Analytical prediction of umbilical behavior under combined tension and internal pressure

Subsea umbilical is being used increasingly in harsh environments which require its mechanical behavior subjected to the axial symmetrical loads to be described. To predict the mechanical behavior of umbilical with multiple layers, a theoretical model is presented in this paper. The feature of the umbilical cross section in the model is a large-diameter central pipe. The contact problem between two adjacent layers contains deformation compatibility of the contact surface. The principle of virtual work is applied in the theoretical model to formulate the governing nonlinear equations and the contact conditions are introduced into the principle of virtual work. A 3D finite element model using ABAQUS is developed to represent the load condition of umbilical under tension and internal pressure. The mechanical behavior correlation between the ABAQUS and theoretical models validates the applicability of the theoretical model. In addition, the theoretical model is used for the assessment of other important parameters, such as the effects of internal pressure, lay angle and diameter-to-thickness ratio on mechanical behavior of umbilical, which are helpful for the design process of umbilical.