World's first Combination of Free Cantilever Construction with External Strand Tendons
The RN 193 national highway in Corsica connects the main city Bastia with the city of Ajaccio. The scenic highway not only crosses beautiful valleys but also masters difficult terrain. This project was initiated to improve the travel time on this main artery of the Corsican traffic infrastructure. The project features unique architecture to match the scenery of the Vecchio Valley.
The structure has a total length of 222m and a main span length of 137.5 m; the deck has a width of 10.35 m for two traffic lanes approximately 60m above the Vecchio river.
The uniqueness of the structure becomes apparent in the design of the free-cantilever segments that get smaller towards mid span, and in the open truss form webs.
This structural combination represents a world premier.
Each cantilever segment is composed of two triangular precast web truss planes that are positioned between the cast-in-place lower and upper deck and post-tensioned by DSI with two to four DYWIDAG bar tendons of various diameters.
After concrete curing all segments are post-tensioned with two DYWIDAG strand tendons 7-0.62" T15S-1860 in the deck.
After the closure segment is cast the entire structure is stressed with external DYWIDAG strand tendons 19-0.62" T15S-1860. The end span stressing is provided by eight DYWIDAG strand tendons 12-0.62" T15S-1860.
The construction schedule anticipated completing main segments in a four-day cycle in order to open the bridge for traffic in February of 1999. Because the form travellers could only advance after stressing of the DYWIDAG bar and strand tendons, the time for the stressing operation had to be kept to a minimum which represented a special challenge that was met by DSI France.