Consideration of directionality in the description of metocean conditions have received increasing attention in the recent years, particularly for floating structures, in relation with issues such as the roll behaviour of a vessel, the design of mooring systems, or the structural response and fatigue of FPSO hulls. In the first part, basic considerations are made on the derivation of directional extremes of individual elements, how they can be defined in a consistent manner, and the resulting impact on structural reliability. In its main body, this paper presents a methodology for the assessment of the directional response of floating structures - mooring systems in the first place. This methodology proposes on a Format of directional criteria, built on reliability/response-based considerations, where the combinations of metocean parameters (such as wind, waves, and current) are defined in terms of both intensity and (relative) direction of the elements, using a Contour approach. Following this format, different sets of criteria are proposed for typical areas. Finally, some results are presented of the comprehensive analyses that have been carried out on the records, obtained by Total E&P Angola in Angola waters (block17), from an extensive acquisition campaign. These results give an illustration of the application of the I-FORM technique to analysis of simultaneous records (intensities and directions), in line with the Format proposed in this paper.
展开▼
