PSI - Issue 64

Marco Carlo Rampini et al. / Procedia Structural Integrity 64 (2024) 2141–2148 Author name / Structural Integrity Procedia 00 (2019) 000–000

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Fig. 2. Schematic drawing of the bridge: top (a) side view (b).

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b

Fig. 3. Representation of the original top anchoring zone (a) and section (b) of the RC hangers.

In 2023, after the recognition of some defects, such as concrete cover detachment and presence of rust on visible bars, the province of Bergamo decided to intervene on the structure, proceeding with the replacement of all the hangers. These members were substituted with steel circular tubes ties with a circular section, as visible on the right side of the bridge Figure 1b. 2.2. Description of the current state of the RC tie rods Prior to the recent intervention with the substitution of all the hangers, the tie rods had probably undergone other maintenance operations. This aspect appeared clear after the visual inspection of the removed ties, from which it was possible to observe: i) the identification of a different tie diameter, around 18 cm, with respect to the original one (Figure 3b); ii) the type of cementitious mortar surrounding the steel bars, showing the presence of short plastic fibers not compatible with bridge age, and its thickness, around 35 mm in comparison to the few mm provided in the design drawing (Figure 3b); iii) the presence of two C-shaped stainless steel external covers, welded together along two side in longitudinal axis, and iv) the presence of a protective paint on the outer