SEISMIC RESPONSE ANALYSIS METHOD FOR SOIL-STRUCTURE INTERACTION SYSTEM OF UNDERLYING RIGID ROCK BASE SOIL CONDITION

The seismic response analysis model of soil-structure system of underlying rigid rock base soil condition is a “semi-open and semi-closed” energy system. Compared with a fully “open” energy system, the analysis model of the “semi-open and semi-closed” energy system employs the seismic input mode of an intra-domain inertial force. This input mode is exactly the same as that in the seismic response analysis model for the rigid rock base-structure system. Different from that of the structures built on rigid rock base, the analysis model of the soil-structure system with underlying rigid rock base soil conditions requires consideration of the influence of semi-infinite soil layers on the truncation boundaries. Many researchers and engineers have misunderstood this issue by assuming the effect of truncation boundaries is only an issue of an artificial boundary condition. Consequently, they have adopted artificial boundary conditions to simulate the impact of truncation boundaries on the radiation energy. In real engineering practice, a more important influential factor, i.e. the free field effect of the soil layer of underlying rigid rock base soil condition has been neglected in the analyses. In order to clarify this issue, based on the direct analysis model, the seismic analysis method for the soil-structure interaction of underlying rigid rock base soil condition was developed in this study. The results indicate that, in a typical engineering experience scale, omitting the free field effect at truncation boundaries would not obtain reasonable calculation results.