The objective of this paper is presenting a new three-dimensional nonlinear elastic damage theory for simulating reinforced concrete elements. More attention was devoted for simulating of the nonlinear behaviour of the reinforced concrete beams with opening based on rigorous thermodynamic basis. The new developed theoretical approach takes into consideration the nonlinear elastic behaviour and the deteriorated state of the concrete materials. Finally, the introduced nonlinear concrete model is verified by various numerical simulation of experiments carried out in order to analyze the proposed behaviour of reinforced concrete beams under monotonic static loading. A comparison with experimental results available in literature is performed in order to validate the proposed model. A very good agreement was achieved.