PSI - Issue 78

Valentina Picciano et al. / Procedia Structural Integrity 78 (2026) 1167–1174

1174

6. Conclusions This article investigates the structural behaviour of Gerber saddles in reinforced concrete bridges, highlighting their vulnerability due to stress concentrations, degradation, and inconsistent detailing. A dedicated database of experimental tests was assembled to analyse key parameters and identify typical failure modes. Inclined reinforcement was found to improve ductility and reduce brittle cracking. Supervised machine learning algorithms were applied to the database to predict load-bearing capacity, showing promising results for rapid, preliminary safety assessments that can complement traditional evaluation methods. Various intervention techniques were reviewed, with a focus on practicality, cost, and impact on bridge operation. Among them, external post-tensioning proved to be the most effective, offering substantial performance gains with minimal disruption. Nonlinear finite element analyses were also conducted to study the influence of pre-tension levels on saddle performance. Combining with the development of a simplified design method based on equilibrium principles, these simulations revealed that increased pre-tension effectively delays cracking but has a limited effect on ultimate strength. The findings provide valuable insights for the assessment and rehabilitation of Gerber saddles, contributing to safer and more resilient bridge infrastructure. Acknowledgements The studies presented here were carried out as part of the activities envisaged by the Agreement between the Italian Department of Civil Protection and the ReLUIS Consortium (DPC-ReLUIS project 2024-26, WP5-Task 5.4 “Interventions of existing bridges”). The contents of this paper represent the authors’ ideas and do not necessarily correspond to the official opinion and policies of DPC. References Asteris, P. G., Armaghani, D. J., Hatzigeorgiou, G. D., Karayannis, C. G., Pilakoutas, K., 2019. Predicting the shear strength of reinforced concrete beams using artificial neural networks. Computers and Concrete, 24(5). Bažant, Z. P., Oh, B. H. , 1983. Crack band theory for fracture of concrete. Matériaux et Constructions, 16(3). Buratti, G., Cosentino, A., Morelli, F., Salvatore, W., Bencivenga, P., Zizi, M., De Matteis, G. , 2019. Alcune considerazioni sull’evoluzione normativa dei carichi da traffico nella progettazione dei ponti stradali in Italia. XVIII Convegno ANIDIS. Cervenka Consulting, 2021. ATENA program documentation, Part 1: ATENA Theory Manual. Di Prisco, M., 2019. Critical infrastructures in Italy: State of the art, case studies, rational approaches to select the intervention priorities. Fib Symposium 2019: Concrete-Innovations in Materials, Design and Structures, 49–58. Di Prisco, M., Colombo, M., Martinelli, P., 2023. Structural Aspects of the Collapse of a RC Half-Joint Bridge: Case of the Annone Overpass. Journal of Bridge Engineering, 28(11). EN 1992-2, 2005. Eurocode 2: Design of concrete structures - Part 2: Concrete bridges - Design and detailing rules. MIT, Ministero delle Infrastrutture e dei Trasporti, 2020. Linee Guida per la classificazione e gestione del rischio, la valutazione della sicurezza ed il monitoraggio dei ponti esistenti. Consiglio Superiore dei Lavori Pubblici. Picciano, V., Santarsiero, G., 2024. Reinforced concrete dapped-end beams’ strength assessment: comparison of analytical and numerical methods. In Proceedings of the 15th fib International PhD Symposium in Civil Engineering, Budapest, Hungary, August 28-30 2024. Precast/Prestressed Concrete Institute, 2010. PCI Design Handbook Precast and Prestressed Concrete. In Concrete Reinforcing Steel Institute (Vol. 53, Issue 9). Rajapakse, C., Degée, H., Mihaylov, B., 2021. Assessment of Failure along Re-Entrant Corner Cracks in Existing RC Dapped-End Connections. Structural Engineering International, 31(2). Rajapakse, C., Degée, H., Mihaylov, B., 2022. Investigation of shear and flexural failures of dapped-end connections with orthogonal reinforcement. Engineering Structures, 260. Santarsiero, G., Picciano, V., 2023. Durability enhancement of half-joints in RC bridges through external prestressed tendons: The Musmeci Bridge’s case study. Case Studies in Construction Materials, 18. Santarsiero, G., Picciano, V., 2024. Post ‐ tension retrofitting of RC dapped ‐ end beams: A numerical investigation. Structural Concrete, 25(5), 3246 3264. Santarsiero, G., Masi, A., Picciano, V., 2021. Durability of Gerber saddles in RC bridges: Analyses and applications (Musmeci Bridge, Italy). Infrastructures, 6(2), 1–23. Santarsiero, G., Picciano, V., Masi, A., 2025. Structural rehabilitation of half-joints in RC bridges: A state-of-the-art review. Structure and Infrastructure Engineering, 21(2), 227-250. The MathWorks Inc., 2023. Statistics and Machine Learning Toolbox: 23.2 (R2023b). The MathWorks Inc. https://www.mathworks.com