Experimental and Numerical Study of a Seismic Rotating Mass Damper (RMD) in an Isolated Floor

Negative stiffness has shown a capable characteristic in reduction of seismic response of structures. In this paper a passive Rotating Mass Damper (RMD) with negative stiffness characteristic, which was conceptually introduced in an earlier study, has been employed experimentally and numerically on an isolated floor to protect the building content during strong ground motions. The equipment was assumed as a rigid block on the isolated floor. The RMD devices force results indicate the negative stiffness characteristic of the damper. It was also observed that the RMD could increase the natural period of the system up to 50 percent without increasing the mass or reducing the stiffness. A numerical model of a seven storey building was employed to investigate the seismic response of the isolation floor in fourth storey. Two RMD models with different specifications and a viscous damper providing 10 percent of critical damping were applied in the study. Seven ground motion records were selected from PEER ground motion database. The time history analysis results indicate that RMD dampers show acceptable performance in terms of reducing both acceleration up to 40% and displacement responses up to 68% simultaneously in comparison with the viscous damper under the applied ground motions. The model was also analyzed employing seven artificial seismic waves. The results in this part also show the capability of the damper model in generating negative stiffness characteristics and a successful performance during excitation.