上跨铁路下承式钢系杆拱桥设计与施工

Design and Construction of Through Steel Tied Arch Bridge Crossing over the Existing Railways

上海市北横通道工程上跨上海火车站机务段和轨道交通3、4号线时,由于铁路与轨道交通之间无法设置桥墩,需一跨跨越。新建桥紧挨既有桥,需与既有桥桥面高程保持一致,结构高度受到限制,因此采用76 m下承式钢系杆拱桥。钢系杆拱桥采用单片拱肋,主梁为单箱三室断面,采用步履式顶推施工。新建桥顶推到位后,切割既有桥人行道板,安装新建桥的翼缘板。介绍该钢拱桥的结构设计特点、新老桥之间的接缝处理、顶推施工方案;建立空间有限元模型,对结构整体受力、整体稳定、疲劳、局部受力和顶推施工阶段受力进行计算分析。结果表明:在平面位置和高程受到限制时,采用单拱肋下承式钢箱梁系杆拱桥是较好的解决方案;上跨铁路钢系杆拱拱桥采用步履式顶推施工,对铁路安全影响较小。

As the north cross passage project of Shanghai crosses over the depot of Shanghai Railway station and rail transit line 3 and line 4,a single span bridge is only required due to the impossibility to set bridge piers between the railway and the rail transit.The new bridge,which is close to the existing bridge,needs to be consistent with the elevation of the existing bridge deck,and its structural height is limited.Therefore,a through steel tied arch bridge with a span of 76 m is used.Single arch rib is adopted for the steel tied arch bridge,the main girder has a single box section with three cells,and stepped incremental launching construction method is employed.After the new bridge is pushed in place,the sidewalk slab of the existing bridge is cut and the flange slab of the new bridge is installed.This paper introduces the structural design features of the steel arch bridge,the joint treatment between the new and old bridges and the incremental launching program.The spatial finite element model is established to calculate and analyze the overall stress,overall stability,fatigue,local stress and force during incremental launching construction.The results show that the single arch rib through steel box girder tied arch bridge is a better solution in the case of limited plane position and elevation,and the stepped incremental launching construction has little impact on railway safety.