Flexural behaviour of different CFSTs cross-section shapes with the same steel cross-sectional area

Concrete-filled steel tubes (CFSTs) have recently been used worldwide as both beams and columns. CFSTs have remarkable advantages as they are independent of the moulding process and there are no maintenance requirements of the infilled concrete. In this paper, the flexural performance of CFST beams which had rectangular, circular, and square cross-sections was investigated. All beams were equal cross-sectional area (1044 mm2) and the same wall thickness (3 mm). Four-point bending tests were performed on a total of twelve CFST beams including three different types of sections filled with concrete with a compressive strength of 40 MPa. Load/moment–displacement curves extracted from the experimental results were presented and discussed. Results showed that circular CFST beams exhibited higher flexural capacities than square and rectangular beams of the same cross-sectional areas. The obtained results were also compared with the theoretical flexural capacities predicted using the practical code provisions of AISC and EuroCode4 as well as the equation developed by Han. Finally, nonlinear finite element models (FEM) were developed using ABAQUS to simulate the experimental tests. The FEM is checked using current experimental results, and good compatibility has been reached on load/moment capacity and load/moment- displacement curves. Additionally, The FEM data were also used to conduct a parametric investigation involving a wider range of compressive and yield strengths.