What are two methods to install simply supported concrete girders segments?

For segmental assembly beam launcher, there are two methods to install simply supported concrete girders segments. One is full span precast girder segments assembly, the other is balanced cantilever method.

overhead beam launcher

Full span precast girder segments assembly method refers that upper structure installs segments to one direction; one span is finished every one time, suitable for simply supported concrete girders. After precision casting concrete segments by ‘matched casting’ method are transported to proper position, suspender of beam launcher (overhead beam launcher) or temporary jack on the main girder (underslung beam launcher) lifts the whole span segments, then coat epoxy resin on the joints, use temporary pre-stressing force to tight the segments, penetrate permanent pre-stressed tendon, and then put the whole span on the support base. The beam launcher moves to next span to continue work with above method. Full span precast girder segments assembly method is more suitable for variable upper structure, such as horizontal and vertical curved bridge.

Segmental assembly beam launcher

Balanced cantilever method is suitable for continuous girders installation, which regards one pier as the centre and installs girder segments symmetrically to two sides. Every segment being connected together with installed segments is regarded as the assembly base for next segment, balanced. For every construction step, cantilever structure can keep safe and stable by tensioning pre-stressed steel tendon in the box girder segments. Girder segments lifting can be finished by bridge deck support crane, guide beam or terrain crane. Main advantage of balanced cantilever method is to greatly reduce the use of scaffoldings and save space below the bridge, thus it is quite suitable for crowed downtown and river where demands not interrupt transportation and shipping.