Bond of reinforcement in concrete under high loading rates

The bond between concrete and reinforcing steel is fundamental to the load bearing capacity of reinforced concrete structures. Several experimental studies indicate strength or rather resistance enhancements coming with increasingly dynamic loading. The phenomenon is known as strain or loading rate effect and its causes are still not fully clarified. The work presented herein provides a numerical view of the bond of reinforcement in concrete and investigates its loading rate dependent behaviour. Finite element analyses focusing on structural and inertia effects are carried out. Modelling is conducted at the rib scale, where bond is predominately controlled by mechanical interaction. In the first step, the model is developed and calibrated. Its quality, credibility, and limitations are assessed by a series of numerical case studies and the results are compared with available experimental data. Numerical parametric studies follow. The loading rate dependence of bond is featured, loading rate dependent characteristics are identified, and conclusions on causes of the phenomenon drawn. It is shown that structural effects are strongly involved and the same holds for hydrostatic pressure stress states and inertia effects. The thesis concludes in reviewing currently available methods for incorporating the results into large-scale simulations and highlighting further investigations and developments that are necessary in order to design dynamic loading-resistant structures in the future