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<p>Pack-rust corrosion is a type of corrosion that affects steel built-up members especially old  bridges. It is a localized corrosion that happens in the crevice between two mating surfaces. Pack-rust corrosion does not only cause section loss like other types of corrosions, but also induces local distortion in the structural members that are not the intention of the original designs. This corrosion can change the behavior of the connection fixity and could also cause instability in the overall  built-up members. The size of distortion and section loss were observed to behave linearly between  the free edge and the first line of fasteners. As the distance is moving toward the free edge, the  distortion in the members and section loss in the base material were observed to be maximum. Another important observation was that pack-rust corrosion does not grow beyond the fastener at the fastener’s line. </p> <p>The literature revealed that there are no comprehensive experimental and analytical studies focused on the behavior and effect of pack-rust corrosion on the overall performance of built-up members and connections in compression. Therefore, this research studies the effects of pack-rust corrosion on the capacity of built-up compression members including but not limited to stiffness, yield strength, maximum capacity, and change in fastener force under applied load. This research was studied by performing large-scale experimental testing of flexural members with simulated pack rust. Pack-rust distortion was simulated by placing washers in the crevice between two plates and then the two plates were drawn together using high-strength fasteners. There were also members with real pack-rust corrosion damage from bridge components that used to be in service, and were tested in axial compression tests. </p> <p>The experimental results were compared with hand calculation using conventional design  equations. Finite element analysis was also studied to compare with the experimental results in  order to calibrate future models, but it is not presented in this report. The findings of the  experimental results of all the specimens show that pack-rust corrosion affects yield strength and  maximum capacity of the member and minimally affects the member’s stiffness. Maximum load  of the member affected by pack-rust corrosion can still be estimated conservatively using the  conventional design equations with some modifications. There was no indication of significant  increase in fastener force under applied load, so the likelihood of fastener failing in tension was  very small as observed from this study.   </p>

<p dir="ltr">In steel girder bridges, corrosion at girder ends is often caused by deicing salts mixed with water that leak through expansion joints, accelerating deterioration in the girder ends. This leads to a loss of cross-sectional area, reducing structural resistance to shear and bearing. This dissertation investigates the impact of corrosion on the structural capacity of steel girders and proposes improved procedures for estimating the residual shear and bearing strength of corroded steel girders. Additionally, this study evaluates the feasibility of close-range photogrammetry (CRP) for section loss measurement and estimating residual strength through finite element analysis.</p><p dir="ltr">Large-scale experiments were conducted on steel girders with three types of end configurations: unstiffened ends, ends with full-depth bearing stiffeners, and ends with partial-depth transverse connection plates. These experiments provided critical insights into failure modes, deformation characteristics, and strength degradation in shear and web local crippling capacities due to corrosion-induced section loss. The findings highlighted the sensitivity of different failure modes to strength reduction, influenced by the length, height, and extent of the section loss, with significant differences observed across the various girder end configurations.</p><p dir="ltr">Finite element models were developed and benchmarked against experimental results to capture failure modes, load-bearing capacity, and force-displacement behavior. Parametric analysis was conducted using these benchmarked models to understand the impact of different corrosion parameters on the strength of corroded steel girders. Reduction factors for practical residual strength estimation were developed from regression analysis of the parametric study results.</p><p><br></p><p dir="ltr">Photogrammetry was employed to reconstruct 3D models of steel girders with section loss. Thickness measurements from the 3D models were validated against ultrasonic thickness gauge results. Finite element models utilizing the thickness measurements from these 3D point cloud models were developed to estimate the strength of the steel girder, and these estimates were validated against experimental results.</p><p dir="ltr">In conclusion, this research advances the understanding of the impact of corrosion on the strength of steel girders and contributes to the advancement of inspection and assessment procedures for corroded steel girders.</p>

Les objectifs de la thèse sont d’étudier l’influence de la pré-fissuration sur le développement de la corrosion des armatures du béton armé, les corrélations entre les pertes de section d’armatures dues à la corrosion et la fissuration du béton d’enrobage en résultant et l'effet de la corrosion sur les propriétés mécaniques des structures en béton armé soumis à un environnement salin. Les essais ont été réalisées pour étudier les différentes propriétés mécaniques comme la résistance à la flexion, la résistance au cisaillement, etc. Le travail expérimental est constitué de deux parties: dans la première partie des petits échantillons annulaires en mortier ont été testés afin d'observer l'effet des fissures sur la corrosion. Les résultats montrent que quelque soit l’ouverture des fissures, la corrosion démarre en fond de fissure et se propage le long de l’interface acier-béton endommagée en fond de fissure par la création de la fissure. Dans la deuxième partie, une étude approfondie a été réalisée sur une poutre en béton armé qui a été corrodée dans un environnement salin pendant 26 ans et une poutre non corrodée de même âge pour mieux comprendre l'effet de la corrosion sur les propriétés mécaniques (flexion, cisaillement , propriétés mécaniques de l’acier corrodé) d’éléments en béton armé. Un nouveau modèle a été proposé pour la relation entre la largeur des fissures de corrosion et la perte de section d'acier / The thesis aims to study the effect of corrosion on the mechanical properties of reinforced concrete reinforced concrete structures in chloride environment. Experiments were carried out in order to investigate the different mechanical properties such as bending strength, shear strength etc. The experimental work consists of two parts; in the first part small annular cement sand mortar samples were tested in order to observe the effect of cracks on corrosion. Results show that cracks whatever their width allows the corrosion onset at bottom of cracks and along the steel-concrete interface damaged zone caused by the creation of cracks. In the second part an extensive study was carried out on a 26-year-old corroded reinforced concrete beam and a non-corroded of same age in order to better understand the effect of corrosion on reinforced concrete members in flexion and shear. Impact of corrosion on the mechanical properties of steel in reinforced concrete was studied. A new model was proposed for the relationship between corrosion cracks width and loss of steel cross-section