Describes a study that focused on addressing the conceptual issues related to classifying and analyzing uncertainties in loads on offshore structures, and on developing a sound and practical methodology for uncertainty analysis. Uncertainties are classified with respect to source: basic uncertainty regarding physical parameters affecting the design load, model uncertainty regarding the calculations used to estimate physical parameters, and distribution uncertainty regarding probability distributions used to model random quantities. A generalized load model that incorporates all uncertainties is described and applied to wave loads on the Hibernia offshore structure. Effects of individual and combined uncertainties on calculated design loads are analyzed and the implications for design code development are discussed.

Describes a study conducted to further develop and test a previously developed methodology for characterization and modelling of uncertainties in the determination of loads on offshore structures. Tasks carried out in the study include a finalization of the methodology; an investigation of the sensitivity of the 100-year load effect with respect to the distribution types used to model uncertain parameters, the degree of non-linearity of the load effect model, and the probabilistic characterization of model uncertainty as fixed or variable in time; and development of design load factors leading to a specified target reliability level for a range of parameters. On the basis of the results, recommendations are developed regarding design code implementation for offshore structures.