Influence of cumulative damage on seismic response modification factors of elastic perfectly plastic oscillators

Abstract

Based upon elastic perfectly plastic oscillators, this research investigates the influence of cumulative damage on seismic response modification factors. To take into account the cumulative damage due to hysteretic energy absorption, the Park–Ang damage index was adopted as the damage measure. A large number of iterative nonlinear response history analyses were conducted for the oscillators with periods and other features representative of conventional civil structures. Analysis results show that a significant portion of the total damage in a system reaching its damage limit state is due to hysteretic energy absorption. Consequently, the maximum tolerable ductility demand in the system under earthquake loading is lower than its ductility capacity determined under the monotonic loading condition. Moreover, the existing formulae for calculating response modification factors are shown to be inadequate to capture the effect of cumulative damage. A new method was developed for improved estimates of the response modification factors.