The objective of this study is to develop test protocols for comparing the effectiveness of fiber-reinforced concrete (FRC) mixtures with high-performance steel fibers. Steel fibers can be added to fresh concrete to increase the tensile strength, ductility, and durability of concrete structures. In order to quantify steel fiber-reinforced concrete (SFRC) mixtures for field applications, a material test capable of predicting the performance of SFRC for field loading conditions is required. However, current test methods used to evaluate the structural properties of FRC (such as residual strength and toughness) are widely regarded as inadequate; a simple, accurate, and consistent test method is needed. It was determined that the Double-Punch Test (DPT), originally introduced by Chen in 1970 for plain concrete, could be extended to fiber-reinforced concrete to satisfy this industry need. In the DPT, a concrete cylinder is placed vertically between the loading platens of the test machine and compressed by two steel punches located concentrically on the top and bottom surfaces of the cylinder. It is hypothesized that the Double-Punch Test is capable of comparing future fiber-reinforcement design options for use in structural applications, and is suitable for evaluating FRC in general. The DPT Research and Testing Program was administered to produce sufficient within-laboratory data to make conclusions and recommendations regarding the simplicity, reliability, and reproducibility of the DPT for evaluating the performance of SFRC. Several variables (including fiber manufacturer, fiber content, and testing equipment) were evaluated to verify the relevance of the DPT for FRC. In this thesis, the results of 120 Double-Punch Tests are summarized and protocols for its effective application to fiber-reinforced concrete are recommended. Also, fundamental data is provided that indicates the DPT could be standardized by national and international agencies, such as the American Society of Testing and Materials (ASTM), as a method to evaluate the mechanical behavior of FRC. This project is sponsored by the Texas Department of Transportation (TxDOT) through TxDOT Project 6348, "Controlling Cracking in Prestressed Concrete Panels and Optimizing Bridge Deck Reinforcing Steel," which is aimed at improving bridge deck construction through developments in design details, durability, and quality control procedures. / text

Le développement futur des véhicules électriques est lié à l’amélioration des performances des batteries qu’ils contiennent. Parallèlement aux recherches sur les nouveaux matériaux ayant des performances supérieures en termes d'énergie, de puissance, de durabilité et de coût, il est nécessaire développer des outils de modélisation pour : (i) simuler l'intégration de la batterie dans la chaine de traction et (ii) pour le système de gestion de la batterie, afin d'améliorer la sécurité et la durabilité. Soit de façon directe (par exemple, la prévention de surcharge ou de l’emballement thermique) soit de façon indirecte (par exemple, les indicateurs de l’état de charge). Les modèles de batterie pourraient aussi être utilisés pour comprendre les phénomènes physiques et les réactions chimiques afin d'améliorer la conception des batteries en fonction des besoins de l’utilisateur et de réduire la durée des phases de test. Dans ce manuscrit, un des modèles les plus communs décrivant les électrodes poreuses des batteries au lithium-ion est revisité. De nombreuses variantes dans la littérature s’inspirent directement du travail mené par le professeur J. Newman et son équipe de chercheurs à l’UC Berkeley. Pourtant relativement peu d’études analysent en détail les capacités prédictives de ce modèle. Dans ce travail, pour étudier ce modèle, toutes les grandeurs physiques sont définies sous une forme adimensionnelle, comme on l'utilise couramment dans la mécanique des fluides : les paramètres qui agissent de manière identique ou opposée sont regroupés et le nombre total de paramètres du modèle est considérablement réduit. Cette étude contient une description critique de la littérature incluant le référencement des paramètres du modèle développé par le groupe de Newman et les techniques utilisées pour les mesurer, ainsi que l’écriture du modèle dans un format adimensionnel pour réduire le nombre de paramètres. Une partie expérimentale décrit les modifications de protocoles mis en œuvre pour améliorer la reproductibilité des essais. Les études effectuées sur le modèle concernent d’une part l’identification des états de lithiation dans la cellule avec un attention particulière sur la précision obtenue, et enfin une prospection numérique pour examiner l’influence de chaque paramètre sur les réponses de la batterie en décharge galvanostatique puis en mode impulsion et relaxation. / The future development of electric vehicles is mostly dependent of improvements in battery performances. In support of the actual research of new materials having higher performances in terms of energy, power, durability and cost, it is necessary to develop modeling tools. The models are helpful to simulate integration of the battery in the powertrain and crucial for the battery management system, to improve either direct (e.g. preventing overcharges and thermal runaway) and indirect (e.g. state of charge indicators) safety. However, the battery models could be used to understand its physical phenomena and chemical reactions to improve the battery design according with vehicles requirements and reduce the testing phases. One of the most common model describing the porous electrodes of lithium-ion batteries is revisited. Many variants available in the literature are inspired by the works of prof. J Newman and his research group from UC Berkeley. Yet, relatively few works, to the best of our knowledge, analyze in detail its predictive capability. In the present work, to investigate this model, all the physical quantities are set in a dimensionless form, as commonly used in fluid mechanics: the parameters that act in the same or the opposite ways are regrouped and the total number of simulation parameter is greatly reduced. In a second phase, the influence of the parameter is discussed, and interpreted with the support of the limit cases. The analysis of the discharge voltage and concentration gradients is based on galvanostatic and pulse/relaxation current profiles and compared with tested commercial LGC cells. The simulations are performed with the software Comsol® and the post-processing with Matlab®. Moreover, in this research, the parameters from the literatures are discussed to understand how accurate are the techniques used to parametrize and feed the inputs of the model. Then, our work shows that the electrode isotherms shapes have a significant influence on the accuracy of the evaluation of the states of charges in a complete cell. Finally, the protocols to characterizes the performance of commercial cells at different C-rates are improved to guarantee the reproducibility.