Tevere IV e Puleto Viaducts, S.S. 3 bis "Tiberina" National Road

The Tevere IV and Puleto viaducts, built in the 1960s, are part of the S.S.3 bis "Tiberina" national road along the E45 "Orte-Ravenna" route. They are located at the border between the Tuscany and Emilia Romagna regions, in the mountainous valley of Alta Val Tiberina. The Tevere IV 62 m high road viaduct has 35 spans, with a total length of 1555 m. The Puleto 46m high road  viaduct  is 198.7 m long, with 5 spans. The viaducts consist of two separate roadways, each with two lanes , supported by concrete piers and a prestressed concrete deck. The evaluation of bridge deterioration was carried out through a detailed survey of the construction details, using both visual technical inspections and drone assistance. Load tests, both static and dynamic, were also conducted to characterize the deformative behavior of the structure and to calibrate a numerical model to calculate the road bridge load-carrying capacity. The investigations utilized Ground-based Radar Interferometry (TInRAR) to record the subsidence of various cross-sections of the deck. Additionally, a monitoring system was designed and implemented, and its data was interpreted to enable the activation of an “early warning” system by setting appropriate alarm thresholds.