PSI - Issue 62

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

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Martini R. et al. / Structural Integrity Procedia 00 (2019) 000 – 000

Figure 2. Summary of the activities performed on the bridges case study within the framework of the Italian Guidelines 2022

From the visual inspections it was noticed that the simply supported spans were in a fair state of preservation and showed defects mainly related to the presence of water infiltration from the road pavement. In particular, all the longer Gerber span (with half-joints), presented defects of significant severity, including an evident permanent deflection at the span 4 of both bridges, presumably related to concrete creep phenomena and/or the pre-stressing loss in conjunction with a poor quality of concrete. In addition, the first half-joint of the UB bridge revealed to be completely closed, producing undesirable inner stress state in the deck. Furthermore, moisture traces along the sides of the box girders were detected, which can be attributed to water infiltration within cables ducts, or at the interface between ducts and concrete. Some pictures taken during the inspection are reported in Figure 3. The DB showed an important and anomalous deformability of the cantilever beams of span 4 under heavy vehicular traffic. In the vicinity of the half-joints, in conjunction with the passage of heavy vehicles, the opening and closing phenomena of the present cracks on the lateral side of the box-girder were noted, also producing noise and concrete dust fall. These phenomena were worsened by the presence of bumps and depressions in proximity of the half-joints, which caused passing vehicles to exert a dynamic input on the structure. The UB also showed a crack pattern in correspondence of half-joints (in particular on the West side of half-joint 2), but with lower severity with respect to DB. For both bridges, the CoA was obtained. As known, the final CoA is a combination of several partial CoA obtained for the structural and foundational risk, the seismic risk, and the hydro-geological risk, the latter obtained by a combination of landslide and hydraulic risks. For the sake of brevity, the several parameters considered in the CoA definition are omitted, and only a summary of the procedure is reported in Table 1. Based on visual inspection outcomes, the ANAS team of engineers decided to close the DB and to move the relevant traffic to the UB, for which some monitoring actions were taken. The decision permitted to guarantee at least one traffic lane in each direction of the route.

Table 1. Definition of the CoA of the bridges case study Bridge Structural and Foundational CoA Seismic CoA Landslide CoA Hydraulic CoA Final CoA DB High High Low Medium-High High UB High High Low Medium-High High