Impact of degradation on the seismic vulnerability of an existing reinforced concrete bridge

The structural safety assessment of existing bridges is a topic of increasingly importance in developed countries, where many assets were originally designed according to now-outdated standards, have exceeded their design life without maintenance actions, were not subjected to adequate seismic and durability provisions. To address these challenges, in Italy, the 2020 guidelines issued by the Ministry of Infrastructure and Transport (MIT) introduced a multi-level approach for risk classification, structural verification and asset management. In this study, the Level 4 procedure of these guidelines has been applied to an existing reinforced concrete bridge, by generating a finite element model (FEM) on which linear and nonlinear static and dynamic analyses have been carried out. Additionally, the effects of corrosion-induced degradation have been investigated by incorporating two distinct scenarios into the structural model. The study demonstrates that increasing levels of material degradation lead to a progressively earlier onset of structural failure during the seismic event, resulting in collapse under lower energy demands and ultimately worsening the overall seismic performance. These findings underscore the critical role of incorporating degradation effects, particularly reinforcement corrosion, into seismic vulnerability assessments of existing bridges, to obtain reliable safety evaluations and to inform the design of effective maintenance and management strategies.