A numerical and experimental analysis of semi-active (SA) control strategies for controlling seismic-excited structures is
presented. A physical model consisting of a two degree-of-freedom (2DOF) mechanical system with a magneto-rheological (MR)
damper was developed to evaluate this concept at LNEC’s shaking table. Linear elastic and viscous models were used to describe
the mechanical behavior of the 2DOF mechanical system. A Modified Bouc-Wen model was used to describe the behavior of the
MR damper. Four distinct control strategies were implemented for numerical and experimental evaluation. The associated
controllers were tuned using the system model and the ground motions information. The strategies were the integral control law,
two linear quadratic regulator strategies and a predictive controller, in conjunction with a clipped on-off algorithm. In both the
numerical and experimental tests the results reveal that the response of the structure is effectively mitigated by all of the analyzed
control methods. It is shown that SA systems can outperform the original structure as well as one using the best passive solution
for most of the strategies. The integral control law exhibits the best performance when collocated control was considered. If more
responses are available for control, the linear quadratic regulator technique exhibits even better performance.