INFLUENCE STUDY OF NATURAL FREQUENCY OF MONOPILE SUPPORTED OFFSHORE WIND TURBINE STRUCTURE UNDER LONG-TERM CYCLIC LOADS

Sun Yilong; Xu Chengshun; Zhai Endi; Du Xiuli; Yang Yurong

doi:10.19912/j.0254-0096.tynxb.2022-0379

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Acta Energiae Solaris Sinica ›› 2022, Vol. 43 ›› Issue (12) : 194-199. DOI: 10.19912/j.0254-0096.tynxb.2022-0379

INFLUENCE STUDY OF NATURAL FREQUENCY OF MONOPILE SUPPORTED OFFSHORE WIND TURBINE STRUCTURE UNDER LONG-TERM CYCLIC LOADS

Sun Yilong¹, Xu Chengshun¹, Zhai Endi^1,2, Du Xiuli¹, Yang Yurong¹

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Abstract

A numerical calculation model is established to obtain the natural frequency of wind turbine structures by employing FLAC^3D software. This model is verified by comparing with the engineering monitored data. The degradation stiffness model （DSM） is embedded into the numerical model to consider the effect of long-term cyclic loads on foundation stiffness. Influences of different amplitude and number of cyclic loads on the natural frequency of the offshore wind turbine structure is explored by using this developed numerical model. Finally, the natural frequency attenuation formula is put forward, and an evaluation method is proposed to evaluate the effect of the long-term cyclic loads on the natural frequency. The results show that the natural frequency of the offshore wind turbine structure decreases with increasing the amplitude and number of cyclic loads. The natural frequency design of the wind turbine structure should be offset towards 3P to ensure the long-term operational safety of the offshore wind turbine.

Key words

offshore wind turbines / cyclic loads / natural frequencies / sand / degradation stiffness model

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Sun Yilong, Xu Chengshun, Zhai Endi, Du Xiuli, Yang Yurong. INFLUENCE STUDY OF NATURAL FREQUENCY OF MONOPILE SUPPORTED OFFSHORE WIND TURBINE STRUCTURE UNDER LONG-TERM CYCLIC LOADS[J]. Acta Energiae Solaris Sinica. 2022, 43(12): 194-199 https://doi.org/10.19912/j.0254-0096.tynxb.2022-0379

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