Peak and residual displacement ratios of the self-centering coupled structural system

This study presents a self-centering coupled system, which consists of a primary structure coupled by a self-centering structure or element, and a comprehensive investigation was conducted to obtain its peak and residual displacement ratios under ground motions from different site categories. The coupled system was idealized as a single degree-of-freedom (SDOF) system with the combination of the elastic-perfect-plastic (EPP) law and the self-centering (SC) law. Several parameters were defined and considered to calibrate SDOF systems in accordance with different contributions of the self-centering system to the primary system, such as the relative yield strength ratio, relative initial stiffness ratio, post-yield stiffness ratio, etc. Finally, 63450 SDOF systems were calibrated, and a total number of 9517500 cases of nonlinear time history analyses were performed. The influence of these parameters on the peak and residual displacement response was also discussed. It was found that the peak response was more sensitive to yield strength reduction factor. The most effective way to eliminate residual response was to increase the post-yield stiffness and the contribution of self-centering system to the primary system, but different trends were observed for systems with different yield strengths. Further, the predicting formulae for estimating the peak and residual displacement ratios were fitted, which were precisely enough to be used for not only the design and quick assessment of new-build self-centering structures but also for the retrofitting of existing/earthquake-damaged structures using self-centering elements.