Dynamic Stability of Thin-Walled Column

The dynamic stability of the free longitudinal vibrations of a thin-walled column of open section is investigated. A criterion to predict the development of flexural and torsional oscillations through nonlinear coupling with the axial motion is presented. In contrast to static buckling of typical thin-walled columns, slenderness ratios exist for which the growth of torsional oscillations takes precedence over the growth of flexural oscillations. The effect of an initial axial load on the boundaries between regions of stability and instability of the axial motion is considered. A substantial interchange of energy between the axial motion and the parametrically excited flexural and torsional motion is demonstrated.