Specification Document for OC6 Phase II: Verification of an Advanced Soil-Structure Interaction Model for Offshore Wind Turbines

The Norwegian Geotechnical Institute (NGI) has developed a new macro-element model that accounts for the soil-structure interaction in offshore wind turbines. This development was done as part of the REDWIN (REDucing cost of offshore WINd by integrated structural and geotechnical design) project. The focus of Phase II of the OC6 project was to integrate REDWIN’s new soil-structure modeling capability into the coupled modeling tools that are used to design fixed-bottom offshore wind systems. The integration was then verified through a series of load cases using an example monopile-based offshore wind system examined within the WAS-XL project. This document provides the details needed to model the system examined in OC6 Phase II, using the new REDWIN modeling approach, as well as other standard modeling approaches, including apparent fixity, distributed springs, and coupled springs.