On the torsional-translational response of wind turbine structures

In the present paper, the torsional–translational response of a prototype wind turbine tower considered as an irregular structure is studied. As a matter of fact, a plethora of wind turbine towers has collapsed during the last decades due to torsional dynamic actions. An effective numerical model of the prototype irregular wind turbine tower is herein developed which has been verified by the application of the continuous model method considering both a fully fixed and a partially fixed foundation. As known, the higher eigenmodes of the tower strongly affect the structural response and may become critical in the case that the tower is subjected to strong dynamic loading, as is, e.g., wind loading, when simultaneously excited by a strong seismic motion. In order to estimate the role of the fundamental torsional modes of the above-mentioned structure in its overall structural response, three pairs of appropriately selected artificial seismic accelerograms having response acceleration spectra (for equivalent viscous damping ratio 0.03) equivalent to the Eurocode elastic acceleration spectra are used and then, applying a type of backwards analysis, an equivalent dynamic or static torsion loading is defined.