PSI - Issue 84

Federica Di Criscio et al. / Procedia Structural Integrity 84 (2026) 1023–1030

1024

1. Introduction The Italian transportation system relies on an exceptionally extensive network of bridges and viaducts, many of which constitute strategic assets for national mobility and economic continuity. Recent investigations have confirmed the advanced age of the national bridge inventory, indicating that only a minor portion of the stock—i.e., approximately 8%—was constructed after the 1980s, while the vast majority consists of structures built before the widespread adoption of modern design and durability standards (Salvatore et al., 2020; Petrangeli et al., 2019). Therefore, these structures typically present potentially critical weaknesses due to the lack of modern seismic, durability, and performance-based design criteria, raising concerns about their current safety and long-term resilience. The collapse of several viaducts and bridges in the past ten years in Italy - from the Annone Brianza overpass to the Morandi Bridge in 2018 - further emphasized the vulnerability of older infrastructure, bringing public attention to the high uncertainties and risks associated with the complex phenomena of mechanical deterioration of reinforced and prestressed concrete components exposed to weathering. Among the degradation mechanisms affecting reinforced concrete (RC) and prestressed concrete (PSC) structures, reinforcement corrosion is one of the most pervasive and structurally critical. Corrosion may develop uniformly, typically due to carbonation, or in a localized manner, often associated with chloride attack. While both mechanisms can significantly affect structural performance, localized corrosion is particularly critical due to the concentration of sectional losses (Alonso et al., 1998; Tuutti, 1997). Over recent decades, several studies have investigated the mechanical consequences of corrosion, especially focusing on its impact on material properties, stress–strain relationships, and bond deterioration (e.g., Imperatore et al., 2017). Moreover, recent research has investigated the effects of corrosion phenomena on the seismic fragility of RC and PSC bridges (e.g., Gentile et al., 2021; Otárola et al., 2022). In response to the latest catastrophic events and the growing need for systematic infrastructure management, the Italian Ministry of Infrastructure and Transport has recently introduced a multi-level methodology for the risk classification and management of existing bridges (MIT, 2020). Within this framework, structures assigned to a medium or medium‑high Class of Attention (“Classe di Attenzione”, in Italian) are required to undergo a Level 3 assessment, conceived as a simplified, rapid evaluation procedure. Currently, the Level 3 methodology relies essentially on a comparison between traffic demands at the time of construction and those prescribed by the current Italian code. However, this approach does not account for the actual load-carrying capacity of the structure. So, it is more based on a comparison between code-based older demand vs. current demand requirements rather than a ratio between actual (yet predicted) capacity vs. code-based demand, as for example recently developed for other disciplines such as earthquake engineering. This limitation highlights the need for a rapid, yet mechanically informed, procedure capable of accounting for the effects of material deterioration in the evaluation process. In this context, this work introduces a simplified framework for estimating the residual capacity of RC and PSC bridges affected by reinforcement corrosion. The proposed methodology links defect-based indicators with degradation-dependent mechanical models, thus providing a coherent procedure to translate observed deterioration into quantitative modification of mechanical material properties and related possible reductions in structural performance. This integration enables the construction of time-dependent safety curves, based on the progressive reduction of structural capacity over the service life, offering a more rational basis for short/medium/long term maintenance planning and decision-making within a life-cycle management perspective. The effectiveness of the framework is demonstrated through an illustrative application on an archetypal case study bridge, considering multiple corrosion scenarios and different locations of deteriorated sections. Results highlight the potential of the proposed method to complement and integrate existing assessment and management guidelines (i.e. the national MIT 2020 guidelines) and provide engineers and asset managers with a practical, transparent tool for the rapid evaluation of ageing concrete bridges.