<b>Abstract</b>— <p>Safe operation of a structure is provided by monitoring its deformation behavior. An important part of it is the vibration response characterized by amplitude-frequency and phase parameters. In this study, the natural frequencies and mode shapes of load-bearing elements of a building structure are evaluated by using FEM. Based on the long-term monitoring of the vibration response on one of the load-bearing reinforced concrete beams, the evolution of the natural frequencies of the structure was obtained. It should be noted that these structural elements were damaged and repaired, which determined the interest of the study. The results of in-situ and numerical experiments are analyzed with respect to the current seasonal changes.</p>