Study on Mechanical Behavior of Integrated Multi-cell Concrete-filled Steel Tubular Stub Columns Under Concentric Compression

Abstract

11 integrated multi-cell concrete-filled steel tubular (CFST) stub columns were tested under concentric compression. The key factors of width-to-thickness ratio (D/t) of steel plates in column limb and prism compressive strength of concrete (fck) were considered and their influence on failure mode, bearing capacity, and ductility of the columns were investigated. The experimental results show that: (1) the constraint effect for concrete provided by the multi-cell steel tube cannot be overlooked; (2) the ductility decreases with the increasing ratio D/t of the connecting steel plates for the multi columns; and (3) the bearing capacity increases, while the ductility decreases, with the increasing fck. The finite element (FE) method was used to simulate the integrated multi-cell CFST stub columns and to verify the test results. A parametric analysis using the FE method was carried out to study the effects of the steel ratio α, steel yield strength fy, concrete strength fck, and D/t on the stiffness, bearing capacity, and ductility of the columns. Furthermore, the measured bearing capacity values were compared to those estimated by the Chinese, European, and American design codes. This study shows that the bearing capacity of integrated multi-cell CFST stub column can be reasonably predicted by the design method specified in GB 50936-2014 or EC4-2004 code.