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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observed behavior has pointed out the suitability of the seismic isolation in facing strong and low energy earthquakes (Clemente et al. 2021, Saitta et al. 2018). In the following paragraphs, remarkable applications of seismic isolation in the retrofit of bridges in Italy are presented.

2000

Seismic Isolation in Bridges in Italy

1600

New Bridges Bridge Retrofits

1200

800

400

0

1976

1980

1984

1988

1992

1996

2000

2004

2008

2012

2016

2020

Year

Fig. 3. Number of applications of seismic isolation in bridges in Italy.

4. Recent notable retrofit intervention on existing bridges 4.1. Bussi interchange bridge

Bussi interchange bridge is located along the Bussi–Popoli exit ramp of the A25 Torano-Pescara highway. This highway crosses the area struck by the 2009 L’Aquila earthquake. It represents the main connection between the A1 Milano-Napoli highway and the A14 Bologna-Taranto highway in central Italy, which run from north to south along the Italian peninsula, near the western and eastern coast, respectively. The two carriageways are contained within a single structure (Fig. 4a), comprising eleven spans of 25 m each, with a total length of 276 m. The deck, 14.44 m wide and 1.5 m high, is a reinforced concrete slab with 1.10 m-diameter lightning holes. The originally static scheme was that of a simply supported girder with a transverse gap of 4 cm at each pier and abutment. The deck weight is about 7600 kN per span, considering both structural and non-structural permanent loads. Piers and abutments are both in reinforced concrete. Each pier has two independent shafts with a rectangular section (2.3x2.9 m). Their height ranges from 6 to 13 m. The foundations consist of reinforced concrete plinths, 2 m high, supported by six piles, having a diameter of 1.2 m. The bridge was realized in 1973, and, unlike the main bridges along the same highway in the same area, it was designed without considering seismic actions. Therefore, a retrofitting intervention was needed, especially for piers and abutments. It included: i) Substitution of the existing lead-steel devices with high damping rubber bearings (HDRB) with an equivalent stiffness of 2.17 kN/mm and a damping of 16% (Fig. 4b and Fig. 4c); ii) Realization of a deck kinematic chain connecting adjacent spans in longitudinal direction using post-tensioning bars (Fig. 4b and Fig. 4c); iii) Abutments reinforcement using passive tie rods; iv) Concrete jacketing with additional steel bars in piers.

(a)

(b)

(c)

Fig. 4. (a) Bussi interchange bridge, (b) Longitudinal section (c) Transversal section (Infraengineering S.r.l, Toto Holding).