Buckling strengths of cold-formed built-up cruciform section columns under axial compression

This paper describes experiments addressing the buckling and collapse behaviour of cold-formed stainless steel cruciform section columns. Doubly symmetrical flanged cruciform section columns were built using six individual press-braked plain channels made of austenitic grade EN 1.4307 assembled back-to-back. Three different column lengths were tested - namely, short (600 mm), intermediate (1200 mm) and long (2400 mm) lengths, and two channel geometries were used in all tests - with cross-section depths of 200 mm and 100 mm. Tests were carried out under pure axial compression and with fixed end support conditions. Tests were repeated two times for each length. It was observed that the buckling patterns were affected both by the global slenderness and by the spacing between the fasteners. Stocky columns experienced local buckling of the individual channel sections. The plastic failure mechanism was dependent on the fasteners spacing. Intermediate slenderness columns were characterised by interaction between global torsional buckling and local buckling whereas more slender columns failed predominantly through torsional buckling. For the latter, the spacing between the fasteners had a minor influence on the ultimate capacity.