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Variable Dampers for Semi-Active Control of Flexible Structures.

pdf icon Variable Dampers for Semi-Active Control of Flexible Structures. (1019 K)
Sadek, F.; Mohraz, B.

Earthquake Engineering, 6th U.S. National Conference. Proceedings. Paper No. 61. Earthquake Engineering Research Institute, Oakland, CA. 1998, 1-12 pp, 1998.


dampers; algorithms; seismic design; semi-active control; structural dynamics; variable dampers


Semi-active control using variable dampers has been suggested for reducing the response of structures to different dynamic loadings. This study is concerned with examining the effectiveness of these devices for seismic applications. Three algorithms for selecting the damping coefficient of variable dampers are presented and compared. They include: a linear quadratic regulator (LQR) algorithm, a generalized LQR algorithm with a penalty imposed on the acceleration response, and a displacement-acceleration domain algorithm where the damping coefficient is selected by representing the response as a point on the displacement-acceleration plane. Two single-degree-of-freedom structures subjected to 20 ground excitations are analyzed using the three algorithms. The analyses indicate that contrary to passive dampers where an increase in damping increases the acceleration response of flexible structures, variable dampers can be effective in reducing the response. Variable dampers, however, are not efficient for rigid structures. The study also indicates that the generalized LQR algorithm is more efficient than the other two in reducing the displacement and acceleration responses. The algorithms are used to compute the seismic response of a isolated bridge modeled as a SDOF system. The results indicate that variable dampers significantly reduce the displacement and acceleration responses of the flexible structure.