Ductility demands on self-centering systems under earthquake loading

This paper describes the seismic response of self-centering single-degree-of-freedom (SDOF) systems in the form of constant-R ductility spectra. Constant-R ductility spectra for self-centering SDOF systems are computed and compared with those of SDOF systems representing conventional reinforced concrete (RC) systems (represented as bilinear elastoplastic and stiffness degrading systems). The self-centering SDOF systems represent hybrid and other post-tensioned seismic-resistant precast concrete structural systems. The SDOF systems are designed considering practical ranges of the global design parameters (strength reduction factor, postyielding stiffness, and hysteretic energy dissipation capacity). It is shown that self-centering systems develop greater ductility demands than conventional RC systems when the lateral strength and postyielding stiffness are the same. When the postyielding stiffness and hysteretic energy dissipation capacity of the self-centering systems are increased, the ductility demands decrease significantly, and the self-centering systems develop levels of ductility demands similar to those of conventional RC systems.