Lever-type active multiple tuned mass dampers (LT-AMTMD) consisting of several
lever-type active tuned mass damper (LT-ATMD) units with a uniform distribution
of natural frequencies have been proposed here for the vibration control of long-span
bridges under the excitation directly acting on the structure, rather than through the
base. The main purpose of selecting this form of excitation is to present guidelines for
the buffeting control design of long-span bridges under wind loads. Estimations have
been made on the performance of the LT-AMTMD with identical stiffness and
damping coefficient and unequal masses for the reduction of harmonically forced
vibrations by resorting to the defined evaluation criteria. The LT-AMTMD with the
actuator set at the mass block is found to have better effectiveness and higher
robustness in alleviating the vibrations of structures in comparison with the
LT-AMTMD with the actuator set at any other location. A new major result is that
both the spring static and dynamic stretching of the LT-AMTMD with the
actuator set at the mass block may be freely adjusted in accordance with the
practical requirements by changing the support locations within the viable
range while practically maintaining the same performance. Numerical results
demonstrate that the LT-AMTMD with the actuator set at the mass block
can highly improve the performance of the LT-MTMD (that is, the passive
counterpart of the LT-AMTMD) and provide better effectiveness than a
single LT-ATMD. Estimations have also been simultaneously carried out on
the LT-AMTMD (a single LT-ATMD) with respect to the hanging-type
AMTMD (a single hanging-type ATMD) as well as on the LT-MTMD (a single
LT-TMD) with reference to the hanging-type MTMD (a single hanging-type
TMD), so as to highlight the improved performance of the proposed control
system.
Keywords
damping, mass dampers, vibration control, harmonically
forced vibrations, lever-type active multiple tuned mass
dampers (LT-AMTMD), static and dynamic stretching of the
spring, long-span bridges
