| 摘要 |
PROBLEM TO BE SOLVED: To provide a seismically isolated structure which is constructed on the ground via a foundation, has a long natural vibration cycle with respect to the foundation of an upper structure, and can avoid transfer of large earthquake ground motion to the upper structure. SOLUTION: According to the seismically isolated structure, a vertical support mechanism 3 is set on the foundation 1 to support the upper structure 2. The vertical support mechanism 3 supports a vertical load via a spherical or a columnar rolling element mounted on a smooth support surface, to thereby accommodate horizontal movement of the upper structure. As a result, transfer of a large earthquake ground motion to the upper structure 2 is avoided. Further, a restoring-damping mechanism 4 formed of rubber as a main material is interposed between the foundation 1 and a footing beam 2a of the upper structure 2. The restoring-damping mechanism 4 need not support a vertical load, and therefore it can be formed of a material which is flexibly deformable, whereby natural period of the upper structure 2 can be elongated.
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