Large-Scale Bending Tests of Slender Tapered Spirally Welded Steel Tubes

A new manufacturing process allows for the production of tapered spirally welded steel tubes. This paper describes a series of eight large-scale tests examining the behavior of such tubes in flexure and investigates the impact of imperfections on the flexural strength of the tube. The tests are performed on tapered circular steel tubes with diameters between 0.7 and 1.1 m and maximum diameter-to-thickness ratios between 200 and 350. Specimen geometries are selected to provide flexural test data at slenderness ratios not commonly tested in the literature and to be representative of tapered tubes applied as wind turbine towers. The geometries of the specimens are measured with laser scanners before and during testing to characterize initial imperfections and the evolution of local buckling. Results are compared to design strengths per Eurocode EN 1993 1-6. All specimens meeting Eurocode manufacturing quality requirements exceed predicted strengths. The location and orientation of the local buckling region are correlated with the spiral seam welds on the specimens.