Effect of pulse-like near-fault ground motions on utility-scale land-based wind turbines

Seismic response of a utility-scale land-based wind turbine to near-fault pulse-like ground motions is presented in this study. The structural model corresponds to the 5-MW prototype developed by National Renewable Energy Laboratory. Response parameters such as tower-top displacement, base shear, and overturning moment are calculated by time history analysis and response spectral analysis using different estimates of response spectra. The results show that peak ground velocity and the frequency of dominant pulse of the ground motion are critical parameters governing the response, while peak ground acceleration has very weak correlation to response. When the pulse period is in the vicinity of structural period, seismic response is found to be much larger than those imposed by extreme events in design wind loads. Response spectral analysis using the actual spectra obtained from actual ground motions yielded results close to those from time history analysis. The spectral model prescribed in Eurocode8 is found to be inadequate in representing near-fault seismic action on the wind turbine.