Fatigue behaviour at elevated temperature of RC slabs strengthened with EB CFRP strips

Abstract Reinforced concrete (RC) structures such as concrete box-girder highway bridges may suffer fatigue damage due to cyclic loads. Externally bonded (EB) carbon fibre reinforced polymer (CFRP) strips can be used to increase the fatigue (and static) load bearing capacity of such elements and to increase the service life of the elements. The EB CFRP strips under the asphalt layer can reach elevated temperatures of up to 50 °C during summer when the asphalt is directly exposed to solar radiation. Therefore, in this study, the fatigue behaviour at an elevated temperature of RC slabs strengthened with EB CFRP strips is evaluated. The focus is on the strengthening of lateral cantilevers of deck slabs of concrete box-girder highway bridges. The fatigue behaviour of RC elements is a complex phenomenon that is influenced by many parameters such as the maximum load, stress oscillation level on the longitudinal steel reinforcement, shear span-to-depth ratio, and quality of concrete. This phenomenon becomes even more complicated when elevated temperatures are considered. Majority of the existing experimental works on fatigue behaviour of EB-strengthened RC structures showed that the typical fatigue failure at room temperature is caused by fatigue failure of the longitudinal steel reinforcement followed by strip debonding. In this study, it was investigated if a different type of failure can be observed at elevated temperatures owing to the changes in epoxy properties.