Abstract:As a dynamic-sensitive structure, the changes in the offshore wind turbine structure are easy to affect the fundamental frequency of the system. The fundamental frequency of the system is key to the structure and foundation design of offshore wind turbines; hence, it is of great engineering significance to accurately calculate the fundamental frequency of the system. Based on the Euler-Bernoulli beam theory, considering the pile-soil interaction, added water mass, and the variable section characteristics of the tower, a calculation method of the transverse fundamental frequency of the single-pile offshore wind turbine system was established using the reverberation-ray matrix method. The accuracy and effectiveness of the proposed method were verified by a practical project, and the fundamental frequency excursion factors of the system were comprehensively analyzed. The analysis results showed that the pile-soil interaction, the added water mass, and the variable section characteristics of the tower all have a significant effect on the fundamental frequency of the system. The sensitivity of the system's fundamental frequency to different parameters is as follows: buried depth of pile foundation ＞ pile diameter ＞ modulus of foundation soil ＞ upper mass ＞ seawater depth ＞ wall thickness of pile foundation. When the buried depth of the pile foundation, the pile diameter, the foundation soil modulus, and the wall thickness of the pile foundation exceed the critical value, the change of parameters has little effect on the fundamental frequency of the system. To a certain extent, this paper revealed the influence law of fundamental frequency excursion factors of the system, thus providing a reference for the structure design of offshore wind turbines.
