Research on mechanical behavior of circular CFT stub column under axial compression

Based on the existing triaxial plastic damage constitutive model of concrete and the elastic–plastic constitutive model for steel, a three‐dimensional solid finite element model of the concrete‐filled circular steel tubular stub column (circular CFT stub column) was developed. The finite element model analysis results of the damage morphology, load–displacement curves, and ultimate bearing capacity are compared with the experimental results. On the basis of existing experimental verification, 72 full‐scale models were established, and parameter analysis was conducted to compare the effects of steel tube strength, concrete strength, and thickness of steel tube on the load–displacement curves. The confined areas, unconfined areas, and the corresponding mean values of concrete Mises stress were determined when circular CFT stub columns reached the ultimate bearing capacity, and the practical calculation formula of ultimate bearing capacity considering the confinement coefficient was proposed. This confinement coefficient is mainly related to the diameter to thickness ratio. The comparison of the ultimate bearing capacity calculated by this formula with the experimental values and FE values proved the accuracy and effectiveness of the formula, which was superior to the formulas suggested by other scholars and specifications.