Strength and ductility demands on wind turbine towers due to earthquake and wind load

In earthquake-prone areas, wind and earthquake loads are assumed to be statistically uncorrelated and therefore their interaction is ignored in existing design guidelines. However, the facts that strong earthquake events are commonly followed by aftershocks and that wind is constantly flowing at high speeds around wind farms increase the probability of their joint occurrence, thus making current design assumptions questionable. This investigation shows that multi-hazard scenarios magnify the strength demands of wind turbine towers designed against isolated load conditions, hence modifying their performance level. It is also shown that, under certain conditions, the probabilities associated with the joint occurrence of earthquake and low to strong wind events match or exceed those related to the original design, thus rendering wind energy infrastructure susceptible to unforeseen damage.