A bond mechanism at the reinforcement-concrete interface is one of the key sources of the comprehensive functioning of reinforced concrete (RC) structures. In order to apprehend the bond mechanism, the study on bond stress and slip relation (henceforth referred as bond-slip) is necessary. On this subject, experimental and numerical investigations were performed on short RC tensile specimens. A double pull-out test with pre-installed electrical strain gauge sensors inside the modified embedded rebar was performed in the experimental part. Numerically, a three dimensional rib scale model was designed and finite element analysis was performed. The compatibility and reliability of the numerical model was verified by comparing its strain result with an experimentally obtained one. Afterwards, based on stress transfer approach, the bond-slip relations were calculated from the extracted strain results. The maximum disparity between experimental and numerical investigation was found as 19.5% in case of strain data and 7% for the bond-slip relation at the highest load level (110 kN). Moreover, the bond-slip curves at different load levels were compared with the bond-slip model established in CEB-fib Model Code 2010 (MC2010). Overall, in the present study, strain monitoring through the experimental tool and finite element modelling have accomplished a broader picture of the bond mechanism at the reinforcement-concrete interface through their bond-slip relationship.

The importance of interaction between concrete and reinforcement for reinforced concrete (RC) mechanics is a known issue, yet its complexity enforces one to perform in-depth investigations at the microscopic level. In this paper, short RC ties with lengths less than transfer length of bond stresses were chosen to investigate contact zones between concrete and reinforcement. A three-dimensional finite element approach (Model-3D) with simplified geometry of ribs (rib-scale model) is modelled. Its effectiveness is checked against the results yielded by a number of double pull-out tests on RC prisms, where the strain distribution of the bars was measured with strain gauges. As it turns out, the considered model shows a good correlation with experimental data at different loading levels, and the most important factor describing the effectiveness is the geometry of ribs.