Uncertainties Propagation within Offshore Flexible Pipes Risers Design

How to account in the most robust manner for uncertainties within the loading has become critical for deriving cost effective and robust design rules for flexible risers. Especially the layer of the flexible riser bearing the tensile load, named tensile armours, is critical in the design in many of the deep-water developments. In this paper, multiple structures designed for west of Africa and the North Sea are investigated through a reliability method. Typical Uncertainties within the global riser motions, the local stress computations and in the stress-life curve resistance are accounted for. Demonstration is made that for the same uncertainties the variables influencing the reliability of the structure differ. Finally, the comparison with actual international design rules is made through the value of the safety factor applied on the design life.