PSI - Issue 62

Ettore De La Grennelais et al. / Procedia Structural Integrity 62 (2024) 763–772 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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Following the completion of the structural inspection, the presence of significant defects in the structure became evident, with particular emphasis on the steel truss structure. These defects were attributed to vehicle impacts or oxidative and corrosive conditions, resulting in a decrease in the overall capacity of the bridge. Construction materials of the bridge were investigated using non-destructive and micro-invasive testing techniques, including the collection of material samples and laboratory tests conducted by official laboratories. Due to space constraints, the results of these activities are not reported in this contribution. 5. Implementation of a finite element analysis model Based on geometric and defect surveys, the results of the experimentation campaign to define the current mechanical characteristics of the construction materials constituting the bridge, and the historical reconstructions obtained from traced archive documents and available information, a Finite Element Analysis (FEA) model was implemented. This model was utilized to determine the current safety level of the structure and to define possible scenarios and intervention strategies. The FEA model, developed in the Straus7 environment, comprises the following elements: - BEAM for most of the beams - TRUSS for the bracings - PLATE for the deck.

Fig. 4. Representation of a span in the Finite Element Analysis model.

The supports at the abutments are typical of a statically determinate bridge and are represented by fixed-base beams at the base with translational end releases (highlighted in cyan) at the top. Rotational end releases are also present at the top, as expected. The wall girders consist of diagonal members (modeled as TRUSS) and members for the upper and lower chords. The chords are constructed with flexural continuity, but care has been taken to release them in torsion at the nodes. The upper chord consists of a connected beam supported by a succession of simple supports and bracing modeled with Truss. The lower chord is also composed of beams with a succession of simple supports on the crossbeams and bracing arranged with Truss. The crossbeams are released in moment along the weak axis and in torsion. The connection between beams and the deck is achieved through pinned connections, as it has been verified that there are no headed studs or connecting elements to consider steel-concrete collaboration. The crossbeams do not act as supports because the position of the upper flange is at the limit of the deck extrados. Nevertheless, the deck is connected to the structure through triplets of pinned links that anchor to the nodes of the lower chord. The portals are modeled in detail to replicate the uprights composed of paired L-section profiles and cross bracings. The walkways are modeled with both Beam elements (with appropriate end releases) and Truss elements for different bracing configurations and the compressed diagonal of the cantilevering brackets.