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1
Hamed, Sarah. "Shear Contribution of Basalt Fiber-Reinforced Concrete Reinforced with Basalt Fiber-Reinforced Polymer Bars". Master's thesis, Université Laval, 2019. http://hdl.handle.net/20.500.11794/34008.
Testo completoAbstract (sommario):
Cette étude évalue expérimentalement et analytiquement le comportement au cisaillement des poutres en béton renforcé de fibres de basalte (BRFB) renforcées longitudinalement avec des barres en polymère renforcé de fibres de basalte (PRFB). Un nouveau type de macro-fibres de basalte a été ajouté au mélange de béton pour produire le mélange de BRFB. Quatorze poutres (152 x 254 x 2000 mm) sans armature transversale ajouté ont été testées sous une configuration de chargement à quatre points jusqu'à la défaillance. Les poutres ont été regroupés en deux groupes A et B en fonction de leurs rapports portée de cisaillement/profondeur, a/d. Les poutres du groupe A avaient un rapport a/d de 3,3 tandis que celles du groupe B avaient un rapport a/d de 2,5. Outre les rapports a/d, les paramètres étudiés comprenaient la fraction volumique des fibres ajoutées (0,75 et 1,5%) et le taux de renforcement longitudinal des barres en PRFB (0,31, 0,48, 0,69, 1,05 et 1,52). Les résultats des tests ont montré que l’ajout de macro-fibres de basalte au mélange de béton améliorait sa résistance à la compression. Une relation directe entre la fraction volumique de fibres, Vf, et la résistance à la compression a été observée. Les cylindres de béton coulés avec une Vf de 0,75 et 1,5% ont entraîné une augmentation de 11 et 30% de leur résistance à la compression par rapport à ceux moulés en béton standard (sans fibres), respectivement. L'ajout de fibres a également amélioré le mode de défaillance des poutres BRFB-PRFB que les poutres de contrôle coulées avec du béton standard. L’augmentation de la fraction volumique des fibres a réduit l’espacement entre les fissures et gêné sa propagation. Une amélioration significative des capacités de cisaillement des poutres testées a également été observée lorsque les macro-fibres de basalte ont été ajoutées à une fraction volumique Vf de 0,75. L'augmentation moyenne des capacités de cisaillement des poutres des groupes A et B, ayant les mêmes taux de renforcement, était respectivement de 45 et 44%, par rapport à celles des poutres de contrôle. Il a été noté que le gain en capacité de cisaillement des poutres testées était plus prononcé dans les poutres avec a/d= 3,3 que dans les poutres avec a/d = 2,5 lorsque le taux de renforcement augmentait. Au cours de la phase analytique, plusieurs modèles ont été utilisés pour prédire les capacités de cisaillement des poutres. Tous les modèles disponibles surestimaient les capacités de cisaillement des poutres testées avec un rapport moyen Vpre/Vexp compris entre 1,29 et 2,64. Cette observation a montré que ces modèles ne permettaient pas de prédire les capacités de cisaillement des poutres BRFB-PRFB. Un nouveau modèle modifié intégrant le type de renforcement longitudinal, le type de béton fibré et la densité du béton est proposé. Le modèle d’Ashour et al. -A (1992) a été modifié en utilisant un facteur égal au rapport entre le module des barres en PRF, Ef, et celui des barres en acier Es. Ce rapport prend en compte la différence de propriétés entre les barres en PRF et celles en acier, négligée par les modèles précédents. Le modèle proposé prédit bien les capacités de cisaillement des poutres BRFB-PRFB testées dans la présente étude avec des rapports moyens Vpre/Vexp = 0,82 ± 0,12 et 0,80 ± 0,01 pour les poutres des groupes A et B, respectivement. Les capacités de cisaillement des poutres en béton léger testées par Abbadi (2018) ont été prédites avec un rapport moyen Vpre/Vexp = 0,77 ± 0,05. De plus, le modèle prédit bien les capacités de cisaillement des poutres coulées avec du béton qui contient des fibres en acier testées par Awadallah et al. (2014) avec un rapport moyen Vpre/Vexp = 0,89 ± 0,07. Cela indique la large gamme d'applicabilité du modèle proposé. Cependant, il est recommandé d’évaluer le modèle proposé sur un ensemble de données plus large que celui présenté dans cette étude.This study evaluates both experimentally and analytically the shear behavior of basalt fiber-reinforced concrete (BFRC) beams reinforced longitudinally with basalt fiber-reinforced polymer (BFRP) bars. A new type of basalt macro-fibers was added to the concrete mix to produce the BFRC mix. Fourteen beams (152 x 254 x 2000 mm) with no transverse reinforcement provided were tested under four-point loading configuration until failure occurred. The beams were grouped in two groups A and B depending on their span-to-depth ratios, a/d. Beams of group A had a ratio a/d of 3.3 while those of group B had a ratio a/d of 2.5. Besides the span-to-depth ratios, the parameters investigated included the volume fraction of the fibers added (0.75 and 1.5%) and the longitudinal reinforcement ratio of the BFRP reinforcing bars (0.31, 0.48, 0.69, 1.05, and 1.52). The test results showed that the addition of basalt macro-fibers to the concrete mix enhanced its compressive strength. A direct relationship between the fiber volume fraction, Vf, and the compressive strength was observed. Concrete cylinders cast with Vf of 0.75 and 1.5% yielded 11 and 30% increase in their compressive strengths over those cast with plain concrete, respectively. The addition of fibers greatly enhanced the shear capacity of BFRC-BFRP beams compared to their control beams cast with plain concrete. The increase of the fiber volume fraction decreased the spacing between cracks and hindered its propagation. A significant enhancement in the shear capacities of the tested beams was also observed when the basalt macro-fibers were added at a volume fraction Vf of 0.75%. The average increase in the shear capacities of beams of group A and B, having the same reinforcement ratios, were 45 and 44%, respectively, in comparison with those of the control beams. It was noticed that the gain in shear capacities of the tested beams was more pronounced in beams with a/d = 3.3 than in beams with a/d = 2.5 when the reinforcement ratio increased. In the analytical phase, several models were used to predict the shear capacities of the beams. All of the available models overestimated the shear capacities of the tested beams with average ratio Vpre/Vexp ranging between 1.29 to 2.64. This finding indicated that these models were not suitable to predict the shear capacities of the BFRC-BFRP beams. A new modified model incorporating the type of the longitudinal reinforcement, the type of FRC used, and the density of concrete is proposed. The model of Ashour et al. –A (1992) was calibrated using a calibration factor equal to the ratio of modulus of FRP bars used, Ef, and that of steel bars, Es. This ratio takes into consideration the difference in properties between the FRP and steel bars, which was overlooked by previous models. The proposed model predicted well the shear capacities of the BFRC-BFRP beams tested in the current study with average ratios Vpre/Vexp = 0.82 ± 0.12 and 0.80 ± 0.01 for beams of groups A and B, respectively. The shear capacities of the lightweight concrete beams tested by Abbadi (2018) were predicted with an average ratio Vpre/Vexp = 0.77 ± 0.05. Moreover, the model predicted well the shear capacities of the SFRC beams reinforced with BFRP bars tested by Awadallah et al. (2014) with an average ratio Vpre/Vexp = 0.89 ± 0.07. This indicates the wide range of applicability of the proposed model. However, it is recommended that the proposed model be assessed on larger set of data than that presented in this study
2
Breña, Sergio F. "Strengthening reinforced concrete bridges using carbon fiber reinforced polymer composites /". Full text (PDF) from UMI/Dissertation Abstracts International, 2000. http://wwwlib.umi.com/cr/utexas/fullcit?p3004223.
Testo completo
3
Hosin, Alyass Azzat. "Fiber reinforced coal combustion products concrete /". Available to subscribers only, 2007. http://proquest.umi.com/pqdweb?did=1342743231&sid=11&Fmt=2&clientId=1509&RQT=309&VName=PQD.
Testo completo
4
Valle, Mariano Oñar. "Shear transfer in fiber reinforced concrete". Thesis, Massachusetts Institute of Technology, 1991. http://hdl.handle.net/1721.1/72749.
Testo completo
5
Al-lami, Karrar Ali. "Experimental Investigation of Fiber Reinforced Concrete Beams". PDXScholar, 2015. https://pdxscholar.library.pdx.edu/open_access_etds/2296.
Testo completoAbstract (sommario):
Shear strength of fiber reinforced concrete beams was studied in this research project. Three types of fibers were examined: hooked-end steel fiber, crimped-steel fiber, and crimped-monofilament polypropylene fibers. The experimental program included five beam specimens. Two of the beams were control specimens in which one was reinforced with minimum shear reinforcement according to ACI 318, while the other one did not have any shear reinforcement. Each one of the other three specimens was reinforced with one of the above mentioned fibers by 1% volumetric ratio. In addition to the beam specimens, three prisms were also made for each type fiber to determine their toughness.
The aim of this research was to investigate the following questions for medium-high concrete strength 1) to evaluate the effectiveness of each type of fibers on the shear strength, 2) to investigate the shear strength, toughness, crack patterns and near ultimate load crack width of each beam, and 3) to determine if using 1% volumetric ratio of fibers as shear reinforcement in beams would provide adequate strength and stiffness properties comparable to reinforcing steel used as minimum shear reinforcement.
The results showed that all three types of fibers increased the shear capacity of the beam specimens more than the beam reinforced with minimum shear reinforcement. Moreover, some of the fibers used could shift the type of failure from a pure shear failure to a combined flexural-shear or pure flexural failure.
6
Hearing, Brian Phillip 1972. "Delamination in reinforced concrete retrofitted with fiber reinforced plastics". Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/9141.
Testo completoAbstract (sommario):
Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2000.Includes bibliographical references (leaves 251-269).
The addition of fiber-reinforced plastic (FRP) laminates bonded to the tension face of concrete members is becoming an attractive solution to the rehabilitation and retrofit of damaged structural systems. Flexural strength is enhanced with this method but the failure behavior of the system can become more brittle, often involving delamination of the composite. This study investigates failure modes including delamination with the use of fiber reinforced plastics to rehabilitate various concrete structures. The focus is on delamination and its causes, specifically in the presence of existing cracks in the retrofitted concrete system. First, delamination processes in FRP retrofitted concrete systems are studied through combined experimental and analytical procedures. The delamination process is observed to initiate in the concrete substrate with micro cracks that coalesce into an unstable macro crack at failure. This macroscopic behavior is modeled through a finite element procedure with a smeared crack approach, which is found to be limited in the ability to represent the stress intensity at the delamination tip. For this reason it is shown that interfacial fracture mechanics can be used to describe the bimaterial elasticity and complex stress intensity at the delamination tip and provide a criterion governing the propagation of delamination using energy methods. Then, peeling processes occurring at existing cracks in the retrofitted system are studied through fracture mechanics based experimental and analytical procedures. An experimental program involving specialized shear notch specimens demonstrates that the location of the notch and laminate development length are influential on the shear crack peeling process. A finite element procedure is used to evaluate the crack driving forces applied at the shear notch crack mouth, and the fracture analysis is extended to evaluate initiation of peeling at the shear notch scenario. Finally, delamination failures in FRP retrofitted reinforced concrete beams representing "real-life" retrofit scenarios are investigated. An experimental and analytical program is conducted to investigate influences on the failure processes. The application of the fracture based peeling analysis to a quantitative design procedure is investigated, and a computational design aid to assist the iterative design procedure is developed.
by Brian Phillip Hearing.
Ph.D.
7
Altoubat, Salah Ahmed. "Early age stresses and creep-shrinkage interaction of restrained concrete". Full text available online (restricted access), 2000. http://images.lib.monash.edu.au/ts/theses/Altoubat.pdf.
Testo completo
8
Paschalis, Spyridon A. "Strengthening of existing reinforced concrete structures using ultra high performance fiber reinforced concrete". Thesis, University of Brighton, 2017. https://research.brighton.ac.uk/en/studentTheses/c07ce9c7-5880-4108-a0f2-68bf6ea50dd5.
Testo completoAbstract (sommario):
Most of the new Reinforced Concrete (RC) structures which are built nowadays have a high safety level. Nevertheless, we cannot claim the same for structures built in the past. Many of these were designed without any regulations, or are based on those which have proved to be inadequate. Additionally, it seems that many old structures have reached the end of their service life and, in many cases, were designed to carry loads significantly lower than the current needs specify. Therefore, the structural evaluation and intervention are considered necessary, so they can meet the same requirements as the structures which are built today. Existing techniques for the strengthening and retrofitting of RC structures present crucial disadvantages which are mainly related to the ease of application, the high cost, the time it takes to be applied, the relocation of the tenants during the application of the technique and the poor performance. Research is now focused on new techniques which combine strength, cost effectiveness and ease of application. The superior mechanical properties of Ultra High Performance Fiber Reinforced Concrete (UHPFRC) compared to conventional concrete, together with the ease of preparation and application of the material, make the application of UHPFRC in the field of strengthening of RC structures attractive. The present research aims to investigate the effectiveness of UHPFRC as a strengthening material, and to examine if the material is able to increase the load carrying capacity of existing RC elements. This has been achieved through an extensive experimental and numerical investigation. The first part of the present research is focused on the experimental investigation of the properties of the material which are missing from the literature and the development of a mixture design which can be used for strengthening applications. The second part is focused on the realistic application of the material for the strengthening of existing RC elements using different strengthening configurations. Finally, in the last part, certain significant parameters of the examined technique, which are mainly related to the design of the technique, are investigated numerically. From the experimental and numerical investigation of the present research it was clear that UHPFRC is a material with enhanced properties and the strengthening with UHPFRC is a well promising technique. Therefore, in all the examined cases, the performance of the strengthened elements was improved. Finally, an important finding of the present research was that the bonding between UHPFRC and concrete is effective with low values of slip at the interface.
9
Elsaigh, W. A. "Steel fiber reinforced concrete ground slabs : a comparative evaluation of plain and steel fiber reinforced concrete ground slabs". Pretoria : [s.n.], 2006. http://upetd.up.ac.za/thesis/available/etd-03032006-154355/.
Testo completo
10
Scott, David Edward. "Characterization of fibrillated polypropylene and recycled waste fiber reinforced concrete". Thesis, Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/19543.
Testo completo
11
Abbadi, Abdulrahman. "Shear contribution of fiber-reinforced lightweight concrete (FRLWC) reinforced with basalt fiber reinforced Polymer (BFRP) bars". Master's thesis, Université Laval, 2018. http://hdl.handle.net/20.500.11794/31848.
Testo completoAbstract (sommario):
Cette étude porte sur le comportement au cisaillement des poutres en béton léger fibré et renforcées par des barres de polymère renforcé de fibres de basalte (PRFB). Dix poutres (150x250x2400 mm) coulées avec du béton fibré ou non-fibré ont été testées en flexion. Deux poutres ont été coulées sans fibres (poutres contrôles) tandis que les huit autres poutres ont été coulées avec du béton contenant des différents types et pourcentages de fibres. Les paramètres étudiés comprenaient le type de fibres ajoutés au béton (fibres de basalte, de polypropylène et d’acier), la fraction volumique des fibres (0, 0,5 et 1,0%) et les taux de renforcement des barres de PRFB (0,95 et 1,37%). Une comparaison entre les résultats expérimentaux et les modèles analytiques actuellement disponibles dans la littérature a été réalisée pour évaluer l'applicabilité de tels modèles pour prévoir la capacité des poutres testées en cisaillement. Les résultats de la présente étude indiquent que la géométrie des fibres joue un rôle important dans l'augmentation du nombre de fissures que celles observées dans les poutres contrôles. L'ajout de fibres a entraîné une défaillance plus ductile et le taux d'ouverture des fissures était retardé. La largeur de la fissure a diminué avec l'augmentation des ratios de renforcement longitudinal et des fractions volumiques des fibres. L'augmentation du taux de renforcement longitudinal a entraîné une rigidité plus élevée et a diminué les flèches à tous les stades du chargement. Les poutres coulées avec 1% de fibres de basalte, de polypropylène et d'acier ont montré une augmentation dans leurs capacités de cisaillement par rapport aux poutres contrôles d'environ 11, 16 et 63%, respectivement. Le type de fibres affectait de manière significative le gain dans les capacités de cisaillement des poutres, ce qui était attribué aux différentes propriétés physiques et mécaniques des fibres utilisées, telles que leurs dimensions, leurs géométries, et leurs mécanismes de liaison avec le béton. Les poutres coulées avec des fibres en acier à 0,5% présentaient des capacités de cisaillement plus élevées que celles coulées avec des fibres de basalte et de polypropylène de 23 et 16% respectivement, alors que les poutres coulées avec des fibres en acier à 1% de volume présentaient un gain de 47 et 41%, respectivement, dans leurs capacités. Les capacités de cisaillement prévues selon les équations de la norme CSA-S806-12 étaient conservatrices avec un rapport moyen Vprév/Vexp de 0,80 (écart type, ÉT = 0,12) pour les poutres sans fibres. Les modèles établis par Shin (1994) et Gopinath (2016) ont fourni de bonnes prévisions quant aux capacités de cisaillement des poutres en béton renforcé de fibres de basalte avec des ratios moyens Vprév/Vexp de 1,34 (ÉT = 0,09) et de 1,35 (ÉT = 0,07), respectivement. De même, le modèle de Shin (1994) a bien prédit les capacités de cisaillement des poutres en béton armé de fibres de polypropylène avec un rapport Vprév/Vexp de 1,34 (ÉT = 0,18). Les modèles de Gopinath (2016), Ashour A (1992) et Shin (1994) ont prédit les capacités de cisaillement des poutres en béton armé de fibres d'acier assez raisonnablement avec des ratio Vprév/Vexp de 1,01 (ÉT = 0,06), 1,07 (ÉT = 0,01) et 1,20 (ÉT = 0,08), respectivement. Un nouveau modèle a été proposé pour prédire les capacités de cisaillement des poutres en béton léger fibré renforcées par des barres longitudinales PRFB. Le modèle proposé prédit bien les capacités de cisaillement des poutres en béton léger (avec des fibres de basalte) avec un rapport Vprév/Vexp de 1,01 (ÉT = 0,05) et celles des poutres en béton léger (avec des fibres de polypropylène) avec un rapport Vprév/Vexp de 0,99 (ÉT = 0,06). Le facteur de liaison et la matrice de liaison d'interface utilisés étaient respectivement 0,75 et 4,18 MPa. En même temps, le modèle proposé prédit bien les capacités de cisaillement des poutres coulées avec des fibres d’acier avec un rapport Vprév/Vexp de 0,9 (ÉT = 0,00) quand le facteur de liaison et la matrice de liaison d'interface utilisés étaient respectivement 1,0 et 6,8 MPa.This study reports on the shear behavior of fiber-reinforced lightweight concrete (FRLWC) beams reinforced with basalt fiber-reinforced polymer (BFRP) bars. Ten beams (150x250x2400 mm) cast with concrete with and without fibers were tested under fourpoint loading configuration until failure occurred. Two beams were cast without fibers and acted as control while the other eight beams were cast with different types and percentages of fiber. The investigated parameters included the fiber type (basalt, polypropylene, and steel fibers), the fibers volume fraction (0, 0.5, and 1.0%), and the beams’ reinforcement ratios (0.95 and 1.37%). Comparison between the experimental results and the analytical models currently available in the literature was performed to assess the applicability of such models for LWC reinforced with BFRP bars. Based on the outcome of the current study, the geometry of fibers played an important role in increasing the number of cracks than those observed in the control beams. The addition of fibers led to a more ductile failure and the rate of crack opening was delayed. Crack width decreased with the increase of the longitudinal reinforcement ratios and the fibers’ volume fractions. Increasing the reinforcement ratio resulted in higher stiffness and decreased its deflection at all stages of loading. Beams cast with 1% of basalt, polypropylene, and steel fibers showed an increase in their shear capacities in compared to control beams about 11, 16, and 63%, respectively. The type of fibers significantly affected the gain in the shear capacities of the beams, which can be attributed to the different physical and mechanical properties of the fibers used such as aspect ratios, lengths, geometries, densities, and their bonding mechanisms. Beams cast with 0.5% steel fibers exhibited higher shear capacities than those cast with basalt and polypropylene fibers by 23 and 16%, respectively, whereas the beams cast with 1% steel fibers showed a gain by 47 and 41%, respectively. The predicted shear capacities according to CSA-S806-12 code provisions were conservative with an average ratio Vpred /Vexp of 0.80 (standard deviation, SD = 0.12) for beams without fibers. Good predictions for the shear capacities of the basalt-fiber reinforced concrete beams (BLWC) were provided by the models derived by Shin (1994) and Gopinath (2016) in which the ratios Vpred /Vexp were 1.34 (SD = 0.09) and 1.35 (SD = 0.07), respectively. Also, the model of Shin (1994) predicted well the shear capacities of the polypropylene-fiber reinforced concrete beams (PLWC) with a Vpred /Vexp ratio of 1.34 and SD of 0.18. The models of Gopinath (2016), Ashour A (1992), and Shin (1994) predicted the shear capacities of steel-fiber reinforced concrete beams (SLWC) fairly reasonable with a Vpred /Vexp ratio of 1.01 (SD = 0.06), 1.07 (SD = 0.01) and 1.20 (SD = 0.08), respectively. A new model was proposed to predict the shear capacities of FRWLC beams reinforced with BFRP longitudinal bars. The proposed model predicted well the shear capacities of BLWC beams with a Vpred /Vexp ratio of 1.01 (SD = 0.05) and those of PLWC beams with a Vpred /Vexp ratio of 0.99 (SD = 0.06). The bond factor and the interface bond matrix used were 0.75 and 4.18 MPa, respectively. The proposed model also predicted well the shear capacities of beams cast with SLWC with a Vpred /Vexp ratio of 0.9 when the bond factor and the interface bond matrix were taken equal to 1.00 and 6.8 MPa, respectively.
12
Krishnaswamy, Vijayarajan. "Durability of nanoclay FRP bars for concrete members". Morgantown, W. Va. : [West Virginia University Libraries], 2006. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=4568.
Testo completoAbstract (sommario):
Thesis (M.S.)--West Virginia University, 2006.Title from document title page. Document formatted into pages; contains xvi, 204 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 155-158).
13
Choi, Jeong-Hoon. "Design and short-term performance of continuously reinforced concrete pavements using glass fiber reinforced polymer rebars". Morgantown, W. Va. : [West Virginia University Libraries], 2008. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=6043.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--West Virginia University, 2008.Title from document title page. Document formatted into pages; contains xvii, 314 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 264-270).
14
Jiang, Liying. "Strain-hardening behavior of fiber reinforced concrete". Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=19709.
Testo completoAbstract (sommario):
Fiber reinforced concrete with postpeak strain hardening type of response contributes significantly to the load carrying capacity, the impact and fatigue resistance and the reduced crack opening width, and is developed for special applications when large energy absorption capacity is required. While the strain hardening fiber reinforced cement paste and mortar are extensively studied, the strain hardening fiber reinforced concrete (SHFRC) with large quantity of coarse aggregates is not readily achievable. In this research, two approaches were investigated to fabricate strain hardening fiber reinforced concrete with polyvinyl alcohol (PVA) fiber and steel fiber: One used polymer addition and the other employed hybrid fiber reinforcement. The results showed that both PVA fibers and steel fibers with hooked flat ends could be used to produce fiber reinforced concrete with strain hardening behavior. With polymer modification and hybrid fiber system, the hardening response was enhanced. Fiber reinforced concretes were tested under severe environmental condition: freeze-thaw cycling and drying shrinkage. The results indicated that PVA fibers were vulnerable to cold temperature change and the strain hardening behavior deteriorated under freeze-thaw cycling. Polymer modification could protect the polymer fibers from frost damage. The strain hardening fiber reinforced concrete did not show its ability to delay crack initiation under severe drying condition. Finally, a toughness method (Ductility factor) was proposed to quantify the strain-hardening behavior.
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SIMOES, LEONARDO CRAVEIRO. "A CONSTITUTIVE MODEL FOR FIBER REINFORCED CONCRETE". PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 1998. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=1511@1.
Testo completoAbstract (sommario):
COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIORNos últimos 40 anos, tem-se observado um crescente interesse por compósitos formados pela adição de fibras a matrizes de concreto, os chamados concretos reforçados com fibras. Esse interesse é justificado, sobretudo, pelo significativo ganho em tenacidade que as fibras proporcionam, atenuando as características frágeis do concreto. De fato, em virtude do mecanismo de reforço promovido pelas fibras, o concreto com fibras é capaz de absorver muito mais energia de deformação até a ruptura, apresentando, no regime pós-fissuração, um comportamento muito mais suave que o concreto simples. Esse comportamento é acompanhado por um processo de fissuração mais uniforme, no qual observam-se fissuras mais finas e menos espaçadas. Além disso, registram-se aumentos nos valores de resistência do material e nos níveis de deformação que ele atinge até seu completo esgotamento. Tendo em vista os benefícios que as fibras aportam ao desempenho do concreto, seu emprego seria recomendável a estruturas em que a ductilidade é um dos parâmetros principais de projeto, ou naquelas feitas com concretos de alta resistência, uma vez que estes apresentam um comportamento ainda mais frágil que os concretos de resistência normal. Além disso, a utilização de fibras no combate aos esforços de cisalhamento mostra-se extremamente vantajosa e promissora. Neste trabalho, apresenta-se um modelo constitutivo para concreto reforçado com fibras baseado na formulação hipoelástica de ELWI E MURRAY (1979), originalmente proposta para concreto simples. As especificidades do comportamento do concreto com fibras frente às mais diversas solicitações, tais como, tração, compressão e cisalhamento, são incorporadas ao modelo através de relações tensão-deformação adequadas a esse material. Tais relações provêm de estudos analíticos e experimentais sobre o assunto, publicados na literatura técnica especializada. O modelo assim obtido é implementado no programa FEPARCS (ELWI E MURRAY, 1980), capaz de realizar análises númericas não-lineares através do método dos elementos finitos. Por fim, utiliza-se esse program para simular a resposta de uma estrutura de concreto com fibras, cujo ensaio experimental aparece minuciosamente descrito em (CRAIG, 1987). Os resultados numéricos obtidos são comparados com os experimentais correspondentes, em termos da curva carga versus deslocamento, desenvolvimento e distribuição de fissuras, progressão do escoamento da armadura longitudinal (convencional) e modo de ruptura. Avalia-se, então, a eficiência da implementação realizada na descrição do comportamento de estruturas de concreto com fibras.
Along the past forty years, an increasing interest on composite materials formed by the addition of discrete fibers to a concrete matrix is being observed. These composites are known as fiber reinforced concretes. The interest on the use of fibers as reinforcement is justified by their significative contribution to concrete thoughness, as they reduce the brittle characteristics of that material. In fact, due to fiber reinforcement mechanism, fiber reinforced concrete can absorb much more strain energy until failure, in comparison to ordinary concrete. The cracking process seems to be more uniform, as the distance between cracks are reduced. Besides that, the material strength and the deformation levels at cracking and rupture are greater, on the case of fiber reinforced concrete. The benefits that fibers bring to concrete behavior indicate that they could be used as complementary reinforcent for concrete structures when ductility is a major design concern, or when high strength concrete is employed, as this class of material tends to be much more brittle then normal strength concrete. Fibers are also effective as shear reinforcement, and they could even replace stirrups in this function. In this work, a constituive model for fiber reinforced concrete is presented. This model is based on the formulation originally proposed by ELWI AND MURRAY (1979) for the case of ordinary concrete. The behavior characteristcs of fiber reinforced concrete are incorporated as adaquated uniaxial stress-strain relations in tension and compression. The behavior under shear stress is also considered. The model is then implemented in the finite element program FEPARCS (ELWI AND MURRAY, 1980). A numerical analysis on the response of a fiber reinforced concrete structure is conducted. Results reported in technical literature (CRAIG, 1987) are compared to those obtained by the finite element analysis. The efficiency of the model is then verified.
En los últimos 40 anos, se ha observado un creciente interés por compuestos formados por la adición de fibras a matrizes de concreto, los llamados concretos reforzados con fibras. Ese interés se debe a la significativa ganancia en tenacidad que las fibras proporcionan, atenuando las características frágiles del concreto. De hecho, en virtud del mecanismo de refuerzo promovido por las fibras, el concreto con fibras es capaz de absorver mucha más energía de deformación hasta la ruptura, presentando, en el régimen posfisuración, un comportamiento mucho más suave que el concreto simple. Este comportamiento se ve acompañado por un proceso de fisuración más uniforme, en el cual se observan fisuras más finas y menos espaciadas. Además, se registran aumentos en los valores de resistencia del material y en los niveles de deformación que alcanza hasta su completa destrucción. Teniedo en cuenta los beneficios que las fibras aportan al desempeño del concreto, sería recomendable su empleo en extructuras donde la ductilidad es uno de los parámetros principales de proyecto, o en aquellas hechas con concreto de alta resistencia, ya que éstos presentan un comportamiento más frágil que los concretos de resistencia normal. En este trabajo, se presenta un modelo constitutivo para concreto reforzado con fibras que tiene como base la formulación hipoelástica de ELWI Y MURRAY (1979), originalmente propuesta para concreto simple. Las especificidades del comportamiento del concreto con fibras frente a las más diversas solicitudes, tales como, tracción, compresión y cisallamiento, se incorporan al modelo a través de relaciones tensión-deformación adecuadas a ese material. Tales relaciones provienen de estudios analíticos y experimentales sobre el asunto, publicados en la literatura técnica especializada. La implementación del modelo obtenido fue realizada a través del programa FEPARCS (ELWI Y MURRAY, 1980), capaz de realizar análisis númerico no lineal a través del método de los elementos finitos. Por fin, se utiliza ese programa para simular la respuesta de una extructura de concreto con fibras, cuyo ensayo experimental aparece minuciosamente descrito en (CRAIG, 1987). Los resultados numéricos obtenidos se comparan con los experimentales correspondientes, considerando la curva carga versus deslocamiento, desarrollo y distribuición de fisuras, progresión del deslizamiento de la armadura longitudinal (convencional) y modo de ruptura. Se evalúa entonces, la eficiencia de la implementación en la descrición del comportamiento de extructuras de concreto con fibras.
16
Stacchini, Marco. "Meso-structural model for Fiber-Reinforced concrete". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2010. http://amslaurea.unibo.it/1063/.
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Kim, SangHun Aboutaha Riyad S. "Ductility of carbon fiber-reinforced polymer (CFRP) strengthened reinforced concrete". Related Electronic Resource: Current Research at SU : database of SU dissertations, recent titles available full text, 2003. http://wwwlib.umi.com/cr/syr/main.
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FILHO, JULIO JERONIMO HOLTZ SILVA. "CARBON FIBER REINFORCED POLYMER TORSION STRENGTHENING OF REINFORCED CONCRETE BEAMS". PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2007. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=10658@1.
Testo completoAbstract (sommario):
CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOEste estudo teórico-experimental analisa o comportamento até a ruptura de vigas de concreto armado reforçadas externamente à torção com compósitos de fibras de carbono (CFC). No programa experimental, sete vigas de concreto armado, com seção transversal de 20 cm x 40 cm e 420 cm de comprimento, com mesma armadura de aço longitudinal e transversal e concreto com mesma resistência à compressão, foram ensaiadas até a ruptura. As vigas testadas foram divididas em três séries, sendo uma viga de referência sem reforço, três vigas com reforço transversal externo e três vigas com reforço externo transversal e longitudinal. Para a realização dos ensaios foi montada uma estrutura auxiliar de aço capaz de transferir às vigas a solicitação de torção pura. No estudo teórico foram desenvolvidas duas formulações. A primeira formulação, baseada no modelo da treliça espacial generalizada com abrandamento de tensões, apresenta uma sistemática para traçado da curva momento torçor x ângulo de torção por unidade de comprimento de vigas de concreto armado reforçadas à torção. A segunda formulação, fundamentada no modelo da Analogia da Treliça Espacial de acordo com a filosofia de dimensionamento do Eurocode 2, apresenta uma sistemática para dimensionamento de reforço com CFC . As duas metodologias adotam um modelo para determinação da aderência entre o substrato de concreto e o reforço. A inclusão da aderência nos modelos desenvolvidos é de grande importância porque em geral a ruptura do elemento estrutural ocorre devido ao descolamento do CFC. Os resultados experimentais obtidos nos testes das vigas foram utilizados para validar as duas formulações teóricas desenvolvidas. Os resultados experimentais apresentaram boa aproximação quando comparados com os modelos propostos. Verificou-se que todas as vigas reforçadas apresentaram um acréscimo de resistência à torção em torno de 40% em relação à viga de referência. Verificou-se que, após a fissuração, as vigas reforçadas apresentaram perda de rigidez inferior à da viga de referência. Observou-se que o ângulo da fissura medido experimentalmente, o ângulo de inclinação calculado pelo estado de deformação e o ângulo de inclinação calculado pelo estado de tensão da viga apresentaram valores próximos para cada viga.
A theoretical-experimental research on the torsional behavior up to failure of reinforced concrete beams strengthened with external carbon fiber composites (CFC) was carried out. The experimental study comprises a series of seven reinforced concrete beams with the same compressive strength of concrete loaded to failure and subjected to torsion. The beams dimensions were 20 cm x 40 cm x 420 cm. The test specimens had the same internal steel reinforcement. The beams were divided in three series: the reference beam without strengthening; three beams with the external strengthening applied transversally and three beams with the external strengthening applied transversally and longitudinally. For the accomplishment of the tests an auxiliary steel structure was mounted, capable to transfer to the beams the pure torsion moment. In the theoretical study two analytical procedures were developed. The first formulation, based on the softened space truss model for torsion, presents a systematic to obtain the curve torsion moment x torsion angle per length unit of the reinforced concrete beams with CFC torsion strengthening. The second systematic, based on the Space Truss Model in accordance with the Eurocode 2, presents the design of the CFC strengthening. Both methodologies adopt the Chen and Teng bond model between concrete and CFC. The consideration of the bond in the developed models is very important because the failure of the concrete members often occurs from debonding of the CFC. The experimental results from the beams tests were used to validate the two analytical procedures. Good agreement was obtained with the experimental and analytical results. For all the strengthened beams the average values of torsion strength were increased by 40% when compared to the reference beam. After cracking, the loss of rigidity in the strengthened beams was lower then in the reference beam. The cracking angle experimentally measured and the strut angles evaluated by strain state and stress state presented close values.
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Kodkani, Shilpa. "Interface durability of externally bonded GFRP to normal and high-performance concrete". Morgantown, W. Va. : [West Virginia University Libraries], 2004. https://etd.wvu.edu/etd/controller.jsp?moduleName=documentdata&jsp%5FetdId=3601.
Testo completoAbstract (sommario):
Thesis (M.S.)--West Virginia University, 2004.Title from document title page. Document formatted into pages; contains xiii, 147 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 141-147).
20
Kalluri, Rajesh K. "Bending behavior of concrete T-beams reinforced with glass fiber reinforced polymer (GFRP) bars". Morgantown, W. Va. : [West Virginia University Libraries], 1999. http://etd.wvu.edu/templates/showETD.cfm?recnum=1147.
Testo completoAbstract (sommario):
Thesis (M.S.)--West Virginia University, 1999.Title from document title page. Document formatted into pages; contains xi, 100 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 96-99).
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Tung, Wang Kei. "FRP debonding from concrete substrate : theoretical and experimental approach /". View Abstract or Full-Text, 2002. http://library.ust.hk/cgi/db/thesis.pl?CIVL%202002%20TUNG.
Testo completoAbstract (sommario):
Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2002.Includes bibliographical references (leaves 109-110). Also available in electronic version. Access restricted to campus users.
22
Lau, Tak-bun Denvid. "Flexural ductility improvement of FRP-reinforced concrete members". Click to view the E-thesis via HKUTO, 2006. http://sunzi.lib.hku.hk/hkuto/record/B38907756.
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Pan, Jinlong. "Crack-induced debonding failure in fiber reinforced plastics (FRP) strengthened concrete beams : experimental and theoretical analysis /". View abstract or full-text, 2005. http://library.ust.hk/cgi/db/thesis.pl?CIVL%202005%20PAN.
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Baczkowski, Bartlomiej Jan. "Steel fibre reinforced concrete coupling beams /". View abstract or full-text, 2007. http://library.ust.hk/cgi/db/thesis.pl?CIVL%202007%20BACZKO.
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Thomas, Jeff Scott. "Plastic fiber rolling for concrete reinforcement". Diss., Rolla, Mo. : University of Missouri-Rolla, 1996. http://scholarsmine.mst.edu/thesis/pdf/Thomas_09007dcc805b0f25.pdf.
Testo completoAbstract (sommario):
Thesis (M.S.)--University of Missouri--Rolla, 1996.Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed November 24, 2008) Includes bibliographical references (p. 117-118).
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Boyd, Andrew James. "Rehabilitation of reinforced concrete beams with sprayed glass fiber reinforced polymers". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/NQ61068.pdf.
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Sheats, Matthew Reed. "Rehabilitation of reinforced concrete pier caps using carbon fiber reinforced composites". Thesis, Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/19490.
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BOY, SERPIL. "RETROFIT OF EXISTING REINFORCED CONCRETE BRIDGES WITH FIBER REINFORCED POLYMER COMPOSITES". University of Cincinnati / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1078508332.
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Ishtewi, Ahmad M. "Shear Capacity of Fiber-Reinforced Concrete Under Pure Shear". University of Dayton / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1354725447.
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Tsang, Terry Kin Chung. "Behaviour of concrete beams reinforced with hybrid FRP composite rebars /". View abstract or full-text, 2006. http://library.ust.hk/cgi/db/thesis.pl?CIVL%202006%20TSANGT.
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Vijay, P. V. "Aging and design of concrete members reinforced with GFRP bars". Morgantown, W. Va. : [West Virginia University Libraries], 1999. http://etd.wvu.edu/templates/showETD.cfm?recnum=720.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--West Virginia University, 1999.Title from document title page. Document formatted into pages; contains xxvii, 205 p. : ill. (some col.) Includes abstract. Includes bibliographical references (p. 188-205).
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Lau, Tak-bun Denvid, e 劉特斌. "Flexural ductility improvement of FRP-reinforced concrete members". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2006. http://hub.hku.hk/bib/B38907756.
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Deng, Jiangang. "Durability of carbon fiber reinforced polymer (CFRP) repair/strengthening concrete beams". Laramie, Wyo. : University of Wyoming, 2008. http://proquest.umi.com/pqdweb?did=1663060011&sid=2&Fmt=2&clientId=18949&RQT=309&VName=PQD.
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34
Tomblin, Josh. "Buried FPR-Concrete Arches". Fogler Library, University of Maine, 2006. http://www.library.umaine.edu/theses/pdf/TomblinJX2006.pdf.
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35
Pros, Parés Alba. "Numerical approach for modeling steel fiber reinforced concrete". Doctoral thesis, Universitat Politècnica de Catalunya, 2012. http://hdl.handle.net/10803/83724.
Testo completoAbstract (sommario):
One alternative to overcome the main drawbacks of plain concrete in tension (its brittleness and weakness) is Steel Fiber Reinforced Concrete (SFRC), a technique introduced in the 70's, which consists of adding steel fibers into the concrete matrix.
Due to the presence of the steel fibers into the concrete matrix, the residual strength and the energy dissipation of the material increase. Moreover, once a crack appears in the concrete, the steel fibers sew this fissure. The shape, the length and the slenderness of the fibers influence on the SFRC behavior. Moreover, the distribution and the orientation of the fibers into the concrete domain must be taken into account for characterizing the material.
In order to characterize the behavior of SFRC, a numerical tool is needed. The aim is to simulate the most standard and common tests (direct and indirect tension tests, flexural test, double punch tes,¿) and more complex setups.
This thesis proposes a numerical tool for modeling SFRC avoiding homogenized models (not accurate enough) and conformal meshes (too expensive). Therefore, the numerical tool accounts for the actual geometry of the fibers, discretized as 1D bars nonconformal with the concrete bulk mesh (2D or 3D domains). The two materials, corresponding to the concrete bulk and the fiber cloud, are defined independently, but coupled by imposing displacement compatibility. This compatibility is enforced following the ideas of the Immersed Boundary methods.
Two different models are considered for modeling the concrete bulk (a continuous one and a discontinuous one). The parametric study of each model is done for only plain concrete, before the addition of the steel fibers.
A phenomenological mesomodel is defined for modeling steel fibers, on the basis of the analytical expressions describing the pullout tests. This phenomenological mesomodel not only describes the behavior of the steel fibers, but also accounts for the concrete-fiber interaction behavior. For each fiber, its constitutive equation is defined depending on its shape (straight or hooked) and the angle between the fiber and the normal direction of the failure pattern.
Both 2D and 3D examples are reproduced with the proposed numerical tool. The obtained results illustrate the presence of the steel fibers into the concrete matrix. The shape of the fiber influences of the SFRC behavior: the residual strength is higher for hooked fibers than for straight ones. Moreover, increasing the quantity of fibers means increasing the residual strength of the material.
The obtained numerical results are compared to the experimental ones (under the same hypothesis). Therefore, the proposed numerical approach of SFRC is validated experimentally.
36
Zhang, Lihe. "Impact resistance of high strength fiber reinforced concrete". Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/705.
Testo completoAbstract (sommario):
Concrete structures may be subjected to dynamic loading during their service life. Understanding the dynamic properties of concrete structures is becoming critical because of the increased concern about the dynamic loading of both civilian and military structures, and especially, the recent increase in terrorist attacks on structures. Fiber reinforced concrete (FRC) is known to exhibit superior performance in its post-peak energy absorption capacity, (i.e., toughness) under flexural and tensile loading. However, the behavior of fiber reinforced concrete under compressive impact has not previously been investigated. In the present research, the response of fiber reinforced concrete was investigated over the full strain rate regime, from static loading to high strain rate loading, and finally to impact loading. The compressive toughness of FRC under static loading was studied using an existing Japanese standard (JSCE SF-5). Then, a test method for FRC under compressive impact loading was developed, involving the use of a high speed video camera system to measure the deformation of FRC cylinders under compressive impact.
The strain rate sensitivity of FRC in both flexure and compression was also fully investigated. FRC was found to have higher strengths under impact loading (both flexural and compressive) than under static loading. The compressive toughness under impact loading increased due to the high peak load and the high strain capacity. FRC under flexural impact loading showed a greater strength improvement than under static flexure. FRC displays a much higher Dynamic Improvement Factor (DIF) under flexural impact than under compressive impact. It gave an overall higher performance under impact than under static loading. It also exhibited a higher strain rate sensitivity than plain concrete in both compression and flexure.
Damage analysis, in terms of loss of strain energy, was carried out based on damage mechanics principles. Damage was found to increase with increasing strain rate. A new constitutive model was proposed to account for the relationship between DIF (Comp) and strain rate and the data derived from the model were found to be consistent with the experimental results.
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Garbis, Leonidia Maria. "Natural fiber reinforced aerated concrete : an experimental investigation". Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/82813.
Testo completoAbstract (sommario):
Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2013.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 51-52).
The purpose of this study is to compare existing research with aerated concrete and fiber reinforcement to original experiments completed investigating the benefits of adding natural fiber tensile reinforcement to aerated concrete. Concrete is a great composite material which can be created in various proportions and with various materials to alter its strength, density and porosity, amongst other properties. Concrete which is used commonly in construction of columns, beams, and slabs acts well in compression but fails under tension. The common solution is to reinforce the structure in areas where it experiences tension with steel. There are other materials besides steel which also take tension well. Natural fibers for example come in various strengths and types and would create lighter and perhaps more sustainable beam designs. Natural fibers have been used for their availability, workability, and high tensile strengths for centuries. This research discovers that the compressive strength of this cellular material can support the construction of a small structure, assuming accuracy of previous experimental results. These previous experiments discover how the natural fibers distribute within the mixture and how they affect the aeration of the concrete, as well as how they affect the strength. Multiple samples are cured with different fiber types and in different proportions within the mixture. Furthermore, similar experimentation is conducted to discover an ideal ratio of aggregate to aerated concrete mix. The aggregate gives the concrete greater strength and economy, but could negatively affect the aeration. The various concrete mixes are poured and allowed to cure to maximum strength before indirect tensile tests and compression tests are conducted. The effects of creating smooth aerated concrete molds are also investigated. All experiments conducted are precursory to an ultimate tensile reinforced aerated concrete beam design with an aggregate mix and smooth surfaces.
by Leonidia Maria Garbis.
M.Eng.
38
Sasher, William C. "Testing, assessment and FRP strengthening of concrete T-beam bridges in Pennsylvania". Morgantown, W. Va. : [West Virginia University Libraries], 2008. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=5876.
Testo completoAbstract (sommario):
Thesis (M.S.)--West Virginia University, 2008.Title from document title page. Document formatted into pages; contains viii, 177 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 130-136).
39
Lau, Shuk-lei. "Rehabilitation of reinforced concrete beam-column joints using glass fibre reinforced polymer sheets". Click to view the E-thesis via HKUTO, 2005. http://sunzi.lib.hku.hk/hkuto/record/B32001630.
Testo completo
40
SCHWARTZ, CHRIS J. "STRUCTURAL INVESTIGATION OF A FIBER REINFORCED PRECAST CONCRETE BOX CULVERT". University of Cincinnati / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1121016977.
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41
Aguiniga, Gaona Francisco. "Characterization of design parameters for fiber reinforced polymer composite reinforced concrete systems". Diss., Texas A&M University, 2003. http://hdl.handle.net/1969.1/61.
Testo completoAbstract (sommario):
Corrosion of steel reinforcement in concrete structures results in significant repair and rehabilitation costs. In the past several years, new fiber reinforced polymer (FRP) reinforcing bars have been introduced as an alternative to steel reinforcing bars. Several national and international organizations have recently developed standards based on preliminary test results. However, limited validation testing has been performed on the recommendations of these standards. High variability of the tensile properties, degradation of tensile strength, direct shear capacity, predicted deflections due to creep, cracking behavior of FRP-reinforced concrete flexural members, bond behavior and development length, and effects of thermal expansion on cracking of FRP reinforced concrete have all been reported, but are areas that need further investigation and validation. The objective of this study is to evaluate the characteristics of glass FRP reinforcing bars and provide recommendations on the design and construction of concrete structures containing these bar types with regard to the areas described. The recently developed ACI 440 design guidelines were analyzed and modifications proposed.
42
Ross, Jason Donald. "Analytical models for reinforced concrete columns retrofitted with fiber-reinforced polymer composites". Connect to resource, 2007. http://hdl.handle.net/1811/25128.
Testo completoAbstract (sommario):
Thesis (Honors)--Ohio State University, 2007.Title from first page of PDF file. Document formatted into pages: contains 67 p.; also includes graphics. Includes bibliographical references (p. 60-62). Available online via Ohio State University's Knowledge Bank.
43
Nunes, Nelson Lúcio. "Contribuição para a aplicação do concreto reforçado com fibras de aço em elementos de superfície restringidos". Universidade de São Paulo, 2006. http://www.teses.usp.br/teses/disponiveis/3/3146/tde-04052006-170328/.
Testo completoAbstract (sommario):
Este trabalho apresenta um estudo para a previsão de comportamento quanto à fissuração e seu controle pelo uso das fibras de aço, em elementos de superfície de concreto restringidos, ou seja, submetidos às tensões de tração induzidas pela retração restringida. Neste estudo, foi desenvolvido um método analítico para calcular o consumo de um determinado tipo de fibra de aço em função do potencial de retração da matriz de concreto e da máxima abertura de fissura, determinada em função de parâmetros de durabilidade e aceitabilidade sensorial. Posteriormente, foram realizados ensaios para caracterização do potencial de fissuração de matrizes de concreto utilizadas em obras de elementos de superfície, onde testou-se um método de estimativa das tensões induzidas por retração restringida no concreto, no momento da primeira fissura. Na etapa final do trabalho, foi realizado um programa experimental, com a construção de pistas de concreto reforçado com fibras de aço (CRFA), com consumos de fibras de 10 kg/m3, 30 kg/m3 e 60 kg/m3, construídas sobre bases com duas condições de restrição: superfície desempenada e superfície jateada com exposição dos agregados. A fissuração destas pistas, nas primeiras idades, foi monitorada através da medida da abertura e do comprimento das fissuras. Com os resultados desta etapa experimental, foi realizada uma retroanálise do método onde concluiu-se que a consideração de valores característicos na previsão da resistência à tração do concreto era um ajuste necessário e coerente com a observação prática. Com o ajuste, os resultados experimentais de abertura de fissura ficaram dentro da faixa de previsibilidade do método, considerando um intervalo de confiança de 90%. Com o desenvolvimento deste método, buscou-se contribuir para a aplicação do CRFA no controle da fissuração por retração restringida de elementos de superfície, ampliando a fronteira do conhecimento no aspecto da escolha e dosagem da fibra para um determinado desempenho esperado quanto à fissuração.This work presents a study for crack prediction and use of steel fibers to crack control in concrete surface elements submitted to tension stress induced by restrained shrinkage. In this study, a method was developed where a certain steel fiber type could be quantified, as function of concrete matrix shrinkage potential and maximum crack width, determined from human sensorial and durability criteria. Afterwards, an experimental program was done in order to characterize the crack potential of concrete matrices commonly used in surface elements. In this program, a method to predict tension stress induced by restrained shrinkage, at first crack moment, was tested. In the final step of this work, another experimental program was done, where steel fiber reinforced concrete (SFRC) tracks were built, with fiber contents of 10 kg/m3, 30 kg/m3 and 60 kg/m3, over substrates with two restriction conditions: smooth surface and rough surface, with exposition of surface aggregates. Lengths and widths of the early age shrinkage cracks in the tracks were monitored. The results obtained in this program were useful to analyze the method, adjusting it with the consideration of characteristic values in prediction of tension strength. With this adjust, experimental crack width results were more compatible with 90% confidence interval for crack width values predicted by the method. With this study, the goal was the contribution to use SFRC in the control of restrained shrinkage cracks in surface elements, amplifying the knowledge border in the aspect of fiber selection and proportioning, for a determined and expected performance in terms of crack width.
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Laranjeira, de Oliveira Filipe. "Design-oriented constitutive model for steel fiber reinforced concrete". Doctoral thesis, Universitat Politècnica de Catalunya, 2010. http://hdl.handle.net/10803/6174.
Testo completoAbstract (sommario):
En los últimos años la industria viene exigiendo el empleo del hormigón reforzado con fibras de acero (HRFA) en aplicaciones estructurales. Debido al hecho de que la resistencia pos-fisuración del material es relevante, la capacidad de coser fisuras concedida por las fibras puede permitir la sustitución, parcial o total, de la armadura de acero convencional. Por consiguiente, una adecuada caracterización del comportamiento a tracción uniaxial del HRFA es de gran interés. Sin embargo, a pesar de la amplitud de trabajo de investigación y de la reciente elaboración de normativas, no existe un consenso respecto al modelo constitutivo a ser empleado en el diseño del HRFA.El cosido de las fibras de acero en las fisuras mejora la tenacidad y la durabilidad del hormigón. El HRFA es un material que, generalmente, presenta una resistencia residual a tracción en régimen fisurado. Sin embargo, en algunas situaciones, el HRFA puede desarrollar endurecimiento en flexotracción debido a su aptitud en redistribuir esfuerzos en la sección de fisura. Estas características vienen contribuyendo para un interés creciente así como un incremento del número de aplicaciones de este material.
En esta tesis doctoral se desarrolla un método directo y lógico para predecir la respuesta a tracción del HRFA para el diseño estructural. Mientras que la comprensión del comportamiento del material se consigue por medio de una investigación experimental, la formulación del nuevo modelo constitutivo se obtiene con un estudio segmentado del comportamiento del material en niveles de menor complejidad y, en seguida, con la caracterización de cada uno de ellos hasta conseguir explicar la respuesta a tracción del HRFA.
Esta tesis está dividida en cinco partes principales: I) Identificación de las motivaciones. II) Obtención de resultados a tracción uniaxial para comprender los principales mecanismos que controlan la resistencia pos-fisuración. III) Desarrollo de dos modelos para predecir la respuesta al arrancamiento de fibras de acero inclinadas, que cubren fibras rectas y con ganchos. IV) Investigación detallada de la orientación de las fibras al nivel individual mediante análisis estadísticos. Luego, aspectos prácticos asociados al proceso de producción son integrados en una metodología innovadora para predecir la orientación de las fibras. V) Formulación y validación del nuevo modelo constitutivo, con base en las Partes III y IV, con los resultados experimentales de la Parte II. El comportamiento a tracción se evalúa mediante un estudio paramétrico y se proponen expresiones ingenieriles para el diseño y optimización (EEDO).
El modelo constitutivo propuesto se distingue de estudios anteriores en varios aspectos y define una nueva filosofía para el diseño de elementos de HRFA. Este modelo es un método directo y práctico para obtener el comportamiento a tracción del material mediante parámetros con sentido físico y basado en conceptos claros: arrancamiento y orientación de las fibras.
Una de las principales aportaciones de este trabajo es la capacidad de predecir curvas tensión-apertura de fisura que reflejan una combinación específica de las propiedades de la matriz y de las fibras empleadas. Además, se introduce una filosofía innovadora en el diseño debido a la incorporación del proceso de producción, las propiedades en estado fresco y el elemento a construir en la definición del diagrama constitutivo.
In the last years, the industry has been demanding for the use of steel fiber reinforced concrete (SFRC) in structural applications. Because the post-cracking strength of this material is not negligible, the crack-bridging capacity provided by fibers may replace, partial or completely, conventional steel reinforcement. Therefore, an appropriate characterization of the SFRC uniaxial tensile behavior is of paramount interest. However, in spite of the extensive research and standards recently advanced, there is no agreement on the constitutive model to be used for the design of SFRC.
The crack-bridging capacity provided by steel fibers improves both the toughness and the durability of concrete. Conventional SFRC is a material which presents softening response under uniaxial tension, but may develop hardening behavior in bending due to its ability to redistribute stresses within the crosssection.
These evidences have been contributing to an increasing interest and growing number of applications of this material.
In this doctoral thesis, a direct and rationale approach to predict the tensile response of SFRC for structural design calculations is developed. While insight on the material behavior is firstly gained through an experimental investigation, the formulation of the new constitutive model follows a bottomup approach: it fragments the material's behavior into levels of smaller complexity and then models each of them until the overall behavior can be explained.
The dissertation is subdivided into five main parts: I) The motivations for this research project are pointed out. II) Uniaxial tensile test results are obtained to understand the major mechanisms governing the post-cracking strength. III) Two models predicting the pullout responses of inclined steel fibers are developed, covering straight and hooked fibers. IV) The orientation of fibers is investigated in detail at the single fiber level through statistical analyses. Then, practical aspects associated to the manufacturing process are integrated within a novel framework to predict fiber orientation. V) Based on Parts III-IV, the new constitutive model is formulated and validated with experimental results from Part II. Further insight on the tensile behavior is gained through a parametric study and Engineered Expressions for Design and Optimization (EEDO) are proposed.
The proposed design-oriented constitutive model differentiates itself from previous studies in multiple aspects and defines a new philosophy for the design of SFRC elements. This model provides a direct and practical procedure to obtain the material's tensile behavior by means of parameters with physical meaning and based on clear concepts: fiber pullouts and orientations.
One of the major contributions of this work is the ability to predict the stress-crack width curves that reflect the specific combination of the properties of the matrix and fibers applied. Furthermore, it introduces a novel philosophy for the material design regarding that the influences of the production process, fresh-state properties and the element to be built are taken into account to define the constitutive diagram.
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Yurtseven, Alp Eren. "Determination Of Mechanical Properties Of Hybrid Fiber Reinforced Concrete". Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12605268/index.pdf.
Testo completoAbstract (sommario):
ABSTRACT
DETERMINATION OF MECHANICAL PROPERTIES OF
HYBRID FIBER REINFORCED CONCRETE
Yurtseven, Alp Eren
M.Sc. Department of Civil Engineering
Supervisor: Prof. Dr. Mustafa Tokyay
Co-Supervisor: Asst. Prof. Dr. . Özgü
r Yaman August 2004, 82 pages Fiber reinforcement is commonly used to provide toughness and ductility to brittle cementitious matrices. Reinforcement of concrete with a single type of fiber may improve the desired properties to a limited level. A composite is termed as hybrid, if two or more types of fibers are rationally combined to produce a composite that derives benefits from each of the individual fibers and exhibits a synergetic response. This study aims to characterize and quantify the mechanical properties of hybrid fiber reinforced concrete. For this purpose nine mixes, one plain control mix and eight fiber reinforced mixes were prepared. Six of the mixes were reinforced in a hybrid form. Four different types of fibers were used in combination, two of which were macro steel fibers, and the other two were micro fibers. Volume percentage of fiber inclusion was kept constant at 1.5%. In hybrid reinforced mixes volume percentage of macro fibers was 1.0% whereas the remaining fiber inclusion was v composed of micro fibers. Slump test was carried out for each mix in the fresh state. 28-day compressive strength, flexural tensile strength, flexural toughness, and impact resistance tests were performed in the hardened state. Various numerical analyses were carried out to quantify the determined mechanical properties and to describe the effects of fiber inclusion on these mechanical properties. Keywords: Fiber Reinforcement, Hybrid Composite, Toughness, Impact Resistance
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Zanganeh, Mehdi. "Mechanical properties of fiber reinforced concrete with ACM applications". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0013/MQ52021.pdf.
Testo completo
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Wytroval, Tanner L. "Bearing strength of nodes confined by fiber reinforced concrete". Thesis, Northern Arizona University, 2013. http://pqdtopen.proquest.com/#viewpdf?dispub=1537822.
Testo completoAbstract (sommario):
In many structural concrete applications, loaded areas are surrounded by steel reinforcement or additional concrete in order to triaxially confine the region. This confinement effectively increases the local bearing strength and ductility. However, this is typically accomplished at the expense of increasing steel congestion and/or providing an inefficient amount of additional concrete. One way of alleviating these complications may be by confining loaded areas with steel fiber reinforced concrete (SFRC). Provisions within ACI 318-11 allow for an increase in the effective bearing strength of concrete based on the ratio of the loaded area to the overall area. However, there has not been a study of the confining capability of SFRC when the loaded area is smaller than the surrounding area. The study presented in this thesis addresses this need.
The current research project examines the influence of SFRC on the bearing strength of triaxially confined nodal regions. As part of this evaluation, twenty-four 12..24-inch cylindrical specimens were loaded to failure through 6- and 3-inch diameter bearing plates. Experimental variables include transverse reinforcement ratios ranging between 0 and 0.80 percent, and steel fiber dosages between 0 and 1.5 percent by volume. Specimens were uniaxially loaded to failure while displacement and load data was recorded.
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Song, Fanbing [Verfasser]. "Steel Fiber Reinforced Concrete Under Concentrated Load / Fanbing Song". Aachen : Shaker, 2017. http://d-nb.info/1138178888/34.
Testo completo
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Guirola, Marcela Renee. "Strength and Performance of Fiber-Reinforced Concrete Composite Slabs". Thesis, Virginia Tech, 2001. http://hdl.handle.net/10919/35431.
Testo completoAbstract (sommario):
The purpose of this research is to evaluate and compare the influence of four types of secondary reinforcement on various component strengths related to composite slabs. These components include the composite slab strength under uniform load, the strength of two types of shear connectors used with composite beams and joists, composite slab strength due to a concentrated load, and the flexural toughness and first-crack strength of fiber-reinforced concrete using ASTM C1018 (1998) standard test. The performance of the specimens reinforced with fibers are compared with that of the specimens reinforced with welded-wire fabric (WWF), with the purpose of determining if fiber-reinforced concrete can be used as an alternative to WWF.Master of Science
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BRODOWSKI, DAVID MICHAEL. "APPLICATION OF STEEL FIBER REINFORCED CONCRETE TO BURIED STRUCTURES". University of Cincinnati / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1123510082.
Testo completo