عنوان مقاله [English]
For the seismic evaluation of structures, it is required to determine the inelastic displacement ratio. Indeed, the inelastic displacement ratio is one of the most important coefficients in codes which is used in force-based design method as well as in performance-based seismic engineering . Single-degree-of-freedom (SDOF) systems subjected to 78 near- and far-field ground motions recorded on site classes C and D (according to NEHRP 2003) were evaluated. Near-field ground motions include records with fling step, forward directivity and non-pulse characteristics. The influence of the period of vibration of the system, pulse period, mean period, significant duration, ductility level and damping ratio were also studied. Moreover, in order to investigate the effects of cyclic deterioration, the bilinear hysteretic behavior using the modified Ibarra-Medina-Krawinkler (IMK) deterioration model was used in the OpenSees software environment. The results show that the equation proposed by FEMA 440 underestimates the inelastic displacement ratio for near-fault records especially for fling step characteristics. Also, records with a larger pulse period lead to larger inelastic displacement ratio. In addition, records with larger duration (except fling step records) and larger mean period result in larger inelastic displacement ratios. The increase in the strength and stiffness deterioration increases the inelastic displacement ratio. Finally, equations were proposed for the inelastic displacement ratio in terms of the period of the system and the level of ductility by means of the nonlinear regression analysis for different types of ground motion records.