Seismic site effects for weak deposits in Korea

Abstract

In a nonlinear site response analysis, small strain damping is modeled as viscous damping through use of various forms of Rayleigh damping formulations. The type of Rayleigh damping formulation is known to have a pronounced influence on the response of deep soil columns. This paper performs a series of nonlinear site response analyses at weak soil profiles in Korea. Analyses highlight the strong influence of the viscous damping formulation even at shallow profiles less than 50 m in thickness, in which the simplified Rayleigh damping formulation significantly overestimates energy dissipation at high frequencies due to artificially introduced numerical damping. When using the full Rayleigh damping formulation, the artificial damping is greatly reduced. Results are further compared to equivalent linear analyses. The equivalent linear analyses overestimate the peak ground acceleration due to the stiffer response at the maximum shear strains for soft and deep soil columns.