Constitutive relation of stiffened square CFST Columns

Using the constitutive model of a square CFST column with binding bars, the constrained mechanism of the stiffened square CFST columns is analyzed in great detail. The equivalent constitutive model under uniaxial compression is established for square CFST columns. The model is then used to describe the stress-strain curve process for concrete and to calculate the bearing capacity. Models of ten concrete-filled square steel tubular columns under axial compression specimens are created with constitutive relation. The results are compared with the axial compression test of an ordinary square CFST specimen column and stiffened square CFST specimens. Our results show that the bearing capacity and stress-strain curves under axial compression are consistent with the actual test measurements. Analysis can be applied to the square stiffened CFST columns, the square CFST columns with binding bars, and the ordinary square CFST columns.