抗风缆对大跨人行悬索桥非线性静风失稳模式的影响

Influence of Wind-resistant Cable on Nonlinear Areostatic Instability Mode of Long-span Pedestrian Suspension Bridge

为研究抗风缆对大跨人行悬索桥非线性静风稳定性的影响,采用风洞试验获取大攻角区间主梁静三分力系数。结合有限元数值模拟计算方法,运用双层迭代算法同步计入悬索桥几何非线性与静风荷载非线性,对420 m主跨人行悬索桥进行了非线性静风响应全过程分析,得到了非线性静风失稳临界风速以及静风位移响应与应力响应。综合分析结果表明:抗风缆是提高大跨人行悬索桥结构刚度的有效结构措施,抗风缆对大跨人行悬索桥动力特性影响显著,可以明显改变大跨人行悬索桥模态发生顺序以及相关频率;不依赖抗风缆结构的大跨人行悬索桥静风稳定性能相对较低,抗风缆能够大幅提高大跨人行悬索桥结构系统刚度和静风稳定性能;抗风缆不仅能够改变大跨人行悬索桥的静风位移发展路径,而且可以改变静风失稳形态,抗风缆悬索桥静风失稳模式是以扭转位移为主的三向耦合变形状态,去掉抗风缆后,静风失稳模式转变为以横桥向位移为主、扭转位移与竖桥向位移为辅的横桥向失稳;抗风缆悬索桥扭转型静风失稳是由主梁扭转位移驱动的缆索系统应力松弛导致的,无抗风缆悬索桥横向型静风失稳是由主梁横桥向位移驱动的悬索桥总体刚度衰减导致的。研究结论可为大跨人行悬索桥抗风设计提供相关参考。

In order to study the influence of wind-resistant cable on the nonlinear aerostatic stability of long-span pedestrian suspension bridge,the aerostatic coefficient of main girder in the wide range of wind attack angle is obtained by wind tunnel test.Combining with the finite element numerical simulation method,the whole process of nonlinear aerostatic response of the 420 m main-span pedestrian suspension bridge is analyzed by using double-layer iterative algorithm considering the geometric nonlinearity and the aerostatic load nonlinearity of the bridge,and the critical wind velocity of nonlinear aerostatic instability,the aerostatic displacement response and aerostatic stress response are obtained.The comprehensive analysis result shows that(1) Wind-resistant cable is an effective structural measure to improve the structural stiffness of long-span pedestrian suspension bridge.Wind-resistant cable has significant influence on the dynamic characteristics of long-span pedestrian suspension bridge,and can significantly change the mode sequence and frequency of long-span pedestrian suspension bridge.(2) The aerostatic stability of long-span pedestrian suspension bridge without wind-resistant cable is relatively low,and the wind-resistant cable can greatly improve the structural system stiffness and aerostatic stability of long-span pedestrian suspension bridge.(3) Wind-resistant cable not only can change the aerostatic displacement development path of long-span pedestrian suspension bridge,but also can change the aerostatic instability mode.The aerostatic instability mode of suspension bridge with wind-resistant cables is a 3-direction coupling deformation state dominated by torsional displacement.After the wind-resistant cables are removed,the aerostatic instability mode changes to the transverse bridge instability dominated by transverse displacement and supplemented by torsional displacement and vertical displacement.(4) The torsional aerostatic instability of the suspension bridge with wind-resistant cables is caused by the stress relaxation of cable-system driven by the torsional displacement of main girder.The transverse aerostatic instability of the suspension bridge without wind-resistant cable is caused by the overall stiffness attenuation of suspension bridge driven by transverse displacement of main girder.The conclusions can provide a reference for wind-resistant design of long-span pedestrian suspension bridge.