The effect of the rupture distance of the earthquake on the seismic response of wind turbine support towers

The global growth in wind energy suggests that wind farms will increasingly be deployed in seismically active regions, with large arrays of similarly designed structures potentially at risk of simultaneous failure under a ma-jor earthquake. The distance between the wind farm and the epicentre of the earthquake affects the frequency content of the seismic action and this may in turn have a significant impact on the performance of the wind tur-bines. This study presents the seismic analysis of a wind turbine subject to a large number of seismic records corresponding to events with different rupture distances, and the nonlinear dynamic analysis of a detailed finite element model of the structure with realistic imperfections. The geometrically and materially nonlinear dynamic analyses conducted demonstrate that apart from the typical long-period vibration modes there are higher-order frequencies of the structure that can have a significant contribution in the response, and the importance of these is affected by the epicentral distance of the earthquake and by the imperfections of the tower.