Effect of existing steel-to-embedded FRP shear reinforcement ratio on the behaviour of reinforced concrete T-beams

This paper examines the behaviour of reinforced concrete (RC) T-beams strengthened in shear withdeep embedment (DE) glass fibre reinforced polymer (GFRP) bars. Tests were conducted on a controlbeam as well as two DE GFRP-strengthened beams with existing steel-to-FRP shear reinforcementratios of 0.44 and 0.88. The shear strength enhancement decreased from 38.1% to 4.8% with theincrease in steel-to-FRP shear reinforcement ratio from 0.44 to 0.88. The strengthened beams had aslightly higher cracked stiffness due to the presence of the DE GFRP bars, which resisted inclined crackopening and consequently controlled deflection. The presence of DE GFRP bars resulted in a 58%reduction in the concrete contribution to shear resistance. The FRP contribution to shear resistancedecreased by 48% with the increase in steel-to-FRP shear reinforcement ratio. Comparison betweenexperimental results and TR55 predictions showed that TR55 significantly underestimate both thestrengthened shear force capacity and the FRP contribution to shear resistance.