Viaduct on river Tiber

Location: A91 motorway Rome-Fiumicino, Magliana, Rome

Author: Riccardo Morandi

Chronology: 1964 | 1967

Itinerary: A hard-working country

use: highway viaduct

The viaduct designed by Riccardo Morandi for the Rome-Fiumicino motorway is actually named after Franco della Scala, an Anas director who was a victim of the terrorist attack that took place at Fiumicino airport in 1985. The pre-stressed reinforced concrete bridge is 145 meters long and is 24 meters wide; it was the first of its kind built in Rome and the only one, among the cable-stayed viaducts of Morandi, which supports a curvilinear road section. In the same area, at the beginning of the ’80s, two iron bridges were built, which convey the collectors of the Magliana area. They are both cable-stayed, but they follow a straight line. Together, all these structures configure an impressive panorama, almost a “gateway” to the city of Rome for those who approach by car, coming from the airport.

The cable-stayed solution was adopted because of a landslide that dragged some pylons of the Rome-Fiumicino highway, then under construction. Among Morandi’s proposals, was chosen the one that allowed to minimize the supports on the ground on a geologically unstable ground. The foundations of the bridge are situated outside the landslide limit. Two pairs of pre-stressed reinforced concrete rods start from the central antennas: the rods facing east (towards Rome) diverge and are anchored to the ground with powerful counterweights, since they do not support the deck but only balance the structure; the second pair of tie rods, facing west (towards Fiumicino), instead attaches the viaduct deck to the central point of the gorge created by the landslide; from there, the remaining section of the viaduct behaves like a beam with two supports, one on the section of carriageway supported by the tie rods, and the other one on the head of the section of the pre-existent viaduct, not affected by the landslide.

The concrete construction uses the technique of prestressing, which allows to give tensile strength to a material that is resistant, by its nature, only to the strength of compression. This allowed the Roman engineer to design very elegant structures from the point of view of the homogeneity of the material.

The technique of prestressing also allowed Morandi to work on thinner sections than those he would have obtained using non-prestressed reinforced concrete, enhancing the thickness of the structure.

Text by Manuela Raitano
Photo by Alessandro Lanzetta