地震频谱特性对独塔斜拉桥纵向地震响应影响

Influence of Ground Motion Frequency Characteristics on Longitudinal Seismic Response of Single Tower Cablestayed Bridges

摘要:

以一座实际的独塔斜拉桥为背景，分别以速度脉冲波和实际地震波作为地震动输入，研究了不同频谱特性地震输入下独塔斜拉桥地震响应特点.结果表明，近断层地震动的长周期速度脉冲对独塔斜拉桥的地震响应影响显著，特别是当地震动峰值速度(VP)与地面运动峰值加速度(aP)比值较大时，速度脉冲波的周期与主梁第一阶竖弯振动周期接近，塔柱、梁体、拉索和支座等受力明显增加，并可能出现支座脱空和拉索松弛等现象.进一步研究了支座脱空和拉索松弛现象，结果表明，支座脱空和拉索松弛对主梁位移、拉索索力和支座竖向反力等响应的影响较大，不考虑支座脱空和拉索松弛可能会低估梁体位移和拉索的地震响应.

Abstract:

Based on a real singletower cablestayed bridge, both velocity pulses and real earthquake waves are used to study the influence of ground motion frequency characteristics on seismic behavior of singletower cablestayed bridges. The analysis results show that long duration velocity pulse contained by nearfault ground motions have significant effects on the seismic response of singletower cablestayed bridges. Especially, when the ratio of peak ground velocity (Vp) to peak ground acceleration (ap) is large, the period of velocity pulses gets close to the period of 1st vertical bending mode of the bridge, and thus the response of the tower, girder, cables and bearings increases significantly with possibility that cable relaxation and end span uplift might occur. The results show that cable relaxation and end span uplift have a significant influence on the response of the structure like deck displacement, cable axial force and bearing vertical reactions. The response of the deck displacement and cable axial force would possibly be underestimated if neglecting influence of cable relaxation and end span uplift.