Hybrid Discrete Method for Seismic Response Analysis of Soil-Structure System with Topographical Site Consideration

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This paper concerns the surface soil response during earthquake motion with particular interest on the topographial condition. In the so-called near field which includes structures, certain distribution exists in soil properties as well as some irregularities in boundary condition. The far field which extends outside the near field is often assumed as a uniform or heterogeneous. The finite element method is taken for the former near field while the boundary element method is used for the latter far field. For the seismic wave incidence, we specify the wave type such as P-, SH-, or SV-wave of plane wave. For the numerical case studies, half-circle, half-ellipse, and trapezoidal alluvium are used with different soil properties. Also, parametric studies are made with changing the wave length of the incident wave and the size of the alluvium. The topographical site effect is clarified in comparison with the results from heterogeneous models.For the soil-structure interaction analysis, interest is placed on deriving the soil impedance function and the effective input motion for certain type foundation. The soil is assumed as axisymmetric layered. The Fourier series expansion is used for describing the response. The parametric studies are performed to discuss the foundation behavior for different incident wave type, angle of its incidence.The effort is made to evaluate the relevant Green functions for the above purposes. The direct stiffness method is applied for evaluating the wave number domain and the numerical inversion is taken to get the inverse Fourier transform for the space domain solution.