This paper presents the test results of an experimental study aimed at investigating the axial behaviour of CFFT columns internally reinforced with steel and FRP bars. A total of eight reinforced concrete (RC) and concrete-filled FRP tube (CFFT) columns were constructed and tested until failure. All columns had 1900-mm in height and 213-mm in diameter. The test parameters were: (1) internal reinforcement type (steel, glass FRP (GFRP), or carbon FRP (CFRP) bars) and amount, (2) GFRP tube thicknesses, and (3) nature of axial loading type (i.e. monotonic and cyclic). The experimental results revealed that the CFFT columns reinforced with GFRP bars exhibited similar responses compared to their counterparts reinforced with steel bars with no significant difference in terms of ultimate axial strength and strain capacities. Providing the GFRP tubes of the CFFT columns significantly enhanced the strength and strain capacities and attributed to change the mode of failure from axially dominated material failure (for the control columns) to instability failure (for the CFFT columns). Furthermore, the envelop curve of the CFFT reinforced column tested under axial cyclic loading is almost identical to the axial stress-strain curve of the same specimen tested under axial monotonic loading. However, the ultimate axial and hoop rupture strain was slightly larger for the specimen subjected to axial cyclic loading. Finally, using FRP bars instead of conventional steel bars in the CFFT columns can provide a step forward to develop a promising totally corrosion-free new structural system
