A New Idea for Controlling the Seismic Response of Structures Based on the Use of Inertia Forces

Abstract eng:
Vibration control is an effective way to improve safety and serviceability of structures. The concept of common active control systems is to constrain the vibration of structures by imposing additional damping or stiffness, and many researchers have tried to propose innovative analytical methods and practical techniques in this regard [1]-[3]. This paper studies a basic idea of a seismic response control system in which the control forces are inertia forces which are created by a set of pre-compressed springs connected to set of masses installed in various parts of the structure, such as building’s floors. The main idea is sudden release of the pre-compressed springs exactly at the moment at which the drift value at a the corresponding level exceeds a pre-set threshold, so that the force in each of the released springs, which tends to push away the mass connected to it, acts in the direction opposite to the direction of motion of the corresponding floor, preventing it from excessive drift. Each of the released masses is locked again, by some stopper, at the moment at which its relative velocity with respect to the corresponding floor reaches zero. To analyze the seismic behavior of such a controlled system, a computer program in MATLAB environment has been developed to evaluate the response of the structure under simultaneous effects of the earthquake excitation and the forces created by the controlling sprig-mass systems, after releasing. By changing the dynamical parameters of the system and controlling masses, including stiffness and damping ratios, and computing the response of the structure in case of each of the given earthquakes, the optimal proportion between the controlling masses and the corresponding floor masses can be evaluated. Regarding the simplicity and relatively lower costs of the proposed control system in comparison with other existing systems, the use of this system can be recommended in new buildings and even existing buildings as a retrofit technique. References [1] A. Tani and H. Kawamura, Fuzzy optimal seismic control systems of buildings in case of active equivalent variable mass system, Proceedings., Second International Symposium on Uncertainty Modeling and Analysis, College Park, MD, USA, pp 611 – 618, 25-28 Apr 1993 [2] Yen-Po Wang, Chien-Liang Lee and Kwang-Ming Chen, Seismic structural control using a novel high-performance active mass driver system, Earthquake Engineering & Structural Dynamics, Volume 29, Issue 11, pages 1629–1646, November 2000. [3] Chien-Liang Lee and Yen-Po Wang, Seismic structural control using an electric servomotor active mass driver system, Earthquake Engineering & Structural Dynamics, Volume 33, Issue 6, pages 737–754, May 2004.

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