Development of hybrid-type mass damper combining active-type with passive-type.

In order to reduce vibration of large-scale bridge towers or supertall buildings induced by wind or earthquake excitations, a two-axis mass damper actively controlled by an AC-servo motor is developed. The feature of this mass damper also includes the passive mechanism of a pendulum by the use of a curve-shaped mass, so that the actuator requires much less power than do the conventional active mass damper. The high performance is verified by a model experiment with a 3m-high tower structure, whose horizontal vibrations in two directions are effectively reduced against wind or earthquake excitations.