Dynamic response of a multi-purpose floating offshore structure under extreme sea conditions

A novel multi-purpose platform (MPP) has been proposed for providing renewable energy to an offshore fish aquaculture system. After having previously analyzed its dynamic response in operational conditions, it is essential to check its survivability under extreme environmental conditions, focusing on wind speeds and wave heights and periods, for checking serviceability criteria and human factors’ requirements. An environmental contour method is applied to derive the 25-year return period extreme metocean conditions, choosing as location the west coast of Scotland (longitude −7°, latitude 56.5°), based on a database of hindcast wind and wave conditions for this location from the start of 2008 till the end of 2017, with a 6 hours granularity. Then, an aero-hydro-servo-elastic coupled model of dynamics of the MPP, in the time domain, is developed, and the dynamic response of the MPP to the 25-year return extreme environment conditions are assessed. The survivability of the MPP under the most extreme environment conditions, have also been checked. The response of the MPP with respect to barge motion and the hub acceleration of wind turbines were observed to fall within the criteria specified in literature.