Steel damper for seismic isolation and seismic isolation structure

A steel damper for seismic isolation installed between a lower part of a structure and a foundation, comprising:

• an upper board fixed to the lower part of the structure;
• a lower board fixed to the foundation to be at the same position in a plan view with respect to the upper board;
• and
• four seismic isolation plates fixed to the upper board and the lower board and extending in a cross direction in a plan view, wherein
• the four seismic isolation plates are members obtained by bending a long steel sheet, and include an upper fixing part and a lower fixing part parallel to each other, an upper inclined part and a lower inclined part that are closer to each other while being separated from the upper fixing part and the lower fixing part, and a connecting part that connects the upper inclined part and the lower inclined part to each other,
• the four seismic isolation plates are fixed to the upper board at a position where the upper fixing parts do not overlap each other, and are fixed to the lower board at a position where the lower fixing parts do not overlap each other,
• the upper fixing part is fixed to the upper board by sandwiching the upper fixing part between the upper board and an upper splice plate and tightening the upper board and the upper splice plate by fastening means,
• the lower fixing part is fixed to the lower board by sandwiching the lower fixing part between the lower board and a lower splice plate and tightening the lower board and the lower splice plate by fastening means,
• the upper splice plate is on a lower surface of the upper fixing part and the lower splice plate is on the upper surface of the lower fixing part, and
• a dimension of the upper inclined part and the lower inclined part in a width direction gradually decreases while being separated from the upper fixing part and the lower fixing part.