISMB

PRIMARY ISMB

OVERLAPPING OF ISMB

ARRANGEMENT OF TIE ROD

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

GEOSYNTHETICS

Polymers used in Geosynthetics

Chemically linked large molecules of carbon atoms with hydrogen or other atoms attached

Polypropylene

Polyethylene

Polyester

Polyamide

Polyamide

Poly vinyl chloride

TYPES OF GEOSYNTHETICS

1. GEOGRID 2. GEOTEXTILES

3.GEONETS 4. GEOSYNTHETICS CLAY LINER

5. GEOMEMBRANES

APPLICATION OF GEOSYNTHETICS

I. Increasing Safe Bearing Capacity of soil :

Geosynthetics material is used as a reinforcing material where the soil

condition is not good

II. Subsurface Drainage system :

Geotextiles : Acts as a filter to allow fluids to pass while preventing the

migration of soil particles

III. Erosion and Sediment control in dam :

Geotextiles : Prevents the erosion of soil particles due to high energy water

flow and is used at the u/s face bottom of dam

IV. Construction of roads and pavements :

Geotextiles : Prevents the intermixing of soft foundation soils with granular

materials thereby maintaining the structural integrity and drainage capacity of

the granular material

V. Reinforced Steepened slopes :

Geogrids : Acts as a reinforcement to maintain the stability of soil by carrying

tensile loads

GEOGRID AT GOTA FLYOVER

Geogrid is used along the length of the approach road of the flyover and the material

of 1.2m width is used along the total approach road of the flyover

The distance between two Geogrid is 800mm and the soil between them is compacted

in 4 layers