A standard loading protocol for bi-axial loading test of U-shaped steel dampers using simple orbit is proposed. Proposed loading protocol consists of an elliptical orbit with aspect ratio of 3:1 and corresponding shear deformation angle of the major axis equal to 135%. The targeted cumulative damage is set at 1/3 of the limit state of U-shaped steel dampers under bi-axial loading. The values of the cumulative damage index D2 and sway index Jf are selected based on analytical results obtained for extremely severe earthquakes.
