Mesoscale modelling of bond performance between deformed steel bar and concrete subjected to dynamic loads

The good bond property is the base for rebar and concrete to work together, influencing the mechanical behaviour of reinforced concrete structures. To investigate the bond-slip performance between deformed steel bars and concrete under dynamic loadings, a three-dimensional meso-scale numerical model was established, considering the inherent heterogeneity of concrete and explicitly modelling the surface characteristics of the rebar. The interaction between the rebar and concrete was implemented by the surface-to-surface contact strategy. The strain rate effect of materials was also taken into account. The rationality and accuracy of the proposed model were verified by the good consistency between the simulation and available test results in terms of failure pattern and bond stress-slip curves. With the help of the meso-scale model, the bond-slip behaviour under various loading rates was simulated and analysed. Finally, a simplified model to describe the dynamic bond stress-slip relationship was developed. It has been found that due to the propagation of stress waves, the cracking process of the specimen varies with the strain rate while the final failure pattern is similar, exhibiting splitting type failure. Thus, a considerable part of pull-out loading was resisted by the inertia of the system at the initial stage. With the increase of strain rate, the shape of the dynamic bond stress-slip curves is similar with a significantly increased bond strength and reduced slip, especially at high strain rates. The ratio between the residual and peak bond stress is approximately constant, irrespective of strain rate. The proposed simplified model is able to effectively characterize the dynamic bond stress-slip relationship between the deformed rebar and concrete.