PSI - Issue 62

R. Martini et al. / Procedia Structural Integrity 62 (2024) 392–399 Martini R. et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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Figure 3. Pictures taken during the visual inspections: (a) permanent deck deflection in correspondence of span 4, (b) damage to the half-joint 1 of DB due to water infiltration, (c) cracks on half-joint 1 and (d) moisture in correspondence of cable ducts 4. Preliminary evaluation of the bridge safety The preliminary safety assessment of the two bridges was done evaluating the performance of the structures under static and seismic actions, following the Guidelines 2022 and the Italian technical code (NTC18, Circular 19) aimed at the design of tests described in the following section. The static assessment of the bridge deck was performed considering the case of adequate bridge, i.e., a bridge that satisfy the actual code verifications at the Ultimate Limit State (ULS) and that can be used without any traffic restrictions. As for the decks, three main components were verified: ( i ) the simply supported span (representative of spans 1, 2, 6, 7, and 8), ( ii ) the continuous Gerber girder with half-joints (spans 3, 4, and 5), and ( iii ) local verifications of the half-joints and the transverse bending of the box cross section. Foundations and abutments were not verified, according to the Italian code since no significant critical situations were found at the foundation level. In order to improve the bridge knowledge, derived from existing design documentation, an investigation campaign on the material mechanical properties was carried out, including the extraction of concrete cores and steel samples from piers, box-girder, abutments, and foundations. This campaign was also completed by tests to investigate the path, the state of conservation, and the stress on cables. The overall level of knowledge acquired through the available material and the additional experimental campaign is consistent with level LC3 defined by NTC18; consequently, a unit confident factor was considered, as suggested by the code. The structural analysis was performed adopting the SAP2000 software, developing different models for the simply supported decks and for the Gerber scheme, which are assumed to be representative of both bridges. All structural components are modelled with frame elements accurately reproducing the bridge geometry, including the variability of the cross-section for the Gerber scheme. The safety verification were performed considering the longitudinal bending moments produced by dead and traffic loads, and the shear forces on the cross-section webs produced by the combined actions of shear forces resulting from the previous loads, the transverse bending moments and the torsion deriving from the distribution of the traffic lanes over the deck. As a general outcome it can be asserted that checks for the longitudinal bending moment were almost satisfied everywhere, while checks for the shear forces depend on the actual prestress level that requires a deeper investigation.