Optimal allocation of material and slenderness limits for the rectangular concrete-filled columns

Abstract

The current American Specification AISC 360–16 for concrete-filled steel tubular (CFT) columns exhibits particular limits in terms of section slenderness and material strengths. This paper proposes a decision tree algorithm, together with a comprehensive compiled experimental database of rectangular CFT columns under concentric loading and reliability analysis, to establish new optimal limits for section slenderness and material strength. The decision tree analysis yielded “data-driven classification rules” indicating that a relative section slenderness of 5, concrete compressive strength of 175 MPa, and steel yield strength of 850 MPa are considered optimal limits for the design equations in the AISC 360–16 in terms of achieving the minimum reliability requirements. The reliability analysis results are used to run a sensitivity analysis on the CFT columns to identify the dominant parameters that affect their axial loading capacity. Based on the sensitivity results, special attention should be given to the variability of concrete strength. The last part of this study demonstrates that the design equation of the high-strength CFT member in the new AISC Specification (AISC 360–22; obtained from a public review draft) can be extended to the conventional materials using the same proposed optimal limits.