Axial compressive behaviour of circular concrete filled fibre reinforced polymer tube (CFFT) columns

Concrete Filled Fibre Reinforced Polymer Tube (CFFT) technique for new reinforced concrete (RC) column construction has attracted significant research attention in recent years. The CFFT acts as a longitudinal and transverse reinforcement and serves as a formwork. The CFFT also acts as a barrier to corrosion accelerating agents and reduces the corrosion phenomenon in RC column specimens. A total of six circular CFFT specimens of 152.5 mm in diameter and 305 mm in height were cast to investigate the axial compressive behaviour of two types of circular CFFT specimens with similar nominal confinement ratios. Type-1 CFFT specimens consisted of 0.5 mm thick Carbon FRP (CFRP) tube and Type-2 CFFT specimens consisted of 1.3 mm thick Glass FRP (GFRP) tube. Test results of CFFT specimens are also compared with FRP sheet confined concrete specimens with similar nominal confinement ratios. Tested CFFT specimens failed in a brittle manner due to rupture of fibres and crushing of concrete. Experimental results showed that CFRP CFFT specimens achieved almost similar confined concrete strengths and confined concrete axial strains to that of 2.6 times thicker GFRP CFFT specimens. Tested CFFT specimens exhibited smaller confined concrete strengths and confined concrete axial strains than FRP sheet confined concrete specimens with similar nominal confinement ratios.