Numerical study and strength model of concrete-filled high-strength tubular flange beam under mid-span load

High-strength steels (HSS) have been increasingly used in building and bridges due to their advantages, such as lightening the self-weight and reducing the carbon emissions. However, these benefits cannot be fully utilised for long-span flexural members because of lateral-torsional buckling (LTB). For an improved buckling resistance, a new concrete-filled high-strength tubular flange beam (HS-CFTFB) is formed, and its strength is theoretically and numerically studied. Theoretical models of the HS-CFTFB are derived to estimate the full plastic strength and the elastic LTB strength. The finite-element models are then built to determine the buckling factor in the inelastic LTB strength model. The FE models are validated and found to be in good agreement experimental results. With these verified numerical models, a comprehensive parametric study is conducted to investigate the effect of geometric and material properties of HS-CFTFBs. Finally, the design formula of HS-CFTFBs and its scope of application are determined on the basis of a parametric study.