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The “Design Wave Philosophy’’ ***** Calculation of the design wave *****

Calculation of the design wave. The “Design Wave Philosophy’’ ***** Calculation of the design wave ***** Wave forces on semi-submersible platforms Wave forces and bending moments in FPSO-ships Platform movements in large waves Examples of heavy weather damage What is a Rogue Wave ?

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The “Design Wave Philosophy’’ ***** Calculation of the design wave *****

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  1. Calculation of the design wave The “Design Wave Philosophy’’ ***** Calculation of the design wave ***** Wave forces on semi-submersible platforms Wave forces and bending moments in FPSO-ships Platform movements in large waves Examples of heavy weather damage What is a Rogue Wave ? Why, where and when ? Shall we design against Rogue and Freak Waves ? What can a platform master do against Rogue and Freak Waves ? Remote-sensing of sea conditions Search And Rescue and emergency operations Decision making in an emergency

  2. Calculation of the design wave

  3. Calculation of the design wave • Data collection • Extrapolation to extremes • Examples

  4. buoy - satellite - hindcast model Data sources

  5. Field measurements: costly short duration local validity often only synthetic parameters reasonably good… Data sources

  6. …but should one trust them at all times ? Data sources

  7. …but should one trust them at all times ? Data sources

  8. Satellite only significant wave height no wave direction very unreliable period estimates sparse sampling both in time and space yet available almost anywhere Data sources

  9. hindcast models costly better calibrated in common conditions than in extreme ones good length databases no individual wave data Data sources

  10. Reconciliation problems when merging buoy - satellite - hindcast model Data sources

  11. Calculation of the design wave • Data collection • Extrapolation to extremes • Examples

  12. Database: 20 years of data available from Frigg QP platform in the North Sea

  13. Database: 1979-1989: mostly 3-hourly measurements, many time-series available. 1991-1999: mostly 20-minute statistics, only reduced parameters

  14. Calculation of the design wave Empirical distribution and duration it represents

  15. Calculation of the design wave Fitted parametric model

  16. Calculation of the design wave Approximated model for maximum over observation duration

  17. Calculation of the design wave Extrapolation to planned duration

  18. Calculation of the design wave • Data collection • Extrapolation to extremes • Example • The Port-Louis case

  19. The Port-Louis case

  20. The Port-Louis case Build a wharf for a coal power generation facility

  21. The Port-Louis case Hs less than 1 m more than 99.7% of the time, yet once in a while...

  22. The Port-Louis case

  23. The Port-Louis case 6 in 40 years, and Port Louis was sheltered on some of them

  24. The Port-Louis case • Variables not “i.i.d.” => 2 options: • cheap one, consider a nearby more exposed location and define risk attenuation from that location • expensive one, run hindcast again sending synthetic hurricanes into the area

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