Evaluating the ductility reduction factors of SDOF self-centering earthquake-resisting structural systems

In the past two decades, considerable research works have been directed toward the development of self-centering (SC) earthquake resisting structural systems that are able to make structures usable and repairable after strong ground motions. The focus of these research works is on eliminating the residual deformations and on preventing the earthquake damage in the primary structural components. In comparison with conventional structural systems, the hysteretic responses of SC structural systems are characterized by high levels of post gap-opening stiffness and with low levels of energy dissipation. This indicates that self-centering structural systems may have spectral response characteristics different from those of conventional systems. In this study, the ductility reduction factor (R-mu) which is required for the estimation of the strength demands is evaluated for SC single degree of freedom systems. The results obtained indicate that SC systems generally have R-mu levels lower than those of conventional systems. Modification factors that can be used to relate the R-mu levels of SC systems to those of conventional structural systems are introduced in this study and found capable of accurately predicting the R-mu levels of SC systems.