大跨度公铁两用斜拉桥群桩基础地震响应研究

Research on seismic response of pile group foundation for long span rail-cum-road cable-stayed bridge

为了解大跨度公铁两用斜拉桥群桩基础的地震响应行为,总结了该类桥梁基础的总体结构特征,探讨了基础的抗震分析模型,提出了估计高桩承台基础地震响应的实用性方法,分析了该类型基础的抗震安全度和地震响应特征。研究表明:承台等效振型参与度大小与地震动长周期成分的频谱特性有关,当忽略该因素影响时其取值分布较为平稳;E2与E1地震作用下桩基抗震安全度的比值平均大小为0.65左右;高桩承台基础最不利位置一般在桩头处,且通常表现为大偏心受压;一般冲刷线以上桩身内力呈线性分布;自一般冲刷线以下,桩身轴力基本保持不变,剪力和弯矩呈先增大后减小的曲线分布规律。

In order to understand the seismic response behavior of group pile foundation for long span rail-cum-road cable-stayed bridge, the general structural characteristics of this foundation are summarized in the present reseach. Besides, the basic seismic analysis model is discussed, and the practical method for estimating seismic response of high pile cap foundation is proposed. In the end, the seismic safety and seismic response characteristics of the foundation are analyzed. The results shows that the participation degree of the equivalent vibration type of the cap is related to the frequency spectrum characteristic of the long period component in earthquake. In addition, distribution of the participation degree value is relatively stable when ignoring the influence of the factor. The average ratio of aseismic safety of piles under the level of E2 to that of E1 is about 0.65. Usually the most unfavorable position of the high pile cap foundation is thought as the pile head which has a characteristic of large eccentric compression. The internal force of the pile body above the general scour line is linearly distributed, and the axial force of the pile body remained the same value as that of the general scour line, and the shear and bending moment increased first and then decreased.