Abstract:
Supplemental damping systems can be substitute for hysteretic or kinetic damping and eliminate the need for additional strength and stiffness for desired performance levels. Supplemental dampers dissipate the energy mechanically and activated through movements of main structural system. Tuned Mass Dampers are examples of motionactivated devices in which flow of energy in the structure is disturbed through the vibration of a secondary system. In the essence tuned-mass dampers (TMDs) or vibration absorbers are mass-spring-dashpot systems that are tuned to a particular vibration mode of the structure on which they are installed. Under a dynamic excitation, the TMD resonates at the same frequency as the main structure but out-of-phase from it, thereby diverting the input energy from the main structure into itself. The environmental loads, such as wind and earthquake loads, possess many frequency components. Therefore, tuned mass dampers are optimized to render them effective for such large bandwidth inputs. To broaden the operational range of a TMD some damping is introduced in the optimization procedure. Although this added damping term smoothens the sharp peaks of frequency response function out of the operating range it also considerably decreases the effectiveness of TMD in the operating range. Thus, in this study it is aimed to constraint the response of the structure in the boundaries of the operating range of TMD, then the requirement for additive damping will be eliminated and TMD can be used in full efficiency. As a consequence a hybrid system is proposed in which the combined plant/nonoptimal TMD structure is equipped with an active controller such that the closed-loop system tracks the response of an oscillator with natural frequency set to the operating frequency of TMD unit. In the proposed system closed-loop states are not regulated to zero. Instead controller tries to help TMD to suppress vibration effectively thus lesser control effort is needed. This is further verified by numerical simulations which show the performance of the proposed approach under wind and earthquake loads.
