Gode Wind Offshore Wind Farm
The Gode Wind OWF monopiles were designed using modified API p-y curves. As part of the design process, GCG were commissioned to undertake 3D FE analyses to predict the behaviour of monopiles at selected locations across the OWF to benchmark and validate the geotechnical design under serviceability and ultimate limit state conditions.
The FE analyses incorporated advanced soil models to accurately represent the small strain stiffness properties of the sands, adopting reasonably conservative parameters. For both limit states, a much stiffer lateral load-displacement response was predicted by the FE analyses as compared to the modified p-y curves. It is worth noting that this is in line with implications from field measurements of WTG frequency responses.
In the case of the serviceability limit state loading, the lateral displacement predicted by the FE analysis was around half of that obtained with the modified p-y curves. Similar conclusions were reached with respect to the moment-rotation behaviour. Although verified to be safe, the FE analysis results showed that conventional p-y based monopile design methods exhibit large margins of conservatism for modern monopile dimensions therefore identifying significant potential to economise the cost of OWFs at the design stage.
References
Schroeder, F. C., Merritt, A. S., Andersen, K. W., Muir Wood, A., Thilsted, C. L. & Potts, D. M. (2015) Predicting monopile behaviour for the Gode Wind offshore wind farm. Proc. Int. Symp. Frontiers in Offshore Geotechnics – ISFOG 2015, Oslo (Ed. V. Meyer)
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