Thin-Walled Structures 40 (2002) 1013–1036 www.elsevier.com/locate/tws Lateral post-buckling analysis of thin-walled open section beams F. Mohri a,c,* , L. Azrar b , M. Potier-Ferry c a EA 1116 (ERIN-MMGC) IUT Nancy-Brabois, De ´partement Ge ´nie Civil, Universite ´ Nancy 1, 54601, Villers les Nancy, France b SDTAS, Faculte ´ des Sciences et Techniques de Tanger, Universite ´ Abdelmalek Essaadi, BP 416, Tanger, Morocco c LPMM, UMR CNRS 7554, ISGMP, Universite ´ de Metz, Ile du Saulcy, 57045 Metz, France Received 7 November 2001; received in revised form 24 May 2002; accepted 28 May 2002 Abstract Thin-walled beams with open sections are studied using a nonlinear model. This model is developed in the context of large displacements and small deformations, by accounting for bending-bending and bending-torsion couplings. The warping and shortening effects are con- sidered in the torsion equilibrium equation. The governing coupled equilibrium equations obtained from Galerkin’s method are solved by a Newton–Raphson iterative process. It is established that the buckling loads are highly dependent on the pre-buckling deformations of the beam. The bifurcated branches are unstable and strongly influenced by shortening effects. Some comparisons are presented with the solutions commonly used in linear stability, like in the standard European steel code (Eurocode 3). The regular solutions appear to be very con- servative, especially for I sections with large flanges.  2002 Elsevier Science Ltd. All rights reserved. Keywords: Thin-walled; Open section; Flexural-torsional; Warping; Shortening effect; Nonlinear beam; Buckling; Post-buckling; Eurocode 3 * Corresponding author. Tel.: +33 3 83 68 25 30; fax: +33 3 83 68 25 32. E-mail address: foudil.Mohri@iutnb.uhp-nancy.fr (F. Mohri). 0263-8231/02/$ - see front matter.  2002 Elsevier Science Ltd. All rights reserved. PII:S0263-8231(02)00043-5