Recent developments in understanding of foundation response for offshore wind turbines indicate significant potential savings for future design, and possible life extension for existing structures. However, design methods are typically based on simplified models and assumptions, and in some cases reduced scale experiments, so it is necessary to demonstrate their accuracy in the complex environment of full scale wind farms. This paper outlines a framework for the application of system identification algorithms to characterise the structural properties of installed offshore wind turbine monopile foundations using monitored vibration data. Stochastic subspace identification methods are adopted to calculate the modal properties, which form a target objective function for the optimisation of the foundation stiffness parameters within a finite element model updating approach. The framework is applied to field monitoring data from an offshore wind turbine and the identified foundation behaviour is compared to that predicted by new (PISA) and existing (API) design methods.
Ross A. McAdam, Anela Bajric, Manolis N. Chatzis, Byron W. Byrne and Cedric Vanden Haute
Keywords: Monopile design, system identification, monitoring
Publisher: DFI