Anchorage Failure of RC beams strengthened with FRP at the bottom face

When RC beams are strengthened by FRP plates bonded to the bottom face of the beam they fail due to the lack of the mechanical anchorage of the plate. This paper shows that it is possible to relate the anchorage failure of tension face FRP-plated beams to the crack sliding capacity of the beams. The method suggested gives the highly desirable occurrence of the critical diagonal shear crack. The occurrence of this crack is suggested as the anchorage failure mechanism of the plate. The failure load that produces the sliding in such crack is shown to be a lower bound to the anchorage failure load of tension face plated beams. The assumption is that the FRP-plate must be extended at least one critical anchorage length beyond the theoretical occurrence of the critical diagonal crack.