In this paper, an adaptive heterogeneous multiscale model, which couples substructures with different length scales into one numerical model, is introduced for the simulation of damage in concrete. In the presented approach, the evolution of microcracks is simulated using a mesoscale model, which explicitly represents the heterogeneous material structure of concrete, namely aggregates, mortar matrix and interfacial transition zone. The mesoscale model is restricted to the damaged parts of the structure, whereas undamaged regions are simulated on the macroscale. As a result, an adaptive enlargement of the mesoscale model during the simulation is necessary. In the first part of the paper, the generation of the heterogeneous mesoscopic structure of concrete, the finite element discretization of the mesoscale model, the applied isotropic damage model and the cohesive zone model are briefly introduced. Furthermore, the mesoscale simulation of a uniaxial tension test of a concrete prism is presented and own obtained numerical results are compared to the experiments. The second part is focused on the adaptive heterogeneous multiscale approach. Indicators for the model adaptation and for the coupling between the different numerical models are introduced. The transfer from the macroscale to the mesoscale and the adaptive enlargement of the mesoscale substructure is presented in detail. A nonlinear simulation of a realistic structure using an adaptive heterogeneous multiscale model is presented at the end of the paper to show the applicability of the proposed approach to large-scale structures.
