Distribution of wave crest maxima in the vicinity of offshore structures

The design of fixed or floating offshore structures requires accurate information of wave crest maxima to avoid topside inundation and minimize the wave impact on the underside of the deck structure. The extreme value theory is utilized to obtain the distribution of wave crest maxima in vicinity of offshore structures. The theory requires the accurate estimates of wave crests distribution especially in the very upper tail of the distribution. In order to include the wave-structure interaction into the model a three-parameter semi-empirical model developed in the earlier studies is utilized. The semi-empirical distribution is developed based on a second order Rayleigh-Stokes model and takes advantage of method of L-moments for parameter estimation. The wave crest distributions obtained from the semi-empirical model are compared with linear and nonlinear models utilizing model test data from a mini-TLP experiment. The analysis indicates that the semi-empirical model is robust in approximating the probability distribution of data and consequently results in more reliable estimates of wave crest maxima. In addition, the spatial variation of wave crest maxima in the vicinity and underneath of the offshore structure and consequently the statistics of wave crest maxima in the area around the offshore structure are studied.