Axial compression behavior of stub square bimetallic steel tubes

In this paper, the axial compression behavior of the stub square bimetallic steel tube was investigated through experiments and finite element analysis. Firstly, a total of twelve specimens were fabricated and subjected to axially compressive loads, and the experimental parameters contained the section type (hollow section or concrete-infilled section) and the breadth-to-thickness ratio. The test results indicated that the ultimate resistance of the bimetallic steel tubes decreased obviously with the increase of breadth-to-thickness ratio due to the early onset of local buckling. Besides, the internal concrete effectively prevented the inward buckling of the steel tube, therefore the ultimate resistance of the concrete-infilled tube was higher than that of the hollow tube, and the improvement increased with the increase of the breadth-to-thickness ratio. Then the finite element models were built and verified by experimental results. The parametric analysis was conducted and three parameters, including the breadth-to-thickness ratio, the percentage of the stainless steel content and the yield strength of the carbon steel, were considered. Finally, the critical breadth-to-thickness ratio of hollow and infilled steel tubes was discussed. The results revealed that the values regulated in AISC 360-16, EN 1993-1-1 and GB 50017-2017 were unsafe for the bimetallic steel tubes with hollow sections, and the values in AISC 360-16 and CECS 159: 2004 were also unsafe for the bimetallic steel tubes filled with concrete.