Effect of Using GFRP Reinforcement on the Behavior of Hollow-Core Circular Concrete Columns

Hollow-core concrete columns are widely used as structural members to reduce the cost and self-weight of concrete structures. This study investigates the axial load-axial deformation behavior of glass fiber-reinforced polymer (GFRP) bar- A nd helix-reinforced hollow-core circular concrete columns. Four specimens of 214-mm outer diameter and 56-mm circular inner hole diameter with a height of 850 mm were tested under axial compression. One specimen was reinforced with steel bars and steel helices, and the remaining three specimens were reinforced with GFRP bars and GFRP helices. It was found that, for a similar amount of longitudinal and transverse reinforcements, the GFRP bar-reinforced specimen achieved 15% and 4% higher effectiveness of confinement reinforcement and ductility, respectively, than the steel bar-reinforced specimen. The effectiveness of confinement reinforcement and ductility of the GFRP bar-reinforced specimen was higher for the smaller pitch of GFRP helices. The GFRP bar-reinforced specimen with helices of 30 mm pitch achieved 46% and 66% higher effectiveness of confinement reinforcement and ductility, respectively, than the GFRP bar-reinforced specimen with helices of 90 mm pitch.