The paper aims validation of a microplane coupled damage-plasticity model with gradient regularization (MCDPMwGR) by simulating concrete behavior in reinforced concrete beams, both prestressed and non-prestressed. It uses experimental data from available papers. Tendons were modelled in a discrete form using one-dimensional finite elements. Prestress force was inflicted by a temperature drop. Contact issues were taken into account, i.e., friction and pressure at the interface between the cable and the duct wall. In the course of the work, it was found that it is possible to obtain satisfactory accuracy of results with the model in use. The adverse effects, present in other models were not observed. These are, among others, overestimate of ultimate load and excessive influence of tensile strength on the ultimate load value. We can observe such effects in plastic models (e.g., Menetrey-Willam or Drucker-Prager model) as well as non-coupled damage models (e.g., damage evolution model, microplane elastic model). Accurate P-Δ (load-deflection) curves, matching with experimental data, were achieved. It is worth mentioning that best curve fitting for beams made out of the same concrete was obtained using the same parameters values. This is true also when comparing prestressed and non-prestressed beams. It suggests significant potential of damage-plasticity model in predicting the true behavior of concrete. There are still some issues that need further analysis.