CONSTRUCTION METHODOLOGY FOR BRIDGE WORKS

        The entire work on bridges will be divided in groups and will be carried out in a phased manner as per construction programme. Work on Various components of bridge structures will be carried out as follows

FOUNDATION

OPEN FOUNDATION

Excavation will be done by excavator/manually as per the requirement. For deep excavation, sides will be protected by timber shoring. Dewatering will be carried out by using suitable no. of pumps. PCC will be laid after reaching to the foundation level. Foundation will be cast after fixing reinforcement with proper shuttering arrangement.

PILE FOUNDATION

            Boring will be done by Hydraulic piling rig / conventional method. After reaching the founding depths, bore will be cleaned. Bore sides will be stabilized against collapsing by providing temporary MS liner and bentonite circulation. Reinforcement cages will be prefabricated in suitable lengths of about 10m. These will be lap welded at site and lowered in to the bore with the help of mobile crane / winch. On placing the reinforcement cage, tremmie pipe elements will be assembled and lowered inside the cage. The bore will be then concreted by termmie method. The tremmie segments will progressively be withdrawn during the process of concreting.

PILE CAP

        The pile cap will be cast by conventional method. Concrete will be fed from centrally located batching plant and transported by transit mixer to location. Concrete will be directly poured from transit mixer or by placer.

SUB STRUCTURE

Abutments, Pier and Pier Cap:

Steel formwork will be designed to suit the Abutment, pier and pier cap dimensions. The Abutment, pier will be cast in suitable lifts. Steel brackets/scaffolding pipes will be used to cast Abutment, pier caps.

SUPER STRUCTURE

Solid Slabs

The super structure consists of construction of cast in-situ solid slabs.

The superstructure will be cast-in-situ by conventional method. Suitable foundation will be constructed for trestles. The formwork will be supported over cross beams, longitudinal beams and trestles. After fixing and checking of reinforcement concreting will be carried out.

The sequence of the casting is as follows:

Ø Erect the supporting arrangement including the formwork.

Ø Fix the reinforcement.

Ø Concrete the slab.

Ø Lower the soffit shutter and remove the same after concrete attains required strength.

Ø Remove the cross girders and main girders.

Ø Remove the trestles.

Ø Shift the supporting arrangement for casting of next span.

Cast in-situ T-beams with slabs.

The Superstructure consists of construction of cast in-situ T-beams and deck slab.

          The sequence of the casting is as follows:

Ø  Erect precast RCC footings at required location as per drawing

Ø  Erect staging pipes / trestles over footings. Provide bracings.

Ø  Place longitudinal and cross beams over staging pipes / trestles.

Ø  Place the reinforcement for beams & deck slab

Ø  Concrete the Beam & Deck slab.

Ø  Lower the soffit shutter and remove the same after concrete attains required strength.

Ø  Remove the cross girders and main girders.

Ø  Remove the staging pipes / trestles. Shift the supporting     

          arrangement to the next span.

Cast in-situ PSC-Beams

The superstructure consists of construction of cast in-situ PSC beams.

PSC girders will be cast in-situ over the steel girder assembly. Thereafter precast girder will be side shifted to actual location. The formwork will be designed and fabricated to suit the shape of PSC girders.

          The sequence of the casting is as follows:

Ø  Erect precast RCC footings at required location as per drawing

Ø  Erect trestles over footings. Provide bracings.

Ø  Place longitudinal and cross beams over trestles.

Ø  Place the reinforcement for beams.

Ø  Concrete the beams.

Ø  Stress the cables after concrete attains required strength and side shift the beam to its actual location.

Ø  Place deck reinforcement.

Ø  Concrete the deck.

Ø  Lower the soffit shutter and remove the same after concrete attains required strength.

Ø  Remove the cross girders and main girders.

Ø  Remove the trestles. Shift the supporting arrangement to the next 

          span.