Strain-rate effect on the bond strength between concrete and reinforcing bars in dynamic pull-out tests

Static and dynamic pull-out tests were conducted to investigate the strain-rate effect on the bond strength between concrete and rebar and figure out the required dynamic development length. The concrete strength and loading rate were considered variables. The test results indicated that the bond strength increased at high strain rates, and the strain-rate sensitivity became more significant with the decrease in concrete strength. Moreover, the bond stress–slip relationship varied with strain rates. Based on these results, dynamic increase factor (DIF) models of bond strength were suggested. The required dynamic development length was evaluated by comparing the suggested bond DIFs to DIF of rebar yield strength. The dynamic development length was similar to or less than the static development length when rebars with yield strength above 400 MPa and concrete with compressive strength below 40 MPa were used. However, the dynamic development length was expected to be longer with concrete above 40 MPa than the static development length. •Pull-out tests were conducted with high strain rates up to 6.14 s−1.•The shape of the bond stress–slip curves varied depending on the strain rate.•A bond strength dynamic increase factor (DIF) was suggested based on test results.•Dynamic development length was evaluated by comparing bond DIF to rebar DIF.