| 摘要 |
PROBLEM TO BE SOLVED: To stably maintain energy adsorption performance by using Sn having specific purity, containing a specific amount ofβ-Sn phase and having a fixed hysteresis stability index within a specific range for a metal material used for a metal plug of a laminated rubber type base isolation structure. SOLUTION: In a base isolation structure installed between a building and a base to support a load and to adsorb vibration energy of an earthquake and the like by using shear deformation of a metal plug, Sn having purity of 95% or more, containingβ-phase equivalent to not less than 95 volume % of entire Sn phase and having a hysteresis stability index within a range of 0.90-1.50 is used for a metal plug material. The hysteresis stability index is expressed by a rate of elastically distorted energy of hysteresis E20 obtained after applying±1% repeated-loading 20 times to elastically distorted energy of hysteresis E1 obtained after applying±1%-cyclic loading one time (E20/E1), when carrying out a repeated tensile and compression test by using a test piece under a designated condition.
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