Project ECSADES

The ECSADES project addressed important and pertinent issues related to the safe design and operation of ships and other marine structures. Such structures need to be design according to tolerable risk levels. However, in order to understand the risks, the understanding of the extreme ocean environments and their interaction with fixed and floating structures is critical. In this regard, design contours are useful in describing the joint behavior of various environmental parameters, structural loading and response variables.

Currently, there are different approaches to establishing environmental contours, and they all have certain strengths and weaknesses and different mathematical and statistical properties. One main objective in this project was to further develop one of the novel approaches to estimating environmental contours with clearly understood probabilistic properties. Moreover, a detailed comparison study involving climate descriptions from different important ocean regions and various structural problems were performed in order to better understand the effect of the estimation method on the resulting design and reliability levels. Furthermore, some interesting and challenging special cases were investigated, and methods for contour estimation in non-trivial cases have been explored. In addition, the conditional extremes model for joint extremes have been explored and a marginal non-stationary and conditional extremes model have been elaborated to account for covariate effects in the description of multivariate extremes modelling. 

Project results are thoroughly documented in various deliverables and publications in form of journal articles and conference presentations. In addition, several seminars have been arranged where project results have been disseminated internally within DNV. Moreover, project results have been implemented in two software packages that have been developed within the project and that are made freely available through the project GitHub site (see below). The first is a MATLAB code for the Penalized Piecewise constant conditional extremes model and the second is an R packages for generating various environmental contours from the conditional extremes model and for a particular conditional model. 

Finally, the DNV recommended practice on environmental conditions and environmental loads has been updated with a description of the direct sampling approach to environmental contours which has been further developed within this project. 

The software developed within the project is available here: https://github.com/ECSADES

Some deliverables from the project are available here: 

LIST OF PUBLICATIONS from the project:

Technical DNV reports (may be obtained from DNV library): 

• D1 - Environmental contours comparison Studies. Erik Vanem. DNV report No. 2017-0163, ECSADES
• D4 – Environmental Contours for Special Cases. Erik Vanem, Odin Gramstad, Bingjie Guo. DNV report No. 2019-1072, ECSADES

Journal papers: 

• A comparison study on the estimation of extreme structural response from different environmental contour methods
  Erik Vanem, Marine Structures. 56, pp. 137-162, 2017
• 3-dimensional environmental contours for structural reliability analysis of ships and offshore structures
  Erik Vanem. Ships and Offshore Structures, 14(1), pp. 74-85, 2019.
• A simple approach to account for seasonality in the description of extreme ocean environments
  Erik Vanem. Marine Systems and Ocean Technology, 13, pp. 63-73, 2018 
• Asymmetric Copula-Based Distribution Models for Met-Ocean Data in Offshore Wind Engineering Applications
  Tiago Fazeres-Ferradosa, Francisco Taveiro-Pinto, Erik Vanem, Maria Teresa Reis, Luciana das Neves. Wind Engineering, 42(4), pp. 304-334, 2018 
• A simulation study on the uncertainty of environmental contours due to sampling variability for different estimation methods
  Erik Vanem, Odin Gramstad, Elzbieta M. Bitner-Gregersen. Applied Ocean Research, 91, 101870, 2019
• Probabilistic Design and Reliability Analysis of Scour Protections for Offshore Windfarms
  T. Fazeres-Ferradosa, F. Taveiro-Pinto, X. Romão, E. Vanem, M.T. Reis, L. Das Neves. Engineering Failure Analysis, 91, pp. 291-305, 2018
• Environmental contours for describing extreme ocean wave conditions based on combined datasets
  Erik Vanem. Stochastic Environmental Research and Risk Assessment. 33(4-6), pp. 957-971, 2019
• Statistical Description and Modelling of Extreme Ocean Wave Conditions for Marine Engineering Applications
  Erik Vanem, Tiago Fazeres-Ferradosa. Ahead of print at Proceedings of the Institution of Civil Engineers.
• Reliability Analysis of Offshore Wind Turbines Under Extreme Resonant Response: Application of Environmental Contour Method
  Joey Velarde, Erik Vanem, Claus Kramhøft, John Dalsgaard Sørensen. Applied Ocean Research, 93, 101947, 2019
• On environmental contours for marine and coastal design
  Emma Ross, Ole Christian Astrup, Elzbieta Bitner-Gregersen, Nigel Bunn, Graham Feld, Ben Gouldby, Arne Huseby, Ye Liu, David Randell, Erik Vanem, Philip Jonathan, In press for Ocean Engineering
• Comparing different contour methods with response-based methods for extreme ship response analysis
  Erik Vanem, Bingjie Guo, Emma Ross, Philip Jonathan. Marine Structures, 69, 102680, 2020
• Environmental contours for circular-linear variables based on the direct sampling method
  Erik Vanem, Andreas Hafver, Gladys Nalvarte. In press for Wind Energy
• Sequential sampling method using Gaussian process regression for estimating extreme structural response
  Odin Gramstad, Christian Agrell, Elzbieta Bitner-Gregersen, Bingjie Guo, Eivind Ruth, Erik Vanem, in submission
• Environmental contours as Voronoi cells – a simple algorithm that works in arbitrary dimensions
  Andreas Hafver, Christian Agrell, Erik Vanem. In preparation
• Estimating surge in extreme North Sea storms
  Emma Ross, Samta Sam, David Randell, Graham Feld, Philip Jonathan. Ocean Engineering, 154, pp. 430-444, 2018.

Conference proceedings papers

• On the influence of environmental contour method in estimating extreme structural response
  Erik Vanem. In proceedings of the 36th International conference on Ocean, Offshore and Arctic Engineering, OMAE 2017, Trondheim, Norway, June 25-30 2017
• Evaluating properties of environmental contours
  Arne B. Huseby, Erik Vanem, Karoline Eskeland. In proceedings of ESREL 2017, Portoroz, Slovenia, June 18-22 2017
• Combined long-term and short-term description of extreme ocean wave conditions by 3-dimensional environmental contours
  Erik Vanem, Arne Bang Huseby. In Proceedings of the twenty-eight (2018) International Ocean and Polar Engineering Conference (ISOPE 2018), Sapporo, Japan, June 10-15 2018, pp. 470-477.
• Uncertainty of Environmental Contours Due to Sampling Variability
  Odin Gramstad, Erik Vanem, Elzbieta Bitner-Gregersen. In Proceedings of the 37th International conference on Ocean, Offshore and Arctic Engineering, OMAE 2018, Madrid, Spain, June 17-22 2018, OMAE2018-77810. 
• Seasonal and Omni-Seasonal Environmental contours for Extreme Sea States
  Erik Vanem, Arne Bang Huseby, In Proceedings of the 7th International Maritime Conference on Design for Safety, DfS 2018, Kobe, Japan, September 16-21. pp148-159. 
• Buffered environmental contours
  Kristina R. Dahl, Arne B. Huseby. In Proceedings of ESREL 2018, Trondheim, Norway, June 17-27 2017
• Comparison of the Environmental Contour Method and Response-Based Analysis Using Response Emulator for Estimating Extreme Ship Responses
  Erik Vanem and Bingjie Guo. In Proceedings of the 38th International conference on Ocean, Offshore and Arctic Engineering, OMAE 2019, Glasgow, Scotland, UK, June 10-14 2019, OMAE2019-95098 
• On environmental contours for marine and coastal design
  Emma Ross, David Randell, Ole Christian Astrup, Elzbieta Bitner-Gregersen, Erik Vanem, Nigel Bunn, Ben Gouldby, Ye Liu, Graham Feld, Arne Huseby, Philip Jonathan, In Proceedings of the 38th International conference on Ocean, Offshore and Arctic Engineering, OMAE 2019, Glasgow, Scotland, UK, June 10-14 2019, OMAE2019-96587
• Environmental contours for mixtures of distributions
  Arne Bang Huseby, Erik Vanem, Maria Hjelset Barbosa. In Proceedings or the 29th European Safety and Reliability Conference, ESREL 2019, Hannover, Germany, September 22-26 2019, pp.839-846
• Environmental contours for safe design of ships and other marine structures
  Erik Vanem, Arne Bang Huseby. In Proceedings of Structural Integrity 2019 (Invited lecture), Aberdeen, Scotland, UK, September 9-10 2019.
• Additional papers are prepared for OMAE 2020.

Conference and workshop presentations: 

• Conditional extremes modelling of ocean surge
  Emma Ross. Presented at EVAN 2017, Southampton, UK, September 5-7 2017.
• Safe Design of Marine Structures Using Environmental contours and Response-Based Methods
  Ye Liu, Erik Vanem, David Randell, Emma Ross. Presented at the 3rd International Conference on Safety and Reliability of Ships, Offshore & Subsea Structures (SAROSS 2018), Wuhan, China, May 22-24 2018
• When does a convex environmental contour exist?
  Arne Bang Huseby. Presented at workshop for extreme ocean wave phenomena, Lancaster, UK, September 11 2019. 
• Sequential sampling method using Gaussian process regression for estimating extreme structural response
  Odin Gramstad. Presented at MUER workshop, Høvik, Norway, 9-10 September 2019. 

International training course

• Statistical modelling of extreme environmental conditions for marine engineering applications.
  Erik Vanem. Lecture at International Offshore Structures Design Course 2019, Porto, Portugal. May 7-10 2019. 

Internal seminars: 

Several internal seminars and presentations have been held at DNV headquarters, to disseminate project results. The presentations from these seminars are made available here: 

Seminar 1: January 26. 2017. 

• On alternative environmental contours (A.B. Huseby, UiO)

Seminar 2: March 8 2017. 

• Mini-course on the use of environmental contours (Ø. Hagen, DNV)
• Mini-course on the conditional extremes model (P. Jonathan, Shell)
• Coastal applications of multivariate extreme value techniques (B. Gouldby, HR Wallingford)

Seminar 3: May 21 2019.

• ECSADES lunch and learn presentation (Erik Vanem, DNV) 

Seminar 4: October 15. 2019: ECSADES final seminar. 
See images from the event here.

• Introduction and welcome (Ole Christian Astrup, DNV)
• Environmental contours: Fundamentals and recommended practice (Philip Jonathan, Shell)
• Constructing and evaluating environmental contours (Arne Bang Huseby, UiO)
• Uncertainty and sensitivity of coastal flood risk modelling chain (Ye Liu, HR Wallingford)
• Sequential sampling method using Gaussian process regression for estimating extreme structural response (Odin Gramstad, DNV)
• Software presentation and demo #1: ECSADES R software and shiny app (Ye Liu, HR Wallingford)
• Software presentation and demo #2: Estimating environmental contours using non-stationary marginal and conditional extreme value analysis (Emma Ross, Shell)

Project partners

• DNV Strategic Research & Innovation
• Shell UK
• Department of mathematics, University of Oslo
• With participation also from HR Wallingford