PSI - Issue 84

Lorenzo Sangiuliano et al. / Procedia Structural Integrity 84 (2026) 1326–1333

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Figure 1: Overview of the bridge

Each span features a steel-concrete composite deck with a double-box-girder configuration, equipped with intermediate and end torsional bracing, as shown in Figure 2. Deck erection was carried out on site using large prefabricated steel segments, each 15 m in length, joined by full-penetration butt welds.

Figure 2: common cross section.

The reinforced concrete deck slab consists of precast predalle panels with an in-situ cast topping, providing a total width of 13.6 m and an approximate thickness of 0.40 m. The support system—comprising fixed, unidirectional, and multidirectional bearings—was designed to mitigate thermal stresses transferred to the superstructure. Circular reinforced concrete piers are rigidly connected to circular pile caps, which form the head of the deep foundation piles. 3.2. Experimental data acquisition and post-processing through standard techniques Within the framework of the European research initiative DETAILS (DEsign for opTimal performance (LCC) of high-speed rAILway bridges by enhanced monitoring systems), the Sesia Viaduct was extensively investigated through both experimental testing and numerical analysis. These efforts enabled the experimental dynamic characterisation of the bridge, as reported by Chellini (2010), and provided essential reference data for assessing the accuracy of different modelling approaches applicable to composite steel–concrete railway bridges. A targeted experimental campaign was undertaken to investigate the global dynamic behaviour of the viaduct using Operational Modal Analysis (OMA) techniques. The results indicated a significant dynamic interaction between neighbouring spans: while the decks are structurally separated, non-structural elements such as ballast and rails act as coupling agents, influencing the overall response. This interaction produces symmetric and antisymmetric vertical mode shapes, which are evident in the vertical vibration modes of the second span. The natural frequencies and