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

Abstract

The bond between reinforcement and concrete is one of the main factors affecting the structural performance. In terms of the bond mechanism, the bond performance of plain round bars is especially sensitive to the stress state of 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. In the present paper, an experiment involving 178 pull-out specimens with various strengths of concrete and bar diameters is performed to analyse the influence of loading rate on the bond behaviour of plain round bars embedded in concrete under uniaxial lateral tensions. The main bond parameters are evaluated quantitatively. The results show that the bond strength is independent of loading rate and the ratio between the residual strength and the bond strength keeps constant, but the slip at the peak bond stress decreases obviously with increasing the loading rate. Finally, an empirical constitutive model of bond stress-slip considering the strength of concrete, the bar diameter, uniaxial lateral tensions, and the loading rate is presented and validated with experimental results.