1 SEISMIC PROTECTION OF WIND TURBINES USING TUNED MASS DAMPERS Okyay ALTAY 1 , Marie Lisanne MEINERZHAGEN 2 , Francesca TADDEI 3 , Christoph BUTENWEG 4 and Sven KLINKEL 5 ABSTRACT The seismic efficiency of tuned mass dampers is numerically analyzed by means of a three-bladed 5 MW onshore reference wind turbine. The calculations are carried out by the aeroelastic dynamic horizontal axis wind turbine simulator FAST with its seismic and structural control codes. Time- histories of five historic earthquakes are used. These are Tokachi-Oki (1968), El Centro (1979), Northridge (1994), Kobe (1995) and Kocaeli (1999). The simulations are performed simultaneously with turbulent wind at 1-25 m/s mean speeds. The optimum TMD parameters are calculated using Den Hartog’s criteria for natural damper frequency and damping ratio. A mass ratio of 5 % is chosen for the analyzed TMD. The acquired results show that TMD can mitigate especially the periodic structural vibrations effectively. This effect is observed both for the wind and for the seismic loading, which shows that the seismic vibration mitigation effort of a TMD mainly depends on the frequency content of the earthquake. During El Centro earthquake, which causes mainly transient vibrations, the efficiency of TMD is not significant. From the analyzed other four earthquakes, particularly the seismic vibrations caused by the Tokachi-Oki earthquake are reduced remarkably, by which the turbine tower without TMD reaches its highest RMS and peak deflection. INTRODUCTION Because of its minor environmental impact, electricity generation using wind power is getting remarkable also in seismic active regions. As shown in Fig.1 large part of the south European coastal areas presents high seismic hazard and such wind conditions, which are sufficiently suitable for financial returns from modern wind turbines. According to the global report of the Global Wind Energy Council the power capacity of the installed wind turbines for instance in Turkey has reached in 2012 2.3 GW by increasing in one year period over 28 % (Fried et al., 2012). The safety and serviceability of these structures mainly depend on their design and analysis, which should include in 1 Dr.-Ing., RWTH Aachen University, Chair of Structural Analysis and Dynamics, Aachen, Germany, altay@lbb.rwth-aachen.de 2 B.Sc., RWTH Aachen University, Aachen, Germany, lisanne.meinerzhagen@rwth-aachen.de 3 M.Sc., RWTH Aachen University, Chair of Structural Analysis and Dynamics, Aachen, Germany, francesca.taddei@lbb.rwth-aachen.de 4 Dr.-Ing., RWTH Aachen University, Chair of Structural Analysis and Dynamics, Aachen, Germany, butenweg@lbb.rwth-aachen.de 5 Prof. Dr.-Ing., RWTH Aachen University, Chair of Structural Analysis and Dynamics, Aachen, Germany, klinkel@lbb.rwth-aachen.de