大跨度桁式加劲梁悬索桥气弹模型等效设计

Equivalent design of aeroelastic model for a long-span suspension bridge with truss stiffening girder

针对大跨度桁架加劲梁悬索桥气弹模型设计中主梁等效刚度计算问题,以矮寨大桥为实例,建立不同长度空间桁架加劲梁节段模型有限元模型,通过悬臂梁位移法反算得到主梁的等效刚度特性,研究了不同荷载施加方式以及不同梁段长度对等效刚度特性的影响。在此基础上,进一步采用等效弹簧模拟桥塔及边主缆对主跨的约束刚度,简化了边主缆和桥塔,设计了刚性桥塔结合主缆串联等效弹簧的等效单主梁气弹模型,使气弹模型更加充分的反映主跨结构的风振响应。

Aiming at calculation of the equivalent rigidity of truss stiffening girder in an aeroelastic model design of a long-span suspension bridge with truss stiffening girder,Aizhai bridge,a super-long -span suspension bridge across deep valley with single span,was taken as an example for investigation. In order to get the accurate equivalent rigidity characters of the truss-stiffening girder,finite element models of the truss-stiffening girder with different length were built,and then the theoretical formula for calculating the deformation of a cantilever girder under concentrate forces was adopted to evaluate the equivalent rigidity value of the truss girder. The analysis results indicated that the influence of local stress due to different load style disappeared at the section which was about two times of section width distance from the load location,and the length of the selected section model should be long enough to make the model have characters of single girder in both of vertical and cross directions. Furthermore,an equivalent spring was designed to simulate the constraint effect of the tower and the side main cable,based on the analysis of finite element model,the equivalent aeroelastic model of single girder with rigid tower was built,its dynamic characters showed good agreement with those of the prototype.