Influence of prebuckling deflections on the elastic lateral-torsional buckling of thin-walled beams with various end supports: Analytical and numerical investigations in the case of doubly-symmetric cross-sections

Abstract

In this paper analytical and numerical studies are presented to investigate the effect of prebuckling deflections on the elastic lateral-torsional buckling of single-span beams with doubly symmetric cross-sections. A special emphasis is placed on various support conditions. New analytical formulae are derived for classic end supports, then numerical studies are performed comparing the critical moments from analytical formulae and beam finite element solutions. Since in standard finite element linear buckling analyses the effect of prebuckling deflections is not accounted for, a specialized iterative buckling analysis is employed. The results prove that the critical moment can efficiently be calculated by classic numerical methods, even if the effect of prebuckling deflection is considered. The existing literature suggests that the prebuckling effect is positive, with the critical moment increase being influenced primarily by the ratio of minor-to-major moment of inertia, however, in this paper it is shown that this can be confirmed only in the case of simply supported beams with small torsional rigidity. Both the analytical formulae and the numerical results clearly show that the torsional rigidity of the cross-section and the length of the beam modify the prebuckling effect, while, unlike suggested by the literature, the effect of prebuckling deflections is strongly influenced by the end supports, with some supports leading to negative prebuckling effect.