Influence of Geometrical Imperfections on Analyses of Door Openings in Tubular Steel Towers for Wind Turbines.

Towers for wind turbines are very sensitive to geometrical imperfections. Pattern and amplitude of imperfections significantly influence the strength of the towers. Rather limited number of experiments exists on a tubular tower like structure and no experiments are available considering door opening in towers with cylindrical or polygonal cross-section. One of the objectives of the RFCS research project “HIGH STEEL TUBULAR TOWERS FOR WIND TURBINES, HISTIWIN2” was to investigate current practice for design of door openings and propose a competitive solution, possibly using higher strength steel grades. A comprehensive experimental program was conceived to gain experimental evidence for the design of stiffening of the door openings.The following compression tests were evaluated in the paper:•4 static down-scaled compression tests of components of circular tubes •4 static down-scaled compression tests of components of polygonal tubes•4 static down-scaled compression tests of components of circular tubes with opening•4 static down-scaled compression tests of components of polygonal tubes with openingPlate thickness is down-scaled to 4 mm thick plate made of S650 steel grade.Most of FE nonlinear analyses of thin walled shell structures were performed using geometrical imperfections according to Eurocode 3. In this approach, geometrical imperfections are based on the pattern that coincides with the critical buckling mode. A comprehensive numerical investigation was made to conclude whether there is need to use a real geometrical imperfection pattern. The real geometry of the imperfections was obtained by laser scan measurements. Both, the measured geometrical imperfections and the geometrical imperfections according to Eurocode 3 were considered. Furthermore, results obtained from polygonal specimens were compared with specimens with circular cross sections.Godkänd; 2014; 20140922 (anhtra