In recent years, semi-active Control has been introduced as a promising method for the seismic Control of structures, potentially combining the benefits of both passive and active Control systems. Magneto-rheological damper (MR) is one of the semi-active devices and its dynamic model is expressed by the Bouc-Wen model. The sliding sector Control (SSC) strategy as a robust Control approach is a class of variable structure (VS) systems for linear and nonlinear continuous-time systems with a special type of sliding sector using a new equivalent sector Control. The purpose of this study is to evaluate the effectiveness of the SSC strategy in determining the optimal voltage of MR at each step of time. For a numerical example, a three-story benchmark shear structure is considered subjected to normal (100%), high (150%), and low (50%) excitation levels of the El Centro earthquake. The results of the numerical simulations show that the semi-active Control system consisting of the SSC strategy and an MR damper can be beneficial in reducing the seismic responses of structures. Furthermore, the efficiency of the SSC strategy is also compared against that of the fuzzy and clipped-optimal Controllers. Comparative results of the numerical simulation confirm the robustness and ability of the SSC strategy.

Structural Control against earthquakes is becoming increasingly important. The linearquadratic optimal Control algorithm is proposed here to design active Control system for buildings against earthquake excitations. Full-state feedback system has been adopted. Active Tuned Mass Damper is used as the Control mechanism. The efficiency of the designed system has been verified against El-Centro earthquake. Active Control gives 35% more reduction in vibration of the structure than passive Control. Mass of the damper has appreciable effects on response parameters than its stiffness. A flexible damper proves to be more effective, but at the cost of actuating forces required. Performance of system is found to be optimum, when mass-damper is tuned to fundamental frequency of the structure. Stability of the structure is also enhanced by Active Control system. A SDOF building is presented to illustrate the study.

Passive, active and hybrid vibration Control of structures during earthquakes were studied. Particular attention was given to hybrid preview Control strategy for protection of structures against earthquakes. A three-story building under fixed-base condition and with laminated rubber bearing base isolation system subject to the El Centro 1940 earthquake were analyzed. The cases that an active Control system with and without preview was present were studied in details. The corresponding structural responses with passive, active and hybrid vibration Control systems were evaluated. Accelerations and displacements responses for active systems with and without preview sensors for fixed-base and base-isolated structures were computed and the results were compared with those for the unprotected building. It was shown that properly designed passive, active and hybrid Control systems could effectively reduce the acceleration transmitted to structures during a major earthquake.It was also shown that the inclusion of the preview sensors in the active Control strategy improved the system performance considerably. The hybrid use of the laminated rubber bearing isolation system with the active Control strategies could provide significant improvement of the protection of buildings during seismic events.

In this paper, a comparison is made between the predictive Control method and a neuro-fuzzy Control algorithm, which has been proposed recently by the authors, for Controlling a benchmark three-story frame structure subjected to earthquakes. Through numerical simulations, it is demonstrated that the proposed neuro-fuzzy Control algorithm can provide comparable and, in some cases, superior results.