Second-order generalised beam theory for arbitrary orthotropic materials

The paper presents the formulation of a second-order Generalised Beam Theory (GBT) developed to analyse the buckling behaviour of composite thin-walled members made of laminated plates and displaying arbitrary orthotropy. The derived second-order GBT equations are compared with the Vlassov-type ones obtained by Bauld and Tzeng and a few remarks are made concerning the cross-section mechanical properties appearing in the non-linear terms. Next, a few ambiguous aspects related to the structural meaning of the results yielded by member linear stability analyses are discussed and clarified. Finally, the application and capabilities of the formulated second-order GBT are illustrated by means of an investigation of the buckling behaviour of thin-walled orthotropic columns and beams, which takes into account both local and global deformation modes.