The Effect of Transverse Stresses in Web on the Lateral-Distortional Buckling of Curved I-Beams

Lateral-distortional buckling of framed structures and curved beams made of I-sections may be significantly overestimated or underestimated if the influence of the loading position of transverse forces is neglected. In this regard, this paper introduces a novel beam element that incorporates warping-distortional coupling effects and features nine degrees of freedom per node, considering both symmetric and anti-symmetric distortion modes. Particular attention is paid to the generation mechanism of transverse stresses in the web, considering both contributions of the in-plane bending and the applied transverse forces. Based on the equation of virtual work, a modified geometric stiffness matrix is derived that fully incorporates the effect of transverse stresses. Numerical examples demonstrate that the proposed beam element yields results in excellent agreement with reference shell models and accurately captures the effects associated with different loading positions of transverse forces. The findings further indicate that applying the transverse force directly to the top flange will weaken the lateral-distortional buckling resistance of curved I-beams.