重庆鹅公岩轨道大桥设计关键技术

Key Design Techniques for Egongyan Railway Transit Bridge

重庆市鹅公岩轨道大桥位于既有鹅公岩大桥上游70 m处,主桥采用(50+210+600+210+50)m半飘浮体系自锚式悬索桥。加劲梁采用钢箱-混凝土混合梁,中跨及边跨为钢箱梁,锚跨及锚固段为混凝土箱梁。桥塔采用门形结构,按全截面受压构件设计。主缆采用PPWS平行钢丝索股,布置为平行双缆面,中心距为19.5 m。全桥边、中跨均设吊索,吊索采用PSS平行钢丝束,上端与主缆索夹采用销铰式连接,下端与加劲梁采用锚箱承压方式连接。2个桥塔单幅承台下均布置9根φ3.0 m钻孔灌注桩。通过在主缆锚固横梁上增设竖向隔板和水平隔板将锚固箱室分成4个小舱室,以优化锚固横梁受力。对该桥总体及局部稳定进行分析,结果表明:桥梁总体及局部稳定均满足相关规范的要求。由于建设条件的限制,该桥开创性地运用“先斜拉后悬索”的方案施工。

The Egongyan Rail Transit Bridge in Chongqing is located 70 m upstream of the existing Egongyan Bridge,the main bridge of which is a self-anchored suspension structure of a semi-floating system,with five spans of 50,210,600,210 and 50 m.The stiffening girder incorporates the steel boxes in the central and side spans and the concrete boxes in the anchor spans and the anchor sections.The towers are portal-frame structures,designed as full-cross-section compressive components.The main cables,composed of steel wire strands installed by PPWS method,are arranged in parallel with center-to-center distance of 19.5 m.The side and central spans all have hanger cables comprising parallel steel strands.The hanger cables are connected with the main cable clamps via pin connection,and anchored to the stiffening girder by anchor boxes.The two legs of the tower have separated pile caps,beneath each pile cap are 9,φ3.0 m bored piles.Vertical and horizontal diaphragms are added on the anchor cross beams to divide the anchor chamber into 4 cells,with the intention of optimizing the load bearing capacity of the anchor cross beams of the main cable.The results of analysis show that the global and local stability of the bridge meets the related code requirements.Restricted by the built conditions,the bridge was constructed first as a cable-stayed structure,and then transformed to be the final suspended structure,which is an innovation in bridge construction.