Delaying delamination by means of a new anchor in concrete beams strengthened with CFRP laminate

A new anchor is developed to delay complete delamination in RC beams externally strengthened with FRP laminate. The anchor is made by cutting NEFMAC grids in the form of π shape. The anchor legs are 90 mm long and the spacing between the legs is either 50 or 100 mm. The anchor spine and legs have the same 10 x 10 mm rectangular cross section. Nine full scale RC beams, 3.0 m long, 250 mm wide and 400 mm deep, were strengthened with CFRP laminate in conjunction with the anchor. The main test parameters were the type and amount of FRP laminate and the presence/absence of the anchor. Test results showed that beams with the anchor had generally 5-10% higher delamination load and reached higher deflection at failure than the companion beams without anchors. Although complete separation of the external reinforcement from the concrete was not observed in any of the beams with anchors, there was substantial slip at one end of the FRP laminate. A significant outcome was that the anchors were effective in limiting the extent of delamination along the interface, thus indirectly contributing to the flexural stiffness of the beam by limiting the extent of cracking along the span.