ABSTRACT
Local and global scour around offshore wind turbine monopile foundations canlead to a reduction in system stiffness, and a consequential drop in the natural frequency of the combined monopile-tower-nacelle structure. If unchecked this could lead to operational problems such as accelerated fatigue damage and de-rating or decommissioning of the turbine. Research exploring the interaction between scour, foundation stiffness, and structural dynamic behaviour is therefore critical if scour formation is to be properly accounted for in predictions of structural performance, and to guide the implementation of scour remediation strategies. This paper describes experimental work that explores these interactions, conducted on a 1:20 scale driven monopile foundation and tower-nacelle superstructure in a prepared sand test-bed at HR Wallingford’s Fast Flow Facility. The flume allowed realistic scour geometries to be developed, providing a means to explore the effectiveness of different remediation strategies. Measured acceleration and strain caused by harmonic lateral loading are interpreted to deduce changes in structural performance as scour develops.
