STUDY ON NATURAL FREQUENCY OF MONOPILE OFFSHORE WIND TURBINE CONSIDERING LONG TERM CYCLIC DEGRADATION EFFECT

Cheng Xinglei; Xing Jianyu; Liu Ju; Wang Piguang; Sun Xiaohan

doi:10.19912/j.0254-0096.tynxb.2023-1777

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Acta Energiae Solaris Sinica ›› 2025, Vol. 46 ›› Issue (3) : 559-566. DOI: 10.19912/j.0254-0096.tynxb.2023-1777

STUDY ON NATURAL FREQUENCY OF MONOPILE OFFSHORE WIND TURBINE CONSIDERING LONG TERM CYCLIC DEGRADATION EFFECT

Cheng Xinglei¹, Xing Jianyu¹, Liu Ju¹, Wang Piguang², Sun Xiaohan¹

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Abstract

This paper establishes a monopile foundation model for offshore wind turbines using the finite element software ABAQUS, combined with the USEFLD subroutine to calculate soil degradation, and uses a simplified spring model to calculate the natural frequency of the monopile wind turbine system. The effects of the number of cyclic load cycles, the magnitude of cyclic load, and the size of the monopile on the natural frequency of the wind turbine system are discussed. The research results show that the natural frequency of the monopile foundation wind turbine system decreases with the increase in the number of cyclic load cycles. Moreover, the greater the cyclic load level, the more significant the degradation of the wind turbine system’s natural frequency. For the wind turbine size and soil conditions considered in this study, after 107 cycles of cyclic loading, the wind turbine’s natural frequency can decrease to as low as 0.954 times its initial value, but it still remains within the 1P to 3P frequency range. Increasing the monopile length, diameter, and wall thickness can reduce the long-term degradation of the monopile wind turbine system’s natural frequency. Under the condition of the same steel usage, increasing the pile diameter is more effective in mitigating the natural frequency degradation of the wind turbine system compared to increasing the pile length and wall thickness, thus ensuring the stable operation of the wind turbine system. ”

Key words

offshore wind turbines / natural frequencies / monopile foundation / degradation / cumulative deformation / cyclic load

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Cheng Xinglei, Xing Jianyu, Liu Ju, Wang Piguang, Sun Xiaohan. STUDY ON NATURAL FREQUENCY OF MONOPILE OFFSHORE WIND TURBINE CONSIDERING LONG TERM CYCLIC DEGRADATION EFFECT[J]. Acta Energiae Solaris Sinica. 2025, 46(3): 559-566 https://doi.org/10.19912/j.0254-0096.tynxb.2023-1777

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