Analysis Of Dynamic Response Of Offshore Wind Turbine Foundation Based On FSI

Now a days, energy problem has always been the focus of attention by people, windenergy as a renewable clean energy is popular by most of countries all around the world, andoffshore wind energy development and utilization in recent years has created a new stage ofwind power utilization. The future offshore wind projects have the trend of the developmentof the deeper waters, along with volume and weight of the fan base is growing. Thus for fantower foundation structure is also put forward higher requirements, so the research foroffshore wind tower bracing structure is necessary. Offshore wind power support structuresystem located in the area of coastal tidal flats. The foundation soil are consist of the silt layerand sand layer, and this kind of foundation and the upper part of the overall structure conformto the response categories of ground motion under the action of the dynamic response is alsothe concern of the designer. Wind turbines are tall structures, in order to ensure the normaloperation of the fan, requires a high degree of horizontal displacement of the structure system,and the vibration of the fan structure under horizontal random load characteristics andstructural system of horizontal displacement have a relationship. So the research of dynamicresponse under random load for the fan support structure system are of great significance andvaluable.In this paper, we analysis based on JiangSu XiangShui offshore wind farm project,through numerical analysis method, using the current general finite element softwareADINA construct a three dimensional model of single pile and pile on the four feet underthe condition of the project sea condition. Have a dynamic analysis based on FSI, input theappropriate ground motion acceleration time history, and Water-structure dynamic interactionis discussed in orther word is FSDI. Prove that structural system in some working conditionsdue to the large horizontal displacement or yield strength of materials will lose its significanceof use. And some design suggestions are given. Here are some results and design suggestions:1、To establish three-dimensional finite element model of single pile foundation ofoffshore fan structure according to the actual data，and take two kinds of working conditioninto consideration，they are no water layer and take water as fluid potential based. Take modal frequency analysis respectively, give a general analysis of the effective of the exist of waterthe natural frequencies on single pile foundation as well as the four piles.2、 This Paper make a comparison of self-vibration frequency between single pile andfour feet pile,come out with the affective of pile style for the self-vibration frequency. Andconclude with the idea that the sensitive of water is lower of four feet pile than that of singlepile.3、Make a seismic response analysis of single pile of supporting system for the windpower at Offshore tidewater settlements. Both from the perspective of material strength anddeformation of structure point of view. In seismic response analysis，come out with theconclusion that structure above the pile body mud layer, and the horizontal displacement oftower drum is bigger,and the displacement increasing from bottom to top, the extreme ofhorizontal displacement is at the top of the tower drum machinery parts.Recommendation isthat designed method should consider of strengthen the overall stiffness of the upper structure.The vertical settlement of silt seam are located around the pile, recommend that measuresshould be made to prevent vibration liquefaction process around the pile. The extreme valuesof Effective stress located at outside surface of upside blower tower barrel, we should attachgreat significance of the Strength of materials issue at the upper tower drum.4、As for fan support structure system of Offshore shallow water,we make a oftenencountered seismic oscillation Based on the fluid-structure coupling conditions, come outwith the idea that: It is necessary to make an analysis of FSDI, when we consider the role ofwater, the vertical displacement of structure pile body and the air blower tower barrel becomelower, and meets the requirement. Displacement of x of the fan structure system Increasegradually from bottom to top, displacement of the shape for the curved shape. Displacementof the bottom sand pile inserted into the foundation part is small, horizontal displacement ofpart of the pile inserts into the silt layer increase gradually from bottom to top. displacementof pile tip is19.4cm.Settling volume of the overlying silt layer happened at the area whicharound the pile,there is much fluctuation in the water, the role of the water wave effect onpile foundation structure which caused by the Ground motion can not be ignored. The extremevalues of effective stress reached308MPa, which lower than the yield strength of steel345MPa.5. Compared with the acceleration time history of the silt layer and pile of single pilefoundation,we make a summary that: peak ground acceleration of silt seam reducedsignificantly with consideration of water, and the timing of peak ground acceleration bringforward, and the time of distribution of outstanding value bring forward significantly. Peakground acceleration of single pile body reduced significantly with consideration of water, and the timing of peak ground acceleration bring forward, and the time of distribution ofoutstanding value bring forward significantly.