Integrated fire resistance analysis of concrete-filled steel tube columns under standard Fire: Design standards, simulations, and experimental validation

The applicability of Appendix 4 of the AISC 360-22 standard, which provides an equation for calculating the fire resistance rating (FR) of concrete-filled steel tube (CFT) columns, is limited by certain parameters. These restrictions reduce the flexibility of FR predictions for CFT columns, particularly for cases involving high slenderness ratios, large cross-sections, or high-strength concrete exceeding the prescribed limits. This study addressed these limitations by proposing a simplified predictive equation to extend the applicability of FR calculations to CFT columns with parameters beyond those specified in Appendix 4. The finite element method (FEM) was employed using ABAQUS software to simulate and analyze the fire performance of the CFT columns based on the ASTM E119-88 fire resistance test standard. The accuracy of the FEM model was validated by comparing it with experimental data from published studies. A comprehensive parametric analysis was conducted using 324 simulation cases. Based on the analyses, modification factors were introduced to enhance the FR formula in Appendix 4 of AISC 360-22, and a new equation with a more conservative approach was developed to predict the FR for cases in which the parameters were beyond the scope of the standard. A case study demonstrating the FR calculation for a CFT column was presented to illustrate the practical application of the proposed method. The extended applicability of the proposed new equation enables engineers to make more accurate FR predictions over a wider design range, thereby improving design efficiency and ensuring structural fire safety.