Experimental study of flexural‐torsional buckling in large‐scale welded cylinders

Abstract

Cylindrical shell structures, such as wind turbine towers, are continuously growing in size, and their structural performance is becoming increasingly governed by buckling. Under the critical loading scenario of combined uniform bending and torsion, these shells develop destabilising compressive meridional stresses together with in‐plane shear stresses. While each of these effects has been extensively studied on its own, their coupled interaction remains insufficiently understood. To address this challenge, an experimental program on large‐scale welded steel cylinders subjected to simultaneous bending and torsion was conducted. The specimens were manufactured by circumferentially welding two cylinders, enabling a detailed assessment of weld‐induced imperfections. In total, five large‐scale cylinders were characterized with micrometric precision and tested, with buckling failure consistently initiating in the vicinity of the weld. The characterization procedure allows to accurately determine the magnitude of the welding imperfections, whereas the experiments revealed a pronounced reduction in the critical load compared with theoretical predictions. These results provide new insights into the imperfection sensitivity of cylindrical shells and highlight the importance of accurately evaluate the effect of imperfections into the design of large‐scale tower structures under complex load case scenarios, such as flexural‐torsional.