Incremental Launching Construction of a Long Span Bridge with Continuous Steel Truss Girder and Flexible Arch

The South Feihe River Railway Bridge is a long span structure with continuous steel truss girder and flexible arch constructed by the incremental launching of the truss girder with the arch.For the launching of the girder with the arch,the construction equipment,principal construction load cases and the related key construction techniques were analyzed.To realize the smooth launching,the auxiliary steel structural systems of the assembling scaffoldings,auxiliary piers and launching nose were arranged in the construction and the launching was carried out,using the multi-point concurrent launching and the integrated machinery,electrical power and hydraulic principle.The launching of the girder with the arch mainly included four load cases of the multi-point launching of the girder to its longest cantilever;the launching of the girder with the arch before formation of the complete flexible arch system;the closure of the flexible arch spring and the final launching of the girder with the arch in place.The software MIDAS Civil was used to establish the model and to conduct the analysis of the launching and according to the results of the analysis,the necessary measures were taken to realize the key construction techniques for the launching,reaching of the launching nose to the front piers and unstressed closure of the arch spring.At the same time,the construction monitoring and control techniques were applied to ensure that the internal forces,stress and geometric shapes of the completed bridge could be accordant with those of the design.