COMPARATIVE STUDY ON THE DYNAMIC SOIL-STRUCTURE INTERACTION SYSTEM WITH VARIOUS SOILS BY USING SHAKING TABLE MODEL TESTS

Through comparing the shaking table tests on dynamic Soil-Structure Interaction (SSI) systems, the effects of various soils on SSI are studied. A flexible container is fabricated to minimize the box effect. Twelve specimens are fabricated, including 7 pile foundations, 3 box foundations and 2 fixed bases. Single column with mass block on its top and 12-story cast-in-place R.C. frame model are used as superstructure, and three types of Shanghai soft soil are employed as model soil. Some important findings from the tests are as follows. (1) Test results indicate that the softer the soil is, the larger the settlement and incline of the superstructure become. The natural frequency of the SSI system is less than that of the structure when SSI is not taken into account and its damping ratio is larger than that of structural materia1. (2) The seismic response indicates that the harder the soil is, the larger the amplification factor of the acceleration response is. (3) Due to the effect of SSI, the rocking motion of foundation is quite notable. The softer the soil is, the less the motion of foundation is. (4) The transfer of earthquake wave in ground soil is related to soil characteristics, excitation magnitude, etc. It is not always amplificatory, but likely to be filter and isolation. (5) The distribution rule of pile strain and contact pressure on pile-soil interface is found.