Flexural behaviour of curved concrete filled steel tubular trusses

A series of tests were conducted on curved concrete filled steel tubular (CCFST) trusses with curved CFST chords and hollowbraces subjected to bending. A total of 8 specimens, including 4 CCFST trusses, 2 straight CFST trusses (referred to as CFST trusses) and 2 curved hollow tubular trusses were tested to study the effect of the rise-tospan ratio and infill concrete on the flexural performance of CCFST trusses. Different failure modes were observed: bending failure for CFST trusses, bending-shear failure for CCFST trusses and local buckling failure for hollow tubular trusses. The experimental result showed that the stiffness and load-carrying capacity of CCFST trusses were larger than those of CFST trusses, but the CCFST trusses experienced a joint failure with relatively low ductility. Meanwhile, the infill concrete provided support to the steel tubular chords and increased the stiffness, load-carrying capacity and ductility. A finite element analysis (FEA) model of the CCFST trusses was developed and verified by the test results. The model was then used to investigate the mechanical behaviour of the truss by full range analysis. A simplified model was proposed to predict the elastic stiffness considering both the flexural and the shear deformation. The load-carrying capacity of the CCFST structure was also discussed.