Reliability Analysis Of Foundation And Tower Of Offshore Wind Turbine In Typhoon Areas

Offshore wind power is in the stage of rapid development in China,the foundation and tower are important support components of wind turbine,the safety of which is the basic condition to ensure the normal operation of wind turbine and depends on the design code.The method of partial safety factors is adopted in current design code of offshore wind farms in China,but the calculation method of load and resistance and the value of partial safety factors are taken from other industry codes,so there is no proof for the rationality of partial safety factors in offshore wind power codes.In addition,offshore wind turbines,which are typhoonsensitive structures,are often attacked by typhoons,so the safety of offshore wind turbine in typhoon areas should be paid attention to.Supported by the project "Reliability analysis of foundation structure of the offshore wind turbine in typhoon areas",the reliability analysis and research on foundation and tower of the offshore wind turbine in typhoon areas is carried out.The specific research contents and conclusions are as follows:(1)Based on the 20-year wind load data of Guangdong,Fujian and Shandong offshore regions provided by Ocean University of China,a statistical analysis of offshore wind speed and wind load is carried out.The analysis shows that the annual maximum wind speeds in the three offshore regions all follow log-normal distribution,the coefficients of mean value of the annual maximum wind speed are 0.7134,0.2516 and 0.7831,and the variable coefficients are 0.1891,0.7990 and 0.1369.(2)Based on the 20-year wave load data of Guangdong,Fujian and Shandong offshore regions provided by Ocean University of China,a statistical analysis of wave elements and wave load is carried out.The analysis shows that the annual maximum wave force and wave moment of pile foundation of wind turbine of the three offshore regions all follow extreme type I distribution;the coefficients of mean value of the annual maximum wave force are 0.3639,0.7186 and 0.3793,and the variable coefficiens are 0.6677,0.3633 and 0.7399;The coefficients of mean value of the annual maximum wave moment are 0.4017,0.6793 and 0.4248,and the variable coefficients are 0.6383,0.4048 and 0.6775;The correlation coefficient of wave load and wind load is 0.85.(3)Based on the test data of 25 steel pipe piles and the existing statistical data of soil parameters,the statistical analysis of the vertical bearing capacity and horizontal bearing capacity of steel pipe pile foundation are carried out.The analysis shows that the vertical bearing capacity and horizontal bearing capacity of steel pipe pile all follow log-normal distribution with coefficients of mean value of 1.3316 and 1.000 and variable coefficients of 0.2196 and 0.1601.(4)According to the probability model that established of wind load,wave load,wind turbine foundation and tower,the first-order second-moment method is used to calculate the reliability index of the foundation and tower with the reqirement of code.The results shows that the annual reliability index of the bearing capacity of vertical,horizontal,pile structure,tower,connection of flange and bolt of the steel pipe pile foundation,and tension and compression of the jacket of offshore wind turbine in three offshore regions of Guangdong,Fujian and Shandong are 4.03,3.74,3.89,4.34,3.17 and 3.23,and the average reliability index during 25-year service period are 3.11,2.82,3.02,3.55,2.07 and 2.14.(5)The reliability indexes of the foundation and tower of the wind turbine calculated in this paper are compared with the objective reliability index of the structure and foundation design for foreign wind turbine.The comparison shows that the annual reliability index of the steel pipe pile,tower and the connection of tower and pile is higher than the annual reliability index 3.09 and 3.3 recommended by the Danish Risk National Laboratory Wind Energy Department for the third and fourth edition of the IEC 61400 international standard,the annual reliability index of the tension and compression elements of jacket is slightly higher than the annual reliability index 3.09 recommended by the third edition of the IEC 61400 international standard,and slightly lower than the annual reliability index 3.3 recommended by the fourth edition of the IEC 61400 international standard.