Stochastic nonlinear ground response analysis: A case study site in Shiraz, Iran

The present study aims to investigate the impact of the uncertainties of dynamic soil property on the ground response analysis in a case study. To this end, nonlinear time-domain ground response analysis and uncertainties of the soil parameters were coupled by a MATLAB code. To take full advantage of the real data, two investigation boreholes were drilled in the site. The analysis was deterministically conducted and then, extended to the stochastic context to consider the variability of the plastic index, shear wave velocity, and unit weight of the soil. Furthermore, the capability of the three different methods including modal analysis, approximate method, and nonlinear method to predict the stochastic fundamental period was investigated. The comparison revealed that the mean value for the approximate method provided closer predictions regarding the fundamental periods obtained through the nonlinear method. In the stochastic analysis, the maximum Coefficient Of Variation (COV) of the peak ground motion parameters including fundamental period, response spectrum, and amplification factor was calculated. The results demonstrated that the heterogeneity of soil parameters had a significant effect on the variation of the surface Peak Ground Displacement (PGD). Among the other stochastic responses, the fundamental period received the least effect from uncertainty of soil parameters.