3d Finite Element Simulation Method Of Long Period Ground Motion

The most seismic input commonly used in seismic analysis of engineering structures is based on the probabilistic seismic hazard analysis. With the constant improvement of strong seismic records and the development of source rupture process, a kind of strong ground motion modeling theory and numerical method with consideration of the rupture mechanism and effects of wave transmission effect has become a new research program and made great progress. The method can reflect the effect of source, transmission and local site conditions.During numerical simulation of strong ground motion with consideration of the finite fault rupture process, the commonly used method is that a finite fault is placed inside of calculation model and dislocation is equivalent to two-Couple according to dislocation theory. Generally, computing model of the method is huge because of comparatively deep seismogenic fault. The explicit finite element method is mentioned in the 24th quoted reference documentation for calculating long-period ground motion (this method is named as exogenous source for short). The three-dimensional computational model only calls for the consideration of Layer thickness of covered soil and below a certain thickness of rock. Then, we can regard mobile dislocation source in the whole space radiating seismic waves as the incident wave applied to area calculated. Thus, computational domain is relatively much smaller and less computational.To prove the correctness and accuracy of this method, the main researches in this thesis are summed up as follows:1 Formula deductions of incident wave generated by the mobile dislocation source of the 24th quoted reference documentation were deduced, and supplementary formulas of the fault at any angle with the surface were derived.2 The present method was used to calculate the displacement of nodes within the region. The finite element numerical solutions were compared with the corresponding analytical solution of full space. The results show that numerical solutions and analytical solutions are the same before reflected wave reaches from the free surface.3 The finite element numerical solutions were compared with calculations of common software COMPSYN (using the finite element discrete wave-number method proposed by OLSON et al), the results of them are basically consistent.4 The near-fault earthquake (Ms=5.4) is synthesized using empirical formula, then, numerical simulation of the earthquake was done by this method.At last, the paper summarized the whole contents, and put forward the further contents that would be researched.