Dynamic Response Research For Offshore Wind Turbine Pile-Foundation And Superstructure Subjected To Wave Loads

This paper based on the Doctoral Scientific Fund Project of the Ministry ofEducation of China (No.20125522110004) and the key research project supported byNatural Science Foundation of CSTC (No. cstc2013jjB3002), with the RudongCounty coastal and tidal zone wind farm construction project in Jiangsu Province asthe engineering background, unions numerical value simulation analysis as well astheoretical analysis methods and so on, analyzes the dynamic response of thefoundation and upper structure for an offshore wind turbine under wave loads, asfollows:(1)Starting with collecting and organizing the actual engineering data, includingthe marine environmental data、geological data and structure design data of theRudong offshore wind farm, and gained an insight into structure type and loadingcondition of offshore wind turbines.(2)Focus on the motion characteristics of sea waves, analyzed and discussed theclassical wave theory and Morison Equation which was used for solving the waveloads on small diameter cylinder. Then established the numerical model of wavemotion by using the nonlinear Stokes five wave theory, and calculated the wave loadthat the offshore wind turbine subjected which was founded on monopole.(3)According to the geological engineering area, used p-y curve method to showsthe deformability under the combined action of pile and soil，which is one of theimportant methods for calculation of laterally loaded pile．On this basis, constitutivemodel of nonlinear elastic soil was established.(4)The specific structure and the actual charge of the offshore wind turbine wasmade a reasonable simplification, using the ANSYS software as developmentplatform, two finite element models of the offshore wind turbines foundation andsuperstructure (FEM), which were founded on monopile and tripod foundation, weredeveloped by using the parametric design language (APDL).(5)Considering the effect of periodic wave load, the dynamic responsecharacteristics of both two FEMs were respectively calculated through the modalanalysis and transient analysis. Therefore, the frequencies and modal shapes ofcomponents and integral structure were obtained.(6)Based on the FEM of the offshore wind turbine founded on monopile, the dynamic stiffness of the key positions on the structure were analyzed，leaded to thecurve of dynamic stiffness along with the wave frequency change. And some designsuggestions were put forward for the offshore wind turbine founded on the monopole.