地震作用下大跨度悬索桥几何非线性影响分析

Analysis of Geometric Nonlinear Effects on Long-span Suspension Bridges Subjected to Earthquakes

大跨度悬索桥几何非线性主要来自3个方面:缆索垂度效应、梁柱效应、大位移引起的几何形状变化。鉴于地震波高频成分振幅大,低频成分振幅小的特点,很难对地震作用下大跨度悬索桥几何非线性的影响做出定性判断。目前大跨度桥梁的几何非线性研究主要集中在斜拉桥,且不同的学者得出了不同的结论。本文以逐级加大振幅的Ⅳ类场地多条地震波为激励,通过对称与非对称的2座典型大跨度悬索桥的几何非线性影响对比分析,探讨了几何非线性对大跨度悬索桥重要地震响应量的影响程度及其原因,并提出了相应的抗震设计参考建议。

Geometric nonlinearity of long-span suspension bridge mainly comes from three aspects：the cable sag effect,the beam-column effect and the large displacement caused by large changes in the structural geometry.Considering the particularity of seismic ground motions,the amplitudes of high-frequency components of which are usually larger than the low-frequency components,it is difficult to make qualitative judgments of the effects of geometric nonlinearity for the long-span suspension bridge under earthquakes. The existing research about the effects of geometric nonlinearity on the long-span bridges focuses on the cable-stayed bridges,and conflicting results can be seen.In this paper,the comparative analysis of the effects of geometric nonlinearity on two typical symmetric and asymmetric long-span suspension bridges are carried out under seismic ground motions with progressively increased magnitudes for four types of sites. The levels of the geometric nonlinear effects on the responses of long-span suspension bridges and corresponding reasons are investigated and some suggestions are offered.