What is working cycle of highway overhead launching gantry?

The overhead launching gantry for highway adopts full span method to install precast girders.

The working cycle of the highway overhead launching gantry is as follows:

1. The full span bridge girder is cast in a special fixed formwork in the pre-cast yard, stressed and cured.
2. The pre-cast girder is lifted from the formwork by means of either a gantry crane or a special straddle carrier. The pre-cast span can also be moved out of the formwork by using special trolleys placed at the bottom of the formwork.
3. The pre-cast girder is loaded onto the multi-axle girder carrier.
4. The girder carrier transports the bridge girder over the previously erected span to the rear part of launching gantry, which is positioned at the span to be erected next.
5. The overhead launching gantry lifts the pre-cast girder.
6. The pre-cast girder is then lowered slowly to proper position and the hanging devices are then released. Meanwhile, the girder carrier returns to pre-cast yard.
7. The overhead launching gantry is now ready for the self-launching phase. Temporary rails are laid on the recently placed span and the machine is launched to another span.