Experimental investigations on material properties and stub column behaviour of high strength steel irregular hexagonal hollow sections

Comprehensive experimental investigations into the material properties and stub column behaviour of cold-formed high strength steel (HSS) irregular hexagonal hollow sections (IHexHS) are presented in this paper. Apart from the tensile coupons taken from the parent plates, tensile coupons extracted from the flat and corner portions from the cross-sections were also tested in order to measure the effect of the fabrication process on material properties. The strength enhancement predictive models proposed by previous studies were compared with the obtained test results from corner coupons with increased strength due to the cold-forming effect. A total of 20 HSS IHexHS stub column specimens were tested under axial compression and the cross-section classification from the existing structural steel design codes of EN 1993-1-12, ANSI/AISC 360–16, AS 4100, AISI S100–16 and design approaches of DSM and CSM were compared and assessed against the obtained results. It was found that the design provisions of cross-section classification in current design codes cannot be extended to the HSS IHexHS stub columns. Based on current codified yield slenderness limits, the strength predictions from design codes exhibit conservatism without the consideration of strain hardening and beneficial effect of element interaction whereas cross-sections with intermediate slenderness values were over-predicted.