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In order to account for the site-response part of the seismic ground motion coherency for sites of interest, an analytical stochastic methodology is proposed in this paper. By combining the pseudo-excitation method with wave motion finite element simulation techniques, a numerical approach for the computation of the coherency function between observation points is developed firstly. Then the orthogonal expansion method is introduced into this approach to study the effect of the uncertainty in soil properties on the coherency function. Finally some numerical examples are given to show the applicability of the methodology. The computational results demonstrate that the lagged coherency values tend to decrease in the vicinity of the resonant frequencies of the site. 相似文献
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This paper presents a theoretical nonstationary stochastic analysis scheme using pseudo-excitation method (PEM) for seismic analysis of long-span structures under tridirectional spatially varying ground motions, based on which the local site effects on structural seismic response are studied for a high-pier railway bridge. An absolute-response-oriented scheme of PEM in nonstationary stochastic analysis of structure under tridirectional spatial seismic motions, in conjunction with the derived mathematical scheme in modeling tridirectional nonstationary spatially correlated ground motions, is proposed to resolve the drawbacks of conventional indirect approach. To apply the proposed theoretical approach readily in stochastic seismic analysis of complex and significant structures, this scheme is implemented and verified in a general finite element platform, and is then applied to a high-pier railway bridge under spatially varying ground motions considering the local site effect and the effect of ground motion nonstationarity. Conclusions are drawn and can be applied in the actual seismic design and analysis of high-pier railway bridges under tridirectional nonstationary multiple excitations. 相似文献
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This paper covers propagation of non-stationary random waves in stratified materials. The layered solid considered is located above the bedrock, whose material properties are assumed to be much stiffer than the solid, and known power spectrum densities of the non-stationary random excitations are input at the bedrock. The governing differential equations are derived in the frequency and wavenumber domain and the response power spectrum densities of the ground are investigated. The solution method presented uses the pseudo-excitation method in combination with the precise integration method and the extended Wittrick–Williams algorithm. The examples have up to three layers. 相似文献
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