Compressive behavior of stiffened steel tubes for wind turbine towers

Abstract

Steel tubes adopted in wind turbine towers generally sustain the combination of compression, bending, and torsion loads. The study of compressive behavior is crucial for investigating the combined bearing capacity of the tower and proposing the corresponding design method. Local buckling tends to affect compressive behavior due to the large diameter-to-thickness ratios of the tubes. Thus, the authors proposed a new form of tower based on longitudinally stiffened steel tubes, which were experimentally and analytically studied in this paper. A total of six tube specimens (four stiffened ones and two unstiffened ones) were tested under axial compression. The experimental results indicate that the local buckling of the tube can be substantially prevented by stiffeners and the T-type stiffener exhibits a superior effect. Finite element models were built and validated by the test results, and the parametric analysis was conducted, indicating that the diameter-to-thickness ratio of the steel tube, the yield strength of steel, and the proportion of stiffener area are the prime sensitive parameters affecting the ultimate strength. Ultimate compressive strength prediction methods in design specifications were evaluated. A practical method for calculating the ultimate strength of stiffened steel tubes was subsequently developed in this paper.