RESUME Au Canada, les parapets de ponts sont dans la majorite des cas fabriques en chantier. Ce type de
fabrication permet d’obtenir des parapets avec une tres bonne resistance mecanique, mais au prix d’un temps de pose eleve et d’une durabilite limite. En effet, a cause de la grande rigidite de la dalle, le retrait restreint du beton des parapets cause une fissuration precoce, augmentant la
penetration des sels de deglacage et les effets des cycles gel-degel. La solution proposee dans ce projet reside dans l’utilisation de parapets prefabriques en betons renforces de fibres (BRF)offrant une resistance mecanique et une durabilite largement superieure au beton ordinaire (BO).
L’utilisation de parapets prefabriques permet d’eliminer le retrait restreint causant la fissuration precoce des parapets coules en chantier. De plus, l’utilisation de parapets prefabriques minimise grandement le temps de construction des parapets et les couts associes aux fermetures de ponts. Ce projet avait pour objectif la conception d’un type de parapet prefabrique monolithique et d’un type de parapet prefabrique hybride, compose d’un coeur en BO et d’une coque en beton fibre ultra-haute performance (BRF120MPa-4%). Ce nouveau type de parapet permet a la fois de profiter des qualites exceptionnelles du BRF120MPa-4% en plus de minimiser les couts de fabrication comparativement a un parapet monolithique. Le deuxieme objectif du projet concernait la conception d’un nouveau type d’ancrage permettant l’installation de parapets
prefabriques sur des dalles de pont nouvelles ou existantes. Un concept d’ancrage avec barres en U et goujons a ete propose. La performance des parapets a ete validee par une serie d’essais statiques et dynamiques sur des parapets de dimensions reelles. Ces essais ont demontre que les parapets prefabriques repondaient aux criteres de la norme canadienne (CSA-S6, 2006) en plus de montrer un endommagement limite lors des essais dynamiques. Les modeles en elements finis developpes ont adequatement
reproduit le comportement et la resistance des parapets prefabriques. Cela a permis d’effectuer des etudes parametriques amenant a des recommandations en termes de conception et d’installation des parapets.----------ABSTRACT
In Canada, concrete bridge parapets are normally built on site. This method construction offers good performance in terms of impact resistance, but it also presents several drawbacks. The construction sequence is highly time-consuming consist of the installation of the formwork, the
concrete casting and a minimum curing time. Moreover these elements are exposed to rigorous environmental conditions such as freeze- thaw cycles and severe exposition to de-icing salts, which accelerate the degradation of concrete structures. These two factors of degradation are
amplified by the early-age cracking due to restrained shrinkage. The proposed solution to the previous problem is the use of precast parapets using fibers reinforced concrete (FRC). FRC offers a superior mechanical resistance and durability compared to normal and high strength
concrete. The use of precast parapets allows a quick installation on the job site and eliminates the early-age cracking due to restrained shrinkage. This research project focuses on the design of two new types of precast concrete parapets. The first is a monolithic parapet composed freeze-thaw resistant FRC. The second is a hybrid parapet
composed of a high tensile strength FRC shell paired with a plain concrete core. This design takes advantage of the outstanding properties of FRC120MPa-4%, and minimizes the cost. In addition, a new anchorage system using U-shape rebars and studs was developed to repair the precast parapets to both new and existing bridges. The mechanical performance of the parapet was validated with both static and dynamic test on full-scale specimens. These tests showed that both of the parapet designs met the design criteria of the Canadian Bridges Code (CSA-S6, 2006). Moreover, the parapets showed little or no sign of damage after dynamic impact tests. A finite elements numerical model (FEM) was then developed, which accurately reproduced the overall behavior of the precast parapets subjected to
static loading. After validating the model, a parametric study on the material and interface property and on the shape of the parapets was performed.
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