12.10: Structural response of high strength steel hollow sections under combined biaxial bending and compression

Abstract

ABSTRACTThe benefits of high strength steel (HSS) as a structural material and its potential to lead to smaller sections and thus lighter structures has increased its use in the construction industry. Current design specifications for HSS are widely based on assumed analogies with normal strength steel, since they are based on a limited number of test data on HSS sections that were available when these specifications were published. Hence, their applicability to HSS requires assessment. Even though research towards this direction has grown, literature on the structural response of HSS under combined biaxial bending and compression is scarce. This paper presents a comprehensive numerical study on the cross‐sectional behaviour of S460 and S690 square and rectangular hollow sections under biaxial bending and compression. Finite element models are developed and validated against experimental results on 12 hot‐finished S460 and S690 stub columns under uniaxial eccentric compression. The numerically generated load‐deformation curves, the ultimate loads and the failure modes accurately replicate the experimental ones. Hence, the FE models are deemed able to predict the behaviour of stub columns subjected to combined compression and bending. Upon successful validation, extensive parametric studies aiming to generate additional structural performance data are executed. Two aspect ratios, eight cross‐sections with different thicknesses, and forty‐three combinations of initial loading eccentricities corresponding to different ratios of axial load to bending moments about both axes, are investigated for both steel grades. The results facilitate the determination of interaction failure surfaces and allow the assessment of relevant design specifications. It is concluded that the capacity of Class 1 and Class 2 cross‐sections is adequately predicted by European design provisions, with some conservative predictions occurring for S460 sections in the stocky slenderness range. For HSS semi‐compact cross‐sections under combined loading, the Eurocode provisions appear rather conservative, whilst the capacity of effective cross‐sections is overall well‐predicted.