Abstract: With the wide application of bucket foundation in China, its performance monitoring in engineering practice has been the key to the operation safety of offshore wind turbines (OWTs). In this study, the vibration displacement of a prototype OWT with a bucket foundation is observed and compared with a monopile foundation OWT. First, based on the measured natural frequencies, foundation stiffness is calculated using the genetic algorithm. Then, the vibration level of the two OWTs are calculated and compared. Results show that of the two foundations, the difference in horizontal stiffness is 7%, while the bucket foundation has a rotational stiffness ten times greater than the monopile. And the bucket foundation OWT features a displacement larger than the monopile type at a wind speed lower than 6 m/s, but above this threshold the trend reverses. At a low wind speed, the occurrence of 3P resonance leads to a larger displacement of the bucket foundation, which, nevertheless, can be reduced by 54.4% through applying an optimized operation strategy. This study shows bucket foundation has superiority in both anti-overturn stability and vibration control.

Key words: offshore wind power, bucket foundation, vibration monitoring, displacement, foundation stiffness, operation strategy