Non-linear buckling analysis of thin-walled beams modeled with 7-parameter shell elements

The non-linear quasi -static buckling of thin -walled beams with arbitrary cross -sections is studied by developing coupling strategies between the composing plates (web, flanges). The element adopted for modeling the plates is a 7 -parameter shell element using the Enhanced Assumed Strain concept (B & uuml;chter et al., 1994). Different nodal shell directors exist at the interface between plates for thin -walled beams with arbitrary crosssections, requiring appropriate strategies. The coupling between plates first considers Lagrange multipliers at the interface, following the mortar method on the surface between the plates. Second a simplified preprocessing method is proposed by modifying the shell directors of the nodes close to the interface. In the case of the quasi -static buckling of thin -walled beams with L-shaped and I -shaped cross -sections, the two coupling strategies are thoroughly assessed by using three different solution procedures: Newton-Raphson, Newton-Riks and Asymptotic Numerical Method (ANM). The pre-processing method is simple and turns out to be robust and efficient.