Horizontal saddle supported storage vessels ― a parametric study of plastic collapse loads

摘要

Previous work by the present authors compared various theoretical methods with simple experiments for the plastic collapse load on end supported vessels loaded centrally by rigid saddles. It was found that the best agreement was obtained by using an elastic-plastic finite element analysis approach. In the present paper the elastic-plastic method has been used to examine the effect of various geometric parameters on the collapse load. A symmetrical model which replicated the geometric features of the experiments can be used to give an indication of the effect of specific isolated geometric variables but for others and for the purposes of undertaking a full parametric survey the model was modified to reflect an actual twin saddle supported vessel. It was found that when the saddle width and/or the saddle embracing angle increased, the collapse load increased; also when the overall length of the vessel increased, the collapse load decreased. An important parameter dictating the plastic collapse load for actual vessel geometries is the distance from the vessel head to the saddle centre. With the modified model a theoretical parametric survey was conducted on a range of vessel geometries with both welded and loose saddle configurations. The collapse loads from the survey are presented as a series of graphs and also in the form of simple equations for use in design.