SEMI-ACTIVE SEISMIC CONTROL OF MID-RISE STRUCTURES USING MAGNETO-RHEOLOGICAL DAMPERS AND TWO PROPOSED IMPROVING MECHANISMS

Abstract- This research examines performance of semi-active control of structures using Magneto-Rheological (MR) dampers. Mechanical specifications of this smart fluid damper change by falling into the magnetic field, so by increasing intensity of magnetic field the resulting damper power consequently increases. In this paper, two models of 9 and 20-story buildings were first selected as case studies and respective specifications of these structures (mass, stiffness and damping matrices) were calculated using valid sources as well as analysis of structures ignoring axial deformations against imposed loads. Then, sample structures were simulated in a Simulink environment. Consequently, optimum force determination processor, control system and MR damper were modeled in Simulink environment and were installed on a structural system. Finally, the obtained results from damper equipped structure were compared with non-controlled structure. In semi-active control case, clipped optimal algorithm was considered as control algorithm and optimal classic linear control method was used to determine control power. Based on the obtained results, it is observed that using this control method will significantly decrease structure response, such that MR damper can be about 12% to 36% effective in reducing maximum lateral drift and up to 21% in reducing maximum acceleration. Two mechanisms are eventually offered to improve the function of dampers and their performance. The proposed mechanism is shown to be effective in reducing the capacity and number of dampers required.