PSI - Issue 78

Samuele Faini et al. / Procedia Structural Integrity 78 (2026) 718–725

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Fig. 5. Results of TMDs nonlinear tuning: (a) reduction of peak transversal drift in short piers as a function of ; (b) comparison between deck’ transversal displacement time-histories calculated for the as-built layout and for that equipped with optimized TMDs (i.e., = 0.875 ) (c) reduction of curvature-demand on short piers’ ; (d)TMDs ’ overall dynamic counterphase force-displacement response.

Fig. 6. Assessment of optimized TMDs (i.e., =0.875 ) robustness: (a) influence of corrosion on arch-deck transversal drift; (b) influence of ground motion components (1D vs. 3D) on deck transversal displacements. 6. Conclusions This study proposed a comprehensive seismic retrofit strategy for existing r.c. arch bridges, using the Valvestino Bridge, located in Gargnano (Italy) and designed by Riccardo Morandi in the late 1950s, as a case study. Diagnostic assessments identified key vulnerabilities, including rebar s’ corrosion, poor seismic detailing, and insufficient shear strength in the shortest spandrel columns near the arch keystone. Nonlinear time-history (NLTH) analyses of the as built configuration confirmed premature shear failures in these critical elements. A retrofit solution was developed combining unidirectional sliding bearings and hysteretic dampers in the longitudinal direction, along with a novel application of low-mass (μ ≈ 1.9%) Tuned Mass Dampers (TMDs) to mitigate transversal seismic actions at deck mid-span. TMDs were optimized through NLTH-based parametric tuning, achieving 41.2% of reduction in transverse drift of (most critical) shortest spandrel piers. A key finding is that low-mass TMDs, typically used to mitigate service-level vibrations in light bridges, can be effectively employed also for seismic protection of heavier and stiffer stiffer r.c. arch bridges, an approach rarely explored in current literature. The proposed retrofit demonstrated robust performances taking into account the materials’ ageing (rebars’ corrosion) and a realistic three-directional ground motion scenario. While promising, the study is limited to a single numerical case without experimental validation. Future works should extend the investigation to broader bridge typologies (e.g., “Maillart - type”) and seismic scenarios.