PSI - Issue 84

L. Fieno et al. / Procedia Structural Integrity 84 (2026) 1127–1135

1133

Figure 8: Views of the structure, its most severe deterioration, and the safety intervention.;

3. Case studies - Lower-deck arch bridge For this structural typology, two significant case studies will be described. The first one, dating back to the 1940s, was designed by Eng. Prof. Giulio Krall, who made a substantial contribution to the development of Nielsen type bridges. The structure consists of a reinforced concrete lower-deck arch bridge, in which the deck is suspended by a series of inclined hangers connected to two large parabolic reinforced concrete arches, with a span of approximately 53.25 m and a crown rise of about 10 m. The deck, with an overall width of approximately 9.0m, is simply supported on single shaft piers and consists of seven equally spaced transverse beams with a composite reinforced concrete slab, as well as two continuous longitudinal girders, which act both as anchorage elements for the hangers and as tie members (arch ties). A total of 28 inclined hangers (14 on each side) are provided, consisting of four plain steel bars with a diameter of 33 mm, protected by a steel tubular casing filled with cementitious grout injection.

Figure 9: Extract from the publication "Ancora sui Ponti quasi arditi" (Prof. Eng. Giulio Krall)

The understanding of the structure was enhanced through laser scanner surveys, covermeter investigations, material testing, endoscopic investigation, and localized exploratory inspections on the hangers. The inspections revealed localized corrosion phenomena, mainly concentrated at the hanger ends, particularly at the connection with the arch. The presence of prestressing in the tie beams was also verified, as confirmed by concrete destress tests that revealed