PSI - Issue 84

P. Saletti et al. / Procedia Structural Integrity 84 (2026) 937–943

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Fig. 1. Sight of S.Ansano bridge

2. Chronicle of the critical event, and instability diagnosis On 6 th of June 2025, Lucca Province’s technical staff highlighted a relevant geometric anomaly on the roadside. A detailed inspection revealed a partial collapse of the second bridge’s column starting from the right side. The instability has been caused by the heavily undermining phenomenon of the column foundation. The erosive action of fluvial flow (Fig.2) removed the structural stones situated at column’s base, triggering his roto translation (Fig.3). This movement produced a vertical collapse of about 15 cm (Fig.4), visible in the lowering of road surface and in important cracking patterns on arc vault and in lateral tympanums.

Fig. 2 – Sights of S.Ansano bridge during some floods before 2025