Innovative externally bonded FRP/concrete hybrid flexural members

A novel hybrid FRP–concrete structural system is proposed in this paper. CFRP sheets with high strengths are axially bonded on the bottom surface of the concrete core to carry tensile load while GFRP sheets with high rupture strains are hoop-directionally wrapped to bear the shear load. The GFRP sheets also provide confinement to concrete core and prevent premature debonding of CFRP sheets. A minimum reinforcement ratio of rebars is used to control the localization and propagation of flexural cracks. Instead of conventional shear keys of hybrid systems, an epoxy resin bonding technique is adopted to assure composite effect between FRP and concrete and hence avoid buckling failure mode of FRP shell. A series of 4-point bending experiments were carried out to study the performances of the proposed hybrid FRP–concrete beams. Based on the principles of strain compatibility and equilibrium, an iterative analytical model is developed to evaluate the flexural behavior of the hybrid beam specimens.