Assessment of the Dynamic Structural Behaviour of Steel Wind Towers when Subjected to Wind Loadings

Resumo

This research work investigates the structural response of a steel tower supported by an octagonal reinforced concrete foundation designed to accommodate a 2 MW wind turbine. The wind tower finite element model was developed based on the use of the Finite Element Method (FEM), utilising the ANSYS computational program, and considering the wind loadings on the rotor and tower, and the soil-structure interaction effect, aiming to obtain a realistic representation of the structure dynamic behaviour. In this investigation, given the stochastic nature of wind load modelling, a statistical analysis of the structures dynamic response was conducted in order to determine maximum values for displacement and stresses. Initially, the static and dynamic analyses have demonstrated that, incorporating geometric nonlinearities leads to a minor increase in the structural response concerning to the translational horizontal displacements and von Mises stresses. Additionally, a parametric study was performed, considering wind loads obtained through several basic wind velocities, with the objective of assessing the dynamic structural behaviour of the steel tower based on the of horizontal displacements, von Mises stresses, and also the fatigue service life. The results revealed that within the operational limit of the turbine, the investigated wind tower complies with the limit states specified in current wind tower design standards. However, for higher basic wind velocities, the steel wind tower structural design no longer meets these requirements.