洞庭湖主跨406m三塔铁路斜拉桥设计关键技术

Key Techniques for Design of Dongting Lake Three-Pylon Railway Cable-Stayed Bridge with Main Span of 406m

蒙华铁路洞庭湖特大桥为(99+140+406+406+140+99)m三塔斜拉桥。为提高该桥的竖向刚度、改善结构受力,采用了设置中塔稳定索的措施。中塔稳定索布置于中塔塔顶与边塔桥面横梁上方的塔柱上,设置双索面,每个索面2根索并行排列。主梁采用竖向刚度较大的新型钢箱-钢桁组合结构。增大尺度的钢桁梁下弦杆与铁路正交异性钢桥面板系统形成分离边箱的边主梁结构,华伦式桁架置于其上。主梁施工分为2个主要阶段,钢箱部分先行成桥承担桥梁主要荷载(恒载),钢桁梁仅承受二期恒载与活载。应用板桁组合结构新型主梁与中塔稳定索的结构措施后,该桥取得了较好的静、动力性能。

Dongting Lake Bridge on Mengxi Huazhong Railway is three pylon cable stayed bridge with span arrangement （99＋140＋406＋406＋140＋99） m. In order to improve the vertical stiffness and structural stress of the bridge, stable cables for middle pylon were adopted. The sta ble cables for middle pylon were placed on the top of middle pylon and pylon columns above the cross members of bridge deck of side pylon. Two cable planes were arranged,with two parallel ca bles arranged in each cable plane. The main girder adopted a new steel box steel truss composite structure with larger vertical stiffness. The lower chord of the enlarged steel truss girder and the orthotropic steel deck system of the railway form the side girder structure with separated side box, on which the Warren truss was placed. The construction of the main girder was divided into two main stages. The steel box part of the bridge was completed first to bear the main load （dead load）, and the steel truss girder only bears the second dead load and live load. With the application of the new type of main girder with plate truss composite structure and the stable cable for middle pylon, the bridge has achieved better static and dynamic performances.