Influence of anchor embedment angle on the strength and behaviour of FRP-to-concrete joints anchored with FRP anchors

The propensity of externally bonded fibre-reinforced polymer (FRP) composites to debond at relatively low strains severely hinders the effectiveness of FRP for the repair and strengthening of reinforced concrete (RC) structures. FRP anchors, which are also known as spike anchors, can enhance the strain capacity of the bonded FRP strengthening material. Depending on the specific strengthening constraints, anchors may be inserted into the concrete at different angles and as a result testing is required to establish the strength and behaviour of such anchored systems. This paper in turn reports the results of a series of tests on 20 single-shear FRP-to-concrete joints of which 16 joints have been anchored with FRP anchors of different embedment angles. The tests reveal that the strengths of the joints increase as the angle between the embedded anchor dowel and the surface of the concrete is increased relative to the direction of FRP plate force. Optimal anchorage arrangements enabled joint strengths of up to 160 % above unanchored control joints to be achieved. In addition, the maximum strain resisted by the FRP plate, relative to the elongation capacity of the FRP plate, was increased on average from 22 % for unanchored control joints to 67 % for optimally anchored joints.