大瑞铁路澜沧江大桥设计及关键技术研究

Design and Key Technology Research of Lancang River Bridge on Dali-Ruili Railway

大瑞铁路澜沧江特大桥为双线铁路桥梁,大桥跨越澜沧江峡谷。结合桥位处的地质、地形及运输条件,经过方案比选,最终确定主桥结构为342 m上承式混凝土提篮拱桥,拱肋箱形混凝土截面由钢管混凝土桁架作为劲性骨架。围绕大桥的设计和施工技术开展一系列研究,采取梁-板单元模拟拱肋复合截面,对全桥进行静力、动力分析,确保全桥结构在列车活载、风荷载和地震荷载作用下受力安全;采取实体元建立拱肋内填外包钢管混凝土复合截面短柱模型,以全桥计算截面内力做外部荷载进行分级加载,最终确定拱肋拱顶复合截面受力安全系数为2.98,大于2.0;研发二次竖转的新型钢拱肋施工工艺,充分适应陡峭的地势,减少拱肋钢劲性骨架施工期间空中大悬臂状态时间。2022年7月22日,澜沧江大桥开通运营,围绕其开展的系列研究成果得以验证。研究成果中钢管混凝土参数体系与分析方法纳入《铁路桥梁钢管混凝土结构设计规范》;研发拱桥拱肋二次竖转施工新工艺,确保澜沧江大桥每岸质量2500 t的拱肋钢劲性骨架通过二次竖转实现合龙,为后期拱肋混凝土及桥面系的施工奠定基础。

The Lancang River Grand Bridge on Dali-Ruili Railway is a double-track railway bridge that spans the Lancang River Valley.Considering the geological,topographical,and transportation conditions at the bridge site,a 342 m concrete basket arch bridge with a deck above the arch was selected as the main bridge structure after scheme comparison.The box-shaped concrete cross-section of the arch rib was reinforced by a concrete truss made of concrete-filled steel tubes as the stiff skeleton.A series of studies on the design and construction techniques of the bridge were carried out.Beam-slab elements were used to simulate the arch rib composite section,and static and dynamic analyses were performed on the entire bridge to ensure structural safety under train live load,wind load,and seismic load.A short column model of the composite section,consisting of inner-filled and outer-encased concrete-filled steel tubes,was established using solid elements.By applying the external forces incrementally based on the internal forces calculated for the entire bridge,the final safety factor of the composite section at the top of the arch rib was determined to be 2.98,greater than 2.0.A new construction technique involving secondary vertical rotation of the steel arch ribs was developed to fully adapt to the steep terrain and reduce the duration of suspension during the construction of the steel stiff skeleton of the arch ribs.On July 22,2022,the Lancang River Bridge was opened for operation,validating a series of research results.The parameters and analysis methods for the concrete-filled steel tubes developed in the study were written into the Code for Design of Concrete-filled Steel Tubular Structures of Railway Bridge.The newly developed secondary vertical rotation technique for arch ribs ensures the successful closure of 2500 ton steel stiff skeleton on each bank of the Lancang River Bridge,laying the foundation for subsequent construction of arch rib concrete and bridge deck system.