超大跨径斜拉桥斜拉索局部振动对地震反应的影响

EFFECT OF CABLE VIBRATION ON SEISMIC RESPONSE OF SUPER-LONG SPAN CABLE-STAYED BRIDGE

摘要:

在以往的斜拉桥地震反应分析中，大都采用单桁架模型来模拟斜拉索（SECS模型），不能反映斜拉索的局部振动的影响。本文以世界第一跨度斜拉桥——苏通大桥为背景，采用将一根斜拉索离散成为多个单元的方法（MECS模型）来分析斜拉索局部振动对超大跨度斜拉桥地震反应的影响，并探讨了斜拉索的合理单元划分方式。结果表明，斜拉索划分为10个单元已能够很好的反映斜拉索局部振动的影响。考虑斜拉索局部振动之后，会出现索梁耦合振型，减小一些振型的参与系数，基频与主梁的竖向振动相近的斜拉索在地震作用下大幅振动，而主梁和主塔的内力反应普遍减小，特别是主塔的地震轴力明显减小。

Abstract:

In the seismic response analysis of cable-stayed bridges, cables were generally modeled using single-element cable system (SECS model), which can not simulate the local vibration of cables. In order to investigate the effect of cable vibration on seismic response of super-long span cable-stayed bridge, the Sutong Bridge, which is the longest span cable-stayed bridge in the world, was taken as an example, and its analytical model was established. In this model, cables were modeled with multiple-element cable system (MECS), and rational discretization manner was discussed. The results show that rational discretization manner is dividing each cable into 10 elements. Cable vibration change the dynamics characteristics of the whole bridge, especially cause the appearance of some cable-deck coupled modes, which cause the reduction of participation factor of some modes, the seismic forces of girder and tower are also reduced, especially the axial force of the tower. Furthermore, cable vibration makes the cables, whose frequency are close to vertical vibration frequency of the girder, vibrate seriously.