五峰山长江大桥上部结构施工控制技术

五峰山长江大桥主桥为主跨1 092m的钢桁梁公铁两用悬索桥,加劲梁采用板桁结合钢桁梁,主缆采用预制平行高强钢丝索股结构,直径1.3m。边跨加劲梁采用支架顶推法施工,中跨加劲梁采用缆载吊机由跨中向两侧对称架设,并在中跨侧靠近桥塔位置处合龙;主缆采用平行钢丝索股法架设。主缆制造时,采用无应力长度法计算各索股的无应力下料长度,并在主缆锚固区每处预留长度为±26cm的垫板空间;主缆架设时,采用4根索股作为基准索股进行架设线形控制,并将主缆长度误差控制在-18～30cm,均在误差控制范围内;加劲梁施工时,通过分析各因素对加劲梁线形的影响规律,提出控制二期恒载的措施;加劲梁合龙时,采取中跨钢梁不动、起顶边跨钢梁的合龙控制措施;在加劲梁合龙后加载二期恒载。加劲梁合龙后标高误差为-5～+63mm,线形控制较好。

Control Techniques for Superstructure Construction of Wufengshan Changjiang River Bridge

The main bridge of Wufengshan Changjiang River Bridge is a steel truss girder suspension bridge with a main span of 1092 m and carries both highway and railway traffics.The stiffening girder adopts the plate-truss composite structure.The main cables are made of parallel prefabricated high-strength steel wires,with a diameter of 1.3 m.The girders in the side spans are erected by the incremental launching method with the assistance of scaffoldings,while the girders in the central span are erected by cable cranes,proceeding symmetrically from the midspan towards the two ends.The stiffening girder is closed in the central span,near to the towers.The main cables are erected by the PPWS method.During the manufacturing of the main cables,the unstressed spreading length of each strand is calculated by the unstressed length method,and a space of±26 cm is reserved at each anchor zone of the main cable for pads.Four strands are taken as the benchmark strands to control the geometrical shape of the main cables in the erection process.so as to limit the length errors of main cables within the range of-18 to 30 mm,which all satisfy the error control requirements.The measures to control the secondary dead loads are proposed based on the analysis of the influence law of different factors on the geometrical shape of the main cables in the construction process.During the closing process of the stiffening girder,the girders in the central span are kept still and the girders in the side spans are jacked up.After the closure of the stiffening girder,the secondary dead loads are applied.The elevation error of the stiffening girder after closure is of-5 to 63 mm,resulting in good girder geometry.