Thạc Sĩ Semi-active modal control for seismic structures with variable friction dampers

Abstract
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The implementation of variable friction dampers for vibration mitigation of seismic structures generally requires an efficient
semi-active control law. In this paper, a semi-active modal control method is proposed to determine the controllable clamping
force of a variable friction damper. By using the Heaviside function, the feedback gain of the proposed method was modified
from that of an active control, so it was able to accommodate the control force constraint of the variable friction dampers. A discrete-
time formulation and numerical procedure for the simulation of the proposed control method is discussed. A comparative
study was performed on a multiple DOF structure controlled by passive friction dampers, variable friction dampers as well as an
active bracing system. Several structural configurations with various damper/sensor deployments were also considered. The study
has shown that by merely using a few sensors and a lesser number of dampers than the passive control case, the proposed semiactive
control method is able to effectively and simultaneously reduce the average maximum responses ofthe floor displacements
and accelerations. It is also shown that as compared with the control performance of its active control counterpart, the proposed
method provides almost equivalent capacity ofenergy dissipation, and an equal level of response reduction.
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Keywords: Variable friction damper; Semi-active control; Modal control; Semi-active damper; Direct output feedback; Seismic structural control