Square concrete-filled stainless steel/carbon steel bimetallic tubular stub columns under axial compression

This paper is an attempt to study the mechanical behavior of square concrete-filled bimetallic tubular (CFBT) stub columns subjected to axial compression. The bimetallic tubes in the CFBT columns in this research comprised an outer layer made of stainless steel and an inner layer made of carbon steel. 200-mm square carbon steel tubes (wall thickness tsc = 3.30 mm) were manufactured first, then the bimetallic tubes were fabricated by cladding the carbon steel tubes with stainless steel sheets. In the experimental program, fourteen CFBT columns and two conventional concrete-filled steel tubular (CFST) counterparts were tested to failure under axial compressive loading. The test parameters included the stainless steel grade (Grade 316, 304, and 202), wall thickness of the stainless steel tube layer (tss = 0.84, 1.32, and 1.88 mm), and cube compressive strength of concrete (fcu = 54.5, 68.4, and 80.5 MPa). A finite element analysis (FEA) model was established and validated against the experimental measurements. The failure mode and mechanical behavior of the square CFBT stub columns were then investigated and compared with those of the conventional CFST columns. Finally, the ultimate loads obtained from the experiments were compared to those predicted by the available design codes.