Performance of hexagonal CFST members under axial compression and bending

• Experiments on the hexagonal CFST subjected to axial compression and bending are conducted.
• Finite element model for the hexagonal CFST column and beam is developed and verified.
• Full-range analysis and parametric study of the compressive and flexural behavior of hexagonal CFST members are conducted.
• Simplified models for the ultimate compressive and flexural strength of hexagonal CFST members are proposed.

The compressive and flexural behavior of the hexagonal concrete-filled steel tubular (CFST) members is investigated in this study. Tests are carried out on the specimens under axial compression and bending. The parameter of the experimental work is the steel ratio of the cross section, and the hollow tubular members are designed for comparison. The failure modes, load versus deformation relations and strain developments are studied. A finite element analysis (FEA) model is established and verified with the test results. The FEA model is then used to conduct the full range analysis on the load versus deformation relation, internal force distribution and stress development. The parametric study on the compressive and flexural behavior is conducted to investigate the effects of various parameters, e.g. the steel ratio, the steel yield strength and the concrete strength. Simplified models are proposed to calculate the ultimate compressive and flexural strength. It is found that the ultimate compressive strength of hexagonal CFST stub columns could be calculated accurately referring to the equations of rectangular CFST columns in DBJ/T13-51-2010 and EC4, and the plastic stress distribution method and the fiber model method achieve good predictions of the ultimate flexural strength of the hexagonal CFST beams.