Elastic-plastic collapse of long tubes under combined bending and pressure load

A study of the elastic-plastic collapse behaviour of long, cylindrical tubes subjected to combined bending and pressure load is presented.Besides the plastic properties of the tube material, the non-linearities accounted for in the analysis cover the Brazier effect and the influence of geometrical imperfections. The imperfections considered are given either by initial ovalization of the tube cross-section or in terms of initial, short-wave axial buckles. Related to ocean pipe laying, i.e. for thick-walled tubes under combined bending and external pressure load, initial ovalization proves to be by far the more severe type of imperfection.