Resolving the API RP 2MET Crest Conundrum for Wave-in-Deck Loading

The API recommended wave load recipe is based on a "design wave approach" which uses a nonlinear regular wave theory such as Stream Function. When using such a nonlinear regular wave theory, a wave with a specified height, period and current has an associated crest that can be deterministically computed. In a random seastate, crest elevations are not deterministically associated with combinations of wave height and period and the highest individual crest is not always associated with the highest individual wave height. In general, the N-year crest elevation estimated using realistic wave distributions is not the same as the crest of the N-year wave. Hence, when computing global loads in an inundation situation, analysts may be confronted with the "crest conundrum" whereby the crest of the N-year wave that they regularly use to compute global jacket loads may not have an associated crest elevation which gives the inundation level indicated by the N-year crest. This paper documents the method recommended by the API Metocean Committee to resolve this so-called "crest-conundrum" and discusses validation of the method over the full range of relevant Gulf of Mexico conditions specified in API RP 2MET.