On the Maximum Wave Height in the Lifetime of a Sea Structure

The maximum wave height in the lifetime of a structure has to be calculated for the design of a sea structures. Usually we assume that the occurrence of highest waves, which occurs during storms, is given by a Poisson process. Therefore, the encounter probability , which is defined as the probability that the high sea waves, for the fixed value of the return period, occurs at least once in the lifetime L of the structure, is equal to 1–exp(–L/R), where R is the return period of high waves exceeding a fixed threshold. In this paper the encounter probability is calculated in some location by using two different models. The first one was given by Krogstad (1985), who obtained an expression of the encounter probability which is exact as L tends to infinite. The second model is based on the new Boccotti’s approach (2000), who introduced the ‘Equivalent Triangular Storm’ (ETS) model. By using the ETS model Boccotti derived the analytical solution for the return period of a sea storm in which the maximum wave height exceeds a fixed threshold. The comparisons are made by processing data of two buoys moored in the Central Mediterranean Sea (off Italy coast – buoy data of the Sea WAve monitoring Network – SWAN – of the SIMN-APAT, Italy) and in the Pacific Ocean (off California coast – buoy data of NOAA National Data Buoy Center – NDBC, USA).