Seismic analysis of a tall metal wind turbine support tower with realistic geometric imperfections

Abstract

analysis of a tall metal wind turbine support tower with realistic geometric imperfections. Earthquake Engineering and Structural Dynamics, 46(2), pp. 201-219. doi: 10.1002/eqe.2785 This is the accepted version of the paper.This version of the publication may differ from the final published version. Permanent AbstractThe 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. KeywordsThin metal shell structure, imperfection sensitivity, seismic response, multiple stripe analysis, near-fault ground motions, vertical ground acceleration.

Seismic vulnerability of offshore wind turbines to pulse and non‐pulse records

“…In near‐fault regions, ground motions have long been known to inherit velocity pulses of large amplitude, being distinctly different from far‐field ground motions . In case of a 1.5MW onshore wind turbine, Sadowski et al showed near‐fault records with pulse‐like effects more damaging than far‐field records. Near‐fault pulses are produced because of either forward propagation of the fault rupture towards the site, i.e., directivity effects, or fault displacement due to rupture, known as fling‐step effects .…”

Motion Control of Pentapod Offshore Wind Turbines under Earthquakes by Tuned Mass Damper

“…On the other hand, Penzien et al [11] recommended that proper plastic response should be considered in the seismic analysis of offshore structures. Therefore, Kim et al [12], Nuta et al [13], and Sadowski et al [14] investigated the inelastic response of OWTs under seismic loads. Kim [11] performed the seismic fragility analysis of OWTs considering the non-linear effects of soil-pile interaction and suggested that the applied ground motion should be calculated for each soil layer to obtain equitable fragility curves of the structure.…”

“…Nuta et al [13] investigated the probability of damage in tubular steel towers at varying seismic hazard levels, defined the fragility curves of the towers by considering different damage states in the analysis, and proved that large safety factors must be considered in the design against the phenomenon of overloading under seismic loads. Sadowski et al [14] researched the responses of the tower under seismic loads with respect to geometric imperfections and discussed the influence of the imperfections on the capacity of the structure.…”

Collapse analysis of wind turbine tower under the coupled effects of wind and near‐field earthquake

“…Therefore, in Greek antiseismic specifications, the elastic acceleration reaction spectrum in near‐field zones requires further improvement. Sadowski et al investigated the dynamic response pattern of a wind turbine tower with a cylinder with an initial defect subjected to near‐field and far‐field ground motion. For the near‐field pulse ground motion, the tower damage was much more severe than the damage from far‐field ground motion.…”