Buckling analysis of thin-walled compressed members using generalised beam theory and FEM

Engineering Beam Theory cannot solve all the buckling modes, which arise in compressed thin-walled structural members since usually the cross sectional deformation must also be included in the analysis. Generalised Beam Theory (GBT) offers the possibility to calculate also the local and distortional buckling capacities, if these important failure modes of thin-walled structures are solved. In this paper the combination of GBT and the well-known finite element method (FEM) is used to analyze buckling capacity of thin-walled compressed members. The method is based on using the linear buckling analysis of FEM to solve individual buckling modes, i.e. bending, torsion and distortional modes, using the cross sectional values of GBT in beam element properties. In the second phase the interaction of these individual modes are combined by formulating a generalized eigenvalue problem and solving it numerically. The method can be used to prismatic structures with arbitrary boundary conditions and end loads. The proposed method is verified by comparing the results obtained from finite element analysis using thin shell elements.