On environmental contours for marine and coastal design

Ross, Emma; Astrup, Ole Christian; Bitner‐Gregersen, Elzbieta M.; Bunn, Nigel; Feld, Graham; Gouldby, Ben; Huseby, Arne Bang; Liu, Ye; Randell, David; Vanem, Erik; Jonathan, Philip

doi:10.1016/j.oceaneng.2019.106194

Cited by 67 publications

(30 citation statements)

References 59 publications

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“…It could be investigated whether these pairs of T -yr values correspond to points of environmental contours proposed by other authors. Nonetheless, the idea is consistent with the approach of using multiple points from the contours to evaluate a system [20].…”

Section: Discussionmentioning

confidence: 63%

“…Moreover, such demands are usually related to given return periods for design purposes; consequently, it is convenient to establish them in terms of return periods. This is also the case for using contour maps in ocean engineering [20].…”

Section: Simplified Approach For Return Period Correlated Valuesmentioning

confidence: 89%

“…Since the maximum Hs and companion V w may not yield the maximum demand in a given system-like the points in an environmental contour associated with a T -yr may not lead to the maximum demand in the system [20]-other pairs of simultaneously recorded data could be considered; one obvious combination is using maximum monthly V w and companion Hs, but also other data pairs could be used, for instance the second largest monthly Hs and companion V w , the second largest V w and companion Hs, the third largest monthly Hs and companion V w and so on. Each of the previous combinations would lead to pairs of T -yr values to which a system could be subjected to for estimating load effects, and the maximum demand could be used for design (in fact, different pairs of T -yr values could be more critical to different elements of the system).…”

Section: Discussionmentioning

confidence: 99%

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Correlation of Concurrent Extreme Metocean Hazards Considering Seasonality

2020

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Simultaneous occurrence of metocean variables can present a multihazard to maritime systems. However, simplified design approaches to assess simultaneous significant wave heights and wind velocities are lacking, especially if seasonality is considered. This is addressed in this study by using extreme significant wave heights and companion wind velocities recorded in the Gulf of Mexico. Time-dependent, generalized extreme value (GEV) models and classical regression are the basis to propose a simplified approach to estimate correlated extreme significant wave heights and wind velocities associated with given return periods, accounting for seasonality and including measures of uncertainty. It is found that the proposed approach is a new but simple method to adequately characterize the concurrent extreme metocean variables and their uncertainty. It is concluded that the method is an effective probabilistic design tool to determine simultaneous extreme significant wave heights and companion wind velocities for desired return periods and seasonality.

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Section: Discussionmentioning

confidence: 63%

Section: Simplified Approach For Return Period Correlated Valuesmentioning

confidence: 89%

Section: Discussionmentioning

confidence: 99%

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Correlation of Concurrent Extreme Metocean Hazards Considering Seasonality

2020

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“…In this region, extreme wave heights have been investigated (see, e.g., Björkqvist et al [32]); however, for the design of offshore RES, additional wave parameters are of interest, such as the wave steepness (which depends on both wave height and period). For identification of extreme waves in North Sea, the environmental contour method has been applied based mainly using I-FORM [26,33,34]. However, the PCA method of Eckert-Gallup et al [27] has not been investigated for the North Sea wave climate, which will be done in this study.…”

Section: Global Atmospheric Reanalysis Datamentioning

confidence: 99%

Comparative Analysis of Environmental Contour Approaches to Estimating Extreme Waves for Offshore Installations for the Baltic Sea and the North Sea

Wrang

Katsidoniotaki

Nilsson

et al. 2021

JMSE

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At the stage of design load analysis for offshore installations such as wave energy systems, a critical step is the determination of environmental cases to be evaluated for the definition of the characteristic design load. A commonly used methodology for load case selection, applied in multiple studies and recommended by technical specifications and guidelines, is the environmental contour approach. Here, 50-year environmental contours were generated for four study sites located in the North Sea, Skagerrak and the Baltic Sea by considering both observations and hindcast (model) data. For the construction of the contours, the well-established inverse first-order method (I-FORM) and a modified version using principal component analysis (PCA) were both examined. Furthermore, a 2-dimensional peaks-over-threshold (2D POT) method was evaluated. It was found that a version of the regular I-FORM was able to produce satisfactory contours which properly accounted for the highest waves. When using PCA, the dependency in the data was not properly captured by the probability functions under consideration. The 2D POT method, where applicable, was found to underestimate the extreme sea states. Comparisons between contours obtained from observations and hindcast data showed that the contours may differ substantially depending on the site and method, and thus care must be exercised when using hindcast data for such purposes.

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“…Another popular method to avoid a complex integral is to use the environmental contour approach, which is derived from the inverse first-order reliability method (IFORM). [12][13][14][15][16][17][18][19] A review on environmental contours for marine and coastal designs was presented by Ross et al 20 The environmental contour contained all environmental parameters with an exceeding probability related to a reliability index, b, and the design environmental parameters corresponded to the maximum structural response along the environmental contour line. [21][22][23][24] Velarde et al 25 applied the environmental contour method to conduct a probabilistic analysis of offshore wind turbines under extreme resonant responses.…”

Section: Introductionmentioning

confidence: 99%

Long-term extreme response analysis for semi-submersible platform mooring systems

Zhao

Dong

2020

Proceedings of the Institution of Mechanical Engineers, Part M:

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The accurate assessment of long-term extreme responses of floating-structure mooring system designs is important because of small failure probabilities caused by long-term and complex ocean conditions. The most accurate assessment would involve considering all conceivable sea states in which each sea state is regarded as a stochastic process and performing nonlinear time-domain numerical simulations of mooring systems to estimate the extreme response from a long-term analysis. This procedure would be computationally intensive because of the numerous short-term sea states involved. Here, a more feasible approach to evaluate the long-term extreme response is presented through immediate integration combined with Monte Carlo simulations. A parameter fitting procedure of the short-term extreme response distribution under irregular wave conditions is employed to solve the long-term response integration. Case studies were conducted on a semi-submersible platform using environmental data measurements of the Gulf of Mexico and a joint distribution model of the environmental parameters was considered. This approach was observed to be effective and the results were compared with those of traditional methodologies (univariate extreme value design and environmental contour methods). The differences were reflected using a reliability analysis of mooring lines, which indicated that the design standards must be stricter when using long-term analysis.

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On environmental contours for marine and coastal design

Cited by 67 publications

References 59 publications

Correlation of Concurrent Extreme Metocean Hazards Considering Seasonality

Correlation of Concurrent Extreme Metocean Hazards Considering Seasonality

Comparative Analysis of Environmental Contour Approaches to Estimating Extreme Waves for Offshore Installations for the Baltic Sea and the North Sea

Long-term extreme response analysis for semi-submersible platform mooring systems

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