For bridge decks greater than 250m in length, the method of incremental launching can be considered. With this method of construction the bridge deck is built in sections by pushing the structure outwards from an abutments towards the pier. It is most suited to the rapid construction of bridges with a constant radius of curvature such as constant depth of box girder segments.
Incremental Launching Method of Bridge Construction
The construction sequence begins behind one abutment where a highly mechanized prefabrication deck mould is set up removing the need for temporary supports with this method. A rigid framework is then attached enabling the production of cast-in-situ segments. In-situ deck segments range in length from 5m to 30m. when each segment is complete it is placed on sliding bearings and pushed through into the span.
A steel nose is also positioned at the front of the first span formwork. This allows for the necessary deck cantilever length as the span approaches the first pier.
Bridge decks of 1km can be built by this method with a rate of construction of 30m per week.