Bond strength of steel reinforcement under different loading rates

This paper addresses the bond strength of steel reinforcement subject to different loading rates. In the experimental programme, a total of 15 pull-out tests were conducted on steel reinforcing bars with various embedment lengths. The loading rate varied from 0.1 mm/s to 100 mm/s. The applied load, slip at the loaded end and strains along the embedment length of steel reinforcement were measured during testing. Bond stresses and strain rates along the embedment length of reinforcement were calculated from the measured strains. Test results suggested that a higher loading rate could increase the bond stress between steel reinforcement and concrete. The increase in bond stress was mainly induced by the rapid slip and the relatively high dynamic yield strength of reinforcement, depending on the stress state of the reinforcement. Finally, conclusions were drawn from the experimental results to facilitate the analysis of the bond-slip behaviour of steel reinforcement under high loading rates.