PSI - Issue 84

L. Fieno et al. / Procedia Structural Integrity 84 (2026) 1136–1143

1141

As part of a detailed inspection campaign aimed at a Level 4 safety assessment, the observed deterioration pattern initially appeared largely consistent with the age of the bridge, with widespread oxidation and localized deterioration, often associated with water leakage from the roadway and localized deficiencies in waterproofing. However, attention was drawn to localized anomalies at the bearings: site inspections highlighted pronounced deterioration of the bearings, including diffuse oxidation, and, most importantly, the failure of a component of the bearing tie‑down device within a bidirectional bearing arrangement. This condition can be interpreted as the result of excessive vertical actions at the supports, which induced an abnormal force demand at the bearings and triggered the observed issue.

Fig. 5. On the left, an intact bearing with tie-down devices in place; on the right, a lifted bearing with the tie-down devices missing.

Subsequent analyses and structural modelling confirmed the need to treat the global behavior of the bridge with particular caution, also in relation to construction stages and long‑term effects, since these mechanisms may lead to changes in bearing reactions up to potentially unfavorable conditions for the devices themselves. This case shows how issues not immediately attributable to classic deterioration of primary members may instead develop in components that can appear secondary, yet are crucial for safety and serviceability, such as bearings and hinges. For this reason, the assessment outcome required operational management measures and targeted interventions, including urgent works, aimed at restoring a consistent load transfer at the supports and ensuring safe operation during the interim period, further confirming the value of detailed inspections and a critical interpretation of structural behavioral anomalies. 5. Evaluation of deterioration effects on preliminary structural safety At the end of the structural investigation plan, once the existing deterioration has been identified and quantified, it is necessary to assess its effects on the estimation of the structural safety of the asset, which represents the final phase of the special inspection. With reference to prestressed reinforced concrete beams, several deterioration mechanisms may affect the conservation state of the prestressing steel, such as rainwater infiltration, the use of deicing salts, design deficiencies, or construction defects. A representative case study is therefore presented, referring to a structure inspected between February and March 2025, for which selected images are reported.

Fig. 6. Degradation on the prestressing cables