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 J3J4

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