Experiments on the Buckling Behavior of Ring-Stiffened Pipelines under Hydrostatic Pressure

Submarine pipelines are deemed as thin-walled structures in which relative external pressure may be created in some cases of fluid transmission. The certain effect of this type of loading is local buckling and its propagation along the considerable length of the line. In this study, an experimental program has been performed, in which the influence of ring stiffeners on the buckling strength of pipelines is investigated. In the tests, only hydrostatic pressure is considered as the major loading case, and the effect of further loads is neglected. The modes of initial buckling, buckling propagation, postbuckling, and development of yield lines and the final collapse of the pipeline have been closely appraised. It is verified that the buckling threshold highly hikes up by attaching some light ring stiffeners. By decreasing the ring spacing, the difference between buckling and failure loads is diminished and torsion-type yield lines at failure mode occur on the pipe skin.