Nonlinear Finite-Element Analysis for Hysteretic Behavior of Thin-Walled Circular Steel Columns with In-Filled Concrete

The strength and ductility of thin-walled steel columns under cyclic loads are considerably upgraded by filling concrete into hollow spaces surrounded by steel tube and diaphragms. The above thin-walled steel columns filled with concrete are referred here to as thin-walled CFT columns. Up to the present, no sufficient and precise research has been conducted on the versatile finite-element model (FE model) analysis that can take into account the upgrading mechanism of thin-walled CFT columns in a direct manner. Herein, an accurate FE model is investigated in order to fully include the important factors such as cyclic local buckling of steel tube, nonlinear behavior of confined concrete, and interface action between steel tube and in-filled concrete. The validity of the proposed models is examined by comparing with the results of cyclic loading experiments on CFT columns. With the proposed model, the effect of in-filled concrete on the upgrading mechanism of thin-walled CFT columns is discussed in detail.