Experimental and analytical investigations of a novel end anchorage for CFRP flexural retrofits

Flexural strengthening of reinforced concrete (RC) structures using fiber-reinforced polymer (FRP) composites has gained ground as a technique preferred over its rival ones. However, premature failure of FRP retrofitting systems in the form of debonding or delamination still remains to be an element of concern when using this technique. Despite many studies devoted to this phenomenon, no consensus has as of yet been gained on a universal anchorage system that is capable of preventing different premature debonding failures. In an attempt to address this issue, a novel end anchorage method is developed in this study and its efficiency evaluated through experimental tests. The proposed method involves squeezing carbon FRP (CFRP) sheets at their ends into a groove and stitching them with CFRP anchors. To evaluate their combined action in precluding different types of debonding, the end anchors are combined with different types of middle ones. The experimental program was comprised of uses six large scale RC beams, five of which are retrofitted with CFRP composite sheets. All the beams are then tested monotonically under a four-point bending setup. The results are reported in terms of loading capacity, ultimate displacement, flexural stiffness, ductility factor, and failure modes. The proposed anchorage technique is found capable of preventing different debonding scenarios that might occur in flexural retrofitting with CFRP composites. Finally, an analytical procedure is implemented to predict the experimental load-displacement curves of the retrofitted specimens.