Experimental evaluation of cyclic deformation capacity of ushaped dampers subjected to bi-directional loadings-Bi-directional characteristics of U-shaped steel dampers for base-isolated structures Part 1- Bi-directional c

Abstract

Evaluation of bi-directional characteristics of base-isolation devices is a very important issue for base-isolated structures. This paper describes a bi-directional loading test of U-shaped steel dampers widely-used for energy dissipation in base-isolated structures. The major findings obtained from the test are as follows: (1) torsion-induced residual deformation leads to contact with damper connections; (2) evaluation method of cyclic deformation capacity, which divides bi-directional orbit into deformations in 0 and 90 degree, is proposed and the validity is verified; (3) cyclic deformation capacity is reduced by cumulative torsion; (4) two indices J and J proposed in this paper can evaluate the limitation of cumulative torsion until contact ith connections and the tendency of torsion- induced reduction of cyclic deformation capacity.