Axial and bending behavior of GFRP bar-reinforced hollow-core polypropylene fiber concrete columns

This study reported the axial (concentric and eccentric) and bending (four-point bending) loadings behavior of glass fiber-reinforced polymer (GFRP) bar-reinforced hollow-core polypropylene fiber concrete (HC-GFRP-PFC) columns. The confinement effect of HC-GFRP-PFC columns with different center-to-center (c/c) spacing of GFRP spirals was also investigated. Twelve hollow-core circular specimens with an outer diameter of 214 mm and an inner (circular hole) diameter of 56 mm were experimentally investigated. Four reference specimens were cast with nonfibrous (normal) concrete, whereas the remaining eight specimens were cast with polypropylene fiber (0.15% by volume of concrete) concrete. It was found that, with a similar ratio of reinforcement, the HC-GFRP-PFC specimens gained 2%-4% higher maximum load (P-Maximum) and 9%-19% higher ductility (mu) than the GFRP bar-reinforced hollow-core nonfibrous concrete (HC-GFRP-NFC) specimens under concentric axial loading and four-point bending. The HC-GFRP-PFC specimens with a 30 mm c/c spacing of the GFRP spiral gained 6%-36% higher P-Maximum and 4%-59% higher mu than the HC-GFRP-PFC specimens with a 60 mm c/c spacing of the GFRP spirals under different loading conditions.