PSI - Issue 84

Galileo Tamasi et al. / Procedia Structural Integrity 84 (2026) 709–716

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The deck's primary system is composed of four longitudinal main girders, each with a constant height of 1.50 m and a width of 0.33 m. These girders are integrated with a 0.20 m thick RC deck slab and transverse diaphragms. Regarding these cross-beams, span diaphragms are 1.40 m high and 0.25 m wide, while diaphragms at the piers and abutments are 1.50 m high and 0.40 m wide. The bearing system consists of steel roller bearings positioned at the abutments and one pier to accommodate thermal expansion, while a fixed RC hinge is located on the remaining pier. The substructure consists of gravity-type abutments in plain concrete, reaching a height of 7.56 m, featuring an external batter of 1/10 and internal stepping with steps varying from 1.50 m to 2.00 m in height. The RC piers have a rectangular cross-section with circular cutwaters and taper upwards with a 1/10 slope from a base thickness of 1.80 m to 0.60 m at the cap. The foundations for the abutments are founded directly on rock using plain concrete blocks with inclined base surfaces, while pier foundations consist of RC mats measuring 9.50 m by 3.00 m and 1.00 m thick, supported by bored and compressed RC piles with a 0.40 m diameter and 13.00 m length.

Fig. 3. Structural geometry and layout. Plant

4.2. Material properties and unit weights The design specified the use of concrete for deck structures with 300 kg/m³ of Type 680 cement, whereas substructures and mats used 250 kg/m³ of Type 500 cement. High-strength Aq 50 steel reinforcement was used for the superstructure, while mild Aq 42 steel was specified for piers and foundation mats. The mechanical properties associated with these materials are consistent with the historical data and statistical distributions typical of Italian bridge heritage, as documented in recent literature (D’Amato et al., 2025). The adopted unit weights for the analysis are 2.5 t/m³ for reinforced concrete, 2.4 t/m³ for plain concrete, 2.0 t/m³ for the road base, 1.5 t/m³ for the asphalt layer, and 40 kg/m for the metal railing. 4.3. Original computational approach The original design methodology followed a rigorous analytical path typical of the pre-software era, utilizing established structural theories for each component (Franciosi, 1956; Frangipani, 1950). The sidewalks were analyzed as cantilever beams, while the deck slab was calculated as a continuous beam applying the Gehler method (Croce, 1948; De Miranda, 1971; Krall, 1947). For the longitudinal girders, the structural response was determined through the three-moment equation (Clapeyron's theorem). The transverse distribution of loads among the girders was evaluated using the Engesser method, specifically to determine the stress distribution on the internal longitudinal ribs (De Miranda, 1980; Leonhardt, 1979). The substructures were analyzed considering different loading conditions. The piers were treated as structural solids subjected to vertical loads and horizontal forces deriving from the braking actions of the indefinite truck train. The abutments were verified under the no-tension condition (limit of eccentricity) by comparing two critical scenarios: the bridge unloaded with the embankment under surcharge, and the bridge loaded