行波效应作用下自锚式悬索桥地震响应分析

为了研究空间性地震动中的行波效应对某自锚式悬索桥的动力响应影响,以某大跨度悬索桥为研究背景,首先确定了符合悬索桥桥址场地特性的抗震设计反应谱,并以此作为目标谱.基于随机振动理论,将目标反应谱转换为当量的加速度时程曲线作为大跨度悬索桥抗震分析的地震动输入.根据地震波视波速的离散性选取400 m/s,800 m/s、1 200 m/s和1 600 m/s来考虑行波效应对大跨度悬索桥动力响应的影响.研究结果表明:视波速小于1 200 m/s时,桥塔塔底剪力随着视波速的增加而增加.视波速大于1 200 m/s时,1号塔塔底剪力随着视波速的增加而减小,2号塔塔底的剪力则在增加.考虑行波效应时,桥塔的弯矩随着视波速的增加而上下波动,但与一致激励情况相比,1号塔塔底处弯矩响应值在一致激励情况下得到的弯矩值处上下波动,2号塔塔底处弯矩一直小于一致激励的弯矩值;桥塔塔顶位移受行波效应的影响较大,其塔顶最大位移响应是一致激励的2倍.大跨度悬索桥抗震设计考虑行波效应是非常必要的.

Analysis on Seismic Response of Self-anchored Suspension Bridge under Traveling Wave Effect

In order to study the influence of traveling wave effect in spatial ground shaking on the dynamic response of a self-anchored suspension bridge, taking a long-span suspension bridge as the study background, a seismic design response spectrum meeting the site characteristics of the suspension bridge site is determined, and is used as the target spectrum. Based on the stochastic vibration theory, the target response spectrum is converted to an equivalent acceleration time history curve, which is used as the ground motion input for the seismic analysis of long-span suspension bridge. According to the dispersion of the apparent velocity of the seismic wave, 400 m/s, 800 m/s, 1200 m/s and 1 600 m/s are selected to consider the influence of traveling wave effect on the dynamic response of the long-span suspension bridge. The results show that when the apparent wave velocity is less than 1 200 m/s, the bottom shearing force of the bridge pylon increases with the increase of the apparent wave velocity. When the apparent wave velocity is greater than 1 200 m/s, the bottom shearing force of Pylon 1 decreases with the increase of the apparent wave velocity, while the bottom shearing force of Pylon 2 increases. When considering the traveling wave effect, the bending moment of the bridge pylon fluctuates up and down with the increase of the apparent wave velocity. However, compared to the consistent excitation case, the bending moment response values at the bottom of Pylon 1 fluctuate up and down at the bending moment values obtained in the case of consistent excitation, and the bending moment at the bottom of Pylon 2 is always smaller than that of consistent excitation. The displacement at the top of the bridge pylon is greatly influenced by the traveling wave effect, and the maximum displacement response of the pylon top is two times that of the consistent excitation. It is very necessary to consider the traveling wave effect in the seismic design of long-span suspension bridges.