海上风机单桩基础疲劳损伤计算方法

Fatigue damage calculation method of monopile supported offshore wind turbine

为提高海上风机基础疲劳损伤计算的准确性,评价不同计算方法的适用性和影响,以海上风机单桩基础为例进行疲劳评价,建立全时域的动力分析模型和基于功率谱密度函数的频域疲劳损伤计算流程,研究气动阻尼比取值、风与波浪联合作用、应力幅概率分布模型对基础疲劳损伤的影响.结果表明:基础疲劳损伤受气动阻尼比影响突出,风致疲劳损伤对气动阻尼比的敏感性大于浪致疲劳损伤;由于风与波浪联合作用对基础的疲劳损伤有较大影响,简单叠加风致疲劳损伤和浪致疲劳损伤得到的结果较风与波浪联合作用时偏小;确定合适的应力幅概率分布模型十分必要,频域法中采用Dirlik模型得到的风致疲劳损伤和采用快速傅里叶逆变换(IFFT)的浪致疲劳损伤分别与时域法的结果相近,但叠加的总疲劳损伤小于风与波浪联合作用时的总疲劳损伤.

The applicability and influence of different calculation methods were evaluated,in order to improve the accuracy of the fatigue damage calculation of offshore wind turbine foundation.The fatigue evaluation of a monopile supported offshore wind turbine was studied.The full time domain dynamic analysis model and the frequency domain fatigue damage calculation process based on power spectral density function were established.The influence of aerodynamic damping,combined wind and wave loads and stress range probability distribution model on the fatigue damage were studied.Results show that the fatigue damage is easily affected by the aerodynamic damping,and the wind-induced fatigue damage is more sensitive to aerodynamic damping than the wave-induced fatigue damage.Since the combined wind and wave loads has great influence on the foundation fatigue damage,the result of simply superimposing wind-induced and wave-induced fatigue damage is less than the result of combined wind and wave loads.It is necessary to determine an appropriate stress range probability distribution model.The wind-induced and wave-induced fatigue damage calculated by Dirlik model and inverse fast Fourier transform(IFFT)in frequency domain method is respectively close to the results by time domain method,but the total fatigue damage of superimposing wind-induced and wave-induced fatigue damage is less than that of combining wind and wave loads by time domain method.