不同场地多层基础隔震结构振动台试验对比研究

Seismic Responses of a Base Isolated MuLti-story Structure with Different Soil Foundations by the Shaking Table Tests

通过开展土-隔震结构动力相互作用体系的大型振动台模型对比试验,研究了刚性地基、硬土地基和软夹层地基3种不同地基上多层隔震结构的地震反应特征和基础隔震效果。结果表明:SSI效应对隔震结构动力特性的影响与地基土性密切相关,当地基土性由刚变柔时,隔震结构体系的一阶自振频率明显降低,阻尼比也明显增大;不同土性地基上SSI效应对隔震结构地震反应的影响并不相同,软夹层地基上SSI效应可能增大也可能减小隔震结构的地震反应强度,而硬土地基上考虑SSI效应时隔震结构的地震反应与刚性地基时的地震反应差别较小;不同土性地基上SSI效应对隔震结构基础隔震效率的影响与地基土性、输入地震动的特性和峰值等相关,其中地基土性的影响最为明显,地基土性越软,基础隔震效率越低。

According to the large-scale shaking table tests, the seismic responses of the base isola- ted multi-story structure and the isolation effectiveness of isolation layer are compared and stud- ied for the structure built on the different soil foundations, such as the rigid foundation, the hard soil foundation and the soft soil foundation. The result shows that the SSI effects on the dynamic characteristics of the base isolated structure are obvious by the type of soil foundation. With the soil foundation softening, the first-order natural frequency of the isolated structure decreases and the damping ratio increases obviously. The effect of the SSI on the seismic responses of the isola- ted structure are also changed by the stiffness of soil foundation. The SSI effects may increase or decrease the seismic response of the isolated structure built on the soft soil foundation However, the SSI effects on the hard soil foundation have the same influence on the dynamic responses of the isolated structure with the rigid foundations. At the same time, the isolation efficiency of iso- lation layer is also affected by the stiffness of foundation and the dynamic characteristics of the in- put ground motions. Especially, the stiffness of foundation has the maximal impact, and the iso- lation efficiency of isolation layer decreases with the decreasing of the stiffness of foundation.