Response of concrete columns reinforced with longitudinal and transverse BFRP bars under concentric and eccentric loading

Abstract

This study investigates the behaviour of concrete columns reinforced with longitudinal and transverse basalt fiber-reinforced polymer (BFRP) bars, the most recent of FRP composites. Twelve full-scale concrete columns reinforced with longitudinal BFRP bars and either steel or BFRP ties were tested under both concentric and eccentric loadings. The investigated parameters included the type and spacing of the transverse reinforcement (BFRP and steel ties) and the load eccentricity-to-width ratio (e/h = 0, 22.2%, 44.4%). The test results showed that reducing the spacing of the BFRP ties improved the ductility and confinement efficiency of the BFRP-reinforced concrete (BFRP-RC) columns. However, reducing the ties’ spacing had an insignificant effect on both the load-carrying capacities of the columns and the contribution of the longitudinal bars to their ultimate capacities. Moreover, BFRP-RC columns confined with BFRP ties exhibited ultimate capacities, bar strength contribution, and confinement efficiency comparable with their counterpart columns confined with steel ties at the same spacing. This study displayed that the current code provisions of CSA-S806-R17 and ACI440.1R-15 for FRP transverse reinforcement can ensure adequate confinement of the concrete core for BFRP-RC columns.