Effect of Bending Moment Changes on the Rate of Axial Bearing of Composite Columns

At present, Concrete Filled Steel Tubes (CFST) are extensively used in modern structures due to their static and vibrating strength specifications. In this research, a new design model is studied for steel-concrete composite columns under the title of steel tube-shaped columns filled with self-consolidating reinforced concrete with high strength. In this composite column, an I- or cruciform steel hollow-square section is placed inside a square steel tube and the self-consolidating concrete with high strength is poured inside the tube. The ABAQUS software was used to analyze by finite element method (FEM) thirteen composite columns exposed to compression and bending. The effects of the concrete strength, the ratio of width to thickness, the ratio of length to width, and the ratio of the steel cross-section on the strength of these composite columns were evaluated. The results showed that the steel hollow-square section paced inside limited the formation of the diametric shear cracks in the concrete core. Therefore, the failure mode and the post-yield behavior change the composite short columns. The load curves against the axial strain; the stress distribution of the composite columns; and also the interaction curves of the nominal axial load and the nominal bending moment are shown. The comparison of the results computed by the use of FEM modeling showed good compatibility with the laboratory results.