Inspection of U-shaped steel dampers based on residual plastic deformation

Hysteretic dampers are widely applied as earthquake-induced energy dissipation devices in the design practice of seismic isolated structures. Therefore, an indispensable condition of urban function recovery determines whether the dampers can be used immediately after an earthquake. The deformation behavior of U-shaped steel dampers under uniaxial (in-plane) loading was the focus of investigation in this study. In this regard, two sets of loading tests on full-scale specimens were conducted: (i) cyclic loading tests with constant deformation amplitude, and (ii) cyclic loading tests with complicated loading histories. Image analysis was used to reproduce the deformation behavior of the dampers in loading tests. According to the obtained results in the tests with constant deformation amplitude, a numerical model that can describe the relation between residual plastic deformation and cumulative damage was adopted. Important findings were provided by the experimental results of the cyclic loading tests with complicated loading histories. Additionally, an evaluation method for the residual plastic deformation-cumulative damage of U-shaped steel dampers that are loaded with in-plan excitations was proposed.