Fragility Analysis Of Monopile Wind Turbine Under Typhoon

With the aggravation of environmental problems and the shortage of traditional energy,countries gradually begin to replace fossil energy with new energy.Wind energy,with its mature technology and abundant resources,has become one of the most powerful new energy sources.In recent years,China has vigorously developed wind power technology,especially offshore wind power.As the most frequently used type in China's offshore wind power projects,the monopile wind turbine is a typical tall structure,whose structural safety is easily affected by the external environment.Among the numerous natural disasters,typhoon is the most common one,and also the biggest threat to wind turbines.At present,there are few researches on typhoon vulnerability of offshore wind turbine in China.This paper choose a sea area in Jiangsu Province as the hypothetical research point and NREL 5MW wind turbine as the research object to conduct typhoon vulnerability analysis.The main work of this paper is as follows:1.The key parameters of real typhoons are counted,a large number of virtual typhoons are simulated based on the local track modeling to make up for the shortage of typhoon samples,and the appropriate wind and wave field model is selected to calculate the wind and wave caused by typhoons at the research point;2.Introduce the method of how to simulate the wind and wave time history and calculate the corresponding wind and wave load.Then,dynamic response analysis of the monopile wind turbine under different working conditions is carried out based on FAST software.And then the probability distribution of the extreme value of the response is given under the condition of considering uncertainty of wind wave fluctuation;3.The pushover analysis of the support structure is carried out in considering the uncertainty of structure size and material,and the probability distribution of the bearing capacity of the support structure is obtained;4.Calculate the failure probability of the wind turbine under typhoon action according to the probability distribution of response extreme value and bearing capacity.The results show that:1.The wind speed caused by typhoon is less than 65m/s,and the significant wave height is basically within 6m;2.The extreme compressive stress values at the base of the tower and monopile obey lognormal distribution,and it is found that yaw failure will cause a large increase in the structural response,which leads to a higher risk of structural damage;3.After the pushover analysis of the structure,it is considered that the buckling failure of the tower is more likely to occur,while the yield failure is the main failure form of the pile foundation.Meanwhile,according to the probability distribution fitting results,it is considered that the bearing capacity of the structure obey the normal distribution;4.According to the response and bearing capacity distribution,the average failure probability of the monopile wind turbine is1.41×10^-4 under the normal yaw condition,and 6.7×10^-3 under the yaw failure condition.