Local Buckling of Stainless Clad Steel Stub Columns with Welded Box Sections under Axial Compression

The local stability performance of stainless clad steel stub columns was investigated by first deriving the critical stress for elastic buckling of stainless clad steel plates using theoretical analysis. Following this, axial compression tests were conducted on seven welded box section stub columns. The flanges and webs of the test specimens were connected using full-penetration welding with a single-sided V-groove. Initial imperfections, including global bending, twisting, distortional and local imperfections, were precisely measured and calculated using a three-dimensional (3D) laser scanner. The failure modes, load–axial displacement curves, load–axial strain curves, initial stiffness, and ultimate bearing capacity were obtained and analyzed in detail. All specimens exhibited failure modes dominated by local buckling. Based on the width-to-thickness ratio, the specimens were categorized into two groups. For specimens with a width-to-thickness ratio less than 20, local buckling occurred after the full section had yielded, and the most pronounced buckling was observed at the ends. In contrast, specimens with larger width-to-thickness ratios exhibited local buckling before the full section yielded. When the normalized width-to-thickness ratio was less than 0.5, the ultimate bearing capacity exceeded the full-section yield capacity, indicating effective utilization of the composite steel’s strengthening phase. Conversely, local buckling occurred earlier in specimens with larger ratios, leading to an ultimate bearing capacity lower than the section’s plastic capacity. Based on the experimental results, a review of the European, Chinese, and US standards and the continuous strength method revealed that current design methods are inadequate for accurately predicting the local stability capacity of stainless clad steel stub columns with welded box sections under axial compression.