Simulation of fully non-stationary spatially varying ground motions considering nonlinear soil behavior

Taking the nonlinear soil behavior into consideration, a novel method for simulating fully non-stationary spatially varying earthquake ground motions (SVEGMs) was proposed. Based on the one-dimensional (1D) wave propagation model, time-varying shear modulus and damping ratio were introduced into the classical transfer function model, where the evolution characteristics of soil properties (i.e., shear modulus and damping ratio) during earthquake were obtained by using a two-dimensional (2D) site response analysis. By using an example of application, the out-of-plane and in-plane fully non-stationary SVEGMs on ground surface were simulated. The acceleration and displacement time-histories were observed, and the auto power spectral density functions (PSDFs) and coherency loss functions of simulated motions were compared with corresponding targets, respectively. The normalized time-frequency spectra of simulated motions were presented to exhibit the spectral non-stationarity. It was shown that the evolution tendency of predominant frequency of simulated motions reflected similar characteristics with that of shear modulus of soil, which demonstrated the validness of the proposed method.