Numerical study on I-section steel-reinforced concrete-filled steel tubes (SRCFST) under bending

The flexural behaviour of I-section steel-reinforced concrete-filled steel tubes (SRCFSTs) was investigated via finite-element (FE) analysis. Different behaviours of the SRCFST beams were compared in terms of moment vs. midspan deflection curves, stress distribution in concrete, contact pressure, and flexural strength. The results indicated that the I-section steel delayed the movement of the neutral axis and the propagation of concrete cracks in bending. The simulation results of the FE model were validated by experimental results with regard to the moment vs. midspan deflection curves, moment vs. curvature curves, moment vs. ultimate tensile strain curves, and flexural strength of the tested specimens. Additionally, a parametric analysis of the verified FE model was performed for various parameters, such as the area of the I-section steel, yield strength and thickness of the outer steel tubes, yield strength of the I-section steel, and concrete strength. The parametric analysis revealed that the yield strength and thickness of the outer steel tubes and the areas of I-section steel were the key parameters influencing the flexural strength of the SRCFST beams. Furthermore, design equations for the flex-ural strength of SRCFST beams were derived according to Han's method and the AISC specification, and both methods provided a safe and conservative prediction for the flexural strength of the SRCFST beams.