Stability Analysis of Circular Beams with Mixed-Mode Imperfections under Uniform Lateral Pressure

The elastic-plastic collapse of circular beams under uniform lateral pressure with an initial imperfection represented by a combination of different modes and amplitudes and with varying material properties is analysed from a computational viewpoint. The work is stimulated by a number of accurate experimental tests recently performed and it is found that both the initial imperfection and the material inhomogeneity along the beam axis can affect the collapse and produce a sensible variation in the carrying capacity of the structure on account of the changes between the underlying buckling modes. This can give reason for some apparently anomalous observed experimental results.