自锚式悬索桥边跨钢箱梁跨既有铁路施工技术

Construction Techniques for Side-Span Steel Box Girder of a Self-Anchored Suspension Bridge Crossing Existing Railway

重庆轨道交通环线新鹅公岩长江大桥为主跨600m自锚式悬索桥,主桥桥跨布置为(50+210+600+210+50)m,主梁采用钢—混凝土混合梁。大桥西岸边跨钢箱梁跨越既有成渝铁路,为减少对既有线运营的影响,提出了低位滑移+双悬臂吊装和高位顶推2种施工方案,通过安全风险、对既有线运营的影响及经济性等方面的比选,确定采用高位顶推施工方案。高位顶推是在桥塔旁搭设钢箱梁拼装支架兼做初始顶推平台,在边跨搭设顶推支架,将钢箱梁节段船运至桥塔旁,利用架梁吊机从主跨侧起吊、拼装,通过同步系统控制,采用步履式顶推器逐节段向边跨侧顶推。跨既有线施工时,一次顶推使钢导梁跨越既有铁路。

The new Egongyan Changjiang River Bridge on the Chongqing rail transit line is a self-anchored suspension bridge with a main span of 600 m.The main bridge is arranged in spans of （50＋210＋600＋210＋50） m, with steel-concrete hybrid girders.The side-span steel box girders on the west bank cross the existing Chengdu-Chongqing Railway.To reduce the influence of construction on the existing railway, two construction schemes of low-level sliding plus double-cantilever lifting and high-level incremental launching were proposed.The latter was finally chosen based on the comparison of the schemes from aspects of safety risk, influence on the operation of the existing railway and economic effect.For the high-level incremental launching, the scaffoldings for steel box assembly, which could also be used as initial incremental launching platform, were installed next to the bridge towers.The supports for incremental launching were erected at the side spans.The steel box girder sections were shipped to the towers, lifted from the main span side and assembled by overhead gantry, and the process was controlled by the synchronous system.The incremental launching progressed segment by segment from the side span using walking pushers.During the construction over the existing railway, the steel launching nose was pushed only once to cross the existing railway.