Shear behavior of two-span continuous concrete deep beams reinforced with GFRP bars

Abstract

To investigate the shear behavior of reinforced concrete (RC) continuous deep beams with glass fiber reinforced polymer (GFRP) bars, four large-scale beams with a constant shear span-to-overall depth ratio of 1.2 and different GFRP shear reinforcement ratios were tested. Digital image correlation technology was used to track the kinematics of diagonal shear cracks in the shear span. It was found that the moment redistribution in the deep beams was very limited. A tie-arch action was confirmed in the tested deep beams with the crack propagation and the strains developed in longitudinal reinforcements. For the beams without GFRP stirrups, the aggregate interlock contribution constituted 46.3% of the total shear resistance. For the beams with GFRP stirrups, however, the shear contribution of aggregate interlock was less significant. As the GFRP shear reinforcement ratio increased from 0% to 0.47%, the failure mode changed from shear compression failure to compression strut failure. As the shear GFRP reinforcement ratio increased from 0.24% to 0.32% and 0.47%, the load-carrying capacity increased by 35.5% and 73.5%, respectively. The minimum required GFRP shear reinforcement in ACI 440.1R-15 was ineffective for the tested GFRP-RC continuous deep beams in terms of shear capacity enhancement and shear crack control. Finally, a database of shear tests on continuous GFRP-RC beams was collected to assess the ability of strut-and-tie methods in three code guidelines.