Seismic assessment of wind turbines: How crucial is rotor-nacelle-assembly numerical modeling?

The cross-section and the structural twist angle of a typical wind turbine blade vary along its span. This complicates realistic modeling in nonlinear dynamic analysis turbines when seismic performance estimates are sought. As result, lumped mass approach is most commonly used to model rotor-nacelle-assembly (RNA). RNA eccentric tower top, blades tend induce rotary inertia on tower. exclusion this rotor eccentricity can impact response as contributes significantly total system. Moreover, long, slender components that vibrate deform independently under excitation. intrinsically considers rigid-body for RNA, which inevitably acts part top. affect vulnerability estimation offshore (OWT) at degree has not yet been properly quantified. To explore issue, present study discusses effects three key parameters, i.e., (i) blades, (ii) eccentricity, (iii) blades’ flexibility, failure fragility OWT shallow crustal earthquakes. Results show affects higher modes, turn influence height zones. It also shown different levels refinement predicted probabilities, particularly pulse-like ground motions, while same overestimated if conventional rigid body used. Even worse, they be underestimated (thus less safe) completely ignored, compared with refined flexible blades. These results revealing highlight hazard indeed pose significant design issue OWTs some regions.