The purpose of this dissertation is the definition of the relevance of the monitoring process on the infrastructures present in Italy. This permit to monitor the changes present in some structural elements or in the overall structure. Firstly, the proper natural frequencies of the structure that have been defined from the acquisition process of the acceleration in the three main directions will be presented. These acquisitions are made by accelerometer which have been installed on the bridge in different points of its span. The acquisition made by them are not continuous, but they are made at a specific time interval. After, a FEM of the overall structure have been made.