Smart Method of FRP Laminates for Shear Strengthening of RC Beam: Research to Practice

Externally bonded method of CFRP laminate has been widely used for shear strengthening of reinforced concrete beam. However, CFRP laminate could be debonded at concrete interface with lower strain as compared to its ultimate strain due to lower bond strength of concrete. The laminate could also debond with concrete cover separation after yielding of internal shear reinforcement because of strain incompatibility behaviour between elastic stiff nature of CFRP laminate and plastic deformation of steel shear reinforcement. Interfacial debonding could be eliminated through appropriate design of laminate with simple mechanical embedded connector anchor system; however, cover separation failure could not be eliminated through anchor systems rather than replacing of CFRP with elastic soft FRP material. In this regard, natural jute fibre-reinforced polymer (JFRP) laminate would have huge potentiality. This research aimed to present guidelines for shear strengthening of RC beam using CFRP and JFRP laminates with embedded connector anchor systems. The parameters of guidelines had been verified through analysis of experimental results of shear-strengthened RC beams. Results showed that the cross-sectional area of CFRP and JFRP laminates obtained from the design guidelines enhanced the maximum shear capacities of strengthened beams. Both CFRP and JFRP laminates strengthened beams had almost similar shear failure loads. The beams had failed after yielding of shear and flexural reinforcements without debonding of laminates. The presented design guidelines of shear strengthening could be used in practice to retrofit RC structures.