Optimal placements of actuators in vibration active control for double-layer spherical grid shell structures

The sensitivity of actuator disposed in the members was defined based on the optimization theory of active control with quadratic performance function in order to ascertain the optimal placements and numbers of actuators in the active control for double-layer spherical grid shell structures. An optimization process to successively delete the insensitive actuators was presented. Meanwhile, a Matlab program was developed. The numerical results for double-layer spherical grid shell structure show that it is better to lay out the actuators in chords than in diagonal members, as well as in upper chords better than in lower chords. Under satisfying the requirements of restricted structural displacements and control forces of actuators, the farther from structural center the actuators are laid out in upper chords, the more sensitive they'll be, and it is better to lay out the actuators circularly than radially. The optimal placements of actuators are in the outermost ring of upper chords for double-layer spherical grid shell structures. Results also show that the effectiveness of active control is apparent under different seismic inputs while the actuators are laid out in the optimal placements.