Numerical and Comparative Investigation of Dynamic and Seismic Behavior of Wind Turbine Towers by Finite Element Method

Turning to clean energy is inevitable, among which wind energy is one of the most common and available. Theuse of wind energy due to its known advantages over other renewable energies has caused the technology of windturbines to grow more, and this has led to the increase in the capacity of wind turbines and the commercialization oflarger sizes. By increasing the capacity of wind turbines, the size of the rotor and consequently the height of thetower necessarily increase. Therefore, the design of wind turbine towers more goes complex day by day, and mustbe done specifically on a case-by-case basis. For this purpose, wind turbines should be modeled completely with alldetails. One of the most expensive parts of wind turbines is its tower. Considering the whole applied forces anddesign criteria and fatigue base on the regulations and guidelines is necessary to achieve a safe performance. Inaddition to these factors, in seismic prone areas the dynamic earthquake forces should be considered in analysis anddesign of towers. Therefore, in this study, we have tried to study the seismic behavior of a real tower model incomparison with other dynamic forces, in order to obtain the amount and manner of effect of each force. Standardsgenerally specify design load combinations for ultimate load and fatigue load analyses. The speed of 11 m/s is thespeed at which, according to the power generation diagram of the studied turbine, the speed of the turbine reaches itsmaximum power, and it is assumed that the turbine will be installed in a site where the wind will be at this speedmost of the time, and the probability of earthquake occurrence at this speed is more than other modes.Therefore, considering the emphasis on considering the earthquake force in seismic areas along with other forcesacting on the wind turbine in the new versions of the regulations in this field, and the seismicity of Iran, acomparative analysis of seismic load with other forces acting on the wind turbine based on Standard GL, chapter 4,Table 4.3.2 for turbulent wind of 11 m/s, in the state of zero deviation angle for the 2 MW national wind turbine ofIran, with an 80-meter steel tower and a 55-meter 3-bladed rotor, in a complete and practical model, with themodeling of the steel tower structure and concrete foundation and soil layers in the case construction. The commenthas been analyzed and investigated by the dynamic finite element numerical method using Abaqus software.Considering the location of this wind turbine, with soil layers 6 meters deep, the maximum change in the location ofthe tip of the tower by considering the seismic load increased by about 7%, but the significant increase in theequivalent stress at the height of 50 meters of the tower, despite the low depth of soil layers. The lack of significantacceleration of the earthquake from the rock bed to the earth's surface was obtained, amounting to 36%. Therefore,the necessity for simultaneous consideration of earthquake load along with the wind load was well concluded.