| At present,with the proposal of the goals of “emission peak” and “carbon neutrality”,the construction of offshore wind farms in China has entered an accelerated period.In this thesis,the performance of the pile foundation with elevated cap of a offshore wind farm project under construction is first analyzed and calculated,and based on Sesam and GH.Bladed software,the effects of structural parameters,wind,wave and current loads in a complex marine environment and geological conditions on the load effect of wind turbine are studied.In addition,a practical method suitable for various wave conditions,through the quickly and simple way to feedback the deformation of pile foundations with different structural parameters,can provide guidance for design and construction in the project.The main contents of this study are as follows:(1)By sorting out the existing normative requirements and related theories systematically,the pile foundation with elevated cap suitable for the offshore wind farm is designed according to the situation of the example wind farm.The pile foundation performance is calculated,which indicates that the bearing capacity,diameter-to-thickness ratio,local pressure and buckling,strength,displacement deformation,etc.of the pile foundation meet the requirements of the code.It is found that the pile foundation considering the pile group effect has a good ability to resist horizontal load,which indicates the pile foundation with elevated cap is suitable for offshore wind farm to resist wind wave and current load.(2)Based on the analysis of structural parameters of pile foundation with high cap,the influence of different pile diameters,steel pipe thicknesses,pile layout radius and pile free lengths on the load effect is studied.The results show that the increase of pile diameter,pile thickness,pile layout radius and pile free length will increase the overall natural vibration frequency,improve the overall stiffness of the structure,reduce the displacement of the structure,which improve the bearing capacity of the pile.(3)Based on the sensitivity analysis of the complex marine environment where the wind turbine is located,the effects of significant wave height,wave spectrum peak period,angle between wave and current and soil elastic modulus and Poisson’s ratio on the load effect are studied,which provides a basis for the selection of working conditions in the design of offshore wind power infrastructure.The results show that the structural displacement and the intensity of the motion will increase as the increase of the height of the righteous wave and the approching of the spectral peak period to the natural vibration period;the smaller the angle of the wave and current will cause the greater the horizontal thrust of the structure,so that the wave and current should be selected in the same direction for the design condition;the larger the elastic modulus of the soil can lead to the lower the degree of deformation at the mud surface of the pile foundation,while the change of Poisson’s ratio for the soil can be ignored because of the little impact on the displacement and angle of the pile foundation mud surface.(4)A practical calculation method that can feedback the deformation of pile foundation quickly and simply is proposed in this thesis.Through regression analysis,a formula for estimating the deformation of the pile foundation under different structural parameters is obtained that can be applied to various wave conditions,based on the data obtained from the small-scale test pile experiment,which can be used to evaluate the ability of the pile foundation to resist deformation,provide a basis for the initial design of offshore wind power infrastructure,and reduce the workload in the structural design process. |
