Effect of Scour Depth on Natural Frequency of Offshore Wind Turbine with Tripod Suction Bucket Foundation

This study proposes that variations in natural frequency can be utilized to evaluate the structural stability of offshore foundations. The tripod suction bucket foundation for offshore wind turbine (OWT) in South Korea was examined using finite element (FE) modeling considering soil–structural interaction (SSI). The FE model combined the beam and plate elements with non-linear soil springs to couple the behavior of both tripod and suction buckets. The change in natural frequency and lateral bearing capacity of tripod suction bucket foundation was examined with various scour depth ratios S/D = [0, 0.06, 0.1, 0.14, 0.19, 0.3]. The result showed that increasing the scour depth ratio from 0 to 0.3 decreased the first natural frequency by approximately 10% and the lateral bearing capacity by roughly 22%.