Este trabalho apresenta estudos, ensaios e análises de resultados a respeito do comportamento à fadiga das estruturas de concreto armadas com barras isoladas e telas soldadas, começando pelas lajes de pontes, seus elementos mais sensíveis à fadiga. A parte experimental desta pesquisa consiste na investigação experimental do comportamento à fadiga de lajes de concreto armado, executadas com e sem pré-lajes armadas com barras de aço isoladas ou em tela soldada. Foram realizados ensaios de fadiga de barra ao ar em 36 corpos de prova de CA50 f10 mm, isoladas e em tela, com o objetivo de construir a Curva de Wöhler dessas barras de produção nacional. Além disso, foram ensaiadas 20 lajes executadas com e sem pré-lajes de concreto, montadas com diversas configurações de armadura, submetidas a ensaios estáticos e dinâmicos. A configuração de armadura adotada nas lajes da pesquisa foi baseada nas utilizadas com freqüência neste tipo de elemento das pontes. A escassez de dados precisos a respeito do comportamento de lajes armadas com barras ou com telas soldadas de fabricação brasileira submetidas a ações cíclicas conduziu ao propósito de se elaborar uma pesquisa de caráter experimental sobre esse tema, cujos resultados e conclusões pudessem fornecer informações mais precisas a respeito do desempenho das lajes. / This research presents the studies, tests and the analysis of the results about the behavior of concrete structures reinforced with rebars or steel mesh due to fatigue loading, starting with bridge slabs which are the most susceptible elements to fatigue. The experimental part of this research consists in testing the behavior due to fatigue of concrete slabs, with or without pre-slabs and reinforced with continuous bars or steel mesh. Axial testing in air of 36 specimens of CA50 f10 mm in continuous bars and mesh were made in order to build the Wöhler Curve for Brazilian conditions. Beyond that, tests were made in 20 concrete slabs with pre-slabs, with several reinforcements arrangement. The 20 slabs were submitted to static and dynamic loading. The reinforcement configuration was based on the commonly used for these elements. The scarcity of more precise data about the behavior of concrete slabs reinforced with rebars or welded mesh made in Brazil submitted to cycle loading was the major reason to make a research based on the testing results about this theme, which results and conclusions are capable of producing more accurate information about the behavior of the slabs.

Este trabalho apresenta estudos, ensaios e análises de resultados a respeito do comportamento à fadiga das estruturas de concreto armadas com barras isoladas e telas soldadas, começando pelas lajes de pontes, seus elementos mais sensíveis à fadiga. A parte experimental desta pesquisa consiste na investigação experimental do comportamento à fadiga de lajes de concreto armado, executadas com e sem pré-lajes armadas com barras de aço isoladas ou em tela soldada. Foram realizados ensaios de fadiga de barra ao ar em 36 corpos de prova de CA50 f10 mm, isoladas e em tela, com o objetivo de construir a Curva de Wöhler dessas barras de produção nacional. Além disso, foram ensaiadas 20 lajes executadas com e sem pré-lajes de concreto, montadas com diversas configurações de armadura, submetidas a ensaios estáticos e dinâmicos. A configuração de armadura adotada nas lajes da pesquisa foi baseada nas utilizadas com freqüência neste tipo de elemento das pontes. A escassez de dados precisos a respeito do comportamento de lajes armadas com barras ou com telas soldadas de fabricação brasileira submetidas a ações cíclicas conduziu ao propósito de se elaborar uma pesquisa de caráter experimental sobre esse tema, cujos resultados e conclusões pudessem fornecer informações mais precisas a respeito do desempenho das lajes. / This research presents the studies, tests and the analysis of the results about the behavior of concrete structures reinforced with rebars or steel mesh due to fatigue loading, starting with bridge slabs which are the most susceptible elements to fatigue. The experimental part of this research consists in testing the behavior due to fatigue of concrete slabs, with or without pre-slabs and reinforced with continuous bars or steel mesh. Axial testing in air of 36 specimens of CA50 f10 mm in continuous bars and mesh were made in order to build the Wöhler Curve for Brazilian conditions. Beyond that, tests were made in 20 concrete slabs with pre-slabs, with several reinforcements arrangement. The 20 slabs were submitted to static and dynamic loading. The reinforcement configuration was based on the commonly used for these elements. The scarcity of more precise data about the behavior of concrete slabs reinforced with rebars or welded mesh made in Brazil submitted to cycle loading was the major reason to make a research based on the testing results about this theme, which results and conclusions are capable of producing more accurate information about the behavior of the slabs.

Ce travail réalisé dans le cadre d'une collaboration industrielle avec la société ALSTOM Transport porte sur l'étude de la dégradation des voies ferrées urbaines. Les composantes de voie retenus pour cette étude sont le rail et la dalle de voie en béton. Concernant le rail, différents problèmes sont abordés : contact roue – rail, usure du rail, usure ondulatoire du rail, et fatigue de contact de roulement (RCF) du rail. Un outil numérique avec des interfaces graphiques, nommé CONUS, est développé pour le problème de contact roue – rail et le problème d'usure du rail. Des théories classiques (Hertz, Kalker, Archard, etc.) sont implantées dans cet outil. La méthode stationnaire est implantée dans un code de calcul par éléments finis pour étudier l'état asymptotique de l'acier du rail sous le chargement répété des trains. Ceci nous permet de prédire les régimes de RCF du rail. La mécanique de l'endommagement est utilisée pour prédire la fatigue du matériau béton. Le formalisme de Marigo couplé avec le modèle d'endommagement de Mazars permet de modéliser la dégradation progressive de la rigidité du matériau sous chargement cyclique. Une campagne d'essais de fatigue du béton en flexion a été réalisée. Elle a pour but de valider le modèle théorique et d'identifier les paramètres du matériau. Le dimensionnement d'une dalle de voie en béton a fait l'objet d'une application de cette méthode. Le modèle de réseau de poutres (lattice model) a été utilisé pour étudier la propagation des fissures dans les structures en béton. Ce modèle a été implanté dans le logiciel de calcul par éléments finis, CESAR-LCPC. Les résultats numériques (propagation de fissures) obtenus pour les structures simples sous chargement statique sont en tout point comparables avec les résultats d'essais expérimentaux. Ce modèle a ensuite été utilisé pour étudier la fissuration sous chargement de fatigue. Pour cela un modèle d'endommagement simple modélisant la dégradation des éléments «poutres» s'est avéré suffisant pour décrire la cinématique de propagation des fissures / This work is part of the collaboration between the laboratory Navier (UMR ENPC /IFSTTAR/ CNRS) and ALSTOM Transport company (TGS/Trackway). It focuses on the study of the degradation of urban railways. The components of track considered in this study are the rail and the concrete slab. Regarding the rail, different problems are discussed : wheel – rail contact, rail wear, rail corrugation and rolling contact fatigue (RCF). A numerical tool with graphical interfaces, called CONUS, is developed to predict the behaviour of the wheel - rail contact, the rail wear, and the rail corrugation problems. Classical theories (Hertz, Kalker, Archard, etc...) are implemented in this tool. The stationary method is implemented in a finite element software to study the asymptotic state of the rail steel under repeated loading of trains.The damage mechanics is used to predict the fatigue life of concrete. Marigo's formalism coupled with Mazars' damage model is used to predict the gradual degradation of material stiffness under cyclic loading. A campaign of fatigue tests for concrete in bending was conducted. It aims at validating the theoretical model and identifying material parameters. We applied this method in order to design the concrete slabs of urban railway. The lattice model was used to study the crack propagation in concrete structures. This model was implemented in the finite element software, CESAR-LCPC. The numerical results obtained for simple structures under static loading are consistent with the results of laboratory experiments. This model was then used to study the crack propagation under fatigue loading. For that purpose, a simple damage model of degradation of the "beams" elements describes the kinematics of crack propagation with a satisfying accuracy

Gegenstand dieser Dissertation ist die Etablierung des Elastizitätsmoduls als Parameter, der qualitative Aussagen über den Schädigungszustand des Baustoffs Straßenbeton ermöglicht. Zu diesem Zweck erfolgte eine systematische Ermüdung von labormaßstäblichen Betonprobekörpern bei zeitgleicher Messung des Elastizitätsmoduls mit Hilfe von unterschiedlichen Verfahren. Im ersten Schritt wurde ein Versuchsprogramm entwickelt, mit dem Probekörper mittels des Spaltzug-Schwellversuchs gezielt in einen definierten Ermüdungszustand versetzt werden können. Hierfür wurde der Parameter des Grenz-Elastizitätsmoduls definiert, welcher, wenn er unterschritten wird, zum Pausieren des Versuchs führt. In diesen systematisch eingehaltenen Lastpausen erfolgten begleitende Untersuchungen der Ultraschalllaufzeit und der Eigenfrequenz zur Bestimmung des Elastizitätsmoduls der Probekörper während des Ermüdungsvorganges. Es zeigt sich zwischen den Ergebnissen aller untersuchten Verfahren eine sehr gute Synchronität hinsichtlich des qualitativen ermüdungsbedingten Verlaufs des Elastizitätsmoduls. Die vier angewandten Verfahren, die sich voneinander unabhängiger physikalischer Phänomene bedienen, ermöglichen neben einer qualitativen Aussage über die Schädigung des Materials die Bestimmung von Absolutwerten des Elastizitätsmoduls. Je nach verwendetem Verfahren weichen die absoluten Elastizitätsmoduln leicht voneinander ab. Der Elastizitätsmodul bestätigt sich als geeigneter Parameter zur Beschreibung der Degradation des Baustoffs Straßenbeton im Zuge des Ermüdungsprozesses. Im zweiten Schritt wurden der Einfluss längerer Lastpausen sowie die Verminderung der Betonfestigkeit im Zuge der Materialermüdung tiefergehend untersucht. Es wurde festgestellt, dass längere Lastpausen in der zyklischen Belastung einen signifikanten Einfluss auf den ermüdungsbedingten Verlauf des Elastizitätsmoduls haben können. Weiterhin legen die Untersuchungen nahe, dass es im Zuge einer starken Ermüdung zu einer zum Teil signifikanten Verminderung der Festigkeit kommt. Als Resultat der Untersuchungen konnten sowohl ein Verfahren zur Bestimmung charakteristischer Verläufe für die Verminderung des Elastizitätsmoduls als auch ein Verfahren zur Abschätzung der materialspezifischen Verminderung der Festigkeit im Zuge der Ermüdung entwickelt werden. Diese Verfahren könnten zukünftig den Regelwerken der RSO Beton und der RDO Beton zugeführt werden, um die ermüdungsbedingte zeitliche Entwicklung des Elastizitätsmoduls und der Festigkeit in den durch die Regelwerke festgeschriebenen Prognose- und Dimensionierungsprozessen zu berücksichtigen. Durch die Einbeziehung zeitlich veränderlicher Werte im Prognoseverfahren, welches als Grundlage für die RSO Beton dienen soll, wird in dieser Dissertation exemplarisch gezeigt, dass die Berücksichtigung der Auswirkungen der Betonermüdung auf diese für die Prognose und die Dimensionierung von Betonfahrbahnbefestigungen sehr relevanten Parameter zur signifikanten Erhöhung der Ausfallrate gegenüber der Verwendung konstanter Werte führen kann. / The subject of this doctoral dissertation is the establishment of the elastic modulus as a parameter that enables qualitative statements about the state of damage of the concrete pavement building material. For this purpose, a systematic fatigue of laboratory-scale concrete specimens was carried out with simultaneous measurement of the elastic modulus by means of different methods. In the first step, a test program was developed for the targeted and systematic fatigue of concrete specimens by means of the cyclic indirect tensile test. For this purpose, a limit value for the elastic modulus was defined. When the elastic modulus fell below the limit, the test was paused to perform accompanying investigations of the ultrasonic transit time and the natural frequency in order to determine the change of the elastic modulus of the specimens during the fatigue process. There is a very good synchronicity between the results of all investigated methods for the qualitative determination of the elastic modulus. The four methods applied, which make use of physical phenomena that are independent of each other, allow, in addition to a qualitative statement about the damage to the material, the determination of absolute values of the elastic modulus. Although there are slight differences between the methods for the determination of the elastic modulus, it is confirmed as a suitable parameter for describing the degradation of the concrete pavement building material in the course of the fatigue process. In the second step, the influence of longer loading pauses and the reduction of concrete strength due to material fatigue were investigated in more detail. It was found that longer loading pauses during cyclic loading can have a significant influence on the fatigue-related course of the elastic modulus. Furthermore, the investigations suggest that in the course of severe fatigue there is a sometimes significant reduction in strength. As a result of the investigations, both a method for determining characteristic curves for the reduction of the elastic modulus and a method for estimating the material-specific reduction of strength in the course of fatigue could be developed. In the future, these methods could be implemented into the RSO Beton and RDO Beton regulations in order to take into account the fatigue-related temporal development of the elastic modulus and the strength in the forecasting and dimensioning processes specified by the regulations. By including time-varying values in the forecasting procedure, which is to serve as the basis for the RSO Beton, this doctoral dissertation exemplifies that the consideration of the effects of concrete fatigue on these very relevant parameters for the forecasting and dimensioning of concrete pavements, can lead to the significant increase of the failure rate compared to the use of constant values.