Smith, Vanessa, authorMahmoud, Hussam, advisorBienkiewicz, Bogusz, committee memberStansloski, Mitchell, committee member2007-01-032007-01-032013http://hdl.handle.net/10217/80316Wind turbines are widely recognized as a renewable energy resource and as such, their safety and reliability must be ensured. Many studies have been completed on the blade rotor and nacelle components of wind turbines under wind and operation loads. While several studies have focused on idealized wind turbine models, significant advancements on the global and local performance of these models under seismic loads in combination with other loads has been lacking. A study on the evaluation and performance of realistic wind turbine models under wind, operation and seismic loads is proposed and successfully completed. First, the geometry and loading for three wind turbine models are developed. A series of finite element analyses is conducted for each model under a variety of load combinations and earthquake records. Both global results and localized behavior were obtained for each analysis in order to identify areas of improvement within the wind turbine structure. Global results include drift ratios, normalized base shear and fast Fourier transformations to evaluate the stability of the wind turbine during operation. Localized performance focused on the welded connection at the base of the turbine and included Von Mises stresses as well as low-cycle fatigue analyses to determine the number of cycles to failure (initiation of through-thickness crack). These results show that certain turbine models are more susceptible to these loads than others. Several analyses indicate yielding at the turbine base and resonant conditions. The results from these analyses identify several critical issues within the wind turbine design and operation protocol.born digitalmasters thesesengCopyright and other restrictions may apply. User is responsible for compliance with all applicable laws. For information about copyright law, please see https://libguides.colostate.edu/copyright.Text