Axial Performance Of A New Type Grouted Connection In Offshore Wind Turbine Foundation

Offshore wind turbine infrastructure design is one of the most important and difficult issues in the construction of offshore wind farms,the grouted connection has been widely used in wind turbine infrastructure because of its advantages of good integrity,convenient construction and low cost.With the increase in wind power capacity,the diameter of pile foundation is increasing,the grouted connection without shear key are easy to slip between the casing when the axial bearing capacity is insufficient,therefore,the DNV-GL specification states that the grouted connection needs to set shear key on the wall of the steel pipe when it is subjected to axial forces.However,there is severe stress concentration phenomenon at the shear key position,it is easy to cause fatigue failure of the grouted connection under the action of reciprocating load.To solve the above problem,the research group propose a wave type grouted connection with wave surface on the wall of the steel pipe to relieve the stress concentration and improve the fatigue life.To verify the feasibility of the method,this paper is based on the comparison and analysis of common grouted connection specifications,use numerical simulation to analyze the static and fatigue performance of wave type and shear key grouted connection under axial load.The main work are listed as follows:(1)The calculation methods of different grouted connection specifications axial capacity are compared,and the relevant test results are collected to compare with the calculation results;It is found that the DNV-GL specification has better applicability when the axial capacity of grouted connection is low,and has better safety assessment performance when the axial capacity of grouted connection is high.(2)The finite element software ABAQUS is used to simulate the grouted connection,The axial load capacity and failure mechanism of wave type grouted connection and shear key grouted connection are analyzed;Comparing the mechanical behavior of wave type grouted connection with shear key grouted connection under the load condition;Proposed a method for design verification of wave type grouted connection.The analysis shows that the maximum stress of the wave grouting material is smaller than that of the shear key grouting material,the stress distribution near each groove is similar,there is no obvious stress concentration at both ends.(3)Fatigue analysis software FE-SAFE is used to analyze the fatigue behavior of the wave type grouted connection and shear key grouted connection under fatigue load;The economic analysis of wave type grouted connection under the condition of meeting the fatigue life is carried out.The results show that comparing with the shear connection,the wave type grouted connection can increase the fatigue life by more than 3 orders of magnitude.Under the premise of satisfying the fatigue life,the cost of wave type grouted connection can be reduced about 42%compared with the shear key grouted connection.(4)The influence of the grouted thickness,the diameter of the steel pipe,the thickness of the steel pipe,the spacing of the wave,the depth of the wave and the length of the grouted connection on the stress distribution of the grouting material under fatigue load are analyzed,to study the effect of different parameters on the fatigue performance of grouted connection,and the suggestion for the value of the corresponding parameters in the actual project design is given.