Seismic performance of structures incorporating magnetorheological dampers with pseudo negative stiffness

Pseudo-negative stiffness control is a control scheme that is aimed to track, in a passive energy dissipation fashion, a target spring force with negative stiffness when possible. In this study, it is proved that systems with pseudo-negative stiffness control have the property of homogeneity even though they are nonlinear systems. The harmonic response analyses reveal that the pseudo-negative stiffness reduces the resonant frequency of the system. Seismic response spectrum analyses show that both acceleration and displacement can be reduced with the pseudo-negative stiffness control when the structural period is long and damping level is not high. Pseudo-negative stiffness control of a five-story base-isolated structure incorporating magnetorheological damper is studied through analytical and real-time hybrid test methods. The results show that displacement and acceleration responses with pseudo-negative stiffness control are lower than those with passive-off control and isolator alone, whereas the displacement response with pseudo-negative stiffness is greater than the passive-on control.