Inelastic displacement ratios of fully self-centering controlled rocking systems subjected to near-source pulse-like ground motions

Modern self-centering controlled rocking (SC-CR) systems are capable of reducing residual drift after severe earthquakes by swaying on their bases and concentrating damage in energy dissipation devices. The present research determines constant-strength (C-R) spectra for SC-CR systems subjected to far-field and near-field pulse-like (NF-pulse) ground motions. SC-CR systems are simulated as single degree of freedom models with a flag shape behavior. Nonlinear time-history analyses are conducted using 91 NF-pulse and 44 far-field records to derive the C-R spectra. Each point of C-R spectrum of a SC-CR system is the ratio of maximum inelastic to maximum elastic displacement. An extensive statistical study is carried out to examine the effects of ground motion and modeling parameters on the C-R spectra. It is found that the influences of pulse period, predominant period of ground motion, and modeling parameters on inelastic displacement ratios (C-R ratios) of SC-CR are significant, while other effects such as the source to-site distance, earthquake magnitude, and site classes are not as much important. Finally, using two stage regression analyses, formulas are developed for determining un-normalized (code-compliant) and normalized C-R spectra of SC-CR systems subjected to far-field and NF-pulse ground motions. (C) 2015 Elsevier Ltd. All rights reserved.