COMBINATION DAMPER AND BASE-ISOLATION STRUCTURE WITH COMBINATION DAMPER INSTALLED THEREIN

PROBLEM TO BE SOLVED: To provide a combination damper producing the effect of damping with efficiency over a wide range from small to large earthquakes, and a base-isolation structure with the damper installed therein. SOLUTION: The combination damper comprises a combination of a metallic damper 4 and a multilayer viscous damper 5. The viscous damper 5 has a plurality of horizontal movable resistance plates 9 installed on a support member 6 in predetermined vertically spaced apart relationship to one another. A plurality of fixed plates 10 horizontally positioned between the upper and lower movable resistance plates 9 and spaced apart from the resistance plates by the appropriate interval for producing viscous shear resistance are installed vertically on the sidewalls of a container 8 while in an arrangement such that the fixed plates cross the resistance plates 9. The lowermost movable resistance plate 9 is appropriately spaced apart from the bottom face of the viscous material container 8 and the horizontal clearance of a resistance part relative to the viscous material container 8 of the viscous damper 5 is set at about 10 cm. The resistance part is collided with the sidewall of the viscous material container by interlayer deformation due to the energy of earthquake motion in a medium or lesser earthquake.