考虑拉索局部振动的斜拉桥地震时程响应分析

Seismic Time-History Response Analysis of Cable-Stayed Bridge with Local Cable Vibration

为探讨拉索局部振动对斜拉桥抗震性能的影响,考虑垂度效应和初始静平衡状态,导出了某大跨度斜拉桥拉索一阶自振频率的解析解,并求得该桥斜拉索自振频率的多段拉索模型有限元解.通过输入2种幅值相等但频谱特性不同的地震动激励,分析了拉索局部振动对主梁振动的影响.结果表明:拉索自振频率的有限元解与解析解吻合较好,表明该有限元模型能正确反映斜拉索的振动特性.当主梁竖向低阶振动模态频率与地震卓越频率不一致时,拉索局部振动对主梁产生"附加阻尼"作用;反之,拉索与主梁耦合振动对主梁产生"振动放大"效应.

To investigate the influence of local cable vibration on the seismic behavior of cable-stayed bridges, the analytical solutions of the first order natural frequency of inclined cables of a cable-stayed bridge were derived with considering the sag effect and the initial equilibrium state, and the FEM （finite element method） solutions of the natural frequency of inclined cables were obtained based on the multi-element cable model. The effect of local cable vibration on girder vibration was analyzed by inputting two kinds of seismic excitations with identical amplitudes but different spectrum properties. The research shows that the analytical solutions are identical with the FEM solutions, this means that the multi-element cable model can correctly reflect the vibration features of inclined cables. When low order vertical vibration mode frequencies of the girder are inconsistent with earthquake dominant frequencies, an additional damping effect on girder vibration will be caused; on the contrary, an amplificatory effect of vibration because of coupled vibration of cables and girder will be result in.