| 摘要 |
PROBLEM TO BE SOLVED: To steppedly switch the attenuation coefficient of a damper in accordance with the size of the amplitude of an earthquake. SOLUTION: A base isolation device 11 is constituted of: a base 14 fixed to a foundation, a support member 20 for supporting a structure, a low-frictional member for reducing the friction between the member 20 and the base 14, four dampers 24a-24d for damping the relative speed between the support 20 and the base 14, and four return springs 26 for returning the relative position between the member 20 and the base 14 to an initial position. The dampers 24a-24d have a damping force generation mechanism for reducing the damping coefficient when the amplitude of the relative displacement between the member 20 and the base 14 has a given value or less, and for increasing the damping coefficient when the amplitude has the given value or more. The mechanism has first and second damping force generating parts having the larger and smaller damping coefficients respectively, and a damping force switching part for closing a passage for hydraulic fluid passing through the second damping force generating part to guide the fluid to the first damping force generating part due to the increase of the amplitude. |
