Cable-stayed bridges: a formal and structural prospective.

The most evident achievements in bridge engineering can be seen in the struggle to overcome the barriers with longer spans. Cable-supported bridges play a decisive role in this challenge: the longest cable-stayed bridge, the Sutong Bridge (China), has a free span of more than 1000 m, the longest suspension bridge, the Akashi-Kaikyo Bridge (Japan), has a free span of almost 2000 m, whilst the planned suspension bridge over the Strait of Messina will almost double this record with a free span of 3300 m. Obviously most of design considerations are lead by the structural aspects, but also formal considerations can play a decisive role in the preference to the cable stayed solution, especially against traditional bridge configurations, because of their aesthetic appearance and uniqueness. Indeed among the various bridge types, cable-stayed bridges offer the most intriguing configurations, able to fit the surrounding landscape with an high visual lightness, justifying why, since their debut, their beauty has captured the people fascination. The paper discuss the various aspect of the process of the choice of a cable stayed bridge, presenting one of the most important works by Fabrizio de Miranda, the “Indian way” bridge near Firenze, that represents the first steel cable-stayed bridge realized in Italy. The figure of Fabrizio de Miranda, indeed, emerges with his studies and realizations in Italy and abroad as one of the major Italian engineers and scholars. In the late Sixties of last century, he started an intense experimentation on long span cable-stayed bridges, culminating with the bridge on the Arno in the area “l’Indiano” in Florence (1969-1978), which represent, at that time and in Italy, the best expression of that peculiar field of research. This work is the result of the brilliant synergy between the architects Adriano Montemagni and Paolo Sica and the engineers Fabrizio de Miranda and Vittorio Scalesse, who developed a project for Finsider, a metal construction company. This project won the competition called by the City of Firenze for the realization of a new viaduct on the Arno river and was later awarded by the European prize assigned by the European Convention for Constructional Steelwork (C.E.C.M.) in Helsinki in 1978.