Experimental and FEM investigation on influence of ring stiffeners on buckling behaviour of subsea pipelines under hydrostatic pressure

摘要

Submarine pipeline is considered as a thin walled structure and, therefore, buckling is an important consideration at design stage. Initial buckling is created on pipeline because of problems such as additional force on a point of pipeline, existing imperfections on it or because of forces increasing and because of this buckling propagation is started on the pipeline. These occurrences cause the estimated strength of pipelines to decrease. For the prevention of this problem the application of ring-stiffeners is a good solution. For this purpose experimental and FEM analysis programs are arranged for investigating the influences of ring stiffeners on buckling strength of pipelines. Pipelines are subjected to many forces such as hydrodynamic and hydrostatic pressure, the dynamic effect of waves, free span and so on. Because of the importance of hydrostatic pressure and experimental limitations, this type of force is modelled and studied in this paper. All models in experimental and FEM methods are geometrically corresponded together. The modes of initial buckling, buckling propagation and post-buckling of pipeline are evaluated and compared in both methods. It was found in this research that these quantities are highly influenced by attached light weight ring stiffeners. Some new phenomena appeared with increasing the number of rings such as torsion effects and lateral displacement on pipeline.