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