Stochastic estimation of the nonlinear response of earth dams to strong earthquakes

Abstract

The paper develops a simple and rational piece-wise linear random vibration procedure to estimate statistics of the nonlinear hysteretic response of earth dams to strong nonstationary stochastic excitation characterized by a Kanai-Tajimi spectrum. The method utilizes published data relating soil modulus and damping to the level of induced shear strain and incorporates a realistic inhomogeneous shear beam model of the dam. It is shown that the method is technically superior and computationally simpler than currently used iterative linear deterministic methods of analysis. Results are presented in the form of variation with time and distribution with depth from the crest of statistical measures of displacements, accelerations, shear strains and seismic coefficients on potentially sliding masses. The influence of the intensity and frequency characteristics of the excitation on the nonlinear response of a broad range of earth dams is graphically illustrated and a set of normalized graphs are presented whereby one can readily obtain preliminary estimates of key response quantities to be experienced by an earth dam during a potential earthquake motion of known rms acceleration and predominant frequency.