Experimental research on CFST member with different sections under combined compression and bending

With the axial load ratio as the changing parameters, the tests of four circular and four dumbbell-shaped concrete-filled steel tubular (CFST) members under combined compression and bending were carried out. The deformation model, the load-deformation curves and the combined compression and bending relation curves of the CFST members with two different sections under the combined compression and bending were compared and analyzed. The results show that the ductility of the two kinds of CFST members is decreased with the increase of the axial load ratio, the ability to resist deformation and moment of dumbbell CFST members were better than that of circular ones under the same axial load ratio for the strong stiffness of the former. Through the analysis of compression-bending correlation curves between circular CFST members and dumbbell-shaped CFST members, it is found to be conservative when the equations for circular ones from the design standards are applied directly to dumbbell ones. Further analysis through the finite element analysis should be used to evaluate the trends of compression-bending correlation curves of dumbbell-shaped CFST members and the equations for dumbbell ones could be given later.