Analysis of interfacial bonding characteristics of CFRP-concrete under fatigue loading

- Failure modes of the CFRP-concrete interface under fatigue load are discussed.
- A formula is proposed to predict the fatigue life of the CFRP-concrete interface.
- A bond-slip model of the CFRP-concrete interface under fatigue load is developed.

The paper presents the results of an experimental and analytical study involving the bond properties of nine specimens externally strengthened with carbon-fiber-reinforced polymer (CFRP) sheets under fatigue loading. The purpose of this study is to investigate the influence of concrete strength and fatigue amplitude on the bond performance of CFRP-concrete interface under fatigue loading. Firstly, modified beam specimens with different concrete strengths were designed and constructed. Secondly, the specimens were tested under fatigue loads with different fatigue amplitudes. The test results show that the fatigue life increased with an increase in concrete strength, but decreased as the fatigue load amplitude increased, and a formula was proposed to predict the fatigue life. Moreover, the concrete strength and fatigue loading amplitude have little effect on the effective bond length under fatigue loading. The test results of bond-slip relationship show that the bond-slip curves continuously degraded with an increase in the number of load cycles, that is, the maximum shear stress decreased with an increase in the number of load cycles. Finally, a bond-slip model was developed considering the effects of concrete strength and fatigue loading amplitude. The comparison between experimental results and this model demonstrated that this developed bond-slip model can be used to describe the bond-slip relationship of the CFRP-concrete interface under fatigue loading.