Consistent Stochastic Modelling of Meteocean Design Parameters

Consistent stochastic models of metocean design parameters and their directional dependencies are essential for reliability assessment of offshore structures. In this paper a stochastic model for the annual maximum values of the significant wave height, and the associated wind velocity, current velocity, and water level is presented. The stochastic model includes statistical uncertainty and dependency between the four stochastic variables. Further, a new stochastic model for annual maximum directional significant wave heights is
presented. The model includes dependency between the maximum wave height from neighboring directional sectors. Numerical examples are presented where the models are calibrated using the Maximum Likelihood method to data from the central part of the North Sea. The calibration of the directional distributions is made such that the stochastic model for the omnidirectional maximum wave height is statistically consistent with the directional distribution functions. Finally, it is shown how the stochastic models can be used to estimate characteristic values and in reliability assessment of offshore structures.