Bond Stress-Slip Behaviour of Concrete and Steel under High-Loading Rates

Understanding the bond behaviour between reinforcing steel and concrete under high-loading rates is becoming more and more important with increasing frequency of natural disasters, impact loadings and a threat of terrorism. This paper aims to obtain a better understanding of the material interactions between the steel rebar and the concrete in the bond zone under different loading rates. During the experimental program push-in tests were conducted under quasi-static and dynamic loading conditions. Both a servo-hydraulic machine as well as an instrumented drop tower were used during the investigation. Samples with short-bond zone in the middle of a cylindrical specimen were used and only a small reinforcement bar diameter (10 mm) was investigated. This approach was chosen to ensure constant bond stress distribution and that the failure occurs during the first pass of the stress wave through the bond zone. Throughout the experimental programme the loading rate was varied from 0.01 mm/s to 8.3 m/s. Bond stress–slip relationships in dependence on the bond stress rate are presented in this paper. The results indicate a bond stress dependence on the loading rate although the scattering of the results is quite high. The experimentally determined dynamic increase factor (DIF) for concrete-steel bond stress is around 1.5 which is a value comparable to other authors.