Circumferential stiffeners as buckle arrestors in long panels

is -well known that certain larger structures are susceptible to a type of collapse which starts locally but under favorable conditions can spread and has the potential of affecting the whole structure. The lowest load which can sustain this spreading of collapse (propagation load) is usually significantly lower than the critical buckling load of the geometrically intact structure. As a result, the option of avoiding the potentiality of propagating collapse by using the propagation load as the design criterion can result in significant penalties in cost and weight. An alternative is to base the design on the critical buckling load of the structure while including periodic stiffeners to arrest potential propagating collapse and keep its effect local. This paper illustrates this new design philosophy through an example involving a long pressure-loaded panel with sparsely spaced circumferential stiffeners cast in the role of buckle arrestors. An analysis is presented which models the process of quasi-static buckle penetration through such a stiffener. A general measure of arresting performance is defined, based on the maximum pressure experienced during the penetration process. A general framework for establishing the dependence of the stiffener arresting efficiency on the problem parameters is developed. Furthermore, fundamental concepts regarding limiting values for stiffener length and thickness are introduced, and results are presented which indicate that in this problem short, thick stiffeners provide the most arresting capacity for a given amount of stiffener material.