The paper presents seismic fragility curves and the seismic reliability assessments for a wind turbine support structure. A National Renewable Energy Laboratory (NREL) 5 MW reference wind turbine finite element model is first built by beam and shell elements using ANSYS finite element package to conduct seismic response spectrum analysis (RSA). The realistic earthquake data reported from Pacific Earthquake Engineering Research Center (PEER) ground motion database are taken into account in this work. Totally 500 earthquake response spectra derived by 100 Taiwan Chi-Chi earthquake data combined with magnification factors of 1,2, 4, 7 and 10 are imposed on the wind turbine support structure model as the loading conditions. Through Monte Carlo simulations (MCS), the peak displacements and peak stresses can be obtained from FEM corresponding to the earthquake peak ground acceleration (PGA) for further analyses. Then the fragility curves could be numerically derived from FEM results using maximum likelihood estimator (MLE). In addition, the Taiwan seismic hazard maps in terms of 475 and 2475 years return period are further considered to estimate the statistical parameters for annual maximum PGA distribution functions. Finally, the annual reliability index of the wind turbine support structure can be thus obtained from the fragility curves and annual PGA distributions.
Wind Energy becomes a swift-growing industry for electricity production to contribute the potential renewable energy. The development of wind turbine as shown in Fig. 1 (Ambrose, 2017) in production capability and in facility size has been rising rapidly in past decades. The World Energy Outlook 2016 report published by International Energy Agency have predicted that wind generation capacity would increase from about 384GW in 2015 to 1,452 GW in 2040 according to the New Policies Scenario (NPS) that incorporates existing energy policies as well as some assessment results risen from possible implementation of announced intentions. It is likely to turn out that the wind turbine facility will become more enormous consecutively.