Damage behaviours of new-to-old concrete interfaces and a damage prediction model of reinforced concrete

The influence of bar reinforcement and the concrete strength on shear properties of new-to-old interface is investigated in this work. Two failure modes of brittle failure (plain concrete) and plastic failure (reinforced concrete) are observed in the test. The amount of steel bars and concrete strength have a strong effect on the failure mode, while the distribution law of the reinforcement bars has almost no influence on the failure mode. Interface shear strength is mainly provided by the bonding force of the new-to-old concrete and the shear resistance of the embedded steel bar. However, the vertical friction force generated by the tensile force of the embedded steel bar has the least influence on the interface shear strength. Based on the micro-damage mechanism of new-to-old concrete interface under condition of reinforcement planting, a damage prediction model of new-to-old concrete interface is proposed in this article. The model can be used to predict the damage degree of new-to- old concrete interface subjected to different planting areas.