Seismic performance of buildings equipped with four-joint rotational friction dampers in mainshock-aftershock sequences

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.