Seismic Response Analysis Of Soil Layer On Complex Sites

It is of great importance to consider seismic response analysis of complex topography for theseismic response of structures and the safety estimation of earthquake resistant. It is a hot researchtopic in the field of earthquake engineering and geotechnical engineering. In this dissertation, basedon the direct FEM, the mechanism of seismic response of soil layer under uniform-andmulti-supported excitations is discussed. Some main achievements of the dissertation are describedas follows:1. Based on lots of literatures, the structural responses for unsynchronized motions, especially,including the interaction of soil-structure are introduced.2. Based on linear visco-elastic assumption, under uniform-and multi-supported excitations,the precision of results with the scope of soil region is analyzed. Under uniform harmonic excitation,the soil layer response varying with artificial boundary, damp coefficient, exciting frequency and theratio of width and depth is discussed. It will be the foundation for how to consider the scope ofseismic response of soil layer, which was calculated by direct finite element method. Based on aboveconclusion, the response a river-crossing topography under seismic excitations was analyzed. Theresults showed that the scope of soil layer is satisfied.3. For the random seismic response analysis of layered sites, by combining the randomvibration and wave theory, the status of inclined body waves and the influence of elastic rock can beanalyzed conveniently. Then the parametric study of single layer on half-space is investigated. Theinfluences of stiffness of rock, different types of wave and angle of incidence for the response of soillayer are discussed.4. Based on the assumption of hysteretic damping, seismic response of soil layer wasanalyzed by using the methods of time domain and frequency domain separately. Under theharmonic and earthquake waves excitations, by compared of the results of time domain andfrequency domain, how to evaluate the damping matrix in the time domain were discussed. Andthe concept of translation frequency of damping coefficient was put forward. After the analysisresults of every earthquake wave were required, an empirical equation, which was used to evaluatethe translation frequency of damping coefficient in the time domain about hysteretic damping, wasestablished. So the hysteretic damping can be analyzed in the time domain.5. In order to consider the nonlinear characteristics of soil site and the spatial variation ofground motion, the incremental-iterative scheme for nonlinear analysis of soil site seismic responseunder multi-support excitations is developed, based direct iteration method and step-by-step timeintegration scheme. In order to decrease the times of evaluation inverse for nonlinear seismicresponse analysis under multi-support excitations, the trial and error iteration method is developedby a trial factor. It can reduce the computational time effectively. According to the proposedcomputational model, a computer program is worked out. It can perform the nonlinear or equivalentlinearization analysis of seismic response under uniform or multi-supported excitations. The resultsshow that the seismic response analysis under multi-support excitations is necessary for large-scalestructures.6. The seismic response of canyon topography is evaluated. The results show that it will leadto considerable vertical motion round canyon because of the influence of canyon.