Flexural strength evaluation of concrete-filled steel tube (CFST) composite girder

The flexural strength of the concrete-filled steel tube (CFST) composite girder was investigated in this study. Firstly, simple equations to evaluate the flexural strength of the CFST composite girder under both positive and negative bending moment were derived based on the plastic stress distribution method (PSDM). A series of tests was then conducted to verify the accuracy of the proposed equation, and to investigate the effect of internal shear connectors between the steel tube and concrete infill. Further, non-linear finite element analysis for each test specimen was performed to demonstrate the failure mechanism, and to set up the verified finite element analysis model. From the results, it was found that the proposed equations provided a reasonably conservative prediction of the flexural strength of the CFST composite girder under both positive and negative bending moment, and the effect of internal shear connectors between the steel tube and concrete infill on the flexural strength was negligible. A series of parametric studies was performed to investigate the effect of the D/t ratio, compressive strength of the concrete infill, and local buckling of the steel tube on the flexural strength of the CFST composite girder. Finally, some design considerations are noted based on the results of the parametric study.