Scale Transition in Steel-Concrete Interaction. I: Model

This paper deals with the analysis of reinforced concrete (RC) structures with special emphasis on modeling of the interaction between concrete and reinforcement. A new mode for consideration of the response of the composite material at the member (structural) scale is proposed. It is obtained from extension of the fracture energy concept, originally developed for the simulation of cracking of plain concrete, to reinforced concrete. Hereby, the fracture energy related to the opening of primary cracks is increased in order to account for bond slip between steel and concrete. This increase is determined from the distribution of bond slip by means of a one-dimensional composite model introduced at the bar scale. The model consists of steel bars and the surrounding concrete. Between these two components, a nonlinear bond stress–bond slip relation is considered. The obtained results at the bar scale, such as the average crack spacing between adjacent cracks and the load-displacement response of the composite material, form the basis for determination of the increase of the fracture energy at the member scale. The performance of the proposed transition of the steel-concrete interaction from the bar scale to the member scale is assessed by means of reanalysis of experiments performed on RC bars. The application of the respective material model for reinforced concrete to real-life engineering structures is reported in Part II of this series.