Research On Fatigue Performance Of Grouting In Transition Section Of Offshore Wind Turbine

Mono-pile foundation is the most widely used offshore wind turbine.In this paper,the fatigue performance of the grouting of the transition section under the combined action of wind load and wave load is studied.The main contents and conclusions of this paper are as follows.According to the environment of offshore wind turbine,the load combination of the fatigue analysis on grouting of transition section is determined.The finite element model of offshore wind turbine is established,the fatigue details and their Tresca stress time history curve are analyzed.According to the linear cumulative damage theory of fatigue,the fatigue S-N curve of grouting and the rain flow counting method,the damage degree of the fatigue details are calculated.In view of the transition section without shear keys,the fatigue performance of the grouting is studied in this paper.The results show that:(1)The cumulative fatigue damage of the lower edge of grouting of transition section is larger than that on the upper edge.(2)When the length of grouting is about 1.5 times of the diameter of pile,the damage degree of grouting is the smallest.(3)With the increase of thickness of grouting of transition section,the decrease of thickness of outer sleeve,the increase of thickness of pile,the increase of length of pile,the decrease of height of tower,the decrease of weight of vane wheel and engine room of wind turbine and the increase of shear modulus of soil,the damage degree of grouting decreases gradually.(4)The parameters such as thickness of grouting,length of grouting,height of tower,weight of vane wheel and engine room of wind turbine have great influence on the damage degree of grouting.(5)The formula of the influence of the design parameters on the fatigue cumulative damage degree of grouting is put forward.(6)With the increase of wave load and wind load on offshore wind turbine,the damage degree of grouting rises significantly and the influence of wind load is much larger than that of wave load.In view of the transition section with shear keys,the fatigue performance of grouting is studied in this paper.The results show that:(1)The existence of the shear keys will increase the cumulative damage degree of the fatigue details.(2)Compared with grouting without shear keys in the transition section,the existence of the shear keys causes the position of the fatigue details of grouting to move from the upper and lower edges of grouting to the shear keys at the top and bottom.(3)When the width of the shear keys is about 2 times of the height of grouting,the damage degree of grouting is the smallest.(4)When the number of the shear keys of each side is about 5(the vertical center distance of the shear keys is about 20 times of the height),the damage degree of grouting is the smallest.(5)With the increase of height of the shear keys in transition section,the damage degree of grouting increases gradually.(6)The variation of the damage degreeof grouting of transition section without of the shear keys is obviously different from that with the shear keys.With the increase of the thickness of grouting,the decrease of the thickness of outer sleeve and the increase of thickness of pile,the damage degree of grouting increases gradually.(7)The width and height of the shear keys,the number of each side(the distance between the vertical center)and the thickness of grouting have great influence on the damage degree of grouting.