Abstract
Since earthquakes are a frequent occurrence in Japan, seismic control devices have long been widely used for civil structures. Seismic control devices are particularly effective for reducing the wind-induced or earthquake-induced response of high-rise buildings. Viscous dampers that are typical seismic control devices have temperature and cyclic load dependency. Therefore, the conventional devices are problematic in that the damping performance is reduced in long-period ground motions. We propose a new eddy-current type damper (eRDT) to improve this issue. This device is converted from linear motion the ball screw to rotational motion of the pole ring by an amplifying mechanism. Permanent magnets are arranged on an outer surface of the pole ring and the braking ring made of steel, which faces the permanent magnets of the pole ring while maintaining a certain gap. When an earthquake occurs, a strong magnetic field is created and an eddy-current is induced in the braking ring. As a result, the Lorentz force is generated and the reaction force acts in the inverse direction of the pole ring rotation. Therefore this device can absorb vibration energy of the building structure. In this paper, we describe the basic structure of eRDT, and report the findings elicited from fundamental tests.
