Structural behaviour of high strength steel hexagonal hollow section stub columns under axial compression

This paper presents a comprehensive experimental investigation into the structural behaviour of the high strength steel (HSS) hexagonal hollow sections (HexHS) stub columns under concentric compression. A total of 18 HSS HexHS stub columns encompassing three fabrication routes were performed. The HSS plates used to fabricate the specimen were delivered in Quenched and Tempered (QT) condition. The material properties within the cross sections of the HSS HexHS were measured. Initial local geometric imperfections for all the examined stub columns were measured. The cross-section slenderness yield limits in the existing design codes of the EN 1993-1-12, ANSI/AISC 360-16, AS 4100 and ASCE/SEI 48-11 were compared and assessed against the experimental results. It was found that the current limits for internal compression plates in HSS rectangular and square sections cannot be extended to cover the cross-section classification for HSS HexHS. In terms of the cross-sectional resistance predictions, all the design codes tend to under-estimate the resistance of HSS HexHS under axial compression. For sections failed by local buckling prior to the attainment of yield load, the AS 4100 yields more accurate predictions compared with those predictions based on the other design codes. Compared with the design approach of Direct Strength Method (DSM), Continuous Strength Method (CSM) provides more consistent and satisfactorily predictions, particularly for stocky sections due to the consideration of strain hardening.