Search

Thin-walled steel tubes have been widely used in wind turbine towers. These towers are commonly subjected to combined compression-bending-torsion loads; thus, the steel tubes are prone to local buckling. Installing stiffeners has proven an effective method to improve the local stability of the thin-walled members. This paper presents an experimental and analytical study of thin-walled steel tubes strengthened by longitudinal stiffeners. Six specimens with different types of stiffeners and various diameter-thickness ratios were tested under a combined compression-bending-torsion load. The failure modes, load–displacement relationships, ultimate strength, and deformability were revealed. The validated finite element model was used to analyze the structural mechanisms of the stiffened steel tubes. The results show that stiffeners can substantially alleviate the local buckling of steel tubes, significantly improving their ultimate strength and plastic deformability. In addition, T-type stiffeners perform better than I-type stiffeners. The ultimate strength of the specimens is preliminarily evaluated using the methods recommended in existing design guidelines. The calculated ultimate strength of the unstiffened specimens shows a good agreement with the test results, whereas the ultimate strength of the stiffened specimens is underestimated. • Six specimens with different stiffener types and diameter-thickness ratios were tested under combined load. • The validated finite element model was developed to further analyze the structural mechanisms of the stiffened steel tubes. • The effects of stiffeners on the static behavior of steel tubes were revealed. • The applicability of the design methods recommended by the existing design guidelines was preliminarily evaluated. • The reasonable stiffener type and stiffening position were suggested. [ABSTRACT FROM AUTHOR]

Steel tubes with large diameter-thickness ratios are widely used in tubular steel towers of wind turbines. These steel tubes are susceptible to local buckling under compression-bending load, thus leading to a failure of the overall structures. In this paper, a new structural form of steel tubes with longitudinal stiffeners was proposed. Six specimens were tested to study the effects of stiffeners forms and diameter-thickness ratios of steel tubes. Finite element models were compared and validated by test results and used to further study the structural mechanisms. Lastly, the ultimate strength of specimens was evaluated by existing design guidelines preliminarily. According to the results, by setting stiffeners, especially the T-type stiffeners under the same consumption of the steel, the local buckling was prevented and the plastic deformability of the steel tubes was increased, resulting in the great enhancement of ultimate strength and ductility. The limits of quantity and width-thickness ratio of stiffeners to obtain a more stable and significant improvement effect were suggested through parametric analysis. The current methods agree well with the test results of unstiffened steel tubes but might be inaccurate for stiffened steel tubes. • Six specimens with different stiffener types and diameter-thickness ratios were tested under compression-bending load. • The finite element models were compared and validated by test results and used to further study the structural mechanisms. • The effects of stiffeners on the compression-bending behavior of steel tubes were revealed. • The limits of quantity and width-thickness ratio of stiffeners to obtain a significant effect were suggested. • The applicability and accuracy of the calculating methods in existing design guidelines were preliminarily evaluated. [ABSTRACT FROM AUTHOR]