Fatigue Analysis Methods of Dynamic Umbilicals

摘要

Dynamic umbilicals are usually exposed to cyclic environmental loadsdue to waves, motions of the host vessel, and current inducedvibrations. These cyclic loads drive the fatigue design of functionalcomponents such as armor wires, steel tubes and conductor wires in anumbilical cross section. Fatigue assessment of umbilical componentsinvolves Finite Element Method (FEM) modelling both globally andlocally. The "global" model is used to predict dynamic responses of anumbilical with equivalent cross-sectional properties in waves andcurrents. Stress calculation in umbilical components requires a special"local" FEM tool such as Uflex2d to correctly capture the interactionmechanics among the components within the cross-section.This paper compares three methods for the combination of global andlocal analysis in order to obtain fatigue estimates. First method can beregarded as exact one and is used to benchmark other two, which areapproximate.