This is a study of vibration control dampers which reduce vibrations in strong winds of long-period structures such as high-rise buildings, tall towers and the main towers of bridges. The damping device makes use of the hydrodynamic force caused by the sloshing of water contained in rectangular tanks located on the tops of such structures. By synchronizing the sloshig period of the water with the fundamental period of the structure, damping effects are obtained by the forces acting on the tank walls. Inside these tanks, wire meshes, or "damping nets," are in- stalled perpendicularly to the movement of the water in order to add a damping effect. The function of the damping nets corresponds to that of the dashpot in a Tuned Mass Damper (T.M.D.). The paper describes the mechanism of the hydrodynamic force of the device, an analytical method of the system, and the hydrodynamic force characteristics in vibration tests using model water tanks, and the damping effects in a case of analysis of a high-rise building. The authors confirmed that the vibration damping system is capable of applying the most suitable damping effect to the structure through appropriate choice of water mass ratio, tank length, or number of damping nets.
