Keywords: semi-active control of vibrations, magneto-rheological dampers, smart structures.

In the last two decades research and development of structural vibration control devices for buildings and bridges has been intensified to respond to construction market needs that demand more effective systems to decrease the damage caused by seismic and wind loading. This is the result of a public necessity to guarantee the serviceability of construction lifelines throughout and after the occurrence of a moderate or severe seismic event [1].

In this paper some on-going research and development on the vibration control of a three degree-of-freedom scaled metallic frame with a magneto-rheological (MR) damper [2,3] is addressed. The three degree-of-freedom frame was subjected to system identification techniques using an impact hammer procedure, to obtain the experimental dynamic properties of this structural system. A laboratory tested MR damper was then assembled in the scaled frame and new identification procedures were carried out to verify the influence of this device in the frame dynamic behavior. Based on these results a numerical model was created simulating semi-active control, in order to investigate and calibrate the frame behavior with the MR damper. The Bouc-Wen model [4] was used for the MR damper that allows modeling nonlinear hysteretic systems.

To study the response of the model structure with the semi-active controller, a few characteristic earthquake records were considered and some Matlab/Simulink routines were developed. Herein the El Centro earthquake record was selected as the input for the Lyapunov based controller, and the El Centro and Kobe-NIS earthquake records for the clipped-optimal control algorithm. The simulated results show that the control algorithms, based on the Lyapunov stability theory and clipped-optimal control, resulted in an improvement over the uncontrolled system.

1

R.C. Barros, R. Bairrão, F. Branco, I. Corbi, M. Kemppinen, G. Magonette, F. Paulet, G. Serino, "Implementation of Structural Control", International Journal of Earthquake Engineering and Engineering Seismology, European Earthquake Engineering 2.05, XIX(2), 51-68, Italy 2005.

2

R.C. Barros, A. Baratta, O. Corbi, M.B. Cesar, M.M. Paredes, "Some Research on Control of Vibrations in Civil Engineering under COVICOCEPAD Project", Third International Conference on Integrity Reliability & Failure (IRF 2009), Silva Gomes, Meguid, (Editors), Porto, Portugal, 20-24 July 2009.

3

M.B. Cesar, R.C. Barros "Semi-Active Control of a Metallic Scaled Frame with a MR Damper: Numerical and Experimental Research", in R. Barros, A. Preumont, (Editors), "School and Symposium on Smart Structural System Technologies (S3T 2010)", Porto, Portugal, 419-440, 6-9 April 2010.

4

S.J. Dyke, B.F. Spencer, M.K. Sain, J.D. Carlson "Modeling and Control of Magneto-Rheological Dampers for Seismic Response Reduction", Smart Materials and Structures, 5(5), 565-575, 1996. doi:10.1088/0964-1726/5/5/006

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