Eigen Buckling of Cylindrical Shells in Offshore Structures : influence of Geometry, Loading and End Conditions

Shell eigen buckling behaviour is investigated for combined axial and lateral pressure loading and with various end conditions. In addition to the more common pinned (P) and clamped (C) end conditions, particular emphasis is placed on shells where one or both of the ends are free (F). The physical behaviour in different geometry ranges is used to develop simple, approximate eigenvalue formulae, which are verified against the predictions of linear shell buckling theory using the method of variations. The different end conditions are treated through multipliers to the well-known pin-ended (P–P) case. It is found that, for practical geometries, P–F shells are very much weaker than C–F shells due to the lack of warping restraint. The results have application to the design of suction caisson foundations for offshore platforms.