Failure Probability Of Foundation Slab Void For Wind Turbine Steel Tower And Evaluation Of Concrete Compression Fatigue Performance

With the development of the wind power industry,the single capacity of wind power unit is also getting larger and larger,the size of the wind turbine tower,the diameter of the impeller is also getting larger and larger,and the installed height is also increasing,which leads to the control and operation system of the wind turbine is becoming more and more complex,and the safety of the wind turbine is also widely concemed.However,in recent years,wind turbines failure accidents have occurred frequently.Among them,the broken tower of wind turbine tower cylinder,the disintegration of the bottom of wind turbine foundation and the disintegration of the base ring and concrete are the three main forms of wind turbine structure failure.This paper has carried out a series of studies on the latter two,and the main work completed is as follows:(1)Taking a 3WM wind power tower system as the structural model,this paper adopts harmonic synthesis method to simulate the wind field under normal operation and extreme load conditions of the wind turbine according to Davenport wind speed spectrum and Kaimal wind speed spectrum.According to the geometric size and mechanical characteristics of the wind turbine,the finite element model of steel tower drum of the wind turbine is established by ABAQUS.Through modal analysis,the first natural frequency of the wind turbine tower cylinder model is obtained,which is close to the data provided by the manufacturer,which verifies the rationality of the modeling.The dynamic time history analysis of the wind turbine under normal operation and extreme load conditions was carried out considering the pulsating wind field and the second-order effect of gravity at the same time.The results show that the dynamic response of the wind turbine is larger when the wind speed is simulated according to Davenport spectrum under normal operation conditions.Under extreme load conditions,the wind speed simulation analysis based on Kaimal spectrum will be more conservative.(2)When the relative slip between the foundation ring and the foundation concrete is not considered,the dynamic time-history analysis of the finite element model of the fan tower drum is carried out.The dynamic response of the steel tower is solved,too.Taking the variations of both load effect history and material density into account,the Monte Carlo method is used to analyze the failure probability of foundation slab void according to the criterion in the code.The results show that the total bending moment and total shear force at the bottom of the wind turbine tower are approximately perfect dependent of each other and have a large coefficient of variation,regardless of normal operating conditions or extreme load conditions;for the selected Davenport wind speed spectrum,the failure probability of the foundation slab void of the wind turbine is about 0.0015 and 0.0031 under normal operation and extreme load conditions,respectively,and for the selected Kaimal wind speed spectrum,the corresponding failure probability is about 0.0026 和 0.0044,respectively;the reliability index increases with the increase of the radius of foundation slab,by no less than 30.87%for both two working conditions when the radius increases to 1.2 times.(3)Through the establishment of the wind turbine-foundation finite element model,the force of the wind turbine foundation concrete under fatigue conditions is clarified.the results show that the wind turbine base in basic ring outside contact with the surface of the concrete foundation of the dynamic response of concrete is the most obvious,and the actual engineering of damage location,and as a fatigue risk point here,the fatigue damage of concrete at the base ring and concrete interface of the fan is calculated.The rain-flow counting method and Goodman straight line are used to process the stress time history of the fatigue dangerous points,and finally the S-N curve method and Palmgren-Miner theory are used to calculate the fatigue damage.The results show that the total damage value in the life is 4.46×10-6 when the average wind speed is 4.3m/s.When the average wind speed is 10.2m/s,the total damage value in the life span is 1.23×10-1.