Seismic Research Of Horizontal Axis Wind Turbines With Tubular Steel Towers

In recent years, the wind power industry has been developing rapidly in China and thewind power technology has reached a high level. Especially the horizontal axis wind turbinewith the tubular steel tower has the advantages of high efficiency, large capacity and hasbeen used widely in various areas. Wind turbines with large capacity instead of small windturbines have become a trend in the future, and hence the structural performance should bestudied. China is a seismic-active region, but many wind farms are built near seismic zones,even high intensity areas. Although the wind power technology has reached a higher level,the structural security is hardly considered. Wind turbine is a kind of high-rising steelstructure, so the seismic action must be taken into account in design. In this thesis, accordingto the seismic hazards of China, the seismic performance of wind turbine isinvestigated.Wind turbines mentioned below are horizontal axis wind turbines.China is a country severely affected by earthquakes and the destruction of structures byearthquakes often occurs, which causes a significant loss. By analyzing the distribution ofwind farms and seismic zones, the importance of the seismic action is emphasized.In accordance with the seismic research of wind turbines, statistics of detailedparameters are gotten. Using the method of fitting analysis, three kinds of empiricalformulae with different parameters are summed up.When the top mass and the tower heightof the wind turbine are known, the natural period can be quickly calculated by using theempirical formulae.The natural frequencies and corresponding characteristics are obtained, which indicatethat the azimuth of the blades doesn’t affect the frequencies. The profile of the bendingmoment, the acceleration along the tower and the bending moment along the blade areobtained by seismic analyses.In the field of structural seismic design of wind turbines，the standard is still blank. Here,the appropriate seismic calculation method is selected. Combining with Chinese seismicstandards, the seismic loads of2MW and5MW wind turbines are calculated. After analyzingthe result, the applicability of existing standards is studied.The single or two degrees of freedom simplified models can be formed in line with themethod for buildings and the seismic loads are calculated by the base shear method. The erroranalysis implies that seismic calculation of wind turbines by the base shear method yields asatisfying accuracy.Studies show that: The natural petiod can be calculated through the empirical formulaeproposed here. Then the single and two degree-of-freedom simplified models are established,which are used to calculate the earthquake action by using the base shear method. Finnally,accuracy results can be received as a basis for structural design.