Flexural Buckling of Pretwisted Columns

The present work deals with the problem of flexural buckling of a thin column supported at its ends. The column has a constant cross section, but its principal axes of inertia rotate as a function of its axial coordinate. The problem is solved with a direct variational method using Fourier series and shows that this particular geometry improves the critical load of the column with respect to the case in which the orientation of the section of the column remains constant. The flexural buckling load increases on increasing the rotation between the two end cross sections of the column (pretwisting). The algorithm converges rather rapidly. However, on increasing the pretwisting of the column a greater number of Fourier series terms must be considered to reach the necessary precision. The calculations have been Carried out hypothesizing that the rotation angle of the principal axes of inertia varies linearly with the axial coordinate. The problem can be easily extended to other modes of varying this angle.