Effect of loading rate on the bond behaviour of plain round bars in concrete subjected to uniaxial lateral tension

The bond between reinforcement and concrete is one of the main factors affecting structural performance. In terms of the bond mechanism, the bond performance of plain round bars is especially sensitive to the stress state of the surrounding concrete. Lateral tensions have been confirmed to significantly weaken the bond properties of plain round bars but the effect of loading rate on such a condition is still not well understood. Experiments involving 178 pull-out specimens with various concrete strengths and bar diameters were performed to analyse the influence of loading rate on the bond behaviour of plain round bars embedded in concrete under uniaxial lateral tension. The main bond parameters were evaluated quantitatively. The results showed that bond strength was independent of loading rate and the ratio of residual strength to bond strength remained constant, but the slip at the peak bond stress decreased obviously with an increase in loading rate. An empirical constitutive model of bond stress-slip considering the concrete strength, bar diameter, uniaxial lateral tension and loading rate was developed and validated with experimental results.