悬索桥断索动力响应有限元模型参数研究

采用有限元方法（FEM）建立考虑主缆局部振动影响因素的悬索桥断索动力分析模型，研究主缆局部振动对悬索桥断索动力响应的影响程度. 对主缆物理抗弯刚度、单元网格密度、索夹质量、模型阻尼比以及吊索应力初始状态等因素进行参数分析，给出提高计算结果精度的建议. 结果表明：在进行悬索桥断索动力分析时，主缆局部振动对计算结果精度具有不可忽略的影响；有限元模型中主缆物理弯曲刚度、单元网格密度和索夹质量均是影响主缆局部振动的关键参数. 结构整体模态阻尼和主缆局部阻尼均能有效抑制断索点主缆振动，分析模型须考虑局部主缆单元阻尼和结构整体模态阻尼的差异. 结构断索动力响应随着断裂吊索初始应力增大而增大，结构断索响应动力放大系数变化幅度不大.

Parameter study on finite element model of abrupt hanger-breakage event induced dynamic responses of suspension bridge

Using the finite element method (FEM), the calculation model of suspension bridge was established to investigate hanger-breakage event induced dynamic responses considering the influence of main cable’s local vibration. The influence degree of main cable’s local vibration on structural dynamic responses of suspension bridge subjected to an abrupt hanger-breakage event was studied. A parametric study was conducted, in which the influencing factors included the physical bending stiffness of the main cable, the grid density of the element, the mass of the clamp, the damping ratio of the model and the initial state of the hanger stress. Some suggestions were given to improve the accuracy of calculation results. The influencing factors included the physical bending stiffness of the main cable, the grid density of the element, the mass of the cable clamp, the damping ratio of the model and the initial state of the hanger stress. Results show that the local vibration of the main cable has an un-neglected influence on the accuracy of the calculation results in the dynamic analysis of the cable breakage of suspension bridges. In the finite element model, the main cable physical bending stiffness, element mesh density and cable clamp mass are the key parameters affecting the local vibration of the main cable. Both the overall modal damping and the local damping of the main cable can effectively suppress the vibration of the main cable at the break point. The difference between the local main cable element damping and the overall modal damping of the structure should be taken account in the analysis model. The dynamic response of structural broken cable increases with the increase of initial stress, but the dynamic amplification coefficient of structural broken cable response changes little.