A simple model for the twisting of I beams including web distortion – Application to members supported along a single flange

Abstract In the analysis of thin-walled members, some types of boundary conditions met in practice cannot be correctly represented by conventional line (1D) models. Of course, both shell models or advanced line models (such as generalised beam theory, GBT, among others) can accurately tackle this type of problems – at the cost, however, of the simple interpretation of results provided by conventional line models. This paper investigates the combined bending and twisting of doubly symmetric I beams supported along a single flange. This type of support precludes the application of the conventional Vlasov’s theory, because it ignores the distortion of the cross section. A simple line model which accounts for web distortion is developed and a mixed 3-field finite element – which can achieve any required accuracy on very coarse meshes – is derived for its numerical implementation. Illustrative examples are also presented.