Bond-test protocol for plate-to-concrete interface involving all mechanisms

Attaching reinforcing material such as steel or fiber reinforced polymer (FRP) plate to the external face of concrete members is a conventional technology used for strengthening concrete structures. Generally, three mechanisms are involved in the composite action between the concrete and the attachment: adhesion, dowel action, and friction. Methods have been developed for the identification of the interfacial bond properties when only one or two mechanisms exist at the interface. However, the existing methods cannot be used when all three mechanisms coexist. A methodology for testing the bond and the corresponding data interpretation procedure are proposed in this work to identify the bond properties of the interface involving all bonding mechanisms. As the bonding mechanisms are coupled and interact with each other, it is impossible to test all of them individually and separately. The proposed test protocol involves an analytical procedure that decouples individual mechanisms from the global response curves. Furthermore, conventional bond test methods involve extensive and labor-intensive strain gauging as well as complicated data regression analyses of test results in order to obtain the bond properties. The proposed method requires only the simplest instrumentation to measure displacement and load, without strain gauging. Test data processing also involves simple graphical interpretations only, without complicated and tedious mathematical data regression analyses. Therefore, the proposed method has advantages over the existing ones and can be easily adopted in engineering practice.