Control of Seismic Response of a Building Frame by using Hybrid System with Magnetorheological Dampers and Isolators

The traditional isolation approach can suppress the seismic responses of upper structure and at the same time induce substantial deformation of isolation layer. Excessive base drift may cause the degradation and even the damage of the isolation system. Therefore, supplemental control devices can be implemented in the common base isolation system to construct hybrid control system and reduce the base drifts of structures. The seismic mitigation of a building frame with hybrid control system is carried out in this study. The mechanical model of magnetorheological (MR) damper is presented by involving the effects of brace stiffness of the damper. The equation of motion of a frame structure with stiffness eccentricity incorporated with intelligent hybrid control system disturbed by seismic excitations is established by considering the effects of both isolators and MR dampers. A clipped-optimal strategy based on fuzzy control principle is proposed for MR dampers. A building frame is taken as the example to examine the feasibility and reliability of the proposed intelligent control approach. The efficacy of the hybrid control approach is compared with the base isolation approach. An extensive parametric study is carried out to find the optimal parameters of MR dampers, by which the maximum reduction of seismic responses may be achieved, and to assess the effects of earthquake intensity and brace stiffness on damper performance. The work on example buildings showed that the installation of the smart dampers with proper parameters and proper control strategy could significantly reduce seismic responses of structures, and the performance of the smart damper is better than that of the common base isolation system. The optimal parameters of the MR dampers could be identified through a parametric study.