A unified model for compressive strength of concrete-filled steel tube short columns with various symmetric sections

Abstract

In concrete-filled steel tube (CFST) short columns with square or circular section, the contribution of steel tube to the confinement and the load-carrying capacity of CFST short columns are affected by the column section shape. However, conventional confinement factor (CF) defines only the strength ratio of steel tube section to concrete section. In the present study, the effect of section shape on the composite action between the steel tube and concrete of CFST short columns was investigated. To consider the effect of section shape, a new confinement factor (MCF) was proposed, and a critical value for the new confinement factor (CMCF) was estimated to predict failure mode of CFST short columns under axial compression. Based on the MCF, a new section of the CFST short column with round corner (RCO-CFST) was proposed to improve the lateral confinement of CFST short column with square section. To verify the validity of the proposed MCF and CMCF, 14 CFST short column specimens with various section shapes were tested. Based on the MCF and CMCF, a finite element model for RCO-CFST short columns was proposed. Further, a unified model for the load-carrying capacity of CFST short columns with circular, square, and round corner sections was also proposed. The proposed model was compared to 411 existing CFST short column test results. The proposed model predicted well the test results of the existing CFST short columns regardless of section shape and material strength, which showed better prediction results than the current design codes for the CFST short columns using high-strength materials.