Wavelet-based non-stationary response analysis of a friction base-isolatedstructure

A wavelet-based stochastic formulation has been presented in this paper for the seismic analysis of a base-isolated structural system which is modelle d as a two-degree-of-freedom (2-DOF) system. The ground motion has been mod elled as a non-stationary process (both in amplitude and frequency) by usin g modified Littlewood-Paley basis wavelets. The proposed formulation is bas ed on replacing the non-linear system by an equivalent linear system with t ime-dependent damping properties. The expressions of the instantaneous damp ing and the power spectral density function (PSDF) of the superstructure re sponse have been obtained in terms pf the functionals of input wavelet coef ficients. The proposed formulation has been validated by simulating a groun d motion process. The effect of the frequency non-stationarity on the non-l inear response has also been studied in detail, and it has been clearly sho wn how ignoring the frequency non-stationarity in the ground motion leads t o inaccurate non-linear response calculations. Copyright (C) 2000 John Wile y & Sons, Ltd.