Evaluation of Axial Compression Slenderness Limits of High and Ultra-High-Strength Steel Circular Hollow Sections

Despite significant advances in metallurgy and the potential to create high and ultra-high-strength steel, all international specifications for steel design provide little information about the limits of slenderness for high-strength steel sections (HSSs) and don’t provide anything about the design of ultra-high-strength steel sections (UHSSs). The current international steel codes such as AISC 360-16 and EC3 can be applied only to steel grades up to S690 and S460, respectively, according to their limitations. These approaches for normal-strength steel are used for HSSs and UHSSs without extensive studies to determine their accuracy in these cases. Therefore, it is one of the main objectives of this study. The behavior of high and ultra-high-strength steel circular hollow sections under axial compression load is studied in this research. Sixteen nonlinear finite element (FE) models were generated to replicate stub column tests that were experimentally tested by others in previous research. Hence, a parametric study was conducted using forty FE models developed to investigate the local buckling behavior under various slenderness ratios comprehensively. The developed models covered slenderness ratios ranging from 20 to 1226 and steel grades S460 and S1100 with yield stress equal to 460 MPa and 1152 MPa, respectively. The FE results were combined with 105 previously collected experimental results to assess the applicability of existing codified design methodologies in the Euro code and the North American codes of cold-formed circular hollow sections (CHSs). Based on the results of this study, new cross-section slenderness limits and new design equations for more efficient simple designs were presented for circular hollow sections of HSSs and UHSSs and compared with the results of experimental tests and FE models