Abstract: A seismic vibration control device for structures which employs a combination of primary and secondary vibratable masses to attenuate the vibration of a structure. The primary vibratable mass is passive and is supported on the structure. One or more active secondary vibratable masses are supported on the primary mass. Control forces are selectively applied to the secondary masses to control the period of the primary mass in a manner which is most effective to attenuate the seismic vibration of the structure.

Abstract: A vibration control device of an active type for a structure comprising a first additional mass body movable relative to the structure; spring means for giving a period to the additional mass body which synchronizes with the natural period of the structure; a second additional mass body supported by and movable relative to the first additional mass body; and drive means for applying a control force between the first and second additional mass bodies in response to a sensed vibrations of an earthquake or the like. Laminated rubber support provides main spring means for synchronizing with the assumed natural period of the structure. Auxiliary spring means, such as laminated rubber or coil springs, is separately provided for fine tuning the period of the device. The responses from the structure are reduced by adjusting the difference between the assumed and actual natural periods of the structure by use of the auxiliary spring means and by providing the control force from the drive means.