Studies on axial compression performance of rectangular concrete-filled hot-rolled-steel tubular flat columns

A new rectangular concrete-filled hot-rolled-steel tubular flat column (RCSTFC) constructed from hot-rolled steel and internal steel plates was proposed in this study. The influence of the internal steel plate thickness (TI), angle steel thickness (Ta), and cell number on the axial compression performance of RCSTFCs was investigated. The test results showed that RCSTFCs exhibit overall instability and local buckling under axial compression. Under D/B = 2.0, 2.67 and 3.0, the changes in TI, Ta and cell number did not significantly influence the failure mode, strength index or axial deformation ductility of RCSTFCs with the same steel ratio. Furthermore, the area of the effectively confined zone and the stress-strain relationship of the confined concrete in the RCSTFCs were deduced, and a new calculation method for the axial load-carrying capacity of RCSTFCs was proposed. Compared to the design methods in GB 50936, CECS 159, AS 5100.6, and AISC 360, the proposed method produced relatively accurate results in the prediction of the axial load-carrying capacity of RCSTFCs. •RCSTFC configuration was studied by axial compression test.•Confined area and stress-strain relationship of concrete in RCSTFC were deduced.•New calculation method of RCSTFC axial load-carrying capacity was proposed.