青海哇加滩黄河特大桥施工控制

Construction Control of Wajiatan Huanghe River Bridge in Qinghai

青海哇加滩黄河特大桥为主跨560m的双塔双索面钢-混组合梁斜拉桥,其主梁采用双悬臂拼装架设,并采用单节段拼装浇筑法施工。为提高主梁架设效率、缩短工期,提出一种优化方案——不增加斜拉索张拉次数的两节段拼装浇筑法。为指导施工,使成桥后内力和线形满足设计要求,采用有限元软件MIDASCivil建立全桥模型,利用正装迭代法对优化方案进行全过程施工及合龙控制分析。结果表明:施工过程钢梁最大应力212.2MPa,桥面板最大拉应力1.42MPa,斜拉索最小安全系数2.31,塔柱最大拉应力1.6MPa,均满足规范要求;主梁合龙精度控制在3mm内;成桥后索力偏差最大值6.8%,索力均匀,主桥线形误差均在±56mm内,桥梁线形平顺。

The Wajiatan Huanghe River Bridge in Qinghai is a steel-concrete composite girder cable-stayed bridge with a main span of 560 m, which consists of double pylons and double cable planes. The main girders are erected by double-cantilevers, and are constructed by single segment erection method. In order to improve the erection efficiency and shorten the construction period, we proposed a two-segment cantilever assembly and concrete pouring method without increasing the times of cable tension. To guide the construction, and to make the internal force and alignment to meet the design requirements in finished state, we established a model of the whole bridge by using the finite element software MIDAS Civil, and analyzed the whole process of construction and closure control by using the forward iteration method. The results show that, in the process of construction, the maximum stress of steel girder is 212.2 MPa, the maximum tensile stress of concrete decks is 1.42 MPa, the minimum safety factor of cables is 2.31, and the maximum tensile stress of pylon is 1.6 MPa, which all meet the specifications. The closure accuracy of main girder is controlled within 3 mm. The maximum deviation of cable force after completion is 6.8%, and the cable force is uniform;the alignment error of main girder is within ±56 mm, and the bridge is in a smooth line shape.