Wave-induced fatigue analysis of deepwater risers based on time-domain scaling

In this paper, first, the relationship between the dynamic response of the deepwater riser and the significant wave height is deduced under a linear assumption, and a correction is further made to allow for nonlinearity. Then, the dynamic response of the riser is obtained by employing the time-domain scaling method, based on which a global fatigue analysis is performed. Finally, the results are compared with those obtained by the accurate calculation method. It is shown that (1) the power-law scaling approach achieves a fatigue life more acceptable in industry while the linear scaling approach is more conservative; (2) the proposed method takes into consideration the system nonlinearity implicitly and helps to obtain accurate results with less computational effort, so that it is suitable for the initial assessment of riser fatigue and the sensitivity analysis of predicted fatigue life to key input parameters; and (3) the proposed method is also suitable for the fatigue evaluation due to its conservatism guaranteed by the scaling from large to small significant wave heights.