Operational modal analysis for supporting the retrofit design of bridges

Ambient vibration tests and operational modal analysis are commonly adopted worldwide to identify the dynamic behaviour of structures because they offer sev-eral advantages such as the use of portable light equipment, the possibility to be performed without interruptions of the structure serviceability, and the use of ambient noise to globally excite the construction. Ambient vibration tests are also usually adopted in structural health monitoring systems to control changes in the dynamic behaviour of structures over the time. In this paper the dynamic identifi-cation of two multi-span simply supported prestressed RC deck bridges in Central Italy is presented. The modal parameters of the structures are identified adopting operational modal analyses based on in-situ ambient vibration measurements. The experimentally identified dynamics is adopted to assess the bridges’ seismic retro-fitting works and to investigate their dynamic behaviour in the retrofitted state.