Corrosion of steel reinforcement has been identified as one of the major problems facing many existing reinforced concrete structures including bridges. The exposure to aggressive environmental conditions such as those with high concentrations of chloride ions due to the use of de-icing salt in cold regions or high concentrations of carbon dioxide due to increased greenhouse gas emissions, accelerate the initiation process of corrosion. As corrosion initiates, the structural performance in terms of load-carrying capacity, ductility, and service life deteriorate over time. Coupling the effect of reinforcement corrosion with service loads may further weaken the structural performance of reinforced concrete bridges due to the presence of transverse load-induced cracks. Accordingly, a research program was conducted to evaluate the structural performance of reinforced concrete beams subjected to coupled effects of service loads and reinforcement corrosion. The research project consisted of combined experimental and numerical investigations. The experimental phase consisted of tests of nine small-scale beams and six large-scale beams. The beams were designed, constructed, instrumented, and loaded under a four-point load test. The primary test variables were the applied corrosion current density, level of corrosion, and level of sustained loading as percentage of beam ultimate capacity (0% Pu, 40% Pu, and 60% Pu). The corrosion level of steel reinforcement was quantitatively assessed using gravimetric weight measurements and three-dimensional laser scanner technique. Test results indicated that failure of corroded RC beams was brittle due to premature rupture of corroded steel bars, which was attributed to the development of localized corrosion at the sections with flexural cracks in beams. Furthermore, it was found that beams subjected to higher levels of service loads, experienced further reductions in ultimate load capacity and ductility. In addition, tensile tests were used to evaluate the effect of corrosion on the mechanical performance of steel bars retrieved from the corroded beams. It was found that the tensile strength of corroded steel bars, based on nominal sectional area, was reduced with the increase of corrosion levels. In contrast, the tensile strength, based on minimum sectional area, was not influenced by the non-uniform distribution and localization of corrosion. In fact, there was a slight increase in strength with the increase of corrosion levels. The numerical phase consisted of finite element analyses of beams using DIANA FE analysis software. A simplified approach was implemented to introduce the damage induced by corrosion into two-dimensional nonlinear FE models, based on the experimental testing of corroded beams and corroded steel bars. The analyses were reasonably accurate in predicting cracking patterns, residual load capacity, residual ductility, and failure modes of corroded beams. Subsequently, the validated model was used to conduct a parametric study on the level of service loads, level of corrosion, strength of concrete, and tensile reinforcement ratio. It was found that the FE model of corroded beams was strongly influenced by the level of service loads, level of corrosion, and tensile reinforcement ratio.

La fissuration d’éléments minces en béton dès le jeune âge correspond à une réalité observée sur des ouvrages en construction. Cette fissuration concerne des bétons courants de bâtiments, pour lesquels les matériaux de qualité optimale ne sont pas toujours disponibles, en particulier au niveau des granulats. Le but de cette thèse est de définir une approche expérimentale d’étude de ces phénomènes et de proposer des interprétations pour les sensibilités relatives à la fissuration en fonction de la nature des granulats et de leurs taux de saturation initiaux. La sensibilité des moyens de mesures existants conçus pour des bétons spéciaux (BAP et BHP) a d’abord dû être<p>vérifiée. Un nouveau dispositif expérimental a été développé dans le but de mieux décrire l’évolution de la résistance et de la capacité de<p>déformation en traction du béton jeune. Les indicateurs globaux (macroscopiques) apparaissent plus sensibles que les indicateurs de la microstructure pour rendre compte des différences de comportement observées. L’évolution du module élastique, du retrait plastique et endogène corrélées à l’évolution de la capacité de déformation et de la résistance en traction permettent de mieux caractériser le risque<p>potentiel de fissuration par retrait empêché. La fin de prise correspond à une phase critique. L’influence de la saturation des granulats est<p>indirecte, et résulte des variations du rapport Eau d’ajout/Ciment, à rapport Eau efficace/Ciment constant. La nature des granulats intervient au niveau des évolutions relatives de la résistance en traction et du module élastique. La méthodologie peut être appliquée à l’étude d’autres types de bétons et d’autres paramètres de formulation. / Doctorat en Sciences de l'ingénieur / info:eu-repo/semantics/nonPublished