大跨悬索桥加劲梁吊装过程强静风安全性研究

Study of Aerostatic Safety of Long-Span Suspension Bridge in Process of Stiffening Girder Hoisting

虎门二桥坭洲水道桥为主跨1688 m双塔双跨钢箱梁悬索桥,加劲梁采用跨缆吊装法施工。为确定强静风作用下加劲梁吊装过程中的危险阶段及提高静风安全性的措施,采用ANSYS软件建立全桥有限元模型,采用非线性静风分析方法分析各施工关键阶段加劲梁的内力和位移响应,针对较高风险阶段提出安全措施。结果表明:合龙前大悬臂阶段和合龙后尚未刚接阶段为加劲梁吊装过程中的两大高风险阶段;提高临时连接件刚度可在一定程度上降低临时连接件的应力水平,使全桥的临时连接件受力更加均匀;但对于合龙阶段应力较高的塔根处,仅提高临时连接件刚度已无法满足强度要求,断开合龙处连接、采用柔性索将梁段和桥塔相连,可有效降低全桥临时连接件应力水平,限制梁端位移。

The Nizhou Waterway Bridge of the Second Humen Bridge is a two-tower,two-span,steel box girder suspension bridge with a main span of 1688 m.The stiffening girder is erected by a cross-cable lifting method.To determine the dangerous stages in the process of stiffening girder hoisting under the action of strong wind and to take measures to improve the aerostatic safety,the software ANSYS was used to establish the finite element model of the overall bridge,the internal forces and displacement response of the stiffening girder in each key construction stage were analyzed by the non-linear aerostatic analysis method,and safety measures were proposed for the stages with higher risk.The results show that the two highly risky stages are the large cantilever stage before closure and the stage after closure but before the rigid connection.To improve the stiffness of the temporary connecting components can reduce the stress level of the temporary connecting components to a certain extent,and allow the loads on the temporary connecting components to be more uniformly distributed.But for the tower roots where the stress level is higher in the closing process,the mere increase of the stiffness of the temporary connecting components cannot meet the strength requirements.To effectively reduce the stress level of the temporary connecting components of the whole bridge and limit the girder end displacement,the connection at the closure location should be cut off and it is better to use flexible cables to connect the girder sections and the towers.