Buckling of elliptical hollow section members under combined compression and uniaxial bending

• Full scale experiments on EHS beam-column members.
• Nonlinear FE simulations of EHS beam-column members.
• Development of design guidance for EHS beam-column members.
• Reliability analysis of design rules.
• Extension of limiting length concept to EHS members under combined loading.

Experimental and numerical investigations into the behaviour of elliptical hollow section beam-columns under axial compression and uniaxial bending have been performed and described in this paper. A large-scale experimental programme, comprising a total of 10 tensile coupon tests and 24 beam-column tests, was carried out. The beam-column tests included 6 pure compression tests, 3 buckling about the major axis and 3 about the minor axis, and 18 eccentric compression tests, 9 inducing compression plus bending about the major axis and 9 inducing compression plus bending about the minor axis. All tested elliptical hollow sections were EHS 150 × 75 × 5, and three member lengths of 1 m, 2 m and 3 m were considered. The test results have been supplemented by numerically generated results based on validated FE models to assess the influence of member slenderness and cross-sectional aspect ratio. On the basis of the experimental and numerical findings, design rules covering instabilities in hot-finished EHS beam-columns have been assessed and verified by statistical analysis. The limiting length concept has also been extended to EHS beam-columns.