Numerical investigation on local buckling behaviour of cold-formed high strength steel irregular hexagonal hollow section stub columns

The local buckling behaviour of cold-formed high strength steel (HSS) irregular hexagonal hollow section (IHexHS) stub columns under concentric compression is studied numerically in this paper. Finite-element (FE) models were developed and validated against the experimental data. The validated FE models were employed to conduct extensive parametric studies. The obtained numerical results together with the experimental data were used to evaluate the applicability of the existing design codes and design approaches to the cold-formed HSS IHexHS under concentric compression. The evaluation shows that the current slenderness yield limit values codified in design codes cannot be applied to cold-formed HSS IHexHS stub columns. The Eurocode 3 (EC3) and the North American code AISC 360-16 provide slightly over-estimated predictions for slender sections whereas the Australian code AS 4100 yields conservative predictions. For stocky sections, all the design codes show high degree of conservatism due to the lack of consideration for strain hardening. Furthermore, design approaches of Continuous Strength Method (CSM) and Generalised Slenderness Resistance Method (GSRM) have been found to provide more accurate predictions than the Direct Strength Method (DSM). Modified design approaches are also proposed to improve the accuracy of the strength predictions.