Dans le domaine du renforcement et/ou de la réparation des structures en béton armé par des matériaux composites à l'aide de la méthode du collage extérieur au moyen d'un adhésif époxy, une des préoccupations de la communauté scientifique est l'intégrité structurelle de ce système dans le cas d'incendie dans lequel la haute température est une caractéristique essentielle et peut atteindre jusqu'à 1200°C. Ce travail de recherche est axé sur le comportement thermomécanique à très haute température des matériaux composites [un composite à base de polymère carbone/ époxy (Carbon Fiber Reinforced Polymer- CFRP), un composite textile/ mortier cimentaire (Textile Reinforced Concrete- TRC) et un adhésif à base d'époxy]. L'évolution des propriétés mécaniques et d'autres aspects mécaniques de ces matériaux composites avec la température a été caractérisée. Une nouvelle procédure expérimentale concernant la mesure de la déformation de l'éprouvette à l'aide du capteur laser est développée et validée. Une étude numérique et expérimentale a été réalisée dans le but de déterminer principalement la température à la rupture des joints « composite/ adhésif/ composite » sous les sollicitations mécaniques et thermiques. L'efficacité de la protection thermique de deux isolants [PROMASPRAY®T (produit commercial de la société PROMAT] et Isolant A (produit développé par le LGCIE site Tusset) a aussi été étudiée dans cette thèse. Enfin, une approche numérique, à l'aide du logiciel ANSYS, est utilisée afin de déterminer, de façon préliminaire et approximative, à l'échelle matériau, les propriétés thermiques des matériaux (composite textile/ mortier cimentaire -TRC et Isolant A) / In the area of the strengthening and/or the reparation of reinforced concrete structures with composites by means of the external bonding method using an epoxy adhesive, one of the preoccupation of the scientific community is the structural integrity of this system in the event of fire in which the high temperature is the essential feature et can reach up to 1200°C. This research focuses on the thermo-mechanical behavior of composite materials [carbon/epoxy adhesive composite (or carbon fiber reinforced polymer (CFRP), textile/cementitious mortar composite (or textile reinforced concrete (TRC)] and an epoxy-based adhesive. The evolution of mechanical properties and other mechanical aspects of these materials with the temperature has been characterized. A new experimental procedure concerning the measurement of sample strain by the laser sensor is developed and validated. An experimental and numerical study has been realized in order to mainly determine the temperature at the failure of "composite/adhesive/composite" joints under thermal and mechanical loadings. The effectiveness of the thermal protection of two insulators [PROMASPRAY®T (a commercial product of the PROMAT company and the insulator A (product developed by the LGCIE site Tuset)] has also been investigated in this PhD thesis. Finally, a numerical approach, using ANSYS software, is used to determine, in the preliminary and approximate way, at material scale, thermal properties of the materials [the textile reinforced concrete (TRC) and the insulator A]

Αντικείμενο της παρούσας Διατριβής Διπλώματος Ειδίκευσης αποτελεί η πειραματική διερεύνηση της αποτελεσματικότητας της περίσφιγξης υποστυλωμάτων οπλισμένου σκυροδέματος με μεγάλο λόγο πλευρών με μανδύες ινοπλισμένων πολυμερών και με μανδύες ινοπλεγμάτων σε ανόργανη μήτρα. Για το σκοπό αυτό διενεργήθηκε εκτενές πειραματικό πρόγραμμα στο Εργαστήριο Μηχανικής και Τεχνολογίας Υλικών του Τμήματος Πολιτικών Μηχανικών του Πανεπιστημίου Πατρών. Το πειραματικό πρόγραμμα περιελάμβανε 18 υποστυλώματα υπό κλίμακα 3/5 ύψους 770 mm τα οποία χωρίστηκαν σε δύο ομάδες, ανάλογα με το λόγο των πλευρών τους (1η ομάδα: με λόγο πλευρών 1:3, 150×450mm, 2η ομάδα: με λόγο πλευρών 1:4, 150×600mm). Δύο από τα υποστυλώματα παρέμειναν χωρίς ενίσχυση και αποτέλεσαν τα δοκίμια αναφοράς για τα ενισχυμένα δοκίμια, τα οποία περισφίχθηκαν με μανδύες ΙΟΠ και ΙΑΜ. Τα συστήματα ενίσχυσης που χρησιμοποιήθηκαν περιελάμβαναν μανδύες ΙΟΠ ινών άνθρακα με μια, δύο ή τρεις στρώσεις, χωρίς ή με αγκύρια ινών άνθρακα μορφής θυσάνου καθώς και μανδύα με δύο στρώσεις περιμετρικά του δοκιμίου και μανδύα μορφής U και αγκύρια ινών. Επιπλέον, εξετάστηκαν και μανδύες με τέσσερεις στρώσεις ινοπλέγματος με ίνες άνθρακα σε ανόργανη μήτρα με και χωρίς αγκύρια ινών άνθρακα μορφής θυσάνου εμποτισμένων σε εποξειδική ρητίνη. Η παρούσα διατριβή αποτελείται από οχτώ κεφάλαια, κάθε ένα από τα οποία διαχωρίζεται σε κατάλληλες ενότητες, υποενότητες και παραγράφους. Στο πρώτο και δεύτερο Κεφάλαιο γίνεται μια εισαγωγή στα σύνθετα υλικά με περιγραφή των επιμέρους συστατικών τους, των χαρακτηριστικών ιδιοτήτων τους καθώς και των παραγόντων που επηρεάζουν τη συμπεριφορά τους. Στο τρίτο Κεφάλαιο πραγματοποιείται βιβλιογραφική ανασκόπηση για την περίσφιγξη υποστυλωμάτων, όπου αρχικά περιγράφονται συμβατικές τεχνικές ενίσχυσης που περιλαμβάνουν νέους μανδύες οπλισμένου σκυροδέματος, μεταλλικά ελάσματα, μεταλλικούς μανδύες κλπ και στη συνέχεια περιγράφονται τεχνικές ενίσχυσης με σύνθετα υλικά. Περιγράφεται ο καταστατικός νόμος που διέπει τη συμπεριφορά του περισφιγμένου με μανδύες σύνθετων υλικών σκυροδέματος και παρουσιάζονται συνοπτικά πειραματικές μελέτες από τη διεθνή βιβλιογραφία που αφορούν τη διερεύνηση της αποτελεσματικότητας της μεθόδου ενίσχυσης µε ΙΟΠ σε υποστυλώματα με μικρό και μεγάλο λόγο πλευρών. Τέλος, το κεφάλαιο ολοκληρώνεται με συνοπτική αναφορά πειραματικών μελετών σε δοκίμια περισφιγμένα με μανδύες σε ανόργανη μήτρα. Στο τέταρτο Κεφάλαιο παρουσιάζεται η πειραματική διαδικασία που ακολουθήθηκε για την κατασκευή των δοκιμίων καθώς και οι παράμετροι που διερευνήθηκαν. Συγκεκριμένα, περιγράφονται όλα τα υλικά που χρησιμοποιήθηκαν, τα διάφορα συστήματα ενίσχυσης που εφαρμόστηκαν καθώς και οι διαδικασίες που ακολουθήθηκαν από την προετοιμασία των δοκιμίων μέχρι την ενίσχυσής τους. Στο τέλος του κεφαλαίου γίνεται μια σύντομη περιγραφή της πειραματικής διάταξης και του επιμέρους μηχανικού εξοπλισμού που χρησιμοποιήθηκε για την υλοποίηση των δοκιμών μονοαξονικής θλίψης. Στο πέμπτο Κεφάλαιο παρουσιάζονται διεξοδικά τα αποτελέσματα όλων των δοκιμίων που συμμετείχαν στο πειραματικό πρόγραμμα. Πιο συγκεκριμένα, περιγράφονται οι τρόποι αστοχίας των δοκιμίων συνοδεία φωτογραφικού υλικού και παρατίθενται οι καμπύλες τάσης – παραμόρφωσης τόσο για κάθε ένα ξεχωριστά όσο και συγκεντρωτικά για κάθε ομάδα. Στο έκτο Κεφάλαιο γίνεται σύγκριση των αποτελεσμάτων όλων των πειραμάτων που διεξήχθησαν στο Εργαστήριο Μηχανικής και Τεχνολογίας Υλικών σε υποστυλώματα με λόγους πλευρών 1:3 και 1:4 περισφιγμένα με μανδύες ΙΟΠ και ΙΑΜ προκειμένου να εξαχθούν γενικότερα συμπεράσματα πάνω στην επίδραση του υλικού της μήτρας, του αριθμού των στρώσεων και της ύπαρξης αγκυρίων στην αποτελεσματικότητα της περίσφιγξης. Στο έβδομο Κεφάλαιο παρουσιάζονται τα αποτελέσματα από ένα αναλυτικό προσομοίωμα που χρησιμοποιήθηκε για την πρόβλεψη του μέγιστου θλιπτικού φορτίου και της οριακής παραμόρφωσης αστοχίας των περισφιγμένων με μανδύες ΙΟΠ και ΙΑΜ. Επιπλέον, γίνεται σύγκριση των αποτελεσμάτων του αναλυτικού προσομοιώματος με τα πειραματικά δεδομένα και εξετάζεται κατά πόσο αυτό το προσομοίωμα μπορεί να χρησιμοποιείται για υποστυλώματα με μεγάλο λόγο πλευρών, μετά από αλλαγή κάποιων παραμέτρων του. Στο όγδοο και τελευταίο Κεφάλαιο, παρουσιάζονται συνοπτικά τα τελικά συμπεράσματα που προέκυψαν αρχικά από την πειραματική διαδικασία και στη συνέχεια από τη χρήση του αναλυτικού προσομοιώματος. Τέλος, γίνονται και μερικές προτάσεις για περαιτέρω έρευνα πάνω σε υποστυλώματα με μεγάλο λόγο πλευρών. / The present study investigates experimentally the effectiveness of the confinement of reinforced concrete (RC) columns with high aspect ratio (wall-like RC columns) retrofitted either with fiber-reinforced polymer (FRP) or with textile-reinforced mortars (TRM) jackets. For this purpose an extensive experimental program was conducted at the Structural Materials Laboratory of the Civil Engineering Department at the University of Patras. A total of 18 identical rectangular reinforced concrete columns were constructed in a scale of 3/5 and 770 mm height so that the slenderness effects could be eliminated and tested in uniaxial compression. The columns were separated in two groups according to their aspect ratio; the first group consisted of seven RC column specimens with cross section dimensions 150mm by 450mm and an aspect ratio equal to 3, and the second group consisted of eleven RC column specimens with cross section dimensions 150mm by 600mm and an aspect ratio equal to 4. To facilitate FRP and TRM wrapping, the four corners were chamfered with a radius equal to 20mm. A number of parameters were investigated such as the kind of the matrix material (organic and inorganic), the number of layers of the jackets (1, 2, 3 and 4), the role of different cross section aspect ratios (3 and 4), the effectiveness of spike anchors (resin-impregnated fiber rovings) and local strengthening with U shape jacketing placed at the smaller sides of the columns. The first chapter provides general information on FRP materials describing their individual components, their characteristic properties, the factors affecting their behavior as well as the basic techniques for their application. The second chapter describes the composite materials in inorganic matrix (TRM) and presents a comparison between the two composite material strengthening systems. In the third chapter a brief literature review is provided about the confinement of columns with conventional techniques (e.g. steel plating, steel jacketing, RC jacketing) as well as with composite materials. The constitutional law of confined concrete with jackets of composite materials is described. Furthermore some experimental studies from the international literature are presented concerning the effectiveness of the confinement with FRP jackets of columns with small and high aspect ratio. Finally, the chapter concludes with a brief reference to experimental studies on specimens confined with jackets in inorganic matrix (TRM jackets). The fourth chapter presents the procedure for constructing and retrofitting the specimens including the materials used (carbon fiber fabric and textile, carbon fiber spike anchors, epoxy resin, inorganic matrix) as well as the equipment used for uniaxial compression tests. In the fifth chapter the results for each specimen are given presenting their failure mode and the corresponding load - displacement curve. In the following chapter the results for each group are compared in order to establish general conclusions on the effect of the kind of the matrix material, the number of layers and the existence of FRP anchors in confinement of wall-like RC columns. The seventh chapter presents the results of an analytical model used to predict the maximum compressive load and the ultimate deformation of specimens confined with FRP or TRM jackets. A comparison between the experimental and the analytical results is made and it is examined whether this model can be used for columns with high aspect ratio after modifying some of the parameters. The eighth chapter summarises the most important conclusions of all investigations carried out by the present project for both the experimental procedure and the analytical model. Finally, some suggestions for further research on columns with high aspect ratio are listed.

A study was undertaken to determine if light-weighting orbital launch vehicles (rockets) improves lifetime environmental impacts of the vehicle. Light-weighting is performed by a material substitution where metal structures in the rocket are replaced with carbon fiber reinforced polymers (CFRP’s). It is uncertain whether light-weighting the rocket in the same way as traditional vehicles are light-weighted would provide similar environmental benefits. Furthermore, the rocket system is significantly different from traditional vehicles and undergoes an atypical lifecycle, making analysis non-trivial. Seventy rocket configurations were sized using a Parametric Rocket Sizing Model (PRSM) which was developed for this research. Four different propellant options, three staging options, and eighteen different lift capacities were considered. Each of these seventy rockets did not include CFRP’s, thus establishing a baseline. The seventy rockets were then light-weighted with CFRP’s, making a total of seventy pairs of rockets. An environmental Life Cycle Assessment (LCA) was performed on each of the rockets to determine lifetime environmental impacts. During the Life Cycle Inventory (LCI), a Carbon Fiber Production Model was developed to determine the environmental burdens of carbon fiber production and to address issues identified with carbon fiber’s embodied burdens. The results of the LCA were compared across all rockets to determine what effects light-weighting had on environmental impact. The final conclusion is that light-weighting reduces lifetime environmental impacts of Liquid Oxygen-Rocket Propellant 1 and Nitrogen Tetroxide-Unsymmetrical Dimethylhydrazine rockets, while it likely benefits Liquid Oxygen-Liquid Hydrogen rockets. Light-weighting increases lifetime environmental impacts of Solid Propellant rockets.

Le but de ce travail est la caractérisation du comportement au délaminage des composites stratifiés en mode mixte I+II+III, en se focalisant en particulier sur le verrou scientifique que représente le mode III pur. Cette thèse repose sur un travail à la fois expérimental et numérique, validant numériquement les tests existants et ceux développés. La mise en perspective des résultats obtenus a permis, d'un coté, de mieux appréhender l'importance de la distribution des taux de restitution d'énergie, GI, GII et GIII, le long du front de fissure sur le la détermination de la ténacité du composite et d'un autre coté, de proposer et d'améliorer les méthodes de caractérisation. Avant d'évoquer le délaminage en mode mixte, nos efforts se sont d'abord concentrés sur la caractérisation du délaminage en mode III pur. Deux essais de type " Edge Crack Torsion " (ECT) disponibles dans la littérature ont été réalisés. La distribution de GIII le long du front de fissure a été déterminée par la méthode des éléments finis (MEF) en utilisant la technique de fermeture virtuelle de fissure (VCCT). La capacité de ces tests est compromise par : 1. La participation du mode II non nul ; 2. La forte variation de GIII près des bords de l'éprouvette. Ces problèmes rendent la détermination de la ténacité en mode III pur, GIIIC, difficile et imprécise. Par la suite, un nouveau test a été proposé, nommé "Edge Ring Crack Torsion" test (ERCT ou ERT-III). Il s'appuie sur une éprouvette possédant une fissure de front circulaire, l'absence d'extrémités sur le front de fissure permet de supprimer les effets de bords. Après l'optimisation et la modification de la géométrie du dispositif dans le test ERCT original, GIII le long du front de fissure reste presque constant avec très peu de modes parasites. La formule proposée par Tada est appliquée pour déterminer GIIIC. Il est démontré qu'en général, si la variation de GIII est faible le long du front de fissure, la ténacité déterminée par une solution " closed-form " concorde bien avec celle obtenue numériquement. En fait, la répartition de GIII peut être influencée par divers facteurs, tels que la nature des stratifiés, la géométrie du dispositif expérimental et la géométrie des éprouvettes. L'interaction de ces facteurs a été aussi abordée dans cette étude. En outre, une étude numérique de sensibilité aux défauts a permis de vérifier la robustesse de l'essai proposé vis-à-vis de différents défauts qui sont inhérent à tout travail expérimental. Enfin, une géométrie d'éprouvette optimisée est donnée avec une méthodologie permettant de réduire les fluctuations de GIII. L'utilisation de l'éprouvette ERC a été généralisée à la caractérisation du délaminage pour deux autres modes purs : l'essai de traction permet de solliciter ERC en mode I pur et celui de flexion sollicite ERC en mode II pur, nommé ERCTE ou ERC-I et ERCF ou ERC-II, respectivement. Les avantages du test ERCT sont bien conservés. La réalisation des essais ERC-I, ERC-II et ERC-III permet de mesurer la ténacité de chacun des trois modes purs sur des éprouvettes ayant la même géométrie. Finalement, nous avons étudié numériquement la faisabilité de réaliser les essais de délaminage en mode mixte I + II, I + III et I + II + III sur les éprouvettes ERC. Il s'avère que le rapport modal en mode mixte peut être obtenu dans une large gamme en faisant varier la géométrie de l'éprouvette et en combinant les modes de chargement. Aucun mode indésirable n'est présent lors des essais en mode mixte I+II ou en mode mixte I+III. Cependant la distribution de GI, GII et GIII ne sont pas complètement uniforme, mais sa variation reste assez petite. En conclusion, les tests ERC proposés dans cette étude sont prometteurs pour la caractérisation du comportement au délaminage en mode mixte des composites. Il serait possible, dans un avenir proche, de proposer un critère de délaminage en mode mixte I+II+III basé sur une étude utilisant des essais sur éprouvettes ERC. / The aim of this research work is to characterize the delamination behavior of laminate composite materials under the three pure modes and mixed modes, focusing especially on the complex issue of mode III. Both experimental and numerical works were performed, validating the existing and new testing methods. Correlation between the results obtained aims, on the one hand to better understand the distribution of strain energy release rates (GI, GII, GIII) along the crack front; on the other hand, to propose and improve testing methods, and to propose and validate simple approaches for determination of delamination toughness. Pure mode III testing methods are studied. Firstly, two kinds of Edge Crack Torsion tests were carried out, the distribution of GIII along the crack front were determined by finite element analysis (FEA) using virtual crack closure technique (VCCT). The performances of these tests are compromised by the drawbacks: (1) A participation of mode II component cannot be completely eliminated; (2) The distribution of GIII along the crack front is not uniform especially near the sides. After a study of existing tests, a novel mode III testing method was proposed, named Edge Ring Crack Torsion test (ERCT or ERC-III later). In the ERC specimen, the total absence of sides in the circular crack front leads to no edge effects. As a result, pure mode III delamination is achieved and the distribution of GIII along the crack front is quite uniform. In fact, the values of GIII along the crack front are nearly constant after optimizing and modifying the geometry of device in the original ERCT test. A closed-form solution proposed by Tada is applied to determine mode III delamination toughness. In ERCT test, the results calculated by Tada formula agree well with the ones calculated by VCCT when the distribution of GIII is relatively uniform. Actually, a numerical study shows that the distribution of GIII can be affected by different factors related to the nature of laminates tested, the geometry of test device and the geometry of the specimens. The interactive effect of above factors was also discussed in this study. In order to understand the influence of potential defaults on the performance of ERCT test, sensitivity study has been performed on the relative position of the crack front, the circularity of the crack front and the specimen shape. Optimum specimen's relative pre-crack geometry is given and a method for reducing the variation is provided. Then the application of ERC specimen was generalized to other pure delamination modes characterization. Pure mode I can be realized if ERC specimens are loaded in tension, named ERCTE or ERC-I, so can pure mode II if ERC specimens are loaded in flexion, named ERCF or ERC-II. The distribution of the strain energy release rates was also evaluated by FEA using VCCT. These tests keep most advantages of ERC-III test. Pure mode I and pure mode II delamination are achieved respectively and the distribution of GI or GII along the crack front is quite uniform. The realization of ERC-I, ERC-II and ERC-III allows to measure the toughness of each of three pure modes without any interference from geometry of specimens. Finally, we have studied numerically the feasibility to realize the delamination tests in mixed mode I+II, I+III and I+II+III by using ERC specimen. Firstly, the mixed mode ratio can be obtained in a large range by varying the geometry of the specimen and by combining loading modes. Secondly, no unwanted mode is presented for mixed mode I+II and mixed mode I+III; Thirdly, the distribution of strain energy release rates are not completely uniform but its variation is small enough to be accepted. In conclusion, ERC tests are promising testing methods for characterization of mixed mode delamination behavior. It will be possible to propose a mixed mode I+II+III delamination criterion based on the investigation by ERC tests in a close future.

The content of the diploma thesis is evaluation of the usability of carbon composites in the space industry. The aim of this work is to assess whether carbon composites can find application in mechanical systems of passive thermal protection of artificial objects. Model examples demonstrate the principle of operation of selected passive thermal protection. The evaluation is realized based on the results of thermal analysis. Analytical formulas from field theory of heat transfer are used as a calculation method. The diploma thesis consists from two parts. The theoretical part briefly describes the mechanisms of heat transfer, selected types of passive thermal protection and properties and applications of carbon composites. The practical part consists of the assignment, calculation and evaluation of three examples. The results show that carbon composites can compete with commonly used materials for specific requirements.

The diploma thesis deals with the study of bent FRP reinforcements with the main focus on the methods of production of bent FRP reinforcement, examples of their application in structures. The work also mentions the effects of aggressive environments on the durability of FRP. In the practical part, a search of the possibilities of testing the properties of bent FRP reinforcement. Subsequently, an experiment is designed and performed to monitor changes in the properties of straight and bent FRP reinforcement exposed to the alkaline environment and water at 20 °C and 40 °C. Finally, the evaluation of changes in mechanical properties and observation of reinforcements using optical and scanning electron microscopy is performed.

No description available.

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[pt] O presente trabalho tem como objetivo analisar a utilização de barras constituídas por material compósito para atuarem como reforço de vigas de concreto submetidas à flexão. As barras analisadas são constituídas por polímero reforçado com fibras de carbono (PRFC), material este que apresenta comportamento linear elástico até a ruptura. Este material possui algumas vantagens em relação ao aço, como por exemplo, resistência à tração consideravelmente superior além de não ser suscetível ao fenômeno da corrosão ocasionada por intempéries ambientais. Durante o desenvolvimento do trabalho foi obtido um artigo o qual demonstra resultados de ensaios de laboratório nos quais os autores utilizaram vigas de concreto submetidas a ensaio de flexão por quatro pontos e reforçadas com barras de PRFC. Neste trabalho, o mesmo ensaio foi simulado no software Atena, programa este que realiza análise não linear para estruturas de concreto, considerando a fissuração deste material. Os resultados obtidos pelo software apresentaram consistência com os resultados registrados em laboratório pelos autores. Foi ainda analisada uma viga contínua de concreto submetida a um carregamento uniformemente distribuído. Essa viga foi reforçada com barras de mesmo diâmetro alterando-se apenas o material dessas barras (aço e PRFC). Dessa maneira, foi analisado o valor de carregamento que ocasiona a ruptura da viga. Foram constatadas duas importantes desvantagens das barras de PRFC em relação ao aço. A primeira desvantagem está no custo superior ao aço e por apresentar comportamento elástico até o rompimento, o PRFC não confere à estrutura de concreto uma ruptura dúctil. Os objetivos deste trabalho foram cumpridos e ao final são propostos novos estudos a serem realizados sobre o tema. / [en] The aim of the present work is to analyze the use of bars made of composite material to act as reinforcement for concrete beams subjected to bending. The analyzed bars are constituted by polymer reinforced with carbon fibers (PRFC), a material that presents linear elastic behavior until rupture. This material has some advantages in relation to steel, such as considerably higher tensile strength in addition to not being susceptible to the phenomenon of corrosion caused by environmental conditions. During the development of the work, an article was obtained which demonstrates results of laboratory tests in which the authors used concrete beams subjected to flexion testing by four points and reinforced with PRFC bars. In this work, the same test was simulated in the Atena software, a program that performs non-linear analysis for concrete structures, considering the cracking of this material. The results obtained by the software were consistent with the results recorded in the laboratory by the authors. It was also analyzed a continuous concrete beam subjected to a uniformly distributed load. This beam was reinforced with bars of the same diameter, changing only the material of these bars (steel and PRFC. In this way, the loading value that causes the beam to break when it is reinforced with steel bars and when it is reinforced with PRFC bars of the same diameter was analyzed. Two important disadvantages of PRFC bars in relation to steel have been noted. Due to its elastic behavior until breaking, this composite material does not give the concrete structure a ductile rupture. In addition, its cost is considerably higher than steel bars, since no suppliers of this type of reinforcement have been identified in Brazil, thus increasing the cost to purchase this product. The objectives of this work were accomplished and, in the end, new studies are proposed to be carried out on the theme.

[pt] Este trabalho tem como objetivo avaliar a resistência à força cortante de vigas de concreto reforçado com barras de fibras de vidro e investigar a contribuição dos diferentes mecanismos de transferência do esforço cortante para a resistência final da viga. Um programa experimental foi conduzido, incluindo ensaios para: caracterização do material, para avaliar o efeito de pino, para avaliar o engrenamento dos agregados e, por fim, ensaios de flexão de quatro pontos em vigas. Diferentes parâmetros foram investigados, como a quantidade de barras longitudinais para o efeito de pino, dimensão máxima do agregado graúdo para engrenamento dos agregados e a presença de estribos para os ensaios de vigas. O monitoramento do desenvolvimento da fissura crítica foi realizado com auxílio de correlação de imagem digital (digital image correlation, DIC, em inglês). Os resultados mostraram que não foi evidenciada diferença no comportamento de efeito de pino e de engrenamento dos agregados através dos ensaios realizados. Para os ensaios de vigas, observou-se que todos os espécimes apresentaram ruptura por tração da diagonal crítica e, para vigas sem estribos, a ação do efeito de pino pareceu contribuir significativamente para a resistência ao cisalhamento após a fissura, quando a carga diminui e as deflexões aumentam, resultado do menor engrenamento dos agregados à medida que a fissura se abre. Foi observado que a presença de estribos aumentou em até três vezes a resistência ao cortante das vigas ensaiadas e que houve ruptura do estribo na parte da dobra. / [en] This work aims to evaluate the shear strength of reinforced concrete beams with glass fiber reinforced polymer bars and to investigate qualitatively the contribution of the different shear transfer mechanisms to the final strength of the beam. An experimental program was conducted, including material characterization, dowel action tests, push-off tests, and finally, four-point bending tests on beams. Different parameters were investigated, such as the number of longitudinal bars for dowel action effect, maximum size of the coarse aggregate for aggregate interlock and the presence of stirrups for the beam tests. The monitoring of the development of the critical crack was performed with the aid of digital image correlation (DIC). The results showed that there was no difference in the behavior of the dowel action effect and the aggregate interlock through the tests performed. For beam tests, it was observed that all the specimens exhibited a concrete diagonal tension failure and for beams without stirrups, dowel action seemed to provide significant contribution to the shear strength after the crack, when the load reduces and the deflections increases, resulting from the loss of aggregate interlock as the crack opens. It was also observed that the presence of stirrups increased up to three times the shear strength of the beams tested and that there was rupture of the stirrup at the bent region.