A small strain and moderate rotation theory of laminated composite thin-walled beams is formulated by generalizing the classical Vlasov
theory of sectorial areas. The proposed beam model accounts for axial, bending, torsion and warping deformations and allows one to predict critical loads and initial post-buckling behaviour. A finite element approximation of the theory is also carried out and several numerical applications are developed with reference to lateral buckling of composite thin-walled members. The sensitivity of critical load to secondorder effects in the pre-buckling range is pointed out
