Experimental Study on Dynamic Behavior of CFRP-to-Concrete Interface

Carbon fiber–reinforced polymer (CFRP) sheets/plates are widely used to strengthen deficient RC structures. Existing studies show that the effectiveness of externally bonded CFRP materials generally depends on the bond between the CFRP element and concrete. Most of the research studies developed so far have focused on the bond behavior of the CFRP sheet-concrete interface under static loading. In this work, the bond behavior was experimentally investigated from the dynamic standpoint, through the drop-mass impact test method, with the aim of highlighting the effect of the loading rate on the bond strength. The test results show that the strain distribution gradient of the CFRP sheets under impact loading was larger than under static loading, and that the loading rate significantly influences the bond strength, while only moderately affecting the effective bond length. A practical bond-slip model is proposed to simulate the CFRP-to-concrete interface bond behavior under dynamic conditions, which considers the strain-rate effect based on the recommendations for the strength of concrete under impact loading. Furthermore, starting from the equations given in some existing guidelines, a design proposal is developed to accurately predict the effective bond length and the bond strength of the CFRP-to-concrete interface under impact loading.