The earthquake response of deteriorating systems

Abstract

This thesis is concerned with the earthquake response of deteriorating systems. A model for stiffness degrading or deteriorating systems is used to describe six different singledegree- of -freedom systems. A numerical investigation of the response of these six systems is performed using an ensemble of twelve earthquakes. The response is studied at nine nominal periods of oscillation. The numerical results are presented as response spectra corresponding to six different ductilities. An approximate analytical method for calculating the earthquake response of deteriorating systems from a linear response spectrum is presented. The method, called the average stiffness and energy method, is based upon the premise that a linear system may be defined which is in some sense equivalent to the deteriorating system. The criterion for equivalence in this method is that the average stiffness of the deteriorating system be equal to the stiffness of the linear system and the average energy dissipated by the linear system be the same as the average energy dissipated by the deteriorating system. The new analytical method is compared to existing methods. Comparison with the numerical results is also made. Based upon these comparisons, it is concluded that the average stiffness and energy method represents a significant improvement over currently available methods for predicting the earthquake response of deteriorating and nondeteriorating systems.