The Roize Bridge
The bridge over the Roize river is situated on the interchange between the A49 motorway and the A48 motorway. Numerous engineers aim was to replace prestressed concrete webs used in traditional decks by lighter elements such as steel webs, either plane or corrugated, or concrete or steel trusses. This latter idea was chosen, but material saving has progressed even by reducing the dead load by two methods: using a steel lower flange, and reducing the top slab thickness by using high performance concrete (HPC), prestressed with bonded strands. Other ideas have led to a process which can be extrapolated to larger bridges. Slabs prestressed at an early age, and previous tests performed on HPC loaded at an early age having shown that their creep coefficient was high, it was found necessary to perform creep tests on test specimens. Slabs are concreted in pairs on a precasting bench equipped with two moulds situated between two anchoring abutments for bonded strands.