Bridges are critical components of road transportation networks. Many existing reinforced concrete (RC) bridges, constructed during the 20th century, are now experiencing material degradation (e.g., corrosion, wear of joints and bearings) and therefore require regular inspection and maintenance to ensure their continued functionality. In Italy, following the collapse of the Polcevera Bridge in Genoa, new guidelines were issued and an extensive nationwide inspection campaign was launched to assess the structural safety of the existing bridge stock. In seismic regions, such inspections are particularly important due to the elevated risk of damage from strong ground motions and earthquake-induced effects.

Typically, numerical models of bridges are developed by structural engineers assuming fixed boundary conditions at the foundations, while geological and geotechnical aspects are addressed separately. This approach may be adequate for certain structures; however, for large and/or vulnerable bridges, incorporating soil-structure interaction (SSI) into the numerical model is essential. A comprehensive model also allows for the accounting ofsite-specific effects, including local geological and topographic influences.

In this context, an isostatic multi-span bridge located in a seismic area is analyzed and modeled using OpenSees/STKO. Nonlinear analyses are performed using ground motion records obtained through a PSHA. The parameters for both the bridge and the soil-foundation system are derived from a detailed inspection campaign conducted on the structure. Preliminary results from the numerical model are presented and compared with data from the dynamic monitoring of the bridge.