Dynamic Behavior of Ground for Seismic Analysis of Lifeline Systems

摘要

A new mathematical formula is derived for the general wave transfer function in multi-layered media with inhomogeneous and nonlinear properties of soil. It is assumed that the ground consists of horizontally stratified layers overlying a homogeneous half-space which is excited by vertically incident, plane shear waves. To formulate the nonlinear harmonic wave solution, the surface layer is regarded as a multi-layered system consisting of infinite numbers of sub-layers with infinitesimal thicknesses. The mode-superposition procedure based on response spectrum provides an expedient tool for dynamic analysis of surficial ground. The characteristic equation for obtaining natural frequencies and free vibration modes is derived by using the proposed wave transfer function. To use the modal analysis for nonlinear systems, which previously has been used only for linear systems, a repetition scheme for calculating the model stiffness and damping is proposed which is an adaptation of the equivalent linearization technique.