Nonlinear Finite Element Assessment of Shear Capacity in Existing Prestressed Concrete Bridge

Prestressed reinforced concrete bridges and viaducts constructed during Italy's 1970s infrastructure expansion present structural adequacy issues when assessed according to contemporary design standards. Conventional verification procedures indicate substantial shear deficiencies in critical sections, suggesting costly strengthening interventions for many of them. This research develops advanced nonlinear finite element methodologies to accurately simulate complex stress distributions and material behaviour in a two-span bridge with simply supported prestressed concrete girders. The modelling approach, fully compliant with NTC2018 and Eurocode 2 provisions, explicitly captures material non-linear capacity and stress redistribution mechanisms. The finite element model is validated through multiple stages, including analytical comparisons, size effects investigation, and crack pattern verification. Results demonstrate that nonlinear analysis reveals adequate shear structural capacity under design loads, contradicting deficiencies predicted by the existing standards. These findings suggest that many bridges currently flagged for strengthening may possess sufficient structural capacity when more properly evaluated, supporting the development of optimized numerical models and assessment procedures that could substantially reduce unnecessary interventions and enable more cost-effective infrastructure management strategies.