Flexural behaviour of round-ended CFST members: Testing, numerical analysis, and design

In this study, the behaviours of round-ended concrete-filled steel tube (RECFST) members under pure bending have been investigated via experimental and numerical analyses. This innovative composite member possesses advantages such as aesthetic appearance, good ductility, and low fluid resistance. Tests were conducted on six RECFST beams with different cross-sectional aspect ratios bending about major and minor axes. The deformation mode, moment-lateral deflection curve, moment-strain response, and longitudinal strains along the cross-section height were discussed. Afterwards, a finite element model was developed and validated with the test data. A parametrical analysis was further conducted to evaluate the effects on aspect ratios, steel ratios, and the strengths of steel and concrete on the ultimate moment of the RECFST beams. Finally, the applicability of standards EN 1994, ANSI/AISC 360, AIJ 2008, BS5400, and CECS 159 for RECFSTs was estimated through the equivalent method. In general, standards EN 1994 and CECS could accurately predict the ultimate moment for RECFST beams with aspect ratios between 1.5 and 3.0.