Optimum Design And Parameter Sensitivity Analysis Of Tripod Foundation For Offshore Wind Turbine

Wind energy is a kind of clean energy with renewable potentiality,wide distribution and unlimited space for development. Land wind energy have been effectively used, and many coastal countries have developed offshore wind power, the foundation of the offshore wind power affects the whole structure's stability and safety,therefore,it is significant to design a economical and safe foundation for the development of offshore wind power. Tripod foundation structure is designed for specific waters, a given installed capacity and hub height in this thesis, interaction analysis between pile and soil, structure optimization and the parameter sensitivity analysis are carried out. The main researches are as the following aspects.(1) compare and analyze 6D equivalent pile length anslysis method witch take no account of the interaction between pile and soil and P-Y curve method considering the interaction between pile and soil, the finite element software ANSYS is employed to establish 6D equivalent model (Abbr. 6D model )and P-Y model respectively,and carry out modal analysis and static analysis, there are small differences between the results of the two models,which verify the 6D equivalent method and the P-Y curve method are consistent and feasible.(2) On the basis of static analysis results,optimize the pile distance of the tripod structure,and determine a reasonable distance. the strength,stiffness and stability are taken as constraint conditions, the weight of the structure as the goal, optimize the main component section of the structure using 6D equivalent model and P-Y model respectively, The optimized total steel consumption is reduced by 22.9% and 29.1% for 6D model and P-Y model respectively. By contrast,the optimization result of P-Y model is better,but there are differences for optimization results in individual components,especially in the middle column,tower and pile legs. Results show that the diameter and wall thickness of the tower and middle column are optimized obviously by 6D equivalent method, for pile legs, optimized obviously by P-Y curve method.(3) In order to study the key parameters of the tripod foundation structure, parameter sensitivity analysis of the tripod structure is carried out, following conclusions are arrived:The turbine wind load is the most sensitive parameters to the top displacement and maximum equivalent of the monopole tripod structure, the most sensitive parameters of the top displacement are the outer diameter of the middle column and the bottom of the tower, the most sensitive parameters of the sleeve's maximum stress is its outer diameter, the most sensitive parameters of the pile legs' maximum stress is the sleeve's outer diameter which connect to it, the most sensitive parameters of the structure' natural frequency is the outer diameter of the middle column and the bottom of the tower.