Structural assessment of a lattice tower for a small, multi-bladed wind turbine

This paper deals with a limit load assessment and preliminary experimental testing of a lattice-type steel tower used to support a newly designed, prototype small wind turbine having nine blades and a rotor diameter of 3.4 m. Small wind turbine and structural engineering codes of standards were followed with the purpose of implementing a system that meets European unio‎n countries’ legislation. The supporting lattice tower structure was subjected to a full-scale load test. This test verified that the structure can withstand the design loads. The finite element software ANSYS Mechanical was used to model and analyse the actual structure, and to determine the possible failure modes and their associated load levels. The most probable mode of failure for such a structure was found to be elastic buckling of the main corner posts. A number of finite element lattice tower models utilising different modelling strategies and solution methods are presented and analysed. The paper highlights the importance of using non-linear analyses as opposed to linear analyses and gives recommendations on the most reliable available modelling technique. Computational analyses’ results are compared with measurements from a full-scale test on the tower structure.