甬江铁路特大桥施工控制

Construction Control for Yongjiang River Railway Bridge

甬江铁路特大桥为主跨468 m半飘浮体系双塔双索面混合梁铁路斜拉桥。混凝土梁采用满堂支架现浇,钢箱梁采用悬臂拼装,桥塔塔柱采用全自动液压爬模施工。为保证施工过程安全、快捷,成桥后线形和内力满足设计及高速列车运行的要求,采用基于无应力状态理论的全过程几何控制法进行施工控制,正装迭代计算采用TDV软件进行。结果表明:基于无应力状态量的计算,利用立模标高、相邻节段转角、无应力索长、梁端索力调整并配合水箱压重进行误差调整,消除了环境温度对梁、塔线形控制的影响,实现了全天候施工和无曲率合龙。成桥后主梁最大高程误差为73 mm,最大塔偏为11 mm;典型混凝土断面施工过程中应力为-8.10~-2.55 MPa;钢-混结合段断面施工过程中混凝土应力为-6.14~-1.18 MPa,钢结构应力为-28.97~-6.45 MPa;索力误差在5%以内;主梁、桥塔的线形和内力均满足设计要求。

The Yongjiang River Railway Bridge is a semi-floating hybrid girder cable-stayed bridge with a main span of 468 m.The bridge has two pylons,with stay cables arranged in double cable planes.The concrete girders were cast in-situ on full scaffoldings,the steel box girders were assembled in cantilevers,and the pylons were constructed by automatic hydraulic climbing formwork.The structural monitoring and control during construction was carried out by the full process geometry control method based on stress-free state theory,with intent of ensuring the safe and rapid construction and allowing the geometry and internal forces of the completed bridge to meet the design requirements and the service conditions for high-speed trains.The forward iterative analysis was conducted by TDV software.The results show that deviations were rectified based on the stress-free state calculation,utilizing the elevation of the formwork,rotation angle between adjoining segments,stress-free cable lengths and girder-end cable forces for adjustment,if necessary,adding water tanks for counterbalancing.The influence of ambient temperature on the geometries of the girders and pylons was reduced,thereby realizing the all-weather construction and curvature-free closure.After closure,the maximum elevation deviation of the main girder was 73 mm and the maximum pylon offset was 11 mm.In construction process,stresses in typical concrete cross-section were between -8.10 and -2.55 MPa,stresses in the cross-section of steel-concrete joint section were about -6.14 to -1.18 MPa,and the stresses in the stress structure were within the range of -28.97 to -6.45 MPa.The error of cable forces was less than 5%.The geometries and internal forces of the main girder and pylons meet the design requirements.