河床冲刷深度变化对大型桩基桥梁地震反应的影响

以一座超大跨度斜拉桥为工程背景,采用解析解和有限元模拟计算相结合的方法,对河床冲刷深度变化对大型桩基桥梁地震反应的影响进行初步探索性研究。建立两质点单墩模型,推导地震反应计算公式,用解析法计算桥墩及其基础的地震反应随河床冲刷深度变化的情况,分析高桩承台基础与桥墩的动力相互作用规律,结果表明,由于承台大质量的存在,桥墩的地震反应会表现出显著的共振效应,当桥墩和基础的自振周期相近时,会出现一个峰值。进一步地,建立斜拉桥的全桥有限元模型,计算边墩、主塔及其基础的地震反应随河床冲刷深度变化的情况,验证了解析法得出的影响规律:河床冲刷深度变化对大型桩基桥梁的地震反应有很大的影响,随着冲刷深度的增加,桥梁结构的地震反应并不是单调减小,而可能出现一个峰值。

Effects of riverbed scouring depth on the seismic response of bridges on pile foundations

Taking a super long-span cable-stayed bridge as the background,a pilot study was carried out to investigate the effect of riverbed scouring depth on the seismic response of a bridge on pile-foundations.A two-particle single-pier model was established to approximately simulate the dynamic behavior of a pier and its high-rise pile cap foundation,the seismic responses corresponding to different scouring depths were calculated,and the dynamic interaction between the pile foundation and the pier was analyzed.The results indicate a significant resonance between the pier and pile foundation because of the large pile-cap mass.Six finite element models corresponding to six riverbed scouring depths of the entire bridge were established,the effects of scouring depth on the seismic response of side piers and towers were analyzed.The conclusion is that the scouring depth has a significant effect on the seismic response of the bridge,and as the scouring depth increases,the seismic response of the bridge does not monotonously decrease,and there possibly is a peak value.