Fatigue Assessment Of The Offshore Wind Turbine Structure Under Combinated Wind And Wave Loading

Offshore wind turbine structures exist the hidden trouble of security because of fatiguefailure under combinated loading of wind and wave. This thesis is to make fatigue strengthanalysis of monopipe of offshore wind turbine structures based on the calculation of wind andwave loading. The main contents are as follows:1、Research on the fatigue assessment methods，which includes time domain estimatemethod，frequency domain estimate method and the fatigue life estimate method under jointloading of wind and wave.2、Calculation of wind loading on wind turbine. The wind turbulence simulation methodand wind loading calculation method are introduced, and wind loading time domain andfrequency domain forms are calculated according to blade element momentum theory and thequasi-steady assumption of downwind fluctuating wind.3、Calculation of wave loading on wind turbine. Calculation method of regular andirregular wave loading are introduced，and wave loading time domain and frequency domainforms are calculated according to wave simulation method and spectrum analysis method.4、Calculation example of fatigue analysis of the offshore wind turbine structures.Calculate respectively fatigue damage due to wind and wave loading. Considering the effectof combinated loading, the fatigue damage is obtained by loading combination method.Calculate and compare the results of damage value of specific sea states using constantamplitude loading, combined spectrum and direct calculation method.5、Finite element analysis of the random vibration. Introduce the random vibration theoryand simulate the response of tower structure under fluctuating wind and random wave. Basedon the analysis result calculate the fatigue damage using Dirlik method.