PSI - Issue 84

Diego Esposito et al. / Procedia Structural Integrity 84 (2026) 1198–1205

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Figure 2. Cross sections of the deck at mid-span and end section

3. Diagnostic investigation In 2015, on behalf of the concessionaire ANAS S.p.A, a first diagnostic investigation campaign was carried out on spans 1 to 3 of the Tevere Viaduct. Visual inspections revealed widespread water seepage from the deck, attributable to the malfunctioning of the drainage system, resulting in streaks on the girders and vertical structures. Areas with exposed reinforcement bars and initial signs of corrosion phenomena were identified, along with a flexural cracking pattern on the girders. About the prestressing reinforcement, endoscopic inspections generally indicated an acceptable condition, except for the edge girder of the north carriageway (span 2), where water was found inside the ducts and grout injection was incomplete. SonReb tests and core compression tests performed on the girders estimated the concrete compressive strength, Battisti (2019) slightly lower than the design values. The final report recommended initiating crack monitoring and conducting an in-depth diagnostic investigation campaign on the prestressing system to verify duct filling, preservation state of the anchorages, Bernardi et al. (2024), residual tendon stress, and to verify potential construction imperfections. In 2021, the ANAS Road Research and Testing Center of Cesano, on behalf of the ANAS Lazio Territorial Structure, was commissioned to perform an advanced diagnostic program, ANAS (2020) to investigate further the critical issues highlighted by both the previous investigation campaign and routine surveillance activities (Italian Ministry of Infrastructure and Transport (2020), Bontempi et al. (2022). The tasks performed included: • Visual inspection of the decks, both indirectly using drones and directly using BB equipment; • Survey of tendon layout and anchorage heads; • Assessment of tendon condition through endoscopic inspections; • Evaluation of the residual stress state of the prestressing tendons by means of strand detensioning tests. The visual inspection revealed moisture stains along the tendon paths, particularly along those anchored in the slab, with a parabolic pattern (Figure 3.a), indicative of probable fill lack or deterioration and water infiltration into the ducts. Furthermore, a complex flexural cracking pattern was observed (Figure 3.b), characterized by 45° inclined cracks near the supports and vertical cracks at midspan, likely related to a reduction of precompression effects. The phenomenon was detected with varying severity and classified into three macro categories: low, medium, and high. Finally, a recurring longitudinal moisture stain was detected near the slab joint between the two precast girders (Figure 3.c).

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Figure 3. The phenomena observed, (a) parabolic pattern, (b) complex flexural cracking pattern, (c) longitudinal moisture staining.