Structural concrete is the most widely used material in the construction of bridges, pave-ments, runways, dams and other infrastructures which are subjected to uctuating loads during its service period. Concrete contains internal aws in the form of micro-cracks as an inherent property. When subjected to fatigue loading, distributed micro-cracks are formed at the sites of pre-existing aws, which subsequently, localize to form a major crack and propagates. The crack growth curve of a structural component when subjected to fatigue loading depicts a sigmoidal pattern. This curve is divided into three distinct regions namely sub-threshold crack propagation (short crack), stable crack propagation (long crack) and unstable crack propagation depending on the crack propagation rate. Most of the fatigue life is spent in the sub-critical stage (small crack) before the for-mation of long cracks. Hence, from the view of estimating the fatigue life, the crack initiation and early crack propagation (short crack stage) phase are the most important and correct concepts need to be developed. Hence, in this work, the behavior of propa-gation and non-propagationof short cracks in concrete when subjected to fatigue loading is addressed. Small non-propagating cracks are usually found at notch roots when the nominal stress range is below certain limits that depend on the notch sensitivity. Analysis is performed on geometrically similar three-point bend beams of three di erent sizes and subjected to fatigue loading in order to determine the important factors that a ect the notch sensitivity and to determine the minimum stress range required for the initiation and propagation of short cracks. A criterion for crack initiation and propagation is proposed based on linear elastic fracture mechanics. Using this criterion, the maximum length of non-propagating crack that can be formed from fatigue loading alone and the minimum stress range required to propagate a crack without arrest are computed. It is observed that the notch sensitivity increases with increase in beam size, decrease in notch-tip aspect ratio and increase in the fatigue limit of the material. Since the probability of formation of a non-propagating crack at a notch tip decreases with increase in notch sensitivity, and since it is desirable not to have a non-propagating crack in experimental investigations, it is essential to design a specimen with higher notch sensitivity. A crack spends a considerable amount of time in the short crack regime. The short cracks are found to propagate at higher rates than the long cracks at the same nominal stress intensity factor which is known as the short crack anomaly. It is important to consider this anomaly in the prediction of the residual life of damaged concrete structures. Hence, in the present work, an analytical model is developed using the principles of dimensional analysis and self-similarity in order to estimate the rate of short crack growth in concrete. The important parameters such as load range, threshold value of stress intensity factor range, modulus of elasticity, tensile strength, fracture energy, stress ratio, crack size and the maximum aggregate size are considered in the development of the short crack growth model. The model is calibrated and validated using the experimental results that are available in the literature. A probabilistic analysis is carried out to determine the sensitivity of each of the di erent parameters that has been considered on the crack growth rate using the coe cient of variation method. It is found that the crack length is the most sensitive parameter to short crack growth rate followed by the load range. A term called `characteristic fatigue life of short crack' is de ned as the number of fatigue cycles that can be applied such that not more than ve percent of the short cracks is expected to proceed to the long crack regime. Furthermore, the fatigue life of a crack spent in the short crack regime is determined through a reliability based study using the Monte Carlo technique. It is found that the smaller sized specimens have larger fatigue life in the short crack regime than the larger specimens.

Le problème initial traité dans cette thèse relève du cadre général de la modélisation des tunnels profonds. Pour cela, on a adopté l'approche basée sur la mécanique linéaire de la rupture. L'étude s'est appuyée sur le critère mixte de Leguillon. Suite à cette étude, on a pu tirer que ce n'est pas le critère mixte qui est insuffisant mais plutôt la façon d'aborder le problème. D'où le passage à la prise en compte de l'hétérogénéité du matériau constitutif et la possibilité d'amorçage d'une fissure sous une contrainte de compression. Une première approche a été entreprise par l'étude d'une bicouche périodique sous contrainte de compression verticale. La couche de grande raideur s'est apparue le siège d'une traction transversale. Effectivement la possibilité d'amorçage d'une fissure est tout à fait probable grâce toujours à la vérification des critères d'énergie et de contrainte. Une deuxième approche consistait à observer au plus près la microstructure du matériau ; on a considéré le problème d'une inclusion elliptique dans une matrice infinie. Par la méthode des variables complexes et la technique de la transformation conforme, on a analysé le champ de contrainte autour de l'inclusion et on a mis en évidence la présence d'une traction qui dépend fortement des paramètres choisis. Par la méthode des éléments finis étendus, on a calculé la variation de l'énergie potentielle mise en jeu par la création d'une fissure. Par une démarche semblable à l'approche précédente, à savoir la vérification des critères d'énergie et de contrainte, on a conclu à la possibilité d'amorçage d'une fissure. Mots clefs : mécanique linéaire de la rupture, critère mixte de Leguillon, énergie potentielle, taux de restitution d'énergie, méthode des éléments finis étendus, bicouche périodique, méthode des variables complexes / The initial problem treated in this thesis falls within the general framework of modeling deep tunnels. For this reason, the approach based on linear fracture mechanics was adopted. The study was based on the mixed criterion of Leguillon. Following This study, the mixed criterion was not insufficient but the way to approach the problem was. Where the transition to the consideration of the heterogeneity of the material component and the possibility of initing a crack under a compressive stress. A first approach was undertaken the study of periodic bilayer under the stress of vertical compression. The layer of the highest stiffness has appeared the seat of a transverse traction. Indeed the possibility to initiate a crack is quite likely always through the verification of the energy and the stress criteria. A second approach was to observe more closer the microstructure of the material; we have considered the problem of elliptic inclusion in an infinite matrix. By the method of complex variables and the technique of conformal mapping, we analyzed the stress field around the inclusion and were revealed the presence of a traction which depends strongly of the selected parameters. By the extended finite element method, we calculated the variation of the potential energy involved by creating a fracture. In a similar approach to the previous one, namely verification of the energy and the stress criteria, we concluded the possibility of initiating a crack. Keywords: linear fracture mechanics, mixed criterion of Leguillon, potential energy, energy release rate, extended finite element method, periodic bilayer, method of complex variables

Parmi les technologies de gazéification de la biomasse, le gazéifieur à lit fluidisé double permet la production d’un gaz de synthèse contenant du méthane. L’étude des processus physicochimiques impliqués dans le gazéifieur est rendue difficile par le fait qu’ils se produisent simultanément. Dans cette thèse, les principales réactions chimiques sont étudiées de manière découplée, indépendamment les unes des autres à l’aide de dispositifs de laboratoire originaux et dans des conditions thermiques semblables à celles du gazéifieur. Les processus intraparticulaires contrôlant la pyrolyse de la biomasse ainsi que les réactions gaz/solide (vapogazéification du charbon et craquage thermique et catalytique des vapeurs sur olivine) sont étudiées au moyen d’un four à image. Les expériences de craquage thermique homogène des vapeurs sont réalisées dans un réacteur parfaitement auto-agité par jets gazeux. Tous les produits formés par les réactions sont recueillis et analysés. Les bilans de matière bouclent de façon très satisfaisante. Le régime de chaque réaction est discuté sur la base d’une analyse de temps caractéristiques. Les paramètres cinétiques des réactions sont déterminés par modélisation des processus et optimisation à partir des résultats expérimentaux. Les mécanismes possibles de formation et de consommation du méthane sont identifiés et discutés. Le gazéifieur est modélisé sur la base d’un modèle de grains (réactions primaires de pyrolyse), des réactions secondaires, de l’hydrodynamique des phases solides et gazeuse et des transferts. La méthodologie de découplage est enfin validée par comparaison des résultats du modèle avec des mesures réalisées sur le gazéifieur de 8 MW de Güssing (Autriche) / Among the biomass gasification technologies, the dual fluidized bed gasifier may be used to produce a methane-rich syngas. Analysis of all the physicochemical phenomena involved inside the gasifier is difficult because they all occur simultaneously. In this thesis, the main chemical reactions are decoupled and studied independently one of each other at the scale of original laboratory facilities in thermal conditions close to those encountered in the gasifier. Intraparticular reactions of biomass pyrolysis and gas/solid reactions (char-steam gasification and catalytic thermal cracking of vapors on olivine) are carried out with an image furnace. Experiments related to gas-phase vapors thermal cracking are performed inside a continuous self stirred tank reactor. All the products formed by the reactions are recovered and analyzed. Mass balance closures are achieved accurately. Controlling steps of each reaction are discussed on the basis of a characteristic times analysis. Kinetic parameters are determined according to both processes modelings and optimizations from the experimental results. Different ways of possible methane formation and consumption mechanisms are identified and discussed. The gasifier is modelled by considering a single-particle model (primary pyrolysis reactions), secondary reactions, solids and gas-phase hydrodynamics and transfers. Finally, the decoupling methodology is validated from the comparison of model results with measurements performed at the 8 MW Güssing gasifier (Austria)

L’IASCC est un mécanisme de fissuration intergranulaire par corrosion sous contrainte (IGCSC) induite par l'irradiation. C’est un phénomène complexe qui peut avoir une influence significative sur le temps et le coût de maintenance des composants internes du coeur des réacteurs à eau pressurisée (REP) et est donc un sujet d'intérêt. Des études récentes ont proposé d'utiliser l'irradiation aux ions (protons) comme une alternative à l'irradiation neutronique afin d’améliorer la compréhension du mécanisme. L'objectif de cette thèse est d’étudier la sensibilité à la fissuration de l’acier austénitique SA 304L irradié aux ions ainsi que les facteurs contribuant à cette fissuration. Deux types d’irradiations aux ions ont été menées (fer et aux protons). Ces deux irradiations ont générées des défauts ponctuels dans la microstructure représentatifs de ceux crées par les neutrons provoquant ainsi le durcissement de l’acier austénitique 304L. Matériel (non irradié et le fer irradié) n'a montré aucune sensibilité à la fissuration intergranulaire sur la soumission à un essai de traction lente SSRT (Slow Strain Rate Test) commencer avec une vitesse de déformation de 5 × 10-8 s-1 jusqu'à 4% de déformation plastique dans un environnement inerte. Il est montré que les deux types d’irradiation aux ions (fer et protons) augmentent la sensibilité à la fissuration intergranulaire du matériau après un essai de SSRT dans un environnement simulé de REP à 340 ° C. La corrélation entre la sensibilité de fissuration et le degré de localisation de la déformation plastique a été étudiée. L’impact de l'irradiation aux ions fer sur l'oxydation du 304L a été aussi étudié grâce à des essais effectués pendant 360 h dans un milieu REP à 340 ° C. Les résultats de cette thèse indiquent que la fissuration intergranulaire de l'acier inoxydable 304L en milieu REP peut être étudiée en utilisant l'irradiation Fe malgré sa faible profondeur de pénétration dans le matériau. Par ailleurs, il est montré que le comportement vis-à-vis de la fissuration est similaire entre une irradiation aux protons et au fer, et ceux malgré une localisation de la déformation moins importante pour ces derniers. Par conséquent, l’irradiation au fer est utilisée pour étudier l'impact de la préparation de surface et des chemins de déformation sur la sensibilité de la fissuration intergranulaire de l’acier 304L. / IASCC is irradiation – assisted enhancement of intergranular stress corrosion cracking susceptibility of austenitic stainless steel. It is a complex degrading phenomenon which can have a significant influence on maintenance time and cost of PWRs’ core internals and hence, is an issue of concern. Recent studies have proposed using ion irradiation (to be specific, proton irradiation) as an alternative of neutron irradiation to improve the current understanding of the mechanism. The objective of this study was to investigate the cracking susceptibility of irradiated SA 304L and factors contributing to cracking, using two different ion irradiations; iron and proton irradiations. Both resulted in generation of point defects in the microstructure and thereby causing hardening of the SA 304L. Material (unirradiated and iron irradiated) showed no susceptibility to intergranular cracking on subjection to SSRT with a strain rate of 5 × 10-8 s-1 up to 4 % plastic strain in inert environment. But, irradiation (iron and proton) was found to increase intergranular cracking severity of material on subjection to SSRT in simulated PWR primary water environment at 340 °C. Correlation between the cracking susceptibility and degree of localization was studied. Impact of iron irradiation on bulk oxidation of SA 304L was studied as well by conducting an oxidation test for 360 h in simulated PWR environment at 340 °C. The findings of this study indicate that the intergranular cracking of 304L stainless steel in PWR environment can be studied using Fe irradiation despite its small penetration depth in material. Furthermore, it has been shown that the cracking was similar in both iron and proton irradiated samples despite different degrees of localization. Lastly, on establishing iron irradiation as a successful tool, it was used to study the impact of surface finish and strain paths on intergranular cracking susceptibility 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.

L’objectif de ce travail est d’améliorer la compréhension des phénomènes de Corrosion Sous Contrainte (CSC) susceptibles d’être rencontrés sur les fils d’armures des conduites flexibles, faits d’aciers ferrito-perlitiques. Dans l’annulaire des conduites flexibles, l’environnement chimique des aciers est constitué d’une « eau de mer » confinée et saturée en CO2. Celui-ci favorise la formation d’une couche protectrice de sidérite qui semble avoir un effet déterminant sur la vitesse de corrosion de l’acier. Les conditions de service entrainant des fluctuations de l’environnement ou des contraintes appliquées s’ajoutant à des contraintes résiduelles peuvent provoquer la rupture des conditions d’équilibre entre l’acier et son environnement protecteur, et amorcer ainsi la CSC.Les paramètres microstructuraux et mécaniques qui gouvernent l’amorçage et la propagation de fissures par CSC dans les aciers ferrito-perlitiques dans un milieu confiné simulé sont identifiés au moyen d’essais de traction lente menés sous différents potentiels électrochimiques sur des éprouvettes lisses et micro-entaillées. La phase d’amorçage met en jeu des effets de synergie entre la localisation de la plasticité et la dissolution de l’acier. Cependant, des effets de l’hydrogène doivent être pris en compte dans la propagation des fissures. L’hydrogène, au travers d’interactions hydrogène/plasticité, entraine l’avancée des fissures. Il a été également démontré que l’emploi de microstructures particulières peut favoriser ou retarder les effets de l’hydrogène sans pour autant affecter la limite d’élasticité de la même manière. / In confined solutions containing dissolved CO2, ferrito-pearlitic steels can suffer Stress Corrosion Cracking (SCC). We could find such situations in the annulus of flexible pipes. In these conditions, a protective corrosion product, the siderite FeCO3, is formed on the steel surface decreasing the corrosion rate. In service, environment fluctuation (such as pH, potential…) and/or an addition of applied stress can disturb the balance between the steel and this protective film, causing the fracture of the latter and leading to SCC.The objective is to understand the mechanism of SCC in such environments and to identify the parameters controlling the initiation and the propagation of cracks. Slow strain rate tensile tests in confined solution are carried out on smooth and notched specimens to study crack initiation and propagation. Crack initiation is controlled by synergistic effects between localized plasticity and the dissolution processes. However, hydrogen effects must be considered to explain crack propagation. Through hydrogen/plasticity interactions, hydrogen ingress leads to crack propagation. It is also demonstrated that the design and use of specific microstructures may promote or delay hydrogen effects, without affecting the yield strength in the same manner. Finally, the influence of a torsional pre-strain on the susceptibility to Environmentally-Assisted Cracking of a cold-worked ferrito-pearlitic steel is studied.

Die Kunststoffschweißverfahren Infrarot- und Vibrationsschweißen sind in der Serienfertigung etablierte Fügetechnologien. Sie sind durch eine wirtschaftliche und effiziente Prozessführung gekennzeichnet und sind verfahrenstechnisch prinzipiell zum Einsatz im Apparate-, Behälter- und Rohrleitungsbau geeignet. Aufgrund fehlender Erkenntnisse und Nachweise zum Zeitstandverhalten ist die Anwendung dieser Verfahren im Halbzeugbereich jedoch nur eingeschränkt möglich. Im Rahmen der Untersuchungen wurden das Vibrations- und Infrarotschweißen hinsichtlich ihres Potentials für Langzeitanwendungen mit dem konventionellen Halbzeugschweißverfahren Heizelementschweißen verglichen und erreichbare Zeitstandzug-Schweißfaktoren ermittelt. Die Ergebnisse zeigen, dass sowohl für das Vibrations- als auch Infrarotschweißen, in Abhängigkeit der Prozessparameter, Zeitstandzug-Schweißfaktoren von ca. 0,7 bis 0,9 erreicht werden. Darüber hinaus führen die Resultate dieser Arbeit zu einer Erweiterung der Wissensbasis über die Mechanismen des Zeitstandbruchverhaltens geschweißter Polyolefinhalbzeuge. Die für die Kurzzeitfestigkeit von Vibrations- und Infrarotschweiß-verbindungen vielfach nachgewiesene Prozess-Struktur-Eigenschaftskorrelation wurde für die Zeitstandfestigkeit erforscht und angewendet. / The infrared and vibration welding processes are joining technologies established in series fabrication. They are characterised by their economically viable and efficient process management and they are suitable for utilisation in apparatus, tank and pipeline construction. However, their application in the field of semi-finished procucts is restricted due to the lack of knowledge and proof in relation to the Environmental Stress Cracking (ESC). Within the framework of the research, the vibration and infrared welding processes were compared with the conventional welding process heated tool butt welding. Furthermore achievable tensile creep welding factors were determined. The results show achievable tensile creep welding factors from ca. 0.7 to 0.9 for the vibration welding process as well as for the infrared welding process dependent on their process parameters. Moreover, the knowledge base of the mechanisms of the failure behaviour of welded joints between semi-finished products undergoing ESC was extended. The process-structure-property correlation, which has been proven for the short-term strength of vibration and infrared welded joints many times, was investigated and applied for the long-term strength.

Composite materials show heterogeneity at different length scales. hence concurrent multiscale analysis is the only reliable method to analyze them. But unfortunately there is no concurrent multi-scale strategy that is efficient, and accurate while addressing all kinds of problems. This lack of reliability is partly because there is no micro-mechanical model which inherently keeps all relevent global information with it. This thesis tries to fill this gap. The presented micro-mechanical model not only homogenizes the micro-structure but also keeps the global information with it. Most of the micro-mechanical models in the literature extract the Representative Volume Element (RVE) from the continuum for analysis which results in loss of information and accuracy. In the present approach also, the RVE has been extracted from the continuum but with the major difference that all the macro/meso-scopic parameters are accounted for. Five macro/meso-scopic one dimensional parameters have been defined which completely define the effect of continuum. 11 for one dimensional stretch, _1 for torsion, __ (_ = 2, 3) for bending and _33 for uniform pressurization due to the presence of the continuum. Further, the above macro/meso-scopic parameters are proven, by the asymptotic, theory to be constant at a cross section but vary, in general, over the length of the fiber. Hence, the analysis is valid for any location and is not restricted to any local domain. Three major problems have been addressed: • Homogenization and analysis of RVE without any defects • Homogenization and analysis of RVE with fiber-matrix de-bonding • Homogenization and analysis of RVE with radial matrix cracking. Variational Asymptotic Method (VAM) has been used to solve the above mentioned problems analytically. The results have been compared against standard results in the literature and against 3D FEA. At the end, results for “Radial deformation due to torsion” problem will be presented which was solved “accidentally.”

Le mécanisme d'endommagement le plus facilement observable lors d'un essai de traction est la micro-fissuration des plis. Ces fissures sont parallèles à la direction des fibres et s'étendent sur toute l'épaisseur du pli. L'apparition et la croissance du nombre de ces fissures engendrent une réduction progressive de la rigidité globale du composite. Lorsque le composite est sollicité mécaniquement, les concentrations de contraintes en pointe de fissures peuvent favoriser la création d'une zone où le pli fissuré et le pli adjacent sont décollés (phénomène de délamination). Il est évident que l'apparition de cette nouvelle forme d'endommagement modifiera la dépendance de l'ouverture et du glissement des lèvres des fissures avec le chargement appliqué. Il est donc nécessaire de trouver un moyen de mesure permettant l'estimation expérimentale des valeurs de l'ouverture moyenne et du glissement moyen des lèvres des fissures. L'objectif principal de cette thèse est de caractériser l'endommagement des matériaux composites (Fibre de carbone/époxy et fibre de verre/époxy) utilisés dans le domaine aéronautique. En utilisant l'interférométrie de speckle (ESPI), des mesures de plein champs de déplacements aux bords des échantillons et dans différentes couches du stratifié ainsi que des études par élément finis ont été effectuées dans le but de calculer l'ouverture et le glissement des lèvres des fissures. L'effet des propriétés élastiques des matériaux sur l'endommagement aussi bien que l'effet d'interaction entre les fissures ont été déterminés. Une discussion essais/calculs est enfin réalisée afin de juger la validité des hypothèses retenues / The macroscopic failure of composite laminates subjected to tensile increasing load is preceded by initiation and evolution of several microdamage modes. The most common damage mode and the one examined in this thesis is intralaminar cracking in layers. Due to this kind of microdamage the laminate undergoes stiffness reduction when loaded in tension. The degradation of the elastic properties of these materials is caused by reduced stress in the damaged layer which is mainly due to two parameters: crack opening displacement (COD) and crack sliding displacement (CSD). The first objective of this thesis is to investigate the effect of crack interaction on COD using FEM and to describe the identified dependence on crack density in a simple and accurate form by introducing an interaction function dependent on crack density. The application of this function to more complex laminate lay-ups is demonstrated. All these calculations are performed assuming that cracks are equidistant. Using FEM, we assume linear elastic material with ideal crack geometry. Fiber bridging over the crack surface is possible which can affect COD and CSD. The only correct way to validate these assumptions is through experiments. The second objective is to measure these parameters for different laminate lay-ups in this way providing models with valuable information for validation of used assumptions and for defining limits of their application. In particular, the displacement field on the edge of a [90/0]s and [903/0]s carbon fiber/epoxy laminates specimens with multiple intralaminar cracks in the surface layer is studied

Submitted by Haroudo Xavier Filho (haroudo.xavierfo@ufpe.br) on 2016-04-15T18:13:42Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Dissertação - Paulo Rodrigo Lopes de Souza.pdf: 3087983 bytes, checksum: 88991d54c050c5fbdd84af04c1508190 (MD5) / Made available in DSpace on 2016-04-15T18:13:42Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Dissertação - Paulo Rodrigo Lopes de Souza.pdf: 3087983 bytes, checksum: 88991d54c050c5fbdd84af04c1508190 (MD5) Previous issue date: 2015-10-09 / A falta de compatibilização de projetos na construção civil pode gerar interferências entre os diversos projetos de uma edificação e o projeto estrutural, uma destas interferências é a passagem de tubulações na alma de vigas. Na maioria das vezes só é constatado que uma tubulação irá passar no meio de uma viga após a mesma já ter sido concretada e nessa situação muitos construtores realizam uma abertura ou furo na viga para realizar a passagem da tubulação na maior parte das vezes sem a devida consulta a um engenheiro calculista e sem respeitar as prescrições da norma ABNT NBR 6118:2014 no que diz respeito às dimensões e posicionamento na alma da viga ocasionando perda da resistência dessas vigas. Com base no exposto, foi analisada neste trabalho a possibilidade de se adicionar fibras de aço à massa do concreto para atuar como reforço parcial junto ao local do furo. Para avaliar a capacidade das fibras que atua como reforços parciais foram conduzidos ensaios experimentais que consistiram na moldagem de vigas de concreto armado com iguais dimensões onde todas elas foram instrumentadas com extensômetros elétricos e medidores de deslocamento tipo LVDT. As vigas possuíam adição de fibras de aço em diferentes teores e uma abertura transversal de igual geometria e posição na alma. Para realização de um estudo comparativo foram analisadas duas vigas, uma de referência sem adição de fibras à massa do concreto e sem abertura transversal na alma e uma sem adição de fibras de aço à massa do concreto, com abertura transversal na alma, porém, com um reforço em armadura de aço junto ao local da abertura que foi calculado pelo método das Bielas e dos Tirantes. Todas as vigas foram analisadas quando a capacidade de carga, deformações do concreto e do aço além de flecha no meio do vão. Os resultados mostraram que as vigas com adição de fibras de aço à massa do concreto, em alguns locais da viga, alcançaram até a carga de ruptura uma discreta melhora na rigidez, que mostra que as fibras de aço foram eficientes no controle da fissuração, porém as fibras de aço sozinhas não conseguiram manter a mesma capacidade de carga da viga de referência. Sugere-se então a utilização da técnica da adição de fibras de aço à massa do concreto em conjunto com um reforço em armadura de aço junto ao local da abertura calculado pelo método das bielas e dos tirantes. / The lack of compatibility of projects in a civil construction can cause interference among the various projects of a building and the structural project, one of these are interferences in the passage of pipes in the beam’s web. In most cases it is only ascertained that a pipe will go through a beam after it has already been concreted, and in this situation many builders perform an opening or hole in the beam to get the pipes through at most times without proper refers to a calculating engineer and without complying with the requirements of the Brazilian standard NBR 6118: 2014 with regard to the dimensions and positioning the beam’s web causing loss of strength on them. Based on this fact presented above, it was analyzed in this study the possibility of adding steel fibers to the concrete mass to act as partial reinforcement at the place of the hole. To evaluate the ability of the fibers act as partial reinforcement, experimental trials were conducted, which consisted of molding reinforced concrete beams with equal dimensions where all of them were instrumented with electric strain gages and LVDT displacement meters. The beams had addition of steel fibers at different levels and a transverse opening of the same geometry and position in the web. To conduct a comparative study two beams were analyzed, one of them being a reference without addition of fiber to the concrete mass and without transverse opening in the web. The other without the addition of steel fibers to the concrete mass, with cross opening in the web, however, with an increase in steel armor at the place of opening which was calculated by the struts an tie method. All beams were analyzed for the load capacity of concrete and steel strains plus arrow in the middle of the span. The results showed that the beams with added steel fibers to the concrete mass, in some places the beam, reached to a discrete breaking load improvement in rigidity, which shows that steel fibers were effective in controlling cracking, but the steel fibers alone do not show the same load capacity of the reference beam. It is then suggested to use the technique of adding steel fibers to the concrete mass together with a reinforcement of steel armor at the place of the opening calculated by the struts and tie method.