Aggregate strength, gradation, and shape play a vital role in controlling asphalt mixture performance. Many studies have demonstrated the effects of these factors on asphalt mixture performance in terms of resistance to fatigue cracking and rutting. This study introduces numerical and analytical approaches supported with imaging techniques for studying the interrelated effects of aggregate strength, gradation, and shape on resistance of asphalt mixtures to fracture. The numerical approach relies on the discrete element method (DEM). The main advantage of this approach is the ability to account for the interaction between the internal structure distribution and aggregate properties in the analysis of asphalt mixture response and performance. The analytical approach combines aggregate strength variability and internal force distribution in an asphalt mixture to predict the probability of aggregate fracture. The numerical and analytical approaches were calibrated and verified using laboratory tests on various aggregate types and mixtures. Consequently these approaches were used to: (1) determine the resistance of various mixture types with different aggregate properties to fracture, (2) study the effects of aggregate strength variability on fracture, (3) quantify the influence of blending different types of aggregate on mixture strength, (4) develop a mathematical expression for calculating the probability of aggregate fracture within asphalt mixture, and (5) relate cracking patterns (cohesive: aggregate - aggregate and matrix - matrix, and adhesive: aggregate - matrix) in an asphalt mixture to internal structure distribution and aggregate properties. The results of this dissertation established numerical and analytical techniques that are useful for developing a virtual testing environment of asphalt mixtures. Such a virtual testing environment would be capable of relating the microscopic response of asphalt mixtures to the properties of the mixture constituents and internal structure distribution. The virtual testing environment would be an inexpensive mean to evaluate the influence of changing different material and design factors on the mixture response.

Aggregate strength, gradation, and shape play a vital role in controlling asphalt mixture performance. Many studies have demonstrated the effects of these factors on asphalt mixture performance in terms of resistance to fatigue cracking and rutting. This study introduces numerical and analytical approaches supported with imaging techniques for studying the interrelated effects of aggregate strength, gradation, and shape on resistance of asphalt mixtures to fracture. The numerical approach relies on the discrete element method (DEM). The main advantage of this approach is the ability to account for the interaction between the internal structure distribution and aggregate properties in the analysis of asphalt mixture response and performance. The analytical approach combines aggregate strength variability and internal force distribution in an asphalt mixture to predict the probability of aggregate fracture. The numerical and analytical approaches were calibrated and verified using laboratory tests on various aggregate types and mixtures. Consequently these approaches were used to: (1) determine the resistance of various mixture types with different aggregate properties to fracture, (2) study the effects of aggregate strength variability on fracture, (3) quantify the influence of blending different types of aggregate on mixture strength, (4) develop a mathematical expression for calculating the probability of aggregate fracture within asphalt mixture, and (5) relate cracking patterns (cohesive: aggregate - aggregate and matrix - matrix, and adhesive: aggregate - matrix) in an asphalt mixture to internal structure distribution and aggregate properties. The results of this dissertation established numerical and analytical techniques that are useful for developing a virtual testing environment of asphalt mixtures. Such a virtual testing environment would be capable of relating the microscopic response of asphalt mixtures to the properties of the mixture constituents and internal structure distribution. The virtual testing environment would be an inexpensive mean to evaluate the influence of changing different material and design factors on the mixture response.

Das Tragverhalten von Textilbeton kann durch den Einsatz von Kurzfasern erheblich verbessert werden. Untersuchungen zeigen eine Anhebung der Erstrisslast, ein dehnungsverfestigendes Verhalten, eine Verfeinerung des Rissbildes sowie eine Anhebung der maximalen Tragfähigkeit. Unklar sind bisher noch die genauen Mechanismen, die eine gezielte Einstellung des Tragverhaltens ermöglichen. Der Beitrag fasst die Untersuchungen zu den einzelnen Bereichen der Spannungs- ehnungslinie von Textilbeton mit Kurzfasern zusammen und versucht möglichst allgemeingültige Zusammenhänge darzustellen. Dabei werden die Erhöhung der Erstrisslast, die Rissüberbrückung und die Auswirkungen auf das Gesamttragverhalten betrachtet. Abschließend wird das zyklische Biegetragverhalten von Textilbeton mit Kurzfasern im gerissenen Zustand dargestellt. / The load bearing behaviour of textile reinforced concrete can be significantly improved by the addition of short fibres. Investigations show an increase of the first crack strength, a strain-hardening behaviour, a better crack pattern distribution as well as an increase of the load carrying capacity. However, the exact mechanisms leading to this behaviour are not yet known such that a prediction of the load bearing behaviour is not possible. This paper summarises the investigations on the different parts of the stress-strain curve of textile reinforced concrete with short fibres and tries to describe general relationships. In this context the increase of the first crack stress, the crack bridging behaviour and the influence on the load-bearing behaviour in general are considered. Finally, the dynamic flexural behaviour of textile reinforced concrete with short fibres in state II is presented.

Das Tragverhalten von Textilbeton kann durch den Einsatz von Kurzfasern erheblich verbessert werden. Untersuchungen zeigen eine Anhebung der Erstrisslast, ein dehnungsverfestigendes Verhalten, eine Verfeinerung des Rissbildes sowie eine Anhebung der maximalen Tragfähigkeit. Unklar sind bisher noch die genauen Mechanismen, die eine gezielte Einstellung des Tragverhaltens ermöglichen. Der Beitrag fasst die Untersuchungen zu den einzelnen Bereichen der Spannungs- ehnungslinie von Textilbeton mit Kurzfasern zusammen und versucht möglichst allgemeingültige Zusammenhänge darzustellen. Dabei werden die Erhöhung der Erstrisslast, die Rissüberbrückung und die Auswirkungen auf das Gesamttragverhalten betrachtet. Abschließend wird das zyklische Biegetragverhalten von Textilbeton mit Kurzfasern im gerissenen Zustand dargestellt. / The load bearing behaviour of textile reinforced concrete can be significantly improved by the addition of short fibres. Investigations show an increase of the first crack strength, a strain-hardening behaviour, a better crack pattern distribution as well as an increase of the load carrying capacity. However, the exact mechanisms leading to this behaviour are not yet known such that a prediction of the load bearing behaviour is not possible. This paper summarises the investigations on the different parts of the stress-strain curve of textile reinforced concrete with short fibres and tries to describe general relationships. In this context the increase of the first crack stress, the crack bridging behaviour and the influence on the load-bearing behaviour in general are considered. Finally, the dynamic flexural behaviour of textile reinforced concrete with short fibres in state II is presented.

Résumé : Les dalles de tabliers de ponts et des stationnements sont exposées à des environnements agressifs en particulier au Québec et en Amérique du Nord en raison de l'utilisation de sels de déglaçage et des cycles de gel-dégel. La substitution des armatures d’acier par des armatures en matériaux composites de polymères renforcés de fibres (PRF) constitue une alternative intéressante qui connait beaucoup de succès ces dernières années. Le béton armé de PRF est durable, car l’armature n’est pas sujette à la corrosion électrochimique. Aussi l’armature de PRF possède une résistance en traction élevée et est légère. En Amérique du Nord, l’utilisation des composites de PRF a suscité une attention toute particulière de la part des ingénieurs et des gestionnaires d’ouvrages. Plusieurs organismes dont des ministères de transport spécifient l’armature de PRF comme matériau structural dans leurs devis techniques pour lutter contre la corrosion et allonger la durée de service de leurs infrastructures. Les dalles en béton armé sont souvent soumises à des efforts de cisaillement critiques. Actuellement les méthodes de calcul au cisaillement (à l’effort tranchant) de dalles unidirectionnelles en béton armé de PRF différèrent d’une norme à une autre. En effet, la majorité des équations proposées dans les normes et guides de conception ont dérivées à partir de relations empiriques. Bien que des efforts de recherche considérables aient été consacrés dans ce domaine au cours de la dernière décennie, une meilleure compréhension du comportement au cisaillement et des mécanismes de rupture de dalles unidirectionnelles en béton armé de PRF est encore nécessaire. Dans cette recherche, un programme expérimental visant à étudier le comportement de dalles renforcées avec différents types de barres en PRF a été mis en place. Vingt-deux dalles unidirectionnelles en béton renforcées avec des barres de PRF ont été construites et testées en flexion a quatre points jusqu’à la rupture. Les paramètres d’étude comprennent : le type et le taux d’armature, le diamètre de la barre, l’espacement et la configuration de l’armature ainsi que la résistance en compression du béton afin d’examiner leur effet sur la résistance au cisaillement des dalles. Le comportement des dalles testées a été examiné en considérant le réseau de fissures, la charge ultime ainsi que les modes de rupture. Aussi, une base de données comprenant 203 poutres et dalles unidirectionnelles en béton armé de PRF rompues en cisaillement a été répertoriée et introduite dans les analyses. Les charges de rupture en cisaillement des dalles testées dans le cadre de cette thèse ainsi que celles de la base de données ont été comparées à celles prédites par les équations de calcul proposées par la normes canadiennes CSA S6-06/S1 et CSA S806-12, ainsi que celles des deux guides de calcul ACI 440.1R-06 et JSCE-97. Les analyses effectuées ont montré que les valeurs prédites par les équations de calcul proposées par l’ACI 440.1R-06 sont très conservatrices, alors que celles prédites par celles de JSCE-97 sont en meilleur accord avec les valeurs expérimentales. Aussi, les résultats obtenus ont montré que les équations de la nouvelle norme CSA S806-12 prédisent bien la résistance au cisaillement expérimentale. Toutefois, une amélioration de l'équation de la norme CSAS806-12, conduisant à de meilleurs résultats, est proposée. Par ailleurs, les résultats obtenus dans le cadre de cette thèse ont mené à une meilleure compréhension des mécanismes de rupture et des facteurs principaux qui contribuent à la résistance au cisaillement de dalles unidirectionnelles en béton armée de PRF. Enfin, des recommandations pour des travaux futurs y sont également formulées. // Abstract : Bridge deck and parking garage slabs are exposed to aggressive environments particularly in the North American regions resulting from the excessive use of de-icing salts. Fiber-reinforced-polymer (FRP) reinforcements have emerged as a practical and sustainable anti-corrosive reinforcing material with superior tensile strength to overcome the corrosion problem. High comfort level and increase use of the material is currently seen. Protection and regulations policies of some Public North American agencies currently include GFRP reinforcing bars as premium reinforcement. Shear behaviour in RC slabs is examined since most of the bridge deck and parking garage slabs are shear critical. However, there is still no agreement in FRP design codes and guidelines for shear strength equations. Several design code equations are still based on empirical relationships while recent developments are based on shear theories. The complex nature of shear phenomena which is influenced by many parameters, in addition to the existence of various schools of thoughts in shear, makes it difficult to find a general agreement on a unified equation. Huge research efforts are being established, however better understanding for the shear behaviour and failure mechanisms for unidirectional FRP RC slabs is still needed. In this research study, an experimental program was designed to investigate the shear behaviour of one-way concrete slabs reinforced with different types of FRP bars. A total of twenty one concrete slabs reinforced with FRP bars in addition to a steel reinforced slab were constructed and tested to failure under two-point loading. The variation in the concrete contribution to the shear strength V[subscript c] is investigated with respect to FRP reinforcement properties. Newly developed GFRP bars with high modulus, which were not previously investigated in the literature, are used. Different FRP reinforcement properties were included in the study such as reinforcement ratio, modulus of elasticity and axial stiffness, type of bars, and reinforcement configuration. Also, normal concrete and high strength concrete were considered in the research program. Analysis of the experimental results included the general behavior of the tested slabs, crack patterns, ultimate capacities, and modes of failure, load deflection relationships as well as the concrete and reinforcement strains. Test results of the present investigation indicate an influence of the reinforcement type, bar diameter, and the shear stiffness of the bars on the mode of failure and the shear strength. The experimental investigation and analysis of test results provided better understanding of concerning mechanisms of failure and factors contributing to the shear capacity of FRP RC slabs. A refined shear model to the CSA S806-12 is introduced and found to provide better results compared to the existing design codes and guidelines. The model is based on regression analysis of an experimental database. The database is assembled from twenty five different studies in addition to the present investigation. The used database includes 203 unidirectional members reinforced with FRP bars (without shear reinforcement) failing in shear. The model was evaluated through the experimental concrete shear capacities (V[subscript c exp]) of the database and found to provide good predictions. The experimental shear capacities of the database ( V[subscript c exp]) was compared to their corresponding predicted shear capacities (Vcpred ) using CSA S806-12, CAN/CSA-S6.1S1, ACI 440.1R-06, and JSCE-97. It was found that the ACI guide is very conservative. It can be noted that using this guide in its present form may reduce the economic competitiveness of fibre-reinforced polymers. JSCE recommendations are in better agreement with the test results. The Canadian CSA S806-12 equation was found to be in good fit with the experimental shear capacities.