Controlling subsea oil and gas production systems requires fibre optics, power cables and tubes for the transportation of chemical for injection and fluid for hydraulic controls. These are arranged in helical bundles in successive layers. Shaped thermoplastic fillers are used to separate components and to fill out voids in the cross section. If necessary, armour is added to provide strength for the dynamic loads. This paper describes the application of 3D finite element method to assess the structural Integrity of subsea umbilicals, including the interaction between the constituent elements. It is suggested to uses a global analysis to determine the internal forces and local analyses (sub-modelling) for detailed stress evaluation. Abaqus is used for this purpose, due to its capability with large size problems under severe discontinuities due contact conditions. This paper also discusses the umbilicals interaction with seabed. The focus of this paper is on the fatigue life calculation.

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