Simulation of Multi-Support and Multi-Component Spatially Variable Ground

Abstract eng:
Spatially variable ground motions should be considered during the seismic response analysis of large-span structures. Based on original spectral representation method (SRM), a simulation method is developed with reasonable spectral density function, coherency function and site transfer function considering spatial correlation ， for the non-stationary multicomponent and multi-support ground motions on both the bedrock and the ground surface of an engineering site, which has varying soil conditions at different structural supports. Two numerical examples are presented to demonstrate the proposed method. Each generated ground motion time history is compatible with the derived power spectral density at a particular point on the site, and any two of the ground motions are compatible with a model coherency function. Results show that amplification and filtering effects on the incident wave from local site conditions lead to obvious changes in the amplitude and frequency components, even much greater than changes caused by wave passage effects and coherency effects under specific site conditions. Hence it’s necessary to use non-uniform spatially variable ground motions with rational consideration of local site effects, when choosing the input for seismic analysis of large-span structures. Simulation of multi-support and multi-component ground motions can be simplified to three independent multi-support one-dimensional ground motions, owing to the critical value of coherency functions through numerical method. Therefore, this simulation method offers an effective way for determine seismic input for the seismic response analysis of large-span structures in practice.

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