大跨度地锚式斜拉桥综合维护关键技术

郧县汉江大桥为主跨414 m的地锚式预应力混凝土双塔双索面斜拉桥,每塔两侧各布置50根斜拉索,跨中设置4个无轴力中间铰。该桥于1994年建成,2014年检测发现斜拉索破损严重,4个无轴力中间铰均出现一端卡死现象,主桥被评定为四类桥梁,需进行全桥综合维护。根据病害情况,先更换损坏严重的21根斜拉索;再按单塔对称、双塔反对称2根索同时更换的原则更换20~25号斜拉索;最后按双塔反对称4根索同时更换的原则更换1~19号斜拉索。全桥200根斜拉索更换后调整索力和梁体标高,采用拖拉法校正无轴力中间铰。无轴力中间铰校正后,在其端部和跨中断缝处安装监测系统,监测其工作状态。监测结果表明,无轴力中间铰能够纵向自由滑移,工作状态良好。

Key Techniques for Integrated Maintenance of Long-Span Earth-Anchored Cable-Stayed Bridge

The Hanjiang River Bridge in Yun County is a two-pylon earth-anchored prestressed concrete cable-stayed bridge with a main span of 414 m.The stay cables are fanned out in double cable planes,on each side of the pylon,a number of 2×25 stay cables are tensioned.Four central hinges without axial forces are installed in midspan.The bridge was opened to traffic in 1994,and the 2014 inspections revealed multiple damages,including the stay cable damage and one end stuck of the axial-force-free central hinges,as a result,the bridge was evaluated as GradeⅣdeteriorated structure,and an integrated maintenance for the whole bridge was needed.According to the degree of damages,the 21 stay cables that were severely damaged were replaced first.Then,the stay cables 20-25 were replaced,two at a time,by the way of replacing the stay cables from the same pylon symmetrically and from different pylons asymmetrically.And the stay cables 1-19 were replaced,four at a time,by the way of replacing the stay cables from different pylons asymmetrically.After all the 200 stay cables were replaced,the cable forces and girder elevation were adjusted,and the central hinges without axial forces were calibrated by the dragging method,then,monitoring system was installed in the girder ends and joints in midspan to monitor their working condition.The results demonstrate that the central hinges without axial forces can move freely in the longitudinal direction and their working condition is good.