New damage quantification method for protected complex offshore foundations: statistical analysis

Accurate damage analysis of scour protections is crucial to ensuring the stability of offshore wind turbines. Traditional methodologies focus on fixed sub-areas of the protection, neglecting damage quantification in intersection zones, thereby increasing uncertainty in classifying the protection’s stability. A recent overlapping methodology proved effective in damage characterisation for monopiles and standard protections. However, it remains sensitive to grid selection and restricted to circular protections. This research develops an improved analysis system for non-standard configurations, successfully applied to jacket foundations and square protections under combined wave-and-current conditions. The novel method accurately captured damage distribution, particularly within critical pile areas. Statistical analysis revealed that maximum and minimum extreme values are highly sensitive to mesh resolution, whereas the mean remains invariant. A new framework is proposed, integrating two evaluation methodologies: a spatial/volumetric loss approach for assessing global scour, which aligns maximum damage with upper-bound percentiles; and a threshold calibration protocol for characterising local scour that effectively reduces sub-area dependency. This ensures a behavioural characterisation consistent with visual assessment across varying mesh resolutions. This combined method establishes the overlapping concept as a versatile approach for damage evaluation in various layouts of scour protections and complex offshore foundations.