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RESEARCH PRODUCT

Numerical and analytical analysis of a monopile-supported offshore wind turbine under ship impacts

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Abstract Offshore wind turbines in the vicinity of ship traffic are exposed to increased risks of ship collisions. To better understand the impact mechanism, this paper evaluates the dynamic responses of a monopile-supported wind turbine under ship impacts, using both numerical and analytical methods. The nonlinear finite element method is applied during the numerical simulations, and the wind load effects, soil conditions, and rigid and deformable ship bows are considered. The analytical approach, originally developed based on the energy method, is extended here to address the damping effects of monopile-supported wind turbines. In the case study, the impacts are studied between a 4600-ton vessel and a 5-MW offshore wind turbine. The effects are presented of the aerodynamic damping, ship impact velocity, mean wind speed, wind direction, and ship bow stiffness on the collision responses. A comparison between the numerical and analytical results shows a generally good agreement for the maximum contact force. Under an impact velocity of 1 m/s and 3 m/s, the discrepancy between the two methods is 5% and 7%, respectively. The developed engineering approaches can be used to address accidental collision problems between ships and bottom-fixed offshore wind turbines.