Variable Dampers for Semi-Active Control of Flexible Structures.
Variable Dampers for Semi-Active Control of Flexible
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.