Walking-Type Bidirectional Incremental Launching and Mid-Span Closure Technology for Steel Box Girders with Long Cantilevers

Unidirectional incremental launching is not applicable for the incremental launching construction of large-span bridges owing to the span capacity of steel box girders is restricted by the cantilever length and the setting of temporary piers. Aiming at the limitation, by taking Qingdao (Shandong Province)-Lanzhou (Gansu Province) expressway bridge crossing over the main canal in the South-to-North Water Diversion Project as the engineering background, a key construction technique, that is, bidirectional incremental launching and mid-span closure of steel box girders with long cantilevers was proposed. On this basis, the walking-type incremental launching device system and the technique of bidirectional incremental launching and mid-span closure were explored and also a finite element analysis model was established to compute the pre-camber. Moreover, the results of the alignment control of structures during the construction were compared and analyzed. The research result showed that during the construction using bidirectional incremental launching and mid-span closure, it was unnecessary to set the steel launching nose and it was able to greatly improve the span capacity of steel box girders and the construction efficiency during incremental launching. The research provides reliable experience in engineering practice for the future similar engineering.