Bridge to the Future

The experimental Roize Bridge, near Grenoble, France, features an innovative composite space truss and unique modular construction methods for efficiency and economy. The Roize Bridge consists of three spans: two 118 ft end sections and a 131 ft long center span. Deck geometry places the structure on a 1,755 ft radial spiral, with a variable cross slope from 0% to 3.5%. A precast concrete deck slab supported by a steel space truss make up the composite superstructure. The space truss is unique, composed of a single hexagonal lower flange, two inclined Warren-type trusses and transverse floor beams spaced 13 ft apart. Each precast deck slab is 40 ft wide and 12 ft 4 in. long. The slabs are supported by the transverse floor beams and are connected by a transverse closure pour. The bridge is posttensioned with continuous draped tendons over the three spans. Concrete piles 40-50 ft long support the bridge structure, with a total of three 40 in. diameter piles under each abutment and two 50 in. diameter piles beneath each of the intermediate piers.