Monopile foundations for offshore wind turbines are used in an aggressive environment. Therefore, they are difficult to access and experience complex dynamic loads. Under these circumstances, the combined effect of corrosion and fatigue is an uncertain factor that highly affects their design and maintenance.
Given the uncertainties in the service life prediction, multi-disciplinary requirements typically result in a sub-optimal design. It is therefore of great importance to properly evaluate the structural performance of monopile foundations and the influence of environmental actions on corrosion and fatigue. In this way, we can effectively optimise the amount of steel and corrosion mitigation efforts. We expect that there is much room for design improvements towards a lighter monopile, which uses less material. These monopiles are easier to install, easier to maintain and require less inspection and corrosion protection. In addition, the monopiles may have extended service life and could provide the possibility for repowering. On the other hand, too optimistic design might lead to unacceptable risks.
In this project, we will develop an advanced corrosion-fatigue model for the service life prediction of monopile foundations. The project evaluates the existing knowledge on corrosion and fatigue of representative offshore wind monopiles, including the effects of environmental conditions and countermeasures. Industrial partners in the consortium bring in current practices in detailed design choices and corrosion protection measures. Field data from industry will provide insight of the environmental conditions in the Dutch North Sea. We will build a deterministic model to describe the interaction of corrosion - including microbiologically influenced corrosion - and fatigue.
By using the new models combined with existing field data we can adequately quantify the influence of environmental factors on corrosion and the effectiveness of corrosion protection on offshore wind energy structures. To ensure that the model will provide direct benefit to their business, the industrial partners bring in practical knowledge and experience and will provide field data on environmental conditions and corrosion.
The project will result in an improved life prediction model including the effect of corrosion protection systems and a structural assessment guidance. The model results will provide direct input to design and maintenance rules of class organisations.
Industrial partners involved in the design and maintenance of monopiles will immediately benefit from the updated design and maintenance recommendations. They will also use the models to calculate the remaining structural life, taking into account different design and maintenance strategies.
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This project is supported with a subsidy by the Dutch Ministry of Economic Affairs and Climate Policy. Find more project information at the TKI Offshore Energy website.Wind and salty water: corrosion and fatigue. Not so fast!