Numerical study of buckling resistance of steel I-section members under two directional bending

Present approach to design of steel I-section beam-columns distinguish two design situations of elements subjected to two directional bending about their principal major axis and compression in which they are sensitive to: a) the flexural failure (second order spatial bending and compression) or b) the flexural-torsional failure (second order spatial bending, warping torsion and compression). This paper refers to the latter case of member failure and aims in the development of finite element numerical modeling technique that would be useful for the verification of analytical buckling resistance criteria of imperfect elements subjected to different loading conditions. Most of recent research investigations have been devoted to beam-columns bent about major axis and subjected to flexural-torsional buckling. Buckling of I-section beams under two directional bending has been rather scarcely considered, hence it is dealt with in this paper. Impact of the in-plane moment gradient on the member buckling resistance is assessed as well as concluding remarks in relation to analytical formulations presented in EN 1993-1-1:2005 are drawn.