On some aspects of torsional buckling of thin-walled I-beam columns

The paper summarises some findings on torsional buckling of thin-walled I-beam columns. The study is divided into two parts. Firstly, the effect of initial deflection on torsional buckling load of thin-walled I-beam column is discussed. Starting from the description of kinematics, strain and stress, the governing differential equations of torsional buckling are derived from the principle of stationary potential energy. The critical load of torsional buckling is determined with the aid of the perturbation approach. The numerical example concerning simply supported I-beam column is presented and discussed on the grounds of the theory of thin-walled members and compared with the result obtained from non-linear 6-parameter theory of shells. Secondly, the localisation of local buckling modes is studied. This effect, observed during the modelling by shell theory, strongly affects the I-beam columns behaviour with relatively wide flanges.