FATIGUE ANALYSIS OF A STEEL CATENARY RISER WITH UNCERTAIN SEABED PARAMETERS

摘要

Steel Catenary Risers (SCRs) are commonly employed in deepwater oilfields. The most problematic aspect of fatigue analysis is the touchdown point, in which the dynamic bending stresses are highest and the uncertainties are most pronounced. From a previous study conducted by the authors, it is found that the fatigue damage is extremely sensitive to several seabed parameters. Thus the uncertainties in the seabed parameters should be properly accounted in order to achieve a reliable and economical SCR design. In this work, reliability analysis is performed with three seabed random variables, namely soil stiffness, soil suction, and seabed trench. The efficient First Order Reliability Method (FORM) is employed in conjunction with the Response Surface Method to yield the probability of fatigue failure. The results are then compared with direct numerical integration. Further, the dependency between the different random variables is investigated.