The main bridge of Huanggang Changjiang River Rail-cum-Road is a steel truss girder cable-stayed bridge with double pylons and double cable planes.To ensure that the completion status of the bridge could meet the design requirements,the spatial model for the whole bridge was established and the corresponding calculation and analysis were made,using the bridge special finite element analysis software 3D-bridge.Two target status of closure and completion of the bridge were set and the construction monitoring and control of the bridge were carried out according to the target status,using the unstressed state control method.The construction of the pylons of the bridge was controlled by way of pre-raising the padding courses of the bearings and the elevation of the stay cable anchoring points.The cantilever erection and the geometric shapes of the steel truss girder were controlled,using the relative coordinate method through adjusting the installation procedures of the members of the girder after the temperature influences were filtered according to the consecutive construction survey.The stay cables of the whole bridge were tensioned in place in two times and the precision of the initially tensioned stay cable forces were effectively controlled,using the cycling iteration method of pulling-out amount.The steel truss girder of the central span of the main bridge was closed,using the active closure method and the precision of the closure was ensured through adjusting the rotation angles,elevation,longitudinal and transverse positions of the girder at the closure gap.After the construction of the ballast trough slabs was completed,the stay cable forces of the whole bridge were then adjusted for the second time.%黄冈公铁两用长江大桥主桥为双塔双索面钢桁梁斜拉桥,为保证成桥状态满足设计要求,采用桥梁专用有限元分析软件3D-bridge建立全桥空间模型进行计算分析,运用无应力状态法,通过设定合龙与成桥两个目标状态进行施工监控.桥塔施工通过预抬支座垫石与斜拉索锚固点标高进行控制;采用相对坐标法,通过不间断施工测量过滤温度影响后调整杆件安装工序来控制钢桁梁悬臂架设线形;全桥斜拉索通过两次张拉到位,采用拨出量循环迭代法对初张拉索力精度进行有效控制;主桥中跨钢桁梁采用主动合龙,通过对合龙口转角、高程与纵横向位置的调整保证合龙精度;在道碴槽板施工完毕开始进行全桥二次调索.
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