Dynamic umbilicals are usually exposed to cyclic environmental loads due to waves, motions of the host vessel, and current induced vibrations. These cyclic loads drive the fatigue design of functional components such as armor wires, steel tubes and conductor wires in an umbilical cross section. Fatigue assessment of umbilical components involves Finite Element Method (FEM) modelling both globally and locally. The "global" model is used to predict dynamic responses of an umbilical with equivalent cross-sectional properties in waves and currents. Stress calculation in umbilical components requires a special "local" FEM tool such as Uflex2d to correctly capture the interaction mechanics among the components within the cross-section.
This paper compares three methods for the combination of global and local analysis in order to obtain fatigue estimates. First method can be regarded as exact one and is used to benchmark other two, which are approximate.
