Dynamic Response Analysis And Bearing Performanceon Of Offshore Wind Power Foundation Under The Combined Wind Wave And Current Loadings

As a clean and environmentally friendly renewable energy,wind energy plays an important role in optimizing energy structure and improving environment.At present,wind energy is a new type of energy which is popularized by all countries in the world.Compared with onshore wind power,offshore wind power has the advantages of low energy consumption and high yield.China has 750 million kilowatts of wind resources,coastal areas from Liaoning to Shandong,and then to Jiangsu,Zhejiang,Fujian,Guangdong,Hainan,is rich in wind resources.However,due to the complexity of marine environmental conditions,the scale and efficiency of the exploitation and utilization of offshore wind resources are greatly restricted.As the main environmental loadings,wind wave and current play a decisive role in the normal operation of offshore wind turbines.At present,many scholars at home and abroad have studied the dynamic response of the onshore wind power foundation,but because of the great difference between land and sea environment,the research methods and results of the onshore wind power foundation can not be fully applied to the offshore wind power foundation.Therefore,it is necessary to study and analyze the dynamic response and bearing capacity of the offshore wind turbine and its foundation under the complex marine environment loadings,and then the research methods and research rules applied to the offshore wind power foundation are obtained.The above research will provide important reference for offshore wind power foundation design and construction.Therefore,based on the large finite element software and the project of Xiangshui wind farm in Jiangsu Yancheng,the finite element model for dynamic interaction of offshore wind power foundation and seabed is established under the combined wind,wave and current loadings,and the dynamic response and carrying capacity of the offshore wind power foundation are analyzed.The specific research work are as follows:1.The wind wave and current loadings on the offshore wind turbine system are calculated.First,the wind loading time history of offshore wind farm is simulated by using the harmonic superposition method and the wind loading formula.Then based on the theory of wave current interaction,the nonlinear wave theory and the Morison equation are used to calculate the wave-current loading on the offshore wind turbine,and the calculation formula of wave-current loading is derived.Finally,the wave pressure acting on the seabed surface is calculated based on the second-order Stokes wave theory,and the formula for calculating the wave pressure is obtained.2.The dynamic response of offshore wind power foundation and seabed under the combined action of wind wave and currents is analyzed.Based on the dynamic interaction model between the offshore wind power foundation and the seabed,in this paper,the Turkstra criterion is used to combine the three main loadings on the offshore wind turbine system.The horizontal displacement and vertical stress of the tower,the horizontal displacement of the foundation are analyzed under different loading combinations.At the same time,the excess pore water pressure of the seabed around the wind power foundation under the joint action of wind wave and current loadings is calculated,and the effect of different loading parameters on the excess pore water pressure of the seabed is investigated.3.The bearing capacity of offshore wind power foundation under the combined action of wind wave and current is calculated and analyzed.Based on the elastoplastic finite element model of the dynamic interaction between the offshore wind power foundation and the seabed,the single loading carrying capacity of the offshore wind power foundation under the horizontal,vertical and bending moment loadings is discussed.The load-displacement joint search method is used to study the bearing capacity envelope and the failure mode of the offshore wind power foundation in V-H,V-M,H-M and V-H-M load space.At the same time,the bearing capacity envelope of the foundation is analyzed in different load spaces.