Effect of Slenderness Ratio on HSC Columns Reinforced with GFRP Bars and Spirals

Abstract

AbstractRecent research has defined the general behaviour of concrete columns reinforced with glass fibre-reinforced polymer (GFRP) bars; however, current design provisions in codes and guidelines for FRP-reinforced concrete (RC) structures still either neglect the compressive strength of GFRP bars or limit their use in slender columns. In this study, six large-scale high strength concrete (HSC) columns reinforced with GFRP bars and spirals were constructed and tested under eccentric axial loading. Test variables included the slenderness ratio (λ = 14, 20 and 28) and the eccentricity-to-diameter ratio (e/D = 0.17 and 0.34). The specimens had a diameter of 350 mm with three different heights: 1,250, 1,750 and 2,450 mm. The specimens were designed to satisfy the Canadian standards for FRP-RC structures. All columns failed by concrete crushing. Test results showed that increasing the slenderness ratio from 14 to 20 and further to 28, decreased the axial capacity by 8.3 and 20%, respectively, for columns with e/D = 0.17. Doubling the eccentricity (e/D = 0.34) resulted in a reduction in the axial capacity by 8 and 22%, respectively, for the same increase in the slenderness ratio. Similarly, the HSC columns showed a reduction in the axial load capacity by 53.7, 53.6 and 54.7% when the e/D increased from 0.17 to 0.34 for columns with slenderness ratio of 14, 20 and 28, respectively. As expected, the lateral displacement increased as the slenderness ratio and the eccentricity increased. It was also found that longitudinal bars were able to effectively contribute to the load carrying capacity of the columns.