Model Updating of different Bridge types using ambient vibration and OMA identification.

Structural Health Monitoring (SHM) to date is an increasingly crucial issue in civil engineering. Many structures like bridges and viaducts nowadays are often older than their design life and show signs of structural deterioration that can potentially affect structural safety. One of the most popular monitoring techniques is dynamic monitoring under environmental vibrations using Operational Modal Analysis (OMA) techniques. OMA needs f.e.m. models that can simulate structural behavior under the real conditions and that can be used for interpretation of monitoring data and for possible damage detection. The study proposes a model updating for two different bridges: a girder and box deck one. After an OMA identification using ambient vibration, through the modal parameter identified, modal updating is performed on f.e.m. models, changing only few essential parameters. All the f.e.m. models are made with beam elements. The study highlights that even a simple f.e.m. model of the structure can describe accurately the dynamic and in general the structural behavior of a complex structure such as bridges and viaducts. The authors also show the differences between a f.e.m. model developed for the design and or verification and a f.e.m. model intended SHM. Model updating is performed through the management of a few parameters of the structure like the stiffness of bearing devices between superstructure and substructure, the deformability of foundation soil, the mechanical properties of concrete and reinforcement and the modal masses. The variation in each of these parameters can have a different role on the behavior of the structure. A good reliability of the f.e.m. model can be achieved through the management of a few structural parameters obtaining results that are sufficient for models that have the purpose of interpreting SHM data and are used to perform damage research.