Évaluation expérimentale et numérique de la capacité résiduelle de dalles prélevées sur un pont existant et de l'effet d'un renforcement en BFUP sur leur résistance en cisaillement

This research project was conducted on a 60 year old bridge. Located in Canada, this bridge was subjected to severe climatic conditions and high mechanical loads. The most significant deterioration observed on the bridge was caused by the corrosion of the rebar. The research project was conducted on slabs from the bridge, to improve the understanding of the mechanical behavior and to allow the validation of new reinforcement methods. One method of strengthening bridge slabs while significantly increasing their durability and capacity is the use of ultra-highperformance fiber-reinforced concrete (UHPFRC). In this project, the residual capacity of the bridge slabs and the shear capacity of the bridge slabs reinforced with UHPFRC are experimentally and numerically evaluated. This bridge has an unconventional design, the objective of this project is to present a repair method applicable to more conventional designs that involve a larger quantity of bridges. This project has the particularity of studying and strengthening naturally aged slabs that have been loaded in service for almost 60 years. The slabs are tested in shear, a failure mode that is more brittle than bending and occurring at higher loads. To reach a shear failure, the a/d ratio, between the loading span and the depth of flexural reinforcement, must be considered. Eleven slabs are tested, two of these are reference slabs and nine are UHPFRC reinforced slabs, with three slabs for each a/d ratio considered: 2.5, 3.25 and 4. The results show that as the a/d ratio is decreased, the capacity increases and the ductility decreases. For slabs with a/d ratios of 4 and 3.25, shear cracks are observed, with ductile failure occurring by cracking of the UHPFRC layer. However, for the slabs with a/d = 2.5, the failure is brittle by slip of the interface between the original concrete (RC) and the UHPFRC layer. The experimental tests carried out in this project have demonstrated the significance of the contribution of UHPFRC in terms of stiffness, strength, and ductility, even for slabs with little reinforcement and an ageing history of more than fifty years. Using conventional surface preparation, and due to the bonding properties of the UHPFRC, the RC-UHPFRC interface was able to transfer large shear forces and was the weakest link only for the tests with a/d = 2.5.»