Investigation of local opening-sliding relationship in the vicinity of deformed bar in concrete by using DIC technique

One of the important factors affecting the behaviour of a reinforced concrete (RC) is the bond between concrete and the reinforcement bars. To model the bond between concrete and the reinforcement in the numerical simulation of a RC, accurately modelling for the reinforcing bar with its ribs in 3D shape is required. So to simulate the bond behaviour between concrete and steel rebar, the contact surface between them is represented by normal and shear behaviours. The characteristics of these springs are modified based on numerical simulations to get best-matched results to the experimental results. Therefore, in this study, the opening-sliding relationships between a deformed bar and surrounding matrix are investigated experimentally by using digital images correlation (DIC) technique. A standard axial tension test was applied to a deformed steel bar that was embedded in concrete and cement paste specimen. The specimen had a trapezoidal “window,” which allows full continues observation and measurements of concrete or cement paste displacements by recording high-resolution digital video that was later analysed by DIC software. The half of the steel bar’s cross-section was removed to see directly the ribs of the rebar and thereby capture the local deformations between these ribs. For that purpose 15 points were chosen, at the tips of the ribs and also between the ribs of the deformed bar, to investigate the relative displacements between the deformed bar and surrounding matrix in X-direction and Y-direction. Based on the results of the experiments, some relationships between opening and sliding in case of cement paste or concrete were established. It was found that the opening between the concrete and the rebar at the tip of the rib is higher than between the ribs. Also, the sliding between the concrete and the rebar at the tip of the rib is higher than between the ribs. A. Okeil, R. Upadhyay, K. Matsumoto and K. Nagai