a.m horr - Ph.D. Student, Dept. of Civil & Mining Engrs, University of Wollongong, Wollongong, NSW ۲۵۲۲, Australia
l.c schmidt - Professor, Dept. of Civil & Mining Engrg., University of Wollongong, Wollongong, NSW ۲۵۲۲, Australia

A method is proposed for analysing the seismic response of a non-linear dynamic base-isolated structure. The method is based on a new, computationaly efficient, spectral method which is formulated in the frequency domain. The spectral (inite element technique proposed in this paper is capable of taking into account the non-linear damping behaviour of different isolation devices, as well as the material damping associated with structural members. The method iterates to obtain the response of the system in the frequency domain, returning to the time domain at each iteration to calculate nonlinearties which cannot be transformed to the frequency domain. Using a computer program, the proposed formulation has been extended to derive the dynamic response of a six story base-isolated structure under an earthquake excitation.