Experimental study on flexural buckling of stainless clad steel long columns with welded box-sections under axial compression

Due to the extreme lack of reports on the global stability of stainless clad steel columns, axial compression tests were conducted on ten long columns with welded box-sections to investigate the global stability performance and supplement relevant data. The connections between the flanges and webs were made using single-sided Vgroove full-penetration welding. Precise 3D scanning and calculations were carried out to assess the global bending, twisting, distortional and local imperfections. The global bending imperfections exhibited an approximate sine wave distribution along the column length, with small amplitudes of less than 1/1000 of the specimen length. The failure modes, load-axial displacement curves, load-lateral displacement curves, load-rotation curves, load-axial strain curves, initial stiffness and ultimate bearing capacity were obtained and thoroughly analysed. All specimens failed due to global bending instability. The load-displacement curves followed a similar pattern, consisting of linear elastic, nonlinear and descending stages. Strain measurements indicated that most specimens reached their ultimate load with plastic deformation occurring across the gross cross section, indicating elastic-plastic instability. Based on the test results, current design methods in the European, Chinese and American standards for stainless steel and carbon steel structures were evaluated. Although, some of the design curves, such as the class b curve in GB 50,017-2017 and design curve for duplex stainless steel in CECS 410: 2015, can better predict the experimental results, most design curves have significant deviations, and the smaller the regularized slenderness ratio, the more obvious the error.