Glass-fiber-reinforced polymer (GFRP) bar has emerged as a preferable alternative to steel bar in reinforced concrete (RC) members in harsh, corrosive, coastal environments in order to eliminate corrosion problems. However, only limited experimental studies are available on the performance and behavior of concrete columns reinforced with GFRP bars under different loading conditions. This study investigates the use of GFRP bars and GFRP helices (spirals) as longitudinal and transversal reinforcement, respectively, in RC columns. A total of 12 circular concrete specimens with 205-mm diameter and 800-mm height were cast and tested under different loading conditions. The effect of replacing steel with GFRP reinforcement and changing the spacing of the GFRP helices on the behavior of the specimens was investigated. The experimental results show that the axial load and bending moment capacity of the GFRP-RC columns are smaller than those of the conventional steel-RC columns. However, the ductility of the GFRP-RC columns was very close to the ductility of the steel-RC columns. It is concluded that ignoring the contribution of the GFRP bars in compression leads to a considerable difference between analytical and experimental results. The experimental results show that the axial load and bending moment capacity of the GFRP-RC columns are smaller than those of the conventional steel-RC columns. However, the ductility of the GFRP-RC columns was very close to the ductility of the steel-RC columns. It Page 2 of 52 is concluded that ignoring the contribution of the GFRP bars in compression leads to a considerable difference between analytical and experimental results.
Fibre Reinforced Polymer (FRP) bars has attracted a significant amount of research attention in the last three decades to overcome the problems associated with the corrosion of steel reinforcing bars in reinforced concrete members. A limited number of studies, however, have investigated the behaviour of concrete columns reinforced with FRP bars. Also, available design standards either ignore the contribution of or do not recommend the use of GFRP bars in compression members. This study reports the results of experimental investigations of concrete specimens reinforced with GFRP bars and GFRP helices as longitudinal and transverse reinforcement, respectively. A total of five circular concrete columns of 205 mm in diameter and 800 mm in height were cast and tested under axial compression. The experimental results showed that reducing the spacing of the GFRP helices or confining the specimens with CFRP sheet led to improvements in the strength and ductility of the specimens. Also, an analytical model has been developed for the axial loadaxial deformation behaviour of the circular concrete columns reinforced with GFRP bars and helices. The model has been validated with the experimental results.
This paper presents analytical and experimental studies on the axial load-bending moment behavior of glass fiber-reinforced polymer (GFRP) bars and helices RC columns. The nominal axial load and bending moment of the columns were analyzed based on the stress-strain behavior of the cross-sectional components. A numerical integration method was used to determine the compressive force of concrete in the compression region. The analytical results were verified with experimental results of 12 circular specimens reinforced with GFRP bars and GFRP helices. Out of these 12 specimens, eight specimens were taken from available literature and four specimens were tested in this study. The influences of different parameters such as loading conditions, spacing of the GFRP helices, and wrapping the specimens with carbon fiber-reinforced polymer (CFRP) sheets on the behavior of GFRP-RC specimens were investigated. A parametric study was also carried out to investigate the effects of longitudinal and transverse GFRP reinforcement ratio and slenderness ratio on the axial load-bending moment diagrams of GFRP-RC columns. It was found that the slenderness effect is more pronounced on the confined cross sections under eccentric loads at the ultimate state condition.
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