Global instability of elliptical hollow section beam-columns under compression and biaxial bending

Abstract

The global instability of elliptical hollow section members under combined compression plus biaxial bending is studied in this paper by means of laboratory testing and numerical simulations. A total of 9 beam-column tests were carried out under different combinations of compression and bending about both principal axes. The material properties of the tested sections were determined by means of tensile coupon tests. All tested elliptical hollow sections were EHS 150755, and three nominal member lengths of 1 m, 2 m and 3 m were considered. Graphs of applied load versus mid-span bending moment, based on theoretical first and second order elastic considerations and the experimental second order inelastic response, are presented and described. Numerical models were initially validated against the experimental data using measured material and geometric properties, including imperfections. The models were subsequently employed in parametric studies to assess the influence of member slenderness and cross-sectional aspect ratio on the structural response. Finally, based on the experimental and numerical findings, design rules for hot-finished EHS beamcolumns were assessed and statistically verified.

Simulation and design of semi-compact elliptical hollow sections

“…Column tests were conducted by Chan and Gardner [30] and Law and Gardner [13] on hot-rolled EHS and by Chen and Young [31] on cold-formed EHS. Beam-column tests on hot-rolled EHS involving both compression plus uniaxial bending and biaxial bending were reported by Law and Gardner [13] and Law and Gardner [14] respectively. Tests on stainless EHS columns were also reported in [25].…”

“…The accuracy of the developed FE models was assessed by comparing the FE results with selected experimental data in terms of ultimate loads, full load-deformation histories and failure modes. Results from 40 stub column tests [10,11,18,19,25], 17 four-point bending tests [18,22], eight short beamcolumn tests [10], 36 column tests [13,25,30] and 27 beam-column tests [13,14] were used for the validation of the FE models. A wide range of geometries were considered, with the larger cross-section dimensions H of the modelled EHS ranging from 85 mm to 500 mm and the lengths of the modelled members spanning from 172 mm to 3190 mm.…”

“…[2,[9][10][11]) and member buckling level (e.g. [12][13][14]). On the basis of this work, design rules were developed and are due to be incorporated into the next revision to EN 1993-1-1 [15].…”