Unified axial compressive bearing capacity model based on Hoek-Brown criterion for concrete filled steel tubular columns with different cross-sectional shapes

As we all know, concrete filled steel tubular columns (CFSTC) have excellent bearing capacity and deformation capacity. Currently, most axial compressive bearing capacity models of CFSTC are empirical models with nonlinear fitting and are suitable for single cross-sectional type and material type, which has obstacles to the calculation of different cross-sectional types and has certain limitations to the application of the models. For this reason, the unified axial compressive bearing capacity model was established based on the Hoek-Brown failure criterion in this paper, considering effective confinement coefficients. The proposed unified model was applied to CFSTC with cross-sections of circle, square, rectangle, and ellipse, considering the slenderness ratio and material type. Finally, the 895 collected test data were used to determine model parameters and evaluate the models established in this paper and the existing models. The evaluation results showed that the model established in this paper can predict the axial compressive bearing capacity of CFSTC with different cross-sectional shapes with high accuracy. The prediction of CFSTC with cross-sections of circle, square, and rectangle had high accuracy, the average value (AV) and integral absolute error (IAE) were 1.008 and 0.095. At the same time, the axial compressive bearing capacity of CFSTC with cross-sections of circle, square, rectangle, and ellipse also can be predicted by the unified model, AV and IAE were 1.008 and 0.096. In a word, the proposed model based on the Hoek-Brown criterion in this paper had superior applicability and accuracy.