秀山大桥主桥钢箱梁施工过程计算分析

秀山大桥主桥为主跨926m的双塔钢箱梁地锚式悬索桥,采用三跨连续弹性支承体系。为了提高钢箱梁吊装过程的结构计算精度,采用MIDAS Civil软件建立全桥施工过程有限元模型,对成桥恒载目标、主缆与加劲梁线形、无索区体系转换及合龙过程中的计算精度影响因素进行分析。结果表明:该桥加劲梁的整体刚度和恒载分配需分阶段形成;采用主缆-索鞍的接触模拟方法计算主缆线形,能有效消除索鞍附近区域主缆线形的计算误差;根据临时连接件的实际开口边界状态模拟加劲梁的铰接状态,可得到较为准确的加劲梁线形;在体系转换及合龙阶段,根据预抬量、预偏量、合龙口位移差等指标对加劲梁的内力和线形进行精确控制,最终使成桥达到预定理想状态。

Calculation and Analysis of Construction Process of Steel Box Girder of Main Bridge of Xiushan Bridge

The main bridge of Xiushan Bridge is a ground-anchored suspension bridge with a main span of 926 m,consisting of double towers and steel box girders,adopting three-span continuous elastic support system.In order to improve the accuracy of structural calculation of steel box girder during hoisting process,we adopted MIDAS Civil finite elements software to establish a finite element model of the whole bridge construction process,and analyzed the factors influencing the calculation accuracy of the dead load target,the alignment of the main cable and stiffening beam,the system transformation of the cable-free zone,and the closure process.The results show that the overall stiffness and dead load distribution of the stiffening girder of the bridge need to be formed in stages.The contact simulation method of the main cable-saddle is used to calculate the main cable shape,so that the calculation error of the main cable shape near the saddle can effectively be eliminated.The articulation state of the stiffening girder can be simulated according to the actual open boundary state of the temporary connector,and the more accurate stiffening girder shape can be obtained.In the stages of system transformation and closure,the internal force and alignment of the stiffening girder are accurately controlled according to the indexes of pre-lifting,pre-deviation and closure displacement difference,so that the completed bridge can reach the desired state.