PSI - Issue 78

Andrea Dhima et al. / Procedia Structural Integrity 78 (2026) 1366–1373

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1. Introduction Throughout their service life, existing reinforced and pre-stressed concrete structures are subject to deterioration, which may compromise their structural reliability (Capacci & Biondini, 2020), particularly in light of the progressive increase in traffic loads (Pugliese, 2022). The primary causes of deterioration include the exposure to aggressive environments, which can lead to the corrosion of the steel reinforcement bars. Numerous studies in the literature have analysed the reduction in the cross-sectional area of the bars induced by this phenomenon (Val et al., 1998). This reduction causes a decrease in both strength and ductility of the bars (Bartolozzi et al., 2022), consequently reducing the load-bearing capacity of the structural elements and potentially leading to brittle failure (Stewart, 2009). The detrimental effect of deterioration, particularly corrosion, on the structural performance of critical infrastructure such as bridges is well known to managers and policymakers in most developed countries, where much of the asset stock is at or beyond its originally intended service life. In this context, the Italian Ministry of Infrastructure and Transport (MIT) issued the "Guidelines for risk classification, safety assessment and structural monitoring of existing bridges" in 2020 (ANFISA, 2022; MIT, 2020). The latter, through a multi-level approach, establishes the criteria for the management and monitoring of such infrastructure (Salvatore et al., 2024). This paper illustrates the application of the Level 4 - accurate assessment, as prescribed by the guidelines, to a real case study: Section 2 details the investigated multi-span viaduct, the assessment methodology adopted, and the modelling strategy implemented to analyse the shear and the flexural capacity of the piers. In-situ inspections revealed that the structure is affected by significant and widespread deterioration. Consequently, the influence of corrosion on the structural performance was further investigated. To this end, Section 3 provides a brief introduction to the mechanisms of corrosion in reinforced concrete structures, while Section 4 defines and analyses various realistic degradation scenarios using corrosion models. The final conclusions are presented in Section 5. 2. Investigated bridge and safety assessment according to Italian guidelines The viaduct (Figure 1), located in the Basilicata region of Southern Italy, was presumably constructed in the early 1960s. It is part of the SS658, a secondary national road consisting of a two-lane, bidirectional carriageway. The viaduct has a total length of 180 m and comprises four spans, configured as a statically determinate girder system. The viaduct features two distinct structural systems: the first consists of three 42 m spans carried by two intermediate piers and end abutments; the second is a single-span unit, 30 m in length, supported by two abutments. The deck girders are post-tensioned: for the 42 m spans, the deck comprises three double-T beams, while the 30 m span features rectangular-section beams. The piers are short and thick elements with rectangular cross-sections. The girders rest on the abutments and on the pier caps via neoprene bearing.

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(d) Fig. 1. Investigated viaduct: (a) overview, (b) close-up of pier P1, (c) corrosion-induced degradation of a beam, (d) schematic plan.