Nonlinear instability of angle section beams subjected to static and dynamic sudden step loads

This paper presents a study on the flattening behaviour of angle section beams subjected to pure bending. Analytical solutions for both static and dynamic instabilities of angle section beams subjected to pure bending about its weak axis are derived using energy methods. The results show that the dynamic instability of angle section beams under the action of a sudden step moment occurs at a moment about 71% of the corresponding critical static moment, but the deformations of the longitudinal curvature and flattening at the critical dynamic state are almost twice of those corresponding to the static instability case.

► Analytical solution of nonlinear instability of angle section beams is presented.
► Influence of section flattening on loading capacity of beams is highlighted.
► It highlights the difference between static and dynamic instabilities.
► The solution is validated using nonlinear finite element analysis methods.