On environmental contours for marine and coastal design. (1st January 2020)

• Record Type: Journal Article
• Authors: Ross, Emma; Astrup, Ole Christian; Bitner-Gregersen, Elzbieta; Bunn, Nigel; Feld, Graham; Gouldby, Ben; Huseby, Arne; Liu, Ye; Randell, David; Vanem, Erik; Jonathan, Philip
• Is Part Of: Ocean engineering. Volume 195(2020)
• Publication Date: 2020-01-01
• Subjects: Extreme -- Structural reliability -- Return value -- Environmental contour -- Structural response -- Joint probability -- IFORM; Ocean engineering -- Periodicals; Ocean engineering; Periodicals; 620.4162
• DOI: 10.1016/j.oceaneng.2019.106194
• Languages: English
• ISSNs: 0029-8018

Abstract

Abstract: Environmental contours are used in structural reliability analysis of marine and coastal structures as an approximate means to locate the boundary of the distribution of environmental variables, and hence sets of environmental conditions giving rise to extreme structural loads and responses. Outline guidance concerning the application of environmental contour methods is given in recent design guidelines from many organisations. However there is lack of clarity concerning (a) the differences between approaches to environmental contour estimation reported in the literature, and (b) the relationship between the environmental contour, corresponding to some return period, and the extreme structural response for the same period. Hence there is uncertainty about precisely when environmental contours should be used, and how they should be used well. This article seeks to provide some assistance in understanding the fundamental issues regarding environmental contours and their use in structural reliability analysis. Approaches to estimating the joint distribution of environmental variables, and to estimating environmental contours based on that distribution, are described. Simple freely-available software for estimation of the joint distribution, and hence environmental contours, is illustrated. Extra assumptions required to relate the characteristics of environmental contours to structural failure are outlined. Alternative response-based methods not requiring environmental contours are summarised. The results of an informal survey of the metocean user community regarding environmental contours are presented. Finally, recommendations about when and how environmental contour methods should be used are made. Highlights: Environmental contours used in structural reliability analysis of marine and coastal structures. Contours locate environmental conditions giving rise to extreme structural responses. Lack of clarity concerning different contour approaches, when to use, pros and cons. Review provides assistance in understanding the fundamental issues regarding environmental contours. Simple (freely-available) software and results of user survey provided.