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First-order natural frequency of offshore wind turbines with large diameter single pile on spring foundation

DOI：10.7511/jslx20220726001

 作者 单位 E-mail 余云燕 兰州交通大学 土木工程学院, 兰州 730070 yuyunyan@mail.lzjtu.cn 许蓉 兰州交通大学 土木工程学院, 兰州 730070 孔嘉乐 兰州交通大学 土木工程学院, 兰州 730070

自振频率是海上风机前期动力设计的主要难点之一,计算精度要求极高,而桩-土相互作用对自振频率影响显著。目前,针对桩-土相互作用普遍采用弹簧地基简化模型,为对比分析不同弹簧地基简化模型的准确性和精度,本文采用回传射线矩阵法,建立固定端、单弹簧、双弹簧和三弹簧这4种地基简化模型,基于Bernoulli-Euler梁理论和Timoshenko梁理论,求解风机系统的自振频率,并与风机基频实测值作对比,进一步分析三弹簧简化地基模型中地基旋转刚度、地基耦合刚度和地基水平刚度对风机系统基频的影响。研究结果表明,桩-土相互作用不可忽略,三弹簧地基简化模型计算风机系统基频精度最高;地基刚度对风机系统基频的敏感性次序为,地基耦合刚度>地基旋转刚度>地基水平刚度;当地基旋转(水平)刚度较小时,地基耦合刚度与地基旋转(水平)刚度的耦合效应对风机系统的基频影响较大;地基耦合刚度与地基旋转刚度的耦合效应对风机系统基频的影响程度大于地基耦合刚度与地基水平刚度的耦合效应。

The fundamental frequency is one of the main difficulties in the preliminary dynamic design of offshore wind turbines,and the calculation accuracy is extremely high,while the pile-soil interaction has a significant impact on the fundamental frequency.At present,the simplified model of spring foundation is generally used for pile-soil interaction.In order to compare and analyze the accuracy of the simplified model of different spring foundations,this paper adopts the reverberation-ray matrix method to establish four simplified models:fixed-end,single-spring,double-spring and three-spring foundations.Based on Bernoulli-Euler beam theory and Timoshenko beam theory,the fundamental frequency of the wind turbine system is determined and compared with the measured values of the wind turbine fundamental frequency.The results show that: the pile-soil interaction is not negligible,and the three-spring simplified foundation model has the highest accuracy in calculating the fundamental frequency of the wind turbine system;the sensitivity of foundation stiffness to the fundamental frequency of the wind turbine system is in the order of: foundation coupling stiffness＞foundation rotational stiffness＞foundation horizontal stiffness;when the foundation rotational (horizontal) stiffness is small,the effect of foundation coupling stiffness and foundation rotational (horizontal) stiffness has a greater influence on the fundamental frequency of the wind turbine system.The effect of foundation coupling stiffness and foundation rotational stiffness has a greater influence on the fundamental frequency of the wind turbine system than the effect of foundation coupling stiffness and foundation horizontal stiffness.