转体跨越运营高铁钢桁梁施工关键技术

Rotation Construction of Steel Truss Girder over In-Service High-Speed Railway

廊坊光明桥为(118+268+118) m上加劲连续钢桁梁桥,上跨多股既有线,与既有京沪高铁交角33°。钢桁梁采用转体法施工,拼装跨度为京沪高铁侧(119+138) m、西牵出线侧(130+119) m,采用带辅助滑道的简支梁体系非对称转体方案。施工过程中,与铁路平行位置采用独柱式拼装支架和带转向功能的龙门吊拼装钢桁梁,京沪高铁侧钢桁梁远离设计转体位置15 m进行拼装,西牵出线侧钢桁梁向边跨预偏30 cm拼装;京沪高铁侧钢桁梁拼装完成后横移至设计转体位置;钢桁梁同步落梁至主墩;采用带大悬臂的简支梁体系进行转体,辅助滑道采用轴承式滚动走行系统;转体后,西牵出线侧钢桁梁利用墩顶特殊设计的永久支座向跨中纵向顶推30 cm;在铁路限界上方采用全封闭防护小车进行合龙施工。该桥多次体系转换施工累积误差可控,成桥精度与设计吻合,确保了高铁运营安全。

The Guangming Bridge in Langfang is an upper-truss stiffened continuous girder bridge with a main span of 268 m and two side spans of 118 m.The main span crosses multiple existing railways,being a 33° skew with the existing Beijing-Shanghai High-speed Railway.The superstructure made up of steel trusses was constructed by a rotation method.The steel trusses were assembled to be a(119+138) m structure(Beijing-Shanghai High-speed Railway side) and a(130+119) m structure(west access road side),and the construction was actually an asymmetrical rotation construction of a simply-supported girder system with auxiliary sliding tracks.On site,a mono-columned assembly support and a gantry crane capable of steering were placed at the location parallel to the railway to assemble the steel trusses.The steel trusses on the Beijing-Shanghai High-speed Railway side were assembled at a location 15 m away from the design rotation location,while the steel trusses on the west access road side were pre-offset by 30 cm towards the side span for assembly.Once the steel trusses on the Beijing-Shanghai High-speed Railway side were all assembled,the whole structure was transversely moved to the design rotation location.The steel trusses were synchronously lowered onto the main piers.The superstructure rotated was actually a simply-supported girder system with long cantilevers,the steel truss structure on the west access road side was pushed 30 cm longitudinally towards the midspan via the tailored pier-top permanent bearings.Over the railway boundaries,the fully-closed trolleys were used for closure construction.Though the bridge experienced several times of system transformation,the accumulated construction errors were still under control,with accuracy after completion of the bridge meeting the design level,and the operation safety of the high-speed railway was also ensured.