摘要
场地地震响应是土动力学、岩土工程和地震工程学研究的重要课题。天津市和平区和南开区在以往历次地震中均表现出明显不同的震害影响,其原因就是南开区土层中存在软弱夹层,和平区土层中则没有。土—结构动力相互作用研究广泛存在于大型动力机械基础、核反应堆、海洋平台、高层建筑、桥梁、大坝等工程领域中,动力激励来自于机器、地震、风、波浪及其它冲击等。土—结构动力相互作用问题十分复杂,涉及到土的动力特性、基础形状,上部结构体系以及动力反应等。考虑土—结构动力共同作用符合结构在动力作用下的特性,对认识结构在动力荷载下的内在反应,进而控制或利用这一反应具有举足轻重的作用,因此这方面的研究有较深远的理论意义及工程意义。
下部土体对上部结构动力输入问题是土—结构相互作用研究的重要问题,即所谓的地基阻抗问题,求解这个问题,对土体的正确模拟很关键。本文利用基于波传播理论的结构分析直接刚度法和间接边界元法求解自由场表面柔度格林函数,进而求解明置基础动力刚度系数,通过若干算例分析了层状场地中含有软弱土层时对明置条形基础动力刚度系数的影响,结果表明:软弱土层在场地的位置和特性对动力刚度系数有很大影响。
The seismic response of the site is an important problem to be studied of soil dynamics, geotechnical engineering and seism engineering. Every earthquake had the obviously different effects on Nankai and Heping district in Tianjin. That is for there’s the soft soil layer in the field in Nankai districts but not in Heping districts. The study of Soil-structure interaction has been applied in many fields such as large-scale dynamic machine base, nuclear reactor, deepwater flat roof, high building, bridge, dam and so on. Dynamic excitations arise from machine, earthquake, wind, wave and other impact. Soil-structure interaction is complex problem which concern dynamic property of soil, form of base, shape of upside structure and dynamic reactor etc. Considering soil-structure interaction accord with the properties of structure under dynamic loads and is important to recognize the inherent action of structure under dynamic loads and control or utilize the rule, thus the study of this term has deeply theoretical and engineering significance.
The study about dynamic input of underside soil domain on upside structure is an important problem, so called base impedance problem. And the key problem to solve it is to simulate the soil domain precisely. The surface flexibleness Green function of free field is calculated by means of direct-stiffness method of structural analysis based on wave propagation and indirect boundary element method. Then the dynamic stiffness of surface strip foundation is calculated. By calculating some examples, the influence of layered site including soft soil layer on dynamic stiffness of surface strip foundation are analyzed. The results show that the place and properties of soft soil layer have an obviously effect on the dynamic stiffness.
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