The effects of ground motion duration and pinching-degrading behavior on seismic response of SDOF systems

This study tries to highlight the importance of considering the influence of pinching-degrading in cyclic behavior to show the destructive effects of the duration on ductility (mu(m)) and hysteretic energy dissipation (E-N) demands for single degree of freedom systems. At first, the effect of duration should be isolated from other ground motion characteristics. At the second step, the aforementioned parameters are calculated for five models, which have periods between 0.05 and 3.0 s and four strength reduction factors for 47 records with long and short durations. The analysis of the results of non-linear response history shows that in pinching-degrading models with short periods, the duration effect not only has a significant influence on the median of E-N but also has substantial effect on mu(m). Moreover, these models are more dangerous under long-duration. Two predictive models are proposed to quantify the effect of duration and finally, they are integrated into Park-Ang damage index to determine the required ductility capacity.