Seismic Performance of Buildings Equipped with Four-Joint Rotational Friction Dampers in Mainshock–Aftershock Sequences

Abstract

This study assesses the effectiveness of retrofitting a steel moment frame structure with four-joint rotational friction (4J-RF) dampers to enhance seismic behavior during mainshock–aftershock sequences. Experimental tests were conducted on 4J-RF dampers with capacities of 500, 300, and 200 kN to evaluate the velocity dependency and validate the finite-element models. The experimental results demonstrated the cyclic responses of the dampers, affirming their stable performance over multiple cycles, which is a crucial factor for consecutive seismic events. A detailed numerical model was developed to simulate the behavior of 4J-RF dampers, and its accuracy was confirmed by comparing the experimental and numerical results. The finite-element models of the dampers were integrated into structural models, and nonlinear finite-element analysis was employed to investigate the response of the structures equipped with dampers during seven actual mainshock–aftershock seismic events. The results indicate that structures retrofitted with these dampers have minimal impact on the displacements or residual displacements caused by aftershocks. The dampers absorbed a considerable portion of the input energy, thereby diminishing the plastic energy absorbed by the structural elements. Consequently, this energy reduction led to a decreased residual displacement and improved seismic resilience. In contrast, without dampers, the drift and residual drift increased by up to 25% and 30%, respectively, during aftershocks.