Viaduc de Briare, Steel bridge in Briare, France

The Viaduc de Briare is a bowstring arch bridge carrying the A77 motorway over the Briare Canal and the Trézée River. Its single axial steel arch, painted pale blue-green, spans 86 m and is tied to the deck by two rows of nine radiating suspenders. The deck is about 37 m wide, built for four lanes and designed for six. A separate 84 m beam bridge crosses the river.

The A77 motorway concession, held by SAPRR between Dordives and Cosne-Cours-sur-Loire, required crossings of the Briare Canal and the Trézée. Two identical bowstring arches were designed, one at Pannes and one at Briare, by architect Alain Spielmann. At Briare the steel arch was launched by pushing it along the access viaduct, which served as a launching ramp, unlike Pannes, built on falsework. The two viaducts cost 99 million francs excluding tax (1997 value).

The viaduct won the Prix des Plus beaux ouvrages from the Syndicat de la construction métallique de France in 2000, in the structures category. It shares its design with the identical Pannes Viaduct, built where the A77 crosses the Orléans canal and the Bézonde. Both arcs were chosen as visual landmarks for the motorway section between Dordives and Cosne-Cours-sur-Loire.

The bridge is easily reached from the A77 motorway, located south of exit 20 in the region. Visitors can view the structure from various vantage points to see the construction and arch design from different angles.

The arch was not built in place on scaffolding like its twin at Pannes: it was launched by pushing it across the access viaduct, which served as a launching ramp. The two structures were built together for 99 million francs excluding tax (1997 value), about 9,000 francs per square metre of deck.