Bond strength of embedded steel reinforcement at high strain rates

Under progressive collapse scenarios, the bond-slip behaviour of steel reinforcement embedded in beam-column joints significantly affects the joint behaviour. To date, extensive static tests have been carried out to study the bond-slip behaviour of steel reinforcement. However, when subject to dynamic loads, the results of static pull-out tests should be re-evaluated in order to consider the effects of strain rates. This paper studies the bond-slip behaviour of embedded steel reinforcement at high strain rates. In the experimental programme, pull-out tests were carried out on steel bar embedded in conventional concrete. The influences of strain rate and embedment length on the bond strength and failure mode were quantified through experimental tests. Conclusions were drawn from comparisons between test data with published results. It was observed that steel reinforcement could develop higher bond strengths by increasing the strain rate. Rebars with relatively short embedment length exhibited pull-out failure. By increasing the embedment length, the fracture of reinforcing bars was observed instead of pull-out failure. Preliminary conclusions could be drawn from the experimental study.