Dynamic Characteristics of an Offshore Wind Turbine with Tripod Suction Buckets via Full-Scale Testing

Abstract

The dynamic characteristics of an offshore wind turbine with tripod suction buckets are investigated through finite element analysis and full-scale experiments. In finite element analysis, an integrated framework is suggested to create a simple yet accurate high fidelity model. The integrated framework accounts for not only the strain dependency of the soil but also for all dynamics in the seabed, including those of the soil, suction bucket skirt, and cap. Hence, the model accurately describes the coupling effect of translational and rotational motions of the seabed. The prediction results are compared to the experimental results obtained via full-scale testing in four stages during construction and in several operational conditions. The comparison shows that the stiffness of the suction bucket cap and strain dependency of the soil play a significant role in predicting natural frequency, suggesting that these two factors should be considered in finite element analysis for the accurate prediction of dynamic responses of an offshore wind conversion system. Moreover, dynamic analysis of the strain and acceleration measured during operational conditions shows that strain is more robust than acceleration with regard to the characterization of the overall dynamics of an offshore wind conversion system because the natural frequency of an offshore wind turbine is very low. It can be inferred that the measurement of strain is a more effective way to monitor the long-term evolution of dynamic characteristics. The suggested integrated framework and measurement campaign are useful not only to avoid conservatism that may incur additional costs during load calculation and design phases but also to establish an intelligent operation and maintenance strategy with a novel sensing technique.

Comprehensive Analysis and Evaluation of the Operation and Maintenance of Offshore Wind Power Systems: A Survey

“…Ref. [66] analyzed the influence of three-legged suction bucket foundations on the dynamic characteristics of offshore wind turbine towers through full-scale tests, and gives corresponding suggestions. In Ref.…”

Closed Form Solutions for Predicting Lateral Response of Tripod Suction Pile for Offshore Wind Turbine Foundation

“…Unlike Europe, Korea adopted a new suction base in the form of a tripod through prior research and decided to perform a full-scale field study to apply it as a lower base for offshore wind power. In this study, a basic design has been created based on a simple analysis of tripod suction piles, which was integrated with the following assessments: safety evaluation through numerical analysis, field stress distribution and cyclic load evaluation through geocentrifuge experiments, and design optimization verification and performance evaluation through full-scale field tests [8][9][10].…”

“…synthesizing the above results, the exponential function ( * ) of the intermediate range is proposed as Equation (11). (L * ) = { ( * ) − ( * )}• { * * * * * * * * * * } + ( * )(11)α then requires the following conditions to satisfy Equation(10).α = 1 + * * * * * *…”