Stochastic seismic response analysis of soft soil sites

A well-known equivalent linearization technique is proposed for the stochastic response analysis in the time-domain of horizontally layered soil deposits under vertically propagating random shear waves. The Bouc-Wen smooth hysteretic model is used and properly extended to better represent the nonlinear-hysteretic shearing stress-strain relation of soils observed under cyclic loading with fixed and variable limits. The earthquake ground motions are modeled as nonstationary Gaussian processes and the soil response is obtained in terms of its response statistics from which the statistics of the surface ground accelerations and site-specific response spectra can be obtained.