近断层脉冲效应对大跨度结合梁斜拉桥地震响应的影响

Influence of near-fault pulse effect on seismic response of long-span composite girder cable-stayed bridge

为了研究近断层脉冲效应对大跨度结合梁斜拉桥地震响应的影响,明确近断层脉冲地震动长周期脉冲和高频分量对大跨度结合梁斜拉桥地震响应的贡献。首先采用基于小波分析的近断层脉冲地震动识别方法从集集地震中选取相同场地下的脉冲/非脉冲2类近断层地震记录,并对脉冲型地震动的长周期速度脉冲进行提取,研究长周期、高幅值速度脉冲对近断层脉冲地震动反应谱的放大效应。最后以某一大跨度结合梁斜拉桥为例,研究近断层速度脉冲效应对其地震响应的影响。研究结果表明:由于大跨度结合梁斜拉桥结构体系较柔,自振周期较长,近断层脉冲效应对其地震响应的影响显著,与非脉冲地震作用相比,近断层脉冲效应使得主梁和桥塔的地震响应都显著增大,最大改变率可达177.9%;主梁和桥塔的地震位移响应主要由长周期脉冲所决定,高频成分的影响相对较小,但是对桥塔内力响应而言,其受近断层地震动高频成分的影响较大,在基于内力控制的结构抗震设计中应该充分考虑长周期脉冲和高频成分2部分的影响。

In order to study the effect of near fault pulse effect on seismic response of long-span combined beam cable-stayed bridge cable-stayed bridge,determine the contribution of long-period impulse and high-frequency component of near-fault impulse ground motion to the seismic response of long-span composite beam cable-stayed bridge.Firstly,two types of near-fault seismic records,namely,pulse/non-pulse,were selected from the Chi-Chi earthquake by using the wavelet analysis-based method,and the long period velocity pulse extracted.The amplification effect of long-period and high-amplitude velocity pulses on seismic response spectrum was studied.Then the influence of the near-fault pulse effect on the seismic response of a cable-stayed bridge with a large span combined beam was compared.The results from this research show that:Because of the flexible structure system of the long-span combined beam cable-stayed bridge,the self-vibration period is longer,and the near fault pulse effect has a significant influence on its seismic response.Compared with the non-pulse earthquake,thenear-fault impulse effect makes the seismic response of the main beam and the bridge tower increase significantly,and the maximum change rate is up to 177.9%;The seismic displacement response of girder and tower is mainly determined by the long period pulse,the influence of high frequency components is relatively small.As for the internal force response of the bridge tower,it is greatly influenced by the high frequency component of the near fault ground motion.In the seismic design based on internal force control,the effect of two parts of the long period pulse and the high frequency component should be fully considered.