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

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.