长周期地震动下软土地基的偏心基础隔震结构振动台试验研究

远场长周期地震动使基础隔震结构地震响应强烈，且软土地基-结构相互作用（SSI效应）使隔震结构地震响应更大，而偏心基础隔震结构在双向水平地震作用下将发生扭转效应，极易导致隔震层位移增加。为研究远场长周期地震动下软土地基SSI效应对偏心基础隔震结构地震响应规律及减震效果的影响，对高宽比为3的4层荷载偏心钢结构缩尺模型进行刚性、软土地基上的双向振动台试验。结果表明:软土地基上结构采用隔震技术后，周期延长比低于刚性地基结构体系，使减震效果下降；SSI效应在一定程度上会降低结构层间扭转响应，但在隔震层会出现较大扭转角；与普通地震动相比，远场长周期地震动下SSI效应对隔震结构响应影响程度更大，隔震层位移可能超限，总体减震效果较差。建议为保证软土地基上基础隔震结构的安全，应考虑SSI效应后进行结构设计，且远场长周期地震动的不利影响不可忽视。

Shaking table test of eccentric base-isolated structure on soft soil foundation under long-period ground motion

The seismic response of long-period structures such as isolated buildings under the far-field long-period ground motion is strong, and the response may be even greater when the soil-structure interaction (SSI effect) of soft soil foundation is considered. Meanwhile, the torsional effect of eccentrically base-isolated structures under two-way horizontal earthquake action may lead to an increase of displacement of isolation layer. To study the influence of SSI effect of soft soil foundation on the seismic response and damping effect of eccentric base-isolated structure under the action of far-field long-period ground motion, the two-way shaking table tests on a scaled model of a 4-story eccentric steel structure with a height width ratio of 3 located on rigid or soft soil foundation were carried out. The results show that the period prolongation ratio of the structure on soft soil foundation after adopting isolated technology is lower than that of the structure system on rigid foundation, and the damping effect is reduced. SSI effect can reduce the inter-story torsional response of the structure to a certain extent, but there is a larger torsion angle in the isolation layer. Compared with the ordinary ground motion, SSI effect has a greater influence on the response of the isolated structure under the far-field long-period ground motion. The displacement of the isolation layer may exceed the limit, and the overall damping effect is poor. It is suggested that in order to ensure the safety of the base-isolated structure on soft soil foundation, the SSI effect should be considered in the design of structure, and the adverse effects of far-field long-period ground motion should not be ignored.