Generalizing AISC360–22's high-strength CFT member design equations for economical and safety-enhanced design

The recently issued AISC360–22 Specification introduces Appendix II, offering provisions for the design of composite members using high-strength materials. This study is the first to evaluate the design equations in the AISC 360–22 over conventional and high-strength rectangular concrete-filled tube (RCFT) members. The evaluation is informed by the most comprehensive and up-to-date experimental database comprising 1350 concentric and eccentric axially loaded RCFT members. Employing a combined Gaussian Process Regression Technique and Monte Carlo simulations approach, the study aims to quantify the reliability index and the corresponding factor of safety for beam, column, and beam-column RCFT members. The analysis demonstrates the applicability of extending the recently adopted high-strength design equations in Appendix II to include conventional strength materials. In contrast to the design equations of conventional strength material, the new design equations of high-strength RCFT members provide a consistent level of reliability, regardless of the material strength. Finally, the study recommends using an increased safety factor ϕ = 0.9 for both beam and column members. This choice aligns with the AISC 360–22 requirement to achieve a minimum reliability index of 2.6 for the commonly used load combinations while promoting a design approach that enhances economic efficiency. •This paper is the first evaluation of the AISC360-22 design equations for conventional and high-strength RCFT members.•The study recommends a factor of safety of 0.9 for RCFT columns and and beams as they satisfy the minimum code requirements.•·The study suggests extending the AISC 360-22 high-strength CFT design equations for all material strengths.