| In virtue of the advantages of fiber-reinforced plastic/polymer (FRP), light-weight, high-strength, nice environmental and fatigue resistibility, it has been broadly used in structural strengthening in the past two decades. In recent years, near-surface mounted (NSM) FRP reinforcement is emerging as a potential strengthening technique in practice and a valuable challenge in research, which, in some cases, presents substantial advantages with respect to externally bonded reinforcement.The bond mechanics of NSM FRP composites to concrete should be obtained first for it is the primary step in the whole investigation of NSM FRP reinforcement.A total of 13 specimens have been investigated in a new modified beam-shear test program in order to study bond behavior of NSM carbon-FRP (CFRP) strips to concrete. Three variables which are suspected influencing bond behavior of NSM CFRP strips to concrete have been investigated, such as: bonded length, adhesive thickness and loading mode. This paper focuses on bond failure modes, failure mechanics, factors influencing bond behavior, bond shear stress-slip relationship.Based on the test results, a debonding mechanics between CFRP strips and epoxy adhesive has been proposed. Based on modeling analysis, a closed-form solution of bond differential equation (when CFRP doesn't slip at free bonded end) has been worked out, and a new indirect procedure of evaluating local bond shear stress-slip relationship has been carried out. The ultimate bond strengths of NSM CFRP strips to concrete have been obtained based on a numerical solution of bond differential equation. In addition, this paper proposes a new modified Bertero-Popov-Eligehausen (BPE) model fitting local bond-slip curves. |
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