Les structures en béton armé sont amenées à répondre à différentes exigences pouvant dépasser la simple résistance mécanique. Pendant le processus de fissuration, les contraintes dans le béton armé sont progressivement redistribuées entre l’acier et le béton via l’interface entre ces deux matériaux. Cette redistribution de contraintes a un impact direct sur l’état de fissuration final et doit donc être prise en compte dans la modélisation. Il existe différents modèles numériques capables de représenter les effets de la liaison acier-béton. Cependant, leur usage est, pour l’instant, incompatible avec les applications concernant les structures de grandes dimensions (difficultés de maillage, coût de calcul…). Dans ce cadre d’application, l’hypothèse de liaison parfaite entre l’acier et le béton (déplacement identique) est donc toujours utilisée. On se propose ici de développer un nouveau modèle éléments finis de liaison acier-béton qui soit à la fois représentatif des phénomènes physiques se produisant à l’interface entre les deux matériaux et compatible avec les contraintes de modélisation des structures de grandes dimensions. Ce travail de thèse se découpe en trois grandes parties : - le développement d’un modèle élément fini de liaison acier-béton adapté aux contraintes de modélisation des structures de grandes dimensions. Ce modèle numérique permet ainsi de tenir compte des interactions mécaniques entre le béton et les armatures d’acier représentées à l’aide d’éléments barres. - la caractérisation du comportement de la liaison acier-béton. Un modèle de loi d’adhérence (évolution de la contrainte d’adhérence en fonction du glissement) basé sur des observations expérimentales (campagne expérimentale de pull-out menée au cours de la thèse et données bibliographiques) est proposé. Il permet en particulier de différencier le cas d’une rupture par arrachement, d’une rupture par éclatement en tenant compte des caractéristiques matériaux et géométriques de la structure. - l’application du modèle proposé à un élément structurel (poutre). Un essai de poutre en flexion quatre points visant à caractériser l’évolution de la fissuration (évolution de l’ouverture de fissure mesurée à l’aide de la technique de corrélation d’images notamment) a ainsi été proposé. Ces résultats ont ensuite été comparés à ceux de simulations numériques tenant compte de la liaison acier-béton d’une part ou de l’hypothèse de liaison parfaite d’autre part. Les deux modélisations donnent une bonne approximation du comportement extérieur de la structure (comportement global et ouvertures de fissure des surfaces extérieures de la poutre). Le modèle de liaison acier-béton apporte cependant une meilleure caractérisation de la phase de fissuration active (apparition des fissures) et modifie plus particulièrement le comportement local de la structure à proximité directe des armatures (limitant le développement de l’endommagement du béton le long des renforts). / Reinforced concrete structures may have to fulfill functions that go beyond their simple mechanical resistance. During the cracking process, stresses are progressively transferred from steel to concrete through the steel-concrete interface. This stress transfer has a direct impact on the crack properties. Taking into account these effects seems thus essential to predict correctly the cracking of reinforced concrete structures. Different models exist to represent the steel-concrete bond behavior. However, these models are rarely compatible with large scale simulations (meshing difficulties, heavy computational cost…). To overcome these difficulties, a perfect relation between steel and concrete (same displacements) is generally considered for structural applications. In this contribution, a new finite element approach is proposed to represent the steel-concrete bond effects in a context adapted for large scale simulations. This thesis is divided in three parts: - the development of a finite element steel-concrete bond model adapted for large scale structural applications . This model takes into account mechanical interactions between concrete and steel reinforcement represented by truss elements. - the characterization of the steel-concrete bond behavior. A model for the bond stress-slip law based on experimental observations (experimental campaign on pull-out test carried out during the thesis and data of literature) is proposed. This model differentiates the case of a pull-out failure and of splitting failure and takes into account the material properties and the geometric characteristics of the structure. - an application of the proposed model on a structural element (beam). A four point bending beam is experimentally tested. This test aims to characterize the crack evolution (in particular the crack opening using the image correlation technique). Experimental results are then compared with numerical simulations taking into account the bond–slip effect between steel and concrete or considering the perfect relation hypothesis. The two simulations give a good approximation of the external behavior of the structure (global behavior and crack opening on the external face of the beam). Nevertheless, the bond model improves the cracking description during the active cracking phase (beginning of crack apparition) and influences the local behavior of the structure especially near the steel bars (avoiding the propagation of the damage of concrete along the steel reinforcement).

A presente pesquisa propõe analisar, avaliar e validar o uso de ensaios de aderência açoconcreto para estimativa da resistência à compressão axial do concreto in loco nas primeiras idades em canteiros de obras, como alternativa ao controle de qualidade tradicional. Alguns pesquisadores propuseram a utilização de um ensaio de aderência modificado, que denominaram Appropriate Pull-Out Test (APULOT), como uma adaptação do método pullout test (POT) tradicional, normalizado pela norma EN12504-3. Para viabilizar o uso do ensaio APULOT como ensaio que possa ser implementado na prática do controle tecnológico do concreto em canteiros de obras e seja representativo da resistência in loco é necessário definir um padrão para o mesmo. O presente trabalho desenvolveu um molde específico para o ensaio, analisou a influência do processo da cura nos resultados da tensão máxima de aderência, estudou como a medição da maturidade no concreto pôde auxiliar na determinação do momento certo para fazer o ensaio de arrancamento e comparou resultados dos ensaios feitos em corpos de prova para teste de aderência com ensaios de arrancamento de barras de aço em painéis de concreto. Para tanto foram feitos nove concretagens empregando diferentes tamanhos e configurações de corpos de prova, ensaios de arrancamento, extrações de testemunhos de painéis de concreto, ensaios à compressão simples e medições de maturidade dos concretos empregados. Também se realizaram registros de temperatura ambiente e velocidade do vento na vizinhança dos painéis, buscando estabelecer relações entre a maturidade e as condições ambientais do canteiro. Os ensaios descritos anteriormente realizaram-se às idades de 3, 5, 7 e 28 dias. Os resultados obtidos mostram que, sob condições padronizadas de ensaio, existe ótima correlação entre a tensão máxima de aderência e a resistência à compressão do concreto e por tanto o ensaio de aderência pode ser utilizado para fazer uma estimativa da resistência à compressão do concreto in loco nas primeiras idades. / This research aims to analyze, evaluate and validate the use of steel-concrete bond tests to estimate the axial compression strength of in situ concrete at early ages on construction sites, as alternative to conventional strength control tests. Some researchers have proposed the use of a modified bond test, named Appropriate Pull-Out Test (APULOT), as an adaptation of the traditional pull-out test method (POT) standardized by the EN12504-3. To implement the APULOT as a strength control procedure for concrete on construction site, standardization is needed. This study developed a specific mold for the test; analyzed the influence of curing process on the results of the maximum bond stress; studied how measuring the maturity in the concrete could help to determine when is the right time to make the pull-out test; compared results of tests made on cores for testing the bond and pull-out tests on steel bars in concrete panels. Therefore, it have been made nine concrete events, pull-out tests using different sizes and configurations of cylindrical concret specimen, pull-out tests and extraction of cores from concrete panels, compressive test and maturity measurements of specific employees. Also, temperature and wind speed records have been performed in the panel´s sourrundings, seeking to establish relationships between maturity and ambiental conditions on construction site. The tests described above were carried out at 3, 5, 7 and 28 days. The results show that, under standardized test conditions, a correlation between the maximum bond stress and the concrete compression strength exists, and therefore, bond test can be used to estimate the in situ compression strength of the concrete in the first ages.

A presente pesquisa propõe analisar, avaliar e validar o uso de ensaios de aderência açoconcreto para estimativa da resistência à compressão axial do concreto in loco nas primeiras idades em canteiros de obras, como alternativa ao controle de qualidade tradicional. Alguns pesquisadores propuseram a utilização de um ensaio de aderência modificado, que denominaram Appropriate Pull-Out Test (APULOT), como uma adaptação do método pullout test (POT) tradicional, normalizado pela norma EN12504-3. Para viabilizar o uso do ensaio APULOT como ensaio que possa ser implementado na prática do controle tecnológico do concreto em canteiros de obras e seja representativo da resistência in loco é necessário definir um padrão para o mesmo. O presente trabalho desenvolveu um molde específico para o ensaio, analisou a influência do processo da cura nos resultados da tensão máxima de aderência, estudou como a medição da maturidade no concreto pôde auxiliar na determinação do momento certo para fazer o ensaio de arrancamento e comparou resultados dos ensaios feitos em corpos de prova para teste de aderência com ensaios de arrancamento de barras de aço em painéis de concreto. Para tanto foram feitos nove concretagens empregando diferentes tamanhos e configurações de corpos de prova, ensaios de arrancamento, extrações de testemunhos de painéis de concreto, ensaios à compressão simples e medições de maturidade dos concretos empregados. Também se realizaram registros de temperatura ambiente e velocidade do vento na vizinhança dos painéis, buscando estabelecer relações entre a maturidade e as condições ambientais do canteiro. Os ensaios descritos anteriormente realizaram-se às idades de 3, 5, 7 e 28 dias. Os resultados obtidos mostram que, sob condições padronizadas de ensaio, existe ótima correlação entre a tensão máxima de aderência e a resistência à compressão do concreto e por tanto o ensaio de aderência pode ser utilizado para fazer uma estimativa da resistência à compressão do concreto in loco nas primeiras idades. / This research aims to analyze, evaluate and validate the use of steel-concrete bond tests to estimate the axial compression strength of in situ concrete at early ages on construction sites, as alternative to conventional strength control tests. Some researchers have proposed the use of a modified bond test, named Appropriate Pull-Out Test (APULOT), as an adaptation of the traditional pull-out test method (POT) standardized by the EN12504-3. To implement the APULOT as a strength control procedure for concrete on construction site, standardization is needed. This study developed a specific mold for the test; analyzed the influence of curing process on the results of the maximum bond stress; studied how measuring the maturity in the concrete could help to determine when is the right time to make the pull-out test; compared results of tests made on cores for testing the bond and pull-out tests on steel bars in concrete panels. Therefore, it have been made nine concrete events, pull-out tests using different sizes and configurations of cylindrical concret specimen, pull-out tests and extraction of cores from concrete panels, compressive test and maturity measurements of specific employees. Also, temperature and wind speed records have been performed in the panel´s sourrundings, seeking to establish relationships between maturity and ambiental conditions on construction site. The tests described above were carried out at 3, 5, 7 and 28 days. The results show that, under standardized test conditions, a correlation between the maximum bond stress and the concrete compression strength exists, and therefore, bond test can be used to estimate the in situ compression strength of the concrete in the first ages.

A presente pesquisa propõe analisar, avaliar e validar o uso de ensaios de aderência açoconcreto para estimativa da resistência à compressão axial do concreto in loco nas primeiras idades em canteiros de obras, como alternativa ao controle de qualidade tradicional. Alguns pesquisadores propuseram a utilização de um ensaio de aderência modificado, que denominaram Appropriate Pull-Out Test (APULOT), como uma adaptação do método pullout test (POT) tradicional, normalizado pela norma EN12504-3. Para viabilizar o uso do ensaio APULOT como ensaio que possa ser implementado na prática do controle tecnológico do concreto em canteiros de obras e seja representativo da resistência in loco é necessário definir um padrão para o mesmo. O presente trabalho desenvolveu um molde específico para o ensaio, analisou a influência do processo da cura nos resultados da tensão máxima de aderência, estudou como a medição da maturidade no concreto pôde auxiliar na determinação do momento certo para fazer o ensaio de arrancamento e comparou resultados dos ensaios feitos em corpos de prova para teste de aderência com ensaios de arrancamento de barras de aço em painéis de concreto. Para tanto foram feitos nove concretagens empregando diferentes tamanhos e configurações de corpos de prova, ensaios de arrancamento, extrações de testemunhos de painéis de concreto, ensaios à compressão simples e medições de maturidade dos concretos empregados. Também se realizaram registros de temperatura ambiente e velocidade do vento na vizinhança dos painéis, buscando estabelecer relações entre a maturidade e as condições ambientais do canteiro. Os ensaios descritos anteriormente realizaram-se às idades de 3, 5, 7 e 28 dias. Os resultados obtidos mostram que, sob condições padronizadas de ensaio, existe ótima correlação entre a tensão máxima de aderência e a resistência à compressão do concreto e por tanto o ensaio de aderência pode ser utilizado para fazer uma estimativa da resistência à compressão do concreto in loco nas primeiras idades. / This research aims to analyze, evaluate and validate the use of steel-concrete bond tests to estimate the axial compression strength of in situ concrete at early ages on construction sites, as alternative to conventional strength control tests. Some researchers have proposed the use of a modified bond test, named Appropriate Pull-Out Test (APULOT), as an adaptation of the traditional pull-out test method (POT) standardized by the EN12504-3. To implement the APULOT as a strength control procedure for concrete on construction site, standardization is needed. This study developed a specific mold for the test; analyzed the influence of curing process on the results of the maximum bond stress; studied how measuring the maturity in the concrete could help to determine when is the right time to make the pull-out test; compared results of tests made on cores for testing the bond and pull-out tests on steel bars in concrete panels. Therefore, it have been made nine concrete events, pull-out tests using different sizes and configurations of cylindrical concret specimen, pull-out tests and extraction of cores from concrete panels, compressive test and maturity measurements of specific employees. Also, temperature and wind speed records have been performed in the panel´s sourrundings, seeking to establish relationships between maturity and ambiental conditions on construction site. The tests described above were carried out at 3, 5, 7 and 28 days. The results show that, under standardized test conditions, a correlation between the maximum bond stress and the concrete compression strength exists, and therefore, bond test can be used to estimate the in situ compression strength of the concrete in the first ages.

Nous avons donc proposé dans cette thèse une stratégie pour suivre l’évolution des fissures dans une structure en béton précontraint. L'objectif principal est de définir des briques de modélisation permettant d'étudier le comportement des fissures dans les enceintes de confinement des centrales nucléaires. Chaque brique de modélisation permet ainsi de représenter un phénomène non-linéaire présent dans ces structures : la fissuration du béton, les grilles d'armatures, les cables de précontrainte, la décohésion de l'acier dans le béton ainsi que le vieillissement du béton. Elles ont été validées grâce à plusieurs essais expérimentaux et appliquées à différentes zones. de l'enceinte de confinement pour simuler l'amorçage et la propagation des fissures. Enfin, une stratégie pour définir un état initialement fissuré a été développé à l'aide de ces différentes briques ainsi qu'une méthode de zoom pour reproduire les conditions limites de la précontrainte et la montée en pression sur une partie de l'enceinte. / The difficulty of predicting cracks on reinforced concrete structures is due to the heterogeneity of the concrete and the dependence on environmental boundary conditions. To overcome this problem, we introduce directly a potential crack at the initial time, using cohesive zone models. A major difficulty will be to juggle the cohesive zone models describing cracking and the phenomena of creep and drying, and thus to consider three types of nonlinearities appearing in the calculation : cracking, decohesion of steelconcrete and creep. We also propose a strategy to represent an initially cracked structure. In this thesis, the crack behavior in different parts of the confinement building are modeled using the above described method.

L'objectif de cette thèse est de mettre en place un cadre numérique qui permet de simuler la réponse de structures en béton armé de taille industrielle soumises à des impacts sévères. Notre modèle repose sur trois ingrédients principaux : 1) la modélisation éléments discrets (ED) du béton, permettant de profiter de la nature « discrète » de cette formulation et de décrire facilement l'apparition et la propagation des discontinuités fortes de la matière ; 2) la modélisation éléments finis (EF) poutre des armatures, donnant la possibilité de représenter toute la complexité du ferraillage que l'on rencontre dans les structures industrielles en béton armé ; 3) un modèle de liaison acier-béton original, que nous avons proposé et mis en œuvre dans le code EUROPLEXUS, et qui constitue le principal apport de cette thèse. Nous avons effectué une étude théorique et numérique sur la stabilité et la précision de ce modèle de liaison, et avons calibré ses paramètres en simulant un essai d'arrachement. En modélisant l'essai de traction d'un tirant (barre en béton contenant une armature), nous avons montré la capacité de notre modèle à reproduire le transfert des efforts entre le béton et l'armature au niveau de l'interface acier-béton. Testé et validé sur des cas-tests élémentaires, le modèle mixte ED-EF a ensuite été appliqué à la simulation de vraies structures en béton armé. Nous avons simulé de manière détaillée quelques essais connus (l'impact mou sur poutre CEA, l'essai Meppen II-4), ce qui a permis de valider l'ensemble de notre approche numérique et de recueillir des éléments pour définir les pistes d'amélioration des modèles que nous avons mis en œuvre. / The aim of this work is to set up a numerical framework to simulate the behaviour of industrial size reinforced concrete structures subjected to severe impacts. Our model is based on three main features : 1) modeling of the concrete with a discrete method to handle easily strong material discontinuities such as initiation and propagation of macro-cracks ; 2) modeling of the reinforcement bars with finite element method to be able to represent complex reinforcement cages of industrial structures ; 3) an original steel-concrete bond model that we proposed and implemented in the dynamic explicit code EUROPLEXUS and that constitutes the main task of this work. We studied theoretically and numerically this model to guarantee its stability and precision during the time integration. We calibrated its parameters by simulating pull-out tests. To verify our model, we simulated a tie-test (a long concrete column which contains a reinforcement bar) and showed that our model ensures the correct transfert of forces between steel and concrete. After testing our model on simple benchmarks, we simulated real reinforced concrete structures subjected to impacts (soft impact on a beam, Meppen test n°II-4), allowing us to validate our numerical approach and to define some perspectives to improve the models we have developped.

L'objectif de cette thèse est de mettre en place un cadre numérique qui permet de simuler la réponse de structures en béton armé de taille industrielle soumises à des impacts sévères. Notre modèle repose sur trois ingrédients principaux : 1) la modélisation éléments discrets (ED) du béton, permettant de profiter de la nature « discrète » de cette formulation et de décrire facilement l'apparition et la propagation des discontinuités fortes de la matière ; 2) la modélisation éléments finis (EF) poutre des armatures, donnant la possibilité de représenter toute la complexité du ferraillage que l'on rencontre dans les structures industrielles en béton armé ; 3) un modèle de liaison acier-béton original, que nous avons proposé et mis en œuvre dans le code EUROPLEXUS, et qui constitue le principal apport de cette thèse. Nous avons effectué une étude théorique et numérique sur la stabilité et la précision de ce modèle de liaison, et avons calibré ses paramètres en simulant un essai d'arrachement. En modélisant l'essai de traction d'un tirant (barre en béton contenant une armature), nous avons montré la capacité de notre modèle à reproduire le transfert des efforts entre le béton et l'armature au niveau de l'interface acier-béton. Testé et validé sur des cas-tests élémentaires, le modèle mixte ED-EF a ensuite été appliqué à la simulation de vraies structures en béton armé. Nous avons simulé de manière détaillée quelques essais connus (l'impact mou sur poutre CEA, l'essai Meppen II-4), ce qui a permis de valider l'ensemble de notre approche numérique et de recueillir des éléments pour définir les pistes d'amélioration des modèles que nous avons mis en œuvre. / The aim of this work is to set up a numerical framework to simulate the behaviour of industrial size reinforced concrete structures subjected to severe impacts. Our model is based on three main features : 1) modeling of the concrete with a discrete method to handle easily strong material discontinuities such as initiation and propagation of macro-cracks ; 2) modeling of the reinforcement bars with finite element method to be able to represent complex reinforcement cages of industrial structures ; 3) an original steel-concrete bond model that we proposed and implemented in the dynamic explicit code EUROPLEXUS and that constitutes the main task of this work. We studied theoretically and numerically this model to guarantee its stability and precision during the time integration. We calibrated its parameters by simulating pull-out tests. To verify our model, we simulated a tie-test (a long concrete column which contains a reinforcement bar) and showed that our model ensures the correct transfert of forces between steel and concrete. After testing our model on simple benchmarks, we simulated real reinforced concrete structures subjected to impacts (soft impact on a beam, Meppen test n°II-4), allowing us to validate our numerical approach and to define some perspectives to improve the models we have developped.

La modélisation de la fissuration du béton armé à l'aide de la méthode des éléments finis nécessite de prendre en compte, outre l'endommagement du béton, trois phénomènes : la spécificité de la liaison acier-béton, l’autocontrainte due au retrait, et l'effet d'échelle probabiliste dû à l'hétérogénéité du béton. Cette recherche s'appuie sur une campagne expérimentale pour obtenir le comportement de la liaison et les caractéristiques des fissures sur des éléments de structures. La technique de corrélation d'images numériques a été utilisée pour observer l'espacement et l'ouverture des fissures.La liaison acier-béton est considérée dans la modélisation à l'aide d'éléments d'interface élasto-plastiques basés sur les résultats expérimentaux des tests de pull-out. Les effets du retrait sont pris en compte via un cadre poro-mécanique. Enfin, l'effet d'échelle probabiliste est intégré dans la modélisation via une méthode de champs aléatoires, puis de maillon faible. La modélisation est appliquée à l'élément de structure en béton armé étudié en laboratoire ce qui permet de quantifier l'importance relative de la liaison acier-béton, des contraintes induites par le retrait empêché, et de l'hétérogénéité du matériau. / The modelling of cracking of reinforced concrete using the finite element method requires taking into account, in addition to the concrete damage, three phenomena: the specificity of the steel-concrete bond, the self-stress due to shrinkage, and the probabilistic scale effect due to the heterogeneity of concrete. This research is based on an experimental campaign to obtain the behaviour of the bond and the characteristics of the cracks on structural elements. The technique of digital image correlation was used to observe the spacing and opening of the cracks.The steel-concrete bond is considered in modelling using elastoplastic interface elements based on the experimental results of the pull-out tests. The effects of shrinkage are taken into account via a poro-mechanical framework. Finally, the probabilistic scale effect is integrated into the modelling via a random field method and then a weakest link one. Modelling is applied to the reinforced concrete structural element studied in the laboratory, which makes it possible to quantify the relative importance on cracking of the steel-concrete bond, the stresses induced by shrinkage, and the tensile strength heterogeneity of the material.

Ces travaux ont pour but d'étudier le comportement mécanique de structures précontraintes et d'évaluer l'influence de la technologie de précontrainte utilisée : précontrainte par torons adhérents, précontrainte par torons non-adhérents TGG. Le champ d'application final porte sur l'analyse de la sûreté et de la durabilité des enceintes de confinement de centrales nucléaires. L'attention est alors portée principalement sur le comportement à la fissuration du béton et au rôle de la liaison mécanique torons de précontrainte-structure.La démarche proposée se décompose en trois étapes successives. Elle débute par la caractérisation expérimentale des mécanismes de dégradation à l'échelle de la structure (essais de flexion 4 points sur poutres précontraintes) et à l'échelle locale du matériau (fissuration, déformations différées du béton, liaisons armatures passives-béton et torons-structure par des essais d'arrachement et de traction sur tirants). Une instrumentation multiple (CIN, fibres optiques) favorise la robustesse de la démarche. Des modèles numériques sont ensuite développés pour décrire les mécanismes caractérisés expérimentalement. Un intérêt particulier est porté à la modélisation mésoscopique de l'interface armatures-béton et macroscopique de l'interface torons-coulis d'injection. L'utilisation des différents modèles, couplée à la prise en compte de l'évolution temporelle des déformations différées du béton, favorise une analyse prédictive du comportement des structures étudiées.L'application à une tranche d'enceinte de confinement permet de prédire l'influence de la technologie de précontrainte utilisée sur le comportement à la fissuration de la structure. / This work aims to study the mechanical behavior of partially prestressed structures and to evaluate the influence of the post-tensioning system: bonded tendons, individual unbonded greased and sheathed strands. Under the scope of the safety and durability of nuclear containments, specific attention is devoted to the concrete cracking behavior and to the role of the mechanical tendons-structure bond. The proposed approach is divided into three successive parts. It starts with an experimental study of damage mechanisms at the structural level (4-point bending tests on prestressed concrete beams) and at the local scale (cracking, delayed strains of concrete, reinforcement-concrete bond, tendons-structure bond with pull-out tests and tension tests on reinforced concrete ties). The used instrumentation (DIC, optical fibers) allows for the robustness of the approach. Numerical models are then developed, based on the previous characterized mechanisms. A particular interest is focused on the meso-modeling of the reinforcement-concrete interface and on the macro-modeling of the tendons-injected grout bond. The use of the developed models, considering in parallel the influence of the evolutive delayed strains of concrete, provides a predictive analysis of the mechanical behavior of the studied prestressed structures. A final application to a part of a nuclear containment offers an accurate prediction of the influence of the post-tensioning system on the cracking behavior of the structure.

No description available.