Hysteretic behavior of thin-walled stiffened rectangular steel columns under cyclic bi-directional loading

A cyclic bi-directional loading experiment is carried out to examine the ultimate seismic behavior of thin-walled stiffened rectangular columns by using the accurate 3D-loading system. So-called a cyclic diamond load is adopted as one of the severest bi-axial loading patterns for rectangular columns. The results obtained from the experiment are also used to confirm the applicability of the nonlinear FEM shell analysis where the three-surface cyclic plasticity constitutive model is implemented. With the nonlinear FEM analysis as well as the experimental results, the seismic performance of the stiffened rectangular columns under cyclic bi-axial loading is extensively examined in comparison with that under in-plane cyclic loading. Finally, formulas are derived to evaluate the seismic performance of arbitrary rectangular steel columns subjected to the cyclic bidirectional loads.