PSI - Issue 84

Francesco Nigro et al. / Procedia Structural Integrity 84 (2026) 183–190

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Fig. 1. Lateral view of the bridge.

Fig. 2. Longitudinal view of the original bridge configuration.

Fig. 3. Plan view of the original bridge configuration.

2.2. Structural interventions

Recent visual inspections have identified advanced deterioration of the concrete cover, with localized reinforcement oxidation primarily concentrated at the Gerber half-joints, abutments, and curbs. Several retrofit interventions were deemed necessary since the safety checks of the original structure highlighted that the drop-in spans were unable to meet the strength criteria for design live loads under the current Italian technical code (Salvatore et al., 2024). Consequently, a comprehensive structural retrofit plan was established for the structure, incorporating various static and seismic strengthening interventions specifically designed to address the vulnerabilities of the Gerber half-joints, whose integrity is vital for the overall stability of the structure. To mitigate the inherent risks of the original isostatic scheme, the design of the retrofit interventions focused on the elimination of these Gerber saddles in favour of a continuous deck configuration, as depicted in Figure 4. To characterize the global structural response, a revised constraint scheme must be defined: full deck continuity is established at all Gerber saddles with the exception of an intermediate joint at Pier 2 (P2 in Figure 4), which is retained to mitigate thermal-induced stresses within the highly hyperstatic system and prevent excessive loading on the pier shafts. Hence, this configuration divides the deck into two independent segments of 57 m and 92 m, as depicted in Figure 4. Due to space constraints, further details are omitted in the present work.