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. 7. Ritiro bridge: (a) view, (b) deck cross section, (c) LRB device used (bottom) at the abutments and (top) one used at the piers (Toto Costruzioni Generali S.p.A, Toto Holding; Seteco Ingegneria S.r.l.; Maurer SE).

All isolators have an equivalent damping factor of about 28%, related to the target displacement of 200 mm. However, a linear dynamic analysis was performed considering a lower value of 24% to analyze the structural response of the bridge. This choice allowed to consider the variability of the design properties. For both the carriageways, a vibration period close to 2.0 s was obtained. In terms of forces, static conditions at the ultimate limit state determine the maximum vertical capacity of the isolators: 4144 kN for the LRBs on the abutments and between 6501 kN and 7596 kN for the LRBs on the piers. In seismic conditions, the horizontal force that causes the lead core plasticization is 818 kN for abutment devices, and it is between 455 and 273 kN for pier devices. 5. Conclusions The paper describes the development of seismic isolation in Italian bridges alongside the evolution of seismic hazard classification. Nowadays, seismic isolation technique is ready for large-scale application in the seismic retrofitting of bridges and viaducts in Italy. Very often, simply replacing existing bearings with anti-seismic isolation and/or dissipation devices is sufficient to achieve seismic retrofitting. In other cases, retrofitting of the vertical structures, piers, and abutments is also necessary, while deck replacement is often linked to concrete deterioration and the need to upgrade the roadway to new standards. The paper also presents the seismic retrofit of three bridges in the Italian highway network that represent typical cases in which isolation devices are installed in place of existing bearings. In the first case study, high damping rubber bearings were inserted to seismically isolate a simple reinforced concrete deck. Contemporarily, a kinematic chain is realized between supported girders to improve the response to horizontal loads while keeping the static scheme unchanged for vertical loads. In the second one, double curved surface sliders were used for prestressed reinforced concrete girders and shock transmitter devices were introduced between spans in correspondence of the piers to connect the deck in seismic condition. In the third example, new lead rubber bearings support a new continuous mixed steel-concrete deck. The interventions allow the structures to be adapted to current Italian standards. The cases illustrated are just a few examples to serve as a guide for future applications. Acknowledgements The authors are grateful to all those who provided data, articles, photos, and project drawings used in this paper. They thank particularly: Carlo Toto, President of Toto Holding, for the Bussi interchange bridge and the Ritiro bridge; Luca Colle of Freyssinet Product Company Italia S.p.A. and Eng. Samuele Infanti and Eng. Luca Marcolin of FIP MEC S.r.l., for the Rivi Freddi bridge; Eng. Luca Crespo of Seteco Ingegneria and Eng. Peter Huber, Luca Paroli and Daniele Varotto of Maurer SE, for the Ritiro bridge.