Risk-based Design of an Offshore Wind Turbine using VoI Analysis
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Monopiles are the most common solution for supporting wind turbines in offshore conditions. At the design phase of a monopile, a frequency check is to be performed to avoid the resonance hazard with the 1P and 3P excitation, i.e. the frequency domains at which the rotor provokes excitations. However, the estimation of the first natural frequency of the structure is associated with large uncertainties, especially due to lack of knowledge about the soil-structure interaction. Resonance with the dynamic excitations results in a reduced fatigue life. In this paper, the frequency check is addressed following a probabilistic formulation. A rational decision framework is proposed to find an optimum design, based on the evaluation of the expected consequences of failure using risk metrics. Furthermore, the value of acquiring further site-specific information on the soil characteristics is addressed by means of a value of information analysis. A Bayesian network is developed to represent the system and facilitate the analysis. The results provide insight on (1) the relation between design parameters and the risk associated with dynamic amplifications; and (2) how to efficiently distribute the resources at the design point in time.