PSI - Issue 84

Federico Scafati et al. / Procedia Structural Integrity 84 (2026) 25–32 F. Scafati et al. / Structural Integrity Procedia 00 (2026) 000–000

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Fig. 6. Rivi Freddi bridge: (a) Longitudinal section; (b) Installation scheme of a shock transmitter device (FIP MEC S.r.l.).

Structural interventions were realized also to improve the performance of the deck in static conditions and its durability over time: i) Demolition and reconstruction of curbs to allow the installation of new H4 class barrier; ii) Reinforcement of deck overhangs with concrete jacketing and additional steel elements; iii) Protective treatments on surfaces exposed to atmospheric agents with waterproofing mortars; iv) Realization of an adequate system for collecting and disposing the platform water. The isolation system comprises 48 DCSSs, 24 for each carriageway. Each DCSS has a diameter of 600 mm for the upper and lower steel plates. They are characterized by a maximum seismic displacement of 300 mm, corresponding to the maximum horizontal force that each device transmits to the substructure elements. The maximum vertical load at the ultimate limit state is 3455 kN. Shock transmitters are designed to allow a maximum displacement of 30 mm in static conditions while they are blocked in seismic ones, transmitting a maximum force of 500 kN along the longitudinal direction of the device. 4.3. The Ritiro bridge The Ritiro bridge in Messina is along the A20 Messina-Palermo highway. The main deck is composed of two separated carriageways, with external ramps connecting the highway to local roads (Fig. 7a). The left carriageway is made of seventeen spans of 45.0 m, two of 34.5 m and one of 33.5 m, for a total length of 867.5 m. The right one has sixteen spans of 45.0 m, two of 35.0 m, three of 34.5 m and one of 33.5 m, for a total length of 927 m. The continuous mixed steel-concrete deck has a width of 11.2 m, including two external curbs of 60 cm. It is composed of two main beams with variable height between 2.0 and 2.3 m and a 20 cm upper reinforced concrete slab (Fig. 7b). Reinforced concrete piers have a hollow rectangular section with a height ranging from 14.0 to 63.0 m (Fig. 7a). Abutments are reinforced concrete type with direct and indirect foundations. The bridge was realized in 1970 in an area that suffered the 1908 earthquake, which is one of the most seismic hazard areas of the entire country. To adapt the bridge to the current technical standards, a retrofitting intervention was needed. The chosen solution, included the following steps: i) Insertion of lead rubber bearings (LRB) isolation system in substitution of existing devices; ii) Replacement of the prestressed reinforced concrete deck with a new steel one, changing the static scheme from simply supported girder to continuous one; iii) Structural reinforcement of abutments and piers and realization of a new steel-concrete pier cap to support the new decks. Due to the complexity of the infrastructure and piers height variability, 6 different kinds of LRBs were used to uniform the transmitted forces from the deck to the substructures (Fig. 7c). Isolators on the abutments (Fig. 7c bottom) are more rigid to optimize displacements and joints behaviour (400 mm in the longitudinal direction and 150 mm in the transversal one). The equivalent horizontal stiffness, related to a combined displacement of 200 mm, is 8.8 kN/mm. The other devices on the piers (Fig. 7c top) are characterized by lower stiffness, between 4.9 and 3.0 kN/mm.