Behaviour and design of fabricated high strength steel columns subjected to biaxial bending. Part 2: Analysis and design codes

This paper considers the behaviour of hollow and concrete filled steel columns fabricated with high strength structural steel plate and subjected to biaxial bending. The columns considered in this paper are fabricated from high strength quenched and tempered structural steel plate of nominal yield stress of 690 (N/mmÃ"šÃ‚²). The principalparameter that has been considered in the test program is the slenderness of the component plates. The results of the experiments have been compared with existing codes for the consideration of steel and steel-concrete composite columns under biaxial loading conditions. These include the Eurocode 3 and 4 document, (British Standards Institution, 1992 and 1994), the Australian AS4100 design provisions for steel (Standards Australia, 1998) and American Standard LRFD (American Institute of Steel Construction, 2000). The experiments did reveal the beneficial effect of the use of concrete infill on delaying the onset of local buckling and thereby the post-local buckling behaviour of the columns. A numerical model to consider the coupled effect of local and global buckling under biaxial conditions has been developed herein. This model considers the behaviour of short and slender concrete filled high strength steel columns under biaxial loading incorporating material and geometric non-linearities. For this analysis the equilibrium of the member is investigated in the deformed state, using the idealised stress-strain relationships for both materials steel and concrete, considering the elastic and plastic ranges. The paper concludes with a suggested design approach and makes suggestions for further research.