较硬分层土-桩基-结构相互作用体系振动台试验

进行了较硬分层土-桩基-框架结构相互作用体系的振动台试验，再现了上部结构和基础的震害现象．得出的主要规律有：体系频率小于不考虑相互作用的结构频率，而阻尼比则大于结构材料阻尼比；体系的振型曲线与刚性地基上结构的振型曲线不同，基础处存在平动和转动．土层传递振动的作用与土层性质、激励大小等因素有关．砂土层一般起放大作用，粘质粉土层一般起减震作用．结构顶层加速度反应组成取决于基础转动刚度、平动刚度和上部结构刚度的相对大小．多向激励下的动力反应规律没有明显差别．

Shaking Table Testing of Hard Layered Soil-Pile Structure Interaction System

Shaking table tests on dynamic interaction system of hard layered soil,pile foundation and frame structure were carried out.The earthquake damage of superstructure and foundation is reproduced.Based on these tests,several key issues about seismic response of the dynamic soil-structure interaction(SSI) system are studied.The natural frequency of the system is less than that of the structure on rigid foundation if the SSI is not taken into account,while its damping ratio is larger than that of the structure.The mode shape of the system is different from that of the structure on the fixed base in that there are rocking and swing at the foundation.Magnification or reduction of vibration transferred by soil is related to soil characteristic,excitation magnitude, and so on.Generally,sand magnifies vibration,while viscous powder soil damps vibration.The components of the acceleration response at the top of superstructure are based on the relative magnitude of rocking stiffness,swing stiffness of foundation and the stiffness of the super-structure.There is little effect of multi-direction excitations on the key issues of the horizontal SSI.