PSI - Issue 62

Giuseppe Colombo et al. / Procedia Structural Integrity 62 (2024) 377–384 Colombo, Mariani, Lambrugo, Giardina/ Structural Integrity Procedia 00 (2023) 000 – 000

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2.5. Box girders rehabilitation With reference to the 45° inclined cracks present on the webs of the beams and observed since the first years of opening to traffic of the structure, the analysis of the numerical model of the structure provided as results the verification of the adequacy of the quantity of reinforcement present to guarantee the safety of the structure again the Ultimate Limit State. However, the use of bent bars with a large diameter (  40 mm) and arranged at a consistent spacing (even greater than 1 m), led to a modest control of the opening of the cracks and the sliding of the bars at the bends. In addition, the very poor quantity of superficial reinforcements of the webs (almost non-existent in the horizontal direction), was not able to offer a valuable contribution in controlling the opening of the cracks. For the surfaces of the external beams, which are more exposed and therefore more subject to environmental aggressions, external reinforcements made of strips of high-strength stainless steel wires STEEL-NET of 2200 g/m 2 grammage glued to an inorganic matrix were applied. This device is therefore suitable to guarantee not only a clogging and closing of the cracks but also a reinforcement capable of limiting the increment of cracks width, which, in these conditions, are strongly conditioned by thermal cycles. 3. Conclusions The works described have made it possible to bring the structure to a level of complete adequacy with the current Italian technical regulations (NTC 2018), both regarding static and seismic actions. What is presented in the article can certainly be considered a virtuous example of the process of managing an important road infrastructure, starting from periodic inspections, investigations and in-depth studies carried out to reach a sufficiently precise level of knowledge of the mechanical and geometric characteristics and of the levels of degradation of the individual components. To finish with the project of retrofitting and its realization that requested the study of innovative equipment. Acknowledgements A special thanks goes to the companies entrusted with the works , with a particular mention for “Fagioli S.p.A.”, tasked with solving the challenging problem of lifts, and the contractor "Costruzioni Ambientali s.r.l." which carried out the works with commitment and dedication, and to its technical director, and owner, Antonino Priolo, who unfortunately passed away after the completion of the works. References Chesi, G., 1960. Ponte sul Po presso Corana – Verbale delle prove di carico. Martinez Y Cabrera, F., Da Rios, G., 1991. Ponte sul fiume Po, Carreggiata Nord. Rinforzo strutturale con rifacimento parziale dell’impalcato. Relazione di calcolo. Melis, L., 2020. Intervento di adeguamento strutturale e sismico del ponte sul fiume Po della carreggiata nord dell’autostrada A 7. Relazione di calcolo. Mancini, G., 2020. Considerazioni sulla trasitabilità del ponte sul fiume Po dell’autostrada A7. Consiglio Superiore dei Lavori Pubblici, 2022. Linee guida per la classificazione e gestione del rischio, la valutazione della sicurezza e il monitoraggio dei ponti esistenti. ANSFISA, 2022. Istruzioni operative per l’applicazione delle linee guida per la classificazione e gestione del rischio, la valutazione della sicurezza e il monitoraggio dei ponti esistenti. Lambrugo, S., 2023. Inte rvento di adeguamento strutturale e sismico del ponte sul fiume Po della carreggiata nord dell’autostrada A7. Rivista “Le Strade”, n. 07/2023.