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 major earthquake. Wind
turbine support towers are often constructed as thin-walled metal shell structures, wellknown
for their imperfection sensitivity, and are susceptible to sudden buckling failure
under compressive axial loading.
This study presents a comprehensive analysis of the seismic response of a 1.5 MW
wind turbine steel support tower modelled as a near-cylindrical shell structure with
realistic axisymmetric weld depression imperfections. A selection of twenty
representative earthquake ground motion records, ten ‘near-fault’ and ten ‘far-field’,
was applied and the aggregate seismic response explored using lateral drifts and total
plastic energy dissipation during the earthquake as structural demand parameters.
The tower was found to exhibit high stiffness, though global collapse may occur soon
after the elastic limit is exceeded through the development of a highly unstable plastic
hinge under seismic excitations. Realistic imperfections were found to have a
significant effect on the intensities of ground accelerations at which damage initiates
and on the failure location, but only a small effect on the vibration properties and the
response prior to damage. Including vertical accelerations similarly had a limited effect
on the elastic response, but potentially shifts the location of the plastic hinge to a more
slender and therefore weaker part of the tower. The aggregate response was found to be
significantly more damaging under near-fault earthquakes with pulse-like effects and
large vertical accelerations than far-field earthquakes without these aspects.