METHODOLOGY FOR PSC GIRDER LAUNCHING FOR BRIDGES

 

 PSC GIRDER LAUNCHING FOR BRIDGES

Purpose of Methodology is to furnish of safe launching system for PSC Girder (40-50 M.T. ) with a objective to construct Deck slab of Bridge/ Flyover. It is assumed Bearing Pedestals are finished as per drawing. Neoprene Bearing is in position. 

 

Equipment & Machinery –

1. Lattice Boom crane – 2 No. of 50/60 MT capacities with suitable Boom Length.
2. Wooden Sleepers of required sizes.
3. High Strength Rope of dia ¾  Inch with suitable Length.
4. Welding Machine – 1 No
5. Re bar pieces / Shim plates

• Sequence of launching.

1.   Arrangement on pier cap

The gaps between pedestals should be filled with suitable thickness of wooden sleepers and up to height of so bearing so that girder can be directly placed over bearing without disturbing the position of Bearing.

2.   Positioning the cranes

Both the crane has to be positioned adjacent to the pier caps, with leaving 4mt approach road for the movement of trailer.

3.   Lifting of Girder

At both the ends from where we have to lift the girder from trailer, suitable wire rope ceiling is required to be tied with embedded wire rope hook of the pre-cast girder with suitable D-shackle.

At both the ends, 4 nos. of High Strength rope (2 no at each end) has to be tied with the dowels of diaphragms bar of suitable length to control the swing of girder. All the 4 ends of High Strength rope should be handed over to 4 nos of Riggers.

 Now after proper tying both the crane will be signalled to lift the girder from trailer. Once girder leaves the trailer bed, trailer will be signalled to make a forward move. Now Crane will be signalled by the Forman to bring down the girder just 1 mtr above the ground level.

4.   Shifting of girder

      Now both the crane will be signalled to make March towards the pier. Once both the                cranes reaches to pier both should be signalled for lifting up to 1mtr above pier cape                pedestals. Again both the crane will be signalled to make a march simultaneously so that        girder comes just above the pedestals.

5.   Placing of girder

Now after required slight movement of crane boom/swing (separately one by one ) girder has to bring just over Bearing. Now girder will be allowed to keep directly over the bearing. Once it is assured that girder position over bearing is as per drawing, sling tied at both end will be allowed to remove.

6.   Safety arrangement 

Entire launching location shall be protected for the movement of public.

After placing End girder Intermediate girder has to be placed. Now both the End girder and Intermediate girder has to be temporarily welded at 3mtr interval with suitable length of reinforcement bar to give frame formation (Cross Bracing) . This process has to be repeated till completion of span launching.

Note –

1. The path of movement should be checked by moving the empty crane two to three times to ensure firmness of the ground.
2. Activity of both the crane has to be synchronized with one and only one signalling Commander. Preferably In charge of launching
3. Before Starting of work Crane capacity  and fitness/Calibration  certificate has to check. After every Girder Launching Nut & Bolt of Crane Boom,Belt should be examined thoroughly.