Conception d'elements prefabriques de ponts avec des betons fibres a haute et ultra haute performance

New types of concrete like high performance fibre reinforced concrete (HPFRC) and ultra high performance fibre reinforced concrete (UHPFRC) present outstanding mechanical and physical properties. Before hardening, they are self-consolidating with a large workability which encourages their use in thin precast products. Furthermore, after hardening, they have high mechanical strengths, a very low permeability and a high ductility.; The first objective of this study is to develop and to characterize an ultra-high performance fibre reinforced concrete produced with locally available basic materials in Qu6bec. The second objective is to optimize the design of precast elements of bridges (prestressed concrete girders and parapets) with different fibre reinforced concrete families (from high performance fibre reinforced concrete to ultra high performance fibre reinforced concrete). This second part of the project is carried out to take advantage of the outstanding properties of these concretes.; Firstly, an experimental program was performed to optimize an ultra-high performance fibre reinforced concrete. Secondly, we have optimized the design of prestressed concrete girders of a typical bridge using an analytical cross-sectional model to compare the performance of the bridge designed using four concrete classes: HPC-50MPa, HPFRC-50MPa, HPRFC-90MPa and UHPFRC-150MPa. The parameters considered in this study for the optimisation of the girder are related to the number of tendons, the cross-section depth and the number of girders. This study showed that HPFRC-90 was the most effective material for this selected application since it allowed a significant reduction of the cross-section's height and the number of girder with a limited increase of the fabrication costs. Finally, we have optimized the design of a precast bridge parapet using finite element nonlinear analysis. Models of the precast parapet were analysed with four concrete classes: HPC-50MPa, HPFRC-50MPa, HPRFC-90MPa and UHPFRC-150MPa. The parameters considered in this study are related to the optimisation of the cross-section of the parapet and the number of anchorages on the bridge deck. This study demonstrated that HPFRC-50 and HPFRC-90 were the most effective materials for precast parapets since these materials allowed a significant reduction of the cross-section and the both materials allowed the elimination of the reinforcement with a decrease of the fabrication costs.