PSI - Issue 84

S. Lorefice et al. / Procedia Structural Integrity 84 (2026) 669 – 676

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4 Investigations and level of knowledge Through in-situ and laboratory investigations aimed at the mechanical characterization of the materials constituting the bridge, together with detailed geometric surveys and reconstruction of construction details for the masonry and concrete structures, a Level of Knowledge equal to LC2 was achieved, corresponding to a Confidence Factor CF=1.20 , in accordance with Eurocode-based assessment procedures. The existing steel structure, being scheduled for replacement, was not subjected to specific investigations or structural testing. 4.1 Six-span arch bridge The structure extends over an overall length of approximately 85 m, consisting of a sequence of six spans. The arches are constructed in concrete, with a thickness of 0.70 m and a transverse width of 4.70 m. Structural investigations indicated an average cylindrical compressive strength of 28.76 MPa . The height of the piers above ground level varies along the bridge, reaching a maximum value of approximately 10.80 m at the central pier, which supports the steel structure. The piers and abutments, characterized by a tapered geometry in both longitudinal and transverse directions, consist of a cyclopean concrete core with an average compressive strength of 27.51 MPa . 4.2 Three-span arch bridge The structure has an overall length of approximately 40 m, arranged in a sequence of three spans. The arches are constructed of solid brick masonry, with a thickness of 0.50 m and a transverse width of 4.70 m. The height of the piers above ground level varies along the structure, reaching a maximum value of approximately 11.20 m at the central pier, which supports the steel structure. The piers and abutments, featuring a tapered geometry in both directions, are characterized by a cyclopean concrete core with an average compressive strength of 27.51 MPa

Fig. 3. Longitudinal view

5 Structural models 5.1 Existing bridges

The two existing approach bridges were analysed separately, adopting a consistent modelling strategy based on the implementation of finite element models (FEM) developed using the software Midas FEA . Several finite element configurations were investigated, with the aim of identifying the numerical model capable of most accurately reproducing the most critical real operating conditions. All structural and non-structural components of the bridges were explicitly modelled, including abutments, piers, arches, spandrel walls, haunching, and fill. The applied actions included the self-weight of the steel structure transferred to the supporting piers, the static active earth pressure, and 30% of the seismic passive earth resistance acting on the abutments. Loads associated with the track system and railway traffic were also considered. With regard to traffic loads, different application schemes were adopted for the two structures in order to identify the most unfavourable loading configurations for the analyses. Eight-node brick finite elements were employed for the discretization. The mesh, with an average element size of 250 mm, was calibrated to achieve an optimal balance between numerical accuracy and computational efficiency. Substructures were modelled as fully fixed at a depth of