Behaviour and design of members with monosymmetric cross-section

Abstract

Columns, beams and beam–columns with monosymmetric cross-sections are very frequently employed in steel structures. In this paper, the realistic, elasto-plastic buckling strength of such members is studied by means of non-linear numerical analyses and compared with the design rules found in Eurocode 3, the British Standard BS5950 and a new design proposal implemented in the Austrian national annex to Eurocode 3. The conservatism of the code regulations is highlighted, along with the codes' inability to capture the characteristic buckling behaviour of monosymmetric sections. For the basic load cases of pure axial compression, N, and pure bending moment, My, the source of the inaccuracy is shown to lie in the use of the buckling curves for flexural buckling as the basis of design. For beam–columns (load case N + My), it is shown that the sign of the bending moment (which can cause compression in either the smaller or the larger flange), in combination with an axial compression force, can cause remarkable differences when compared to the behaviour of double-symmetric sections.