Research On Fatigue Reliability Of Wind Turbine Foundation Under Wind Load

Wind energy is a safe,clean and renewable energy source.It is of great significance to alleviating the current shortage of traditional energy and improving environmental pollution.It has become an important part of many countries' sustainable development strategies.In recent years,the wind power industry has developed rapidly.With the growth of technology,the rated power,cabin weight and tower height of wind turbines are also increasing.These developments have shown considerable advantages in terms of power generation.But they also face many structural challenges.In actual engineering,the wind turbine foundation is an important structure for carrying the upper power generation system.To ensure its safe production,it is necessary to ensure the structural safety of the wind turbine foundation.Wind turbines are typical high-rise structures.Their structures are subjected to complex external loads and vibrations generated by the operation of the upper tower and the fan impeller,which together affect the stability of the lower foundation.During the long life of the wind turbine for 20 years,the wind turbine foundation will experience more than 10 million vibrations.Therefore,based on the existing engineering examples,the force analysis of the random dynamic cyclic load of the wind turbine foundation is carried out.The fatigue reliability of the foundation concrete dangerous nodes is evaluated.The main research contents of this thesis are as follows:1.In this paper,the stochastic process of wind speed fluctuation is expressed as the finite sum of the deterministic time function and the corresponding uncorrelated random coefficient by the orthogonal expansion method.Similarly,the random field is represented as a combination of Karhunen-Loeve decomposition with only a small number of random variables.The uncorrelated random coefficients are selected by the number theory.Use matlab programming to achieve the above calculations,complete the generation of random wind speed time history,and calculate the wind load time history acting on the wind turbine.2.Abaqus finite element software is used to model according to actual working conditions.The modal analysis of the fan is used to obtain the natural vibration frequency of the structure.The wind load calculated in the previous step is loaded onto the finite element model of the fan to solve the dynamic response of the fan.The response calculation results verify the position of the fatigue hazard point in the actual working condition,and further take out the stress time history of the basic dangerous point for the calculation of fatigue damage.3.According to the idea of rain flow counting method,matlab programming is carried out,and the hysteretic stress rain flow count of stress time history calculated by dynamic response is obtained,and the calculated result is further subjected to stress correction to substitute the linear accumulation theory of fatigue damage,combined with previous experiments.Out of the SN curve,using Matlab programming to calculate the fatigue damage of the foundation concrete.4.Using the probability density evolution method,the virtual time process is constructed with the fatigue damage value.The initial specified probability obtained by the number theory selection point is brought into the probability density evolution theory for numerical calculation.The evolution of fatigue damage is calculated by numerical method using matlab programming.The numerical solution of probability density,according to the fatigue theory,the fatigue density of the fatigue damage value is less than 1 to obtain the fatigue reliability of the structure.