Influence of uncertain geotechnical data in dynamic CPT-based Winkler models for OWT monopiles

Abstract

The strive to meet renewable energy targets has revealed new challenges in structural health monitoring procedures for offshore wind turbine foundations. The lack of available data on the realtime performance of monopile foundations in offshore environments has raised questions about the serviceability of monopiles after many years of operation. This requires novel approaches to ensure substructure deflections remain within serviceability limits to provide a safe and serviceable product. It is important for dynamic models to encapsulate damping appropriately, and one of the major contributors to a monopileﾒs energy dissipation is due to the nonlinearity in the pile-soil interaction. This is particularly important during intense storm events where large amplitude motion will generate hysteretic behaviour in the soil. This paper details the development of a dynamic Winkler model that re-purposes monotonic CPT-based p-y functions by defining discrete hysteretic stress paths using Modified Masingﾒs rules. The geotechnical uncertainty is investigated by generating stochastic CPT ground profiles that vary the spatial variability of the end resistance. Results demonstrate that the variability in the synthetic CPT data has a negligible effect on the performance of the nonlinear dynamic model, suggesting the influence of CPT variation in models encapsulating hysteretic damping is minor.