商合杭铁路芜湖长江公铁大桥2号墩桥塔钢锚梁定位测量技术

商合杭铁路芜湖长江公铁大桥主桥为主跨588 m的双塔双索面高低塔箱桁组合梁斜拉桥,该桥2号墩桥塔采用塔梁同步施工,索塔锚固区采用钢锚梁拉索锚固体系与平行钢丝环向预应力锚固体系相结合的方式锚固。为提高测量精度,精确定位钢锚梁,在分析钢锚梁定位精度影响因素的基础上进行主桥施工控制网优化;在自然环境“零”状态、外部荷载“零”状态下对塔柱变形进行监测,获取施工误差引起的塔柱变形量,用于修正钢锚梁定位坐标;采用全站仪精密三角高程测量法、三角高程差分法、侧边交会法相结合的办法将施工控制网高程、平面坐标传递至塔柱待施工段基准点,获取塔柱待施工段基准点在施工控制网投影面的三维坐标,采用相对设站法完成钢锚梁高精度、快速定位。

Positioning and Measuring Techniques for Steel Anchor Beams in Pylon at Pier No.2 of Wuhu Changjiang River Rail-cum-Road Bridge on Shangqiu-Hefei-Hangzhou Railway

The main bridge of Wuhu Changjiang River Rail-cum-Road Bridge carrying part of Shangqiu-Hefei-Hangzhou Railway is a two-pylon cable-stayed bridge with a main span of 588 m.The bridge has a high pylon and a low pylon,the main girder adopts the steel box and truss combined composite girder and the stay cables are fanned out in double cable planes.The pylon at pier No.2 was constructed in parallel with the construction of the girder.In the cable-to-pylon anchorage zone,the cables,made of parallel steel wires,are anchored to the pylon by the steel anchor beams and the loop prestressing tendons.To improve the measuring accuracy and accurately position the steel anchor beams,the construction control network was optimized based on the analysis of the influential factors of the positioning accuracy of the steel anchor beams.The deformation of the pylon columns were monitored without counting the influence of the natural environment and the external loads,and the deformation amounts of the pylon columns induced by the construction errors were obtained to modify the positioning coordinates of the steel anchor beams.The elevation and plan coordinates of the construction control network were transmitted to the benchmark points by the combined use of a variety of methods,including the accurate triangular elevation measuring method,triangular elevation difference method and rectangular intersect method using the total station.The spatial coordinates of the benchmark points of the pylon columns waiting for construction on the projection surface of the control network were gained,and the data acquisition stations were set accordingly to complete the positioning of the steel anchor beams rapidly and with high precision.