Combining experimental data and numerical modeling to analyze train-structure interaction on the historic san michele bridge (Italy, 1889)

As part of ongoing efforts to study and preserve the San Michele Bridge, a remarkable example of 19th-century iron architecture and a true symbol of Italian industrial archaeology, an experimental campaign was conducted on it in May 2024. Completed in 1889 by the Società Nazionale delle Officine di Savigliano (SNOS), the San Michele Bridge spans 266 meters across the Adda River, connecting the towns of Paderno d’Adda (Lecco bank) and Calusco d’Adda (Bergamo bank) in Lombardy, northern Italy. Its innovative design features a doubly built-in parabolic arch and an upper continuous beam, supporting both railway and road traffic. During the experimental campaign, accelerometers were deployed both on the bridge structure and on a crossing railway vehicle, allowing for the simultaneous collection of acceleration data from both systems, aiming at investigating the dynamic behavior of the bridge under vehicle-bridge interaction effects, which constitutes a significant excitation mechanism for the bridge structure. This study presents a preliminary dynamic analysis on the bridge that first models the railway vehicle crossings as moving loads through a finite element model of the bridge, enabling numerical simulations of the system’s dynamic response. Then, it foresees a comparison of numerical predictions with experimental data, in order to refine the FEM model and gain insight into the dynamic interaction of the coupled vehicle-bridge system under operating conditions. This research is part of a broader initiative to establish a comprehensive Structural Health Monitoring (SHM) platform for the San Michele Bridge. Such a system would enhance long-term monitoring, facilitate early damage detection, and support the preservation and safety of this historic viaduct. The findings highlight the importance of integrating advanced experimental techniques with numerical modeling to safeguard valuable, historic infrastructure.