Resistance of Circular and Polygonal Steel Towers for Wind Turbines : Down scale component experiments and Finite element analysis

Abstract: With increasing demand of sustainable energy production, the harvesting of wind power by using wind turbines have become increasingly important over the last few decades. Most of the wind turbine towers are made from steel. Towers are an important part of the investment in wind parks and contribute about 20% of costs for the onshore towers. It supports the nacelle and is designed to sustain wind load and load caused by the operation of the wind turbine. This thesis presents results of experimental and numerical investigations on behavior of the steel tubular tower components made of circular and polygonal cross sections focusing on resistance of the door opening. An experimental program was planned to investigate the material and initial geometrical imperfections of the down scale specimens. Investigation of the basic material properties of the down scale specimens was carried out by using coupon specimens cut off from the down scale specimens. Influences of cold forming on the properties of the material were also studied by using coupon specimens with different cold formed angles. 3D scanning laser was used to determine initial geometrical imperfection of the down scale specimens. The measured data was analyzed by Matlab and Gom Inspect software. Results from these experiments were used as input data for the numerical models. Experiments on down scale specimens of the tubular tower with polygonal and circular cross sections were performed in order to investigate structural resistance. Finite element program Abaqus was used to simulate the tested specimens in order to compare their results to the experiments. Elastic, nonlinear geometry and nonlinear materials analyses were performed in order to investigate the ultimate resistance of the down scale specimens. Comparison of resistances of the circular and polygonal cross sections with Eurocode 3 was carried out.