An Alternative Methodology to Evaluate the Fatigue Life of Risers Based on Regular Waves

In the last years, the increasing knowledge about environmental data has also increased the number of sea states that are used in the fatigue analysis of risers. These analyses demand high computational resources and, consequently, methodologies to reduce this cost become very attractive. One of the most studied alternatives in this area is the utilization of regular waves, represented by block diagrams. Based on distributions such as the one proposed by Longuet-Higgins, irregular waves are decomposed in regular waves, originating deterministic scatter diagrams. The Longuet-Higgins distribution, however, has a tendency to generate an unrealistic number of waves at high periods and, consequently, it is usual do set a maximum cutoff level for the periods. In this work, a different approach to generate the regular waves scatter diagrams is investigated. It is based directly on the generation of time series of sea surface elevations, allowing an easy identification of heights and periods of regular waves. The obtained results indicate the feasibility of the proposed method, based on comparisons with irregular waves results.