Assessing scour prediction models for monopiles in sand from the perspective of design robustness

Scour constitutes an inevitable occurrence around the monopile foundations of offshore wind turbines (OWTs). The internal forces and deformation of the monopile are profoundly influenced by the scour depth, which can be assessed using various scour prediction models. However, owing to the presence of uncertainties stemming from the intricate marine environment subjected to wave and current loads, these scour prediction models often fail to yield a unique design for a monopile designs. The prudent selection of an appropriate scour prediction model assumes paramount importance in OWT design and safety, particularly for designers who lack extensive experience in this domain. This study introduces a framework designed to evaluate and compare six existing scour prediction models, with a focus on robust design. This framework concurrently accounts for safety, design robustness, and cost. To illustrate its practical applicability, the framework is employed in a 5-MW OWT example. Consequently, this study recommends the most favorable scour prediction model and the optimal design for monopiles in OWTs, emphasizing design robustness and precision. Additionally, the investigation delves into the influence of soil parameter variability on the selection of the preferred model and its impact on the design robustness.