Shear behavior of FRP-reinforced concrete beams with basalt FRP grids as shear reinforcements

This study proposes transversely continuous basalt FRP (BFRP) grids as shear reinforcement and self-compacting seawater sea-sand concrete as casting material to overcome limitations of conventional FRP stirrups. Eight beam specimens with shear span-to-depth ratios (λ) ranging from 1.5 to 2.5 were tested under four-point bending to explore shear performance, especially focusing on arch action. The effects of BFRP grid layers and beam heights were analyzed through failure modes, crack patterns, load-deflection responses, and load-strain relationships. All specimens exhibited shear-compression failure, but installation of BFRP grids or reduced λ ratios slowed critical diagonal crack propagation and delayed failure. Mid-span load-deflection curves showed bi-linear ascending behavior. BFRP grids, lower λ ratios, and greater beam heights enhanced the slope of the second ascending segment, with λ reduction having the most significant impact due to a shift of resisting mechanism from beam action to arch action. Size effect tended to emerge after the initial diagonal shear cracks, becoming more pronounced during diagonal cracking. Among design codes, CSA S806–12 provided the closest shear capacity predictions, with an average error of 25.7 % for all specimens. The findings highlight the potential of BFRP grids to improve shear performance of FRP-reinforced concrete beams, and demonstrate the influences of λ ratios and beam height on structural behavior. This study offers insights into optimizing FRP-reinforced concrete structures, particularly in marine environments.