Nowadays, the use of operational modal analysis (OMA) plays a significant role in the health assessment of existing structures, as it allows the identification of modal parameters under operational conditions. By using these parameters as targets, numerical models can be calibrated to reduce modelling uncertainties and obtain a model that accurately represents current structural conditions. In this context, the Italian DM 204/2022 code recognizes the relevance of OMA to support the calibration of numerical models in view of the structural assessment of existing bridges. The case study analysed in the present paper focuses on a reinforced concrete highway arch bridge in Southern Italy. The development of a detailed FE model using Ansys Mechanical ADPL is presented. Then, the major uncertainties associated with numerical modeling are highlighted as well as the discussion on model refinement. Finally, the key insights gained from this application are summarized.