San Giulano Viaduct, in Italy

Abstract

This viaduct is part of the Sun Roadway, along the western coast of Italy. It is a reinforced concrete structure, with prestressed girders. It runs over a deep ravine, through which water flows intermittently into the Tiber river, a little below the bridge. As the hillside is not highly stable, the possibility of building a large arch was excluded, since the thrusts at the springers would be large. The total length to be bridged, 376 m, has been divided into three approach spans, each 32 m long, on one side, a further five spans, of similar length, on the other side, and a central 100 m long span. The remaining 20 m are taken up with the width of the piles. The project consists of two independent, twin bridges, since there is a separate structure for each of the two traffic directions. The width of each runway is 7.50 m. The planform of the bridge is S shaped, with a central straight section of 106 m length, and a maximum height of 74 m. The piles, of great height, are hollow columns, of rectangular cross section, and concreted by means of sliding formwork. The central span is the most Important feature of the project. It constitutes a portal fram .together with the two supporting piles. These slope towards the centre of the span. The intrados is arched shaped, and the extrados is the deck itself. The attachment of this central span with the springers is through hinged joints, consisting of reinforced neoprene plates. The straight sections of the bridge, of 32 m length, have been spanned with prestressed, prefabricated beams.