Experimental study on bond behavior of corroded reinforced concrete under coupling effect of fatigue load and elevated temperature

•The fatigue bond behavior at damaged interface was investigated under the coupling effect of corrosion, sustained load, and high temperature.•The calculated methods of failure slip considering sustained load and corrosion is proposed.•A semi-empirical slip-location constitutive model is proposed. The bond properties of corroded reinforcing bars in concrete are mainly determined by the failure time and ultimate capacity of reinforced concrete (RC) structures. In this study, 98 cube specimens were used to study the corrosion effect on the bond failure mechanism of RC structures under transient high temperature. Firstly, an electrification accelerated corrosion test was carried out to fabricate the corroded specimen with various corrosion degrees (0 %, 5 %, 10 %, and 15 %). Secondly, the undamaged specimen was conducted by pull-out test at ambient temperature to obtain the initial bond strength, and then a transient temperature test under sustained load was also performed to analyze the effects of different load ratios, concrete strength, and corrosion degrees on the bond behavior. SEM (Scanning Electron Microscope) was conducted to verify the damage level by comparing the interfacial transition zone. Test results indicate that the coupling effect of corrosion, fatigue load, and high temperature increases the carbonization level of the specimens and reduces the concrete compressive strength after bonding damage. The ultrasonic pulse velocity decreases with increasing corrosion degree and sustained load level and decreases with increasing concrete strength grade. Under the coupling effect of corrosion, high temperature, and sustained load, the bonding failure time is significantly affected by the sustained load ratio, and the failure slip is determined by corrosion and temperature. Finally, an empirical slip-location constitutive model was proposed, incorporating the sustained load ratio, corrosion degree, and temperature. The accuracy of the predicted model agrees with the error requirement, and the constitutive model provides a theoretical basis for the collapse warning of corroded structures under fire.