The Beipanjiang Bridge on the Bijie-Duge Expressway is a two-pylon seven-span steel truss girder cable-stayed bridge with a main span of 720 m.The main girder is a composite system formed of steel truss girders and orthotropic steel deck plates.According to the special con-struction condition in the mountainous region,the steel truss girder takes the steel plate-truss composite system in w hich the orthotropic steel deck plates also contribute to the load bearing ca-pacity of the bridge.The spatial shell-link finite element analysis method was used in the calcula-tion,which automatically takes into account of the effective distribution width of the orthotropic steel deck plates.The fabrication,transportation and erection of the steel truss girders and the deck plates follow the principle of dividing the w hole components into individual elements before-hand and then assembling the individual elements to be whole components.And a supporting floor beam system for the orthotropic steel deck plates in a plate-truss composite system was proposed for the first time.The webs of the upper and secondary floor beams are connected to the lower flange and the main truss by high-strength bolts and the steel deck plates were connected by full penetration butt welding.According to the characteristics of the bridge site,the side spans was constructed by incremental launching and the central span by the cantilever assembly method with derrick crane.The methods used helped resolve the complexities in the construction of long-span steel truss girder cable-stayed bridge in the mountainous region.%毕都北盘江大桥为主跨720 m的双塔七跨钢桁梁斜拉桥,主梁采用钢桁梁与正交异性板组合的结构体系.结合山区特殊建设条件,钢桁梁选用正交异性钢桥面板参与受力的板桁组合结构体系;计算分析采用了空间板壳 -杆系有限元分析方法,自动考虑正交异性钢桥面板的有效分布宽度;钢桁梁及桥面板的制造、运输和架设采用"化整为零、集零为整"的方式,并首次提出正交异性钢桥面板横梁支撑体系;上横梁和次横梁的腹板及下翼缘板与主桁之间采用高强度螺栓连接、桥面板全熔透对接焊的栓焊混连;钢桁梁施工因地制宜采用边跨顶推、中跨桥面吊机悬臂拼装的架设方案,解决了山区特大跨径钢桁梁斜拉桥施工难题.
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