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  • Shear design of FRP reinforced concrete beams without transverse reinforcement

     Mari Bernat, Antonio Ricardo; Cladera Bohigas, Antoni; Oller Ibars, Eva; Bairan Garcia, Jesus Miguel
    Composites Part B: Engineering
    Date of publication: 2014-02
    Journal article

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    A simple and rational model for the prediction of the shear strength of FRP reinforced concrete beams without shear reinforcement is presented. The method is based on the principles of structural mechanics and on the experimentally observed behavior of RC beams at shear-flexural failure. It is assumed that, just before failure, the shear is resisted exclusively by the concrete flexural compression head at the critical section, placed at the tip of the shear crack closer to the support. Failure is considered to occur when the principal tensile stress at the concrete head reaches the concrete tensile strength. Simple design equations are provided, which explicitly account for those parameters governing the shear strength, such as the concrete tensile strength, the amount of longitudinal reinforcement ratio and the ratio between the elastic modulus of the longitudinal reinforcement and the concrete. The accuracy of the proposed method has been verified by comparing the model predictions with the results of 144 tests on CFRP and GFRP reinforced concrete beams and with a previously published database on steel reinforced concrete beams failing on shear, providing better results than those obtained using the design equations of current codes of practice, which are mainly empirically based.

  • Long-term bond stresses and debonding failure of FRP-strengthened RC cracked members

     Oller Ibars, Eva; Mari Bernat, Antonio Ricardo
    Composites Part B: Engineering
    Date of publication: 2013-09
    Journal article

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    Most of the existing models to prevent debonding failure in beams externally strengthened by fiber reinforced polymer (FRP) laminates were developed focusing on the short term response. This paper studies the effect of concrete creep on the interfacial shear stresses and consequently, on the debonding failure load. A simplified formulation for the instantaneous and time-dependent bond stresses under sustained load is provided. Its reliability is analysed through the results obtained by a non-linear time-dependent analysis model. Previously, this model has been checked to evaluate the long-term response of existing experimental programmes in terms of deflections and strains.

  • Dimensionamiento del refuerzo a flexión con laminados de polímeros reforzados con fibras (FRP) evitando su desprendimiento prematuro

     Oller Ibars, Eva; Mari Bernat, Antonio Ricardo; Bellido Recoder, Lucia
    Informes de la construcción
    Date of publication: 2013-10
    Journal article

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    According to the available experimental research related to structures flexurally strengthened by bonding fiber reinforced polymer (FRP) laminates, the laminate debonds in a brittle manner in most tests. This debonding failure usually initiates in the most loaded regions due the effect of intermediate cracks (intermediate crack debonding). From the beginning of this technique, several models have been developed to avoid this premature failure. However, some of them present a significant scatter in relation to the experimental data. This paper presents a comparative analysis of the existing formulations through a database of tests compiled by the authors. Afterwards, a design procedure based on a shear-bending moment interaction diagram related to intermediate crack debonding is presented. This interaction diagram depends on the maximum shear force between crack discontinuities. Finally, the proposed method is compared to the rest of the models obtaining satisfactory results when predicting the failure load.

  • Numerical analysis of shear critical RC beams strengthened in shear with FRP sheets

     Ferreira, Denise; Oller Ibars, Eva; Mari Bernat, Antonio Ricardo; Bairan Garcia, Jesus Miguel
    Journal of composites for construction
    Date of publication: 2013-12
    Journal article

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    The objective of this paper is to contribute to the understanding of the shear resisting mechanisms in RC beams shear-strengthened by externally bonded fiber-reinforced polymer (FRP) sheets. For this purpose, a fiber beam model of RC frames subjected to combined normal and shear forces, previously developed by the authors, has been extended to include the response of externally bonded FRP shear reinforcement in a wrapped configuration. No FRP delamination phenomena or tensile strength reductions in the corner zones are taken into account in the model. The numerical results have been compared with eight existing experimental results and the influence of the FRP sheets on the shear strength of the beam has been studied. The effects of the contribution of FRP ratio on the concrete, on the transversal steel strains and stresses, on the longitudinal tensile steel stresses, and on the diagonal compression struts have been analyzed. It is concluded that the presence of FRP reinforcement modifies the inclinations of cracks and struts, the concrete confinement stresses, and other parameters related to the shear response, producing an interaction between the concrete, internal steel, and FRP components of the shear strength.

  • Nuevo proceso constructivo de viaductos con cimbra autolanzable y nueva secuencia evolutiva

     Díaz De terán lópez, Jose Ramon
    Defense's date: 2013-09-12
    Universitat Politècnica de Catalunya
    Theses

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  • Simplified method for the calculation of long-term deflections in FRP-strengthened reinforced concrete beams

     Mari Bernat, Antonio Ricardo; Oller Ibars, Eva; Bairan Garcia, Jesus Miguel; Duarte Gomez, Noemi
    Composites Part B: Engineering
    Date of publication: 2013-02
    Journal article

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  • The contribution of FRP laminates to the shear strength of Externally Bonded Reinforced (EBR) concrete structures

     Oller Ibars, Eva; Pujol Sanchez, Mireia; Mari Bernat, Antonio Ricardo; Bairan Garcia, Jesus Miguel
    Concrete Structures for Sustainable Community
    Presentation's date: 2012-06-13
    Presentation of work at congresses

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  • Numerical simulation of the structural effects of the deterioration in concrete structures

     Mari Bernat, Antonio Ricardo; Bairan Garcia, Jesus Miguel; Oller Ibars, Eva; Fernández Pérez, Ignasi
    Concrete Structures for Sustainable Community
    Presentation's date: 2012-06-11
    Presentation of work at congresses

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  • Analysis of reinforced concrete elements strengthened by prestressed FRP laminates through non-linear and evolutive models

     Oller Ibars, Eva; Mari Bernat, Antonio Ricardo; Bairan Garcia, Jesus Miguel
    Congreso Nacional de Materiales Compuestos
    Presentation's date: 2011-07-06
    Presentation of work at congresses

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    In this paper a non-linear and time dependent evolutive analysis model, previously developed by the authors, is applied to the prediction of the response of reinforced concrete structures strengthened in flexure by FRP prestressed laminates throughout the elastic, cracked and ultimate ranges. The model considers the structural effects of changes in geometry, structural scheme, material properties and applied loads that may occur along the structure service life, including those due to strengthening.

  • Refuerzo a cortante de vigas de hormigón armado, mediante laminados de polímeros reforzados con fibras (FRP)

     Pujol, Mireia; Bairan Garcia, Jesus Miguel; Oller Ibars, Eva; Mari Bernat, Antonio Ricardo
    Congreso de la Asociación Científico-Técnica del Hormigón Estructural
    Presentation's date: 2011-10-27
    Presentation of work at congresses

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    En la actualidad, la aplicación de laminados de polímeros reforzados con fibras (FRP) en el campo de la reparación y del refuerzo de estructuras de hormigón resulta cada vez más frecuente. Si bien los mecanismos de rotura están bien definidos a flexión, no sucede lo mismo en el caso del cortante. De acuerdo con la base de datos experimentales recopilada por los autores, existe una gran dispersión entre los resultados obtenidos experimentalmente y los obtenidos analíticamente siguiendo recomendaciones o guías de diseño vigentes. Con el fin de identificar la contribución real a la resistencia a cortante de los laminados FRP, se ha planteado la realización de una campaña experimental de diez vigas reforzadas con laminados de fibra de carbono adheridos en forma de U. Se ha realizado una predicción de resultados aplicando las recomendaciones vigentes y se han comparado con las obtenidas mediante un modelo numérico de análisis no-lineal.

  • Laminate debonding process of FRP-strengthened beams

     Oller Ibars, Eva; Cobo Del Arco, Diego; Mari Bernat, Antonio Ricardo
    Structure and infrastructure engineering
    Date of publication: 2011-01
    Journal article

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  • Predicting the response of FRP-strengthened reinforced-concrete flexural members with nonlinear evolutive analysis models

     Mari Bernat, Antonio Ricardo; Oller Ibars, Eva; Bairan Garcia, Jesus Miguel
    Journal of composites for construction
    Date of publication: 2011-10
    Journal article

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  • EVALUACIÓN DE LOS EFECTOS DEL DETERIORO, REPARACIÓN Y REFUERZO EN ESTRUCTURAS. MODELO TEORICO Y VERIFICACIÓN

     Bairan Garcia, Jesus Miguel; Oller Ibars, Eva; Etxeberria Larrañaga, Miren; Alegre Heitzmann, Vicente; Fernandez Perez, Ignasi; Pujol Sanchez, Mireia; Santos Ferreira, Denise Carina; Mari Bernat, Antonio Ricardo
    Participation in a competitive project

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  • REHABCAR: Rehabilitación de carreteras y autopista

     Casas Rius, Joan Ramon; Bairan Garcia, Jesus Miguel; Oller Ibars, Eva; Duarte Gomez, Noemi; Mari Bernat, Antonio Ricardo
    Participation in a competitive project

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  • REHABCAR: Rehabilitación de carreteras y autopista

     Martinez Reguero, Adriana Haydee; Bairan Garcia, Jesus Miguel; Casas Rius, Joan Ramon; Mari Bernat, Antonio Ricardo; Oller Ibars, Eva; Botella Nieto, Ramon; Miro Recasens, Jose Rodrigo
    Participation in a competitive project

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  • Interface behaviour in FRP-strengthened beams subjected to transverse loads. Maximum transferred force

     Oller Ibars, Eva; Cobo Del Arco, Diego; Mari Bernat, Antonio Ricardo
    Journal of composites for construction
    Date of publication: 2009-02
    Journal article

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  • Peeling failure in beams externally strengthened by plate bonding: a design proposal

     Oller Ibars, Eva; Cobo Del Arco, Diego; Mari Bernat, Antonio Ricardo
    Structural concrete (London, 1999)
    Date of publication: 2009-06
    Journal article

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  • GRUP DE TECNOLOGIA D'ESTRUCTURES

     Arnedo Pena, Alfredo Bernardo; Agulló Fité, Luís; Roca Fabregat, Pedro; Casas Rius, Joan Ramon; Bairan Garcia, Jesus Miguel; Ramos Schneider, Gonzalo; Molins Borrell, Climent; de la Fuente Antequera, Alberto; Chacon Flores, Rolando Antonio; Valdes Lopez, Manuel; Real Saladrigas, Esther; Garcia Vicente, Tomas; Oller Ibars, Eva; Aparicio Bengoechea, Angel Carlos; Aguado De Cea, Antonio; Mirambell Arrizabalaga, Enrique; Estrada Palacios, Immaculada; Mari Bernat, Antonio Ricardo
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  • Formigó armat i pretensat: exercicis curts de bases de càlcul i estats límit, adaptat a la instrucció EHE-08

     Mari Bernat, Antonio Ricardo; Molins Borrell, Climent; Bairan Garcia, Jesus Miguel; Oller Ibars, Eva
    Date of publication: 2009
    Book

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  • Design proposal to avoid peeling failure in FRP-strengthened reinforced concrete beams

     Oller Ibars, Eva; Cobo Del Arco, Diego; Mari Bernat, Antonio Ricardo
    Journal of composites for construction
    Date of publication: 2009-10
    Journal article

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  • A new design proposal to prevent peeling failure in beams strengthened by plate bonding

     Oller Ibars, Eva; Cobo Del Arco, Diego; Mari Bernat, Antonio Ricardo
    8th International symposium on fiber reinforced polymer reinforcement for concrete structures
    Presentation of work at congresses

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  • Maximum transferred force along the interface in an FRP-strengthened beam subjected to transverse loads

     Oller Ibars, Eva; Cobo Del Arco, Diego; Mari Bernat, Antonio Ricardo
    8th International symposium on fiber reinforced polymer reinforcement for concrete structures
    Presentation of work at congresses

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  • Peeling failure in beams externally strengthened by plate bonding: a design proposal

     Oller Ibars, Eva
    International FIB Symposium: Concrete structures: stimulators of development
    Presentation of work at congresses

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  • Peeling failure in beams strengthened by plate bonding. A design proposal  Open access

     Oller Ibars, Eva
    Defense's date: 2005-10-28
    Department of Construction Engineering, Universitat Politècnica de Catalunya
    Theses

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    La necesidad de refuerzo estructural en una infraestructura existente puede venir motivada por la aparición de nuevos condicionantes de uso o por la degradación de los materiales. Desde finales de los años sesenta, la técnica del refuerzo mediante la adhesión de platabandas metálicas se ha llevado a la práctica como alternativa a otros métodos de refuerzo tradicionales. Sin embargo, las platabandas metálicas presentan algunas desventajas, como son su peso y su posible corrosión por agentes atmosféricos, que pueden solventarse sustituyéndolas por laminados de polímeros reforzados con fibras (FRP). Estos materiales poseen relaciones resistencia/peso y rigidez/peso mayores que el acero, facilitando su colocación, reduciendo costes y plazos de ejecución.En numerosos estudios empíricos se observa como la aplicación de laminados encolados puede resultar en una rotura frágil que conduce al desprendimiento prematuro del refuerzo antes de alcanzar la carga última.El principal objetivo de este trabajo es el desarrollo de un método simple y efectivo para dimensionar y comprobar el refuerzo de estructuras existentes con laminados adheridos de tal forma que se eviten los modos prematuros de rotura que conducen al desprendimiento del laminado. Se ha dedicado especial atención a la transferencia de tensiones de laminado a hormigón que resulta el punto clave del correcto comportamiento de este tipo de refuerzo.En el Capítulo 2, tras una revisión histórica de las líneas de investigación existentes, experimentales y teóricas, se ha evaluado mediante una base de datos experimental la fiabilidad de los modelos teóricos existentes para pronosticar y prevenir los modos de rotura prematuros antes mencionados. Esta base de datos experimental incluye resultados de la literatura existente y de una campaña experimental llevada a cabo por el autor en el Laboratorio de Tecnología de Estructuras de la Universidad Politécnica de Cataluña.Para resolver las deficiencias de los modelos teóricos existentes, en el Capítulo 3, se ha aplicado la teoría de la Mecánica de Fractura No Lineal a un caso de corte puro para modelizar el comportamiento de la interfase y sus roturas prematuras. Se han obtenido las distribuciones de tensiones en la interfase y en el laminado junto a la fuerza máxima transferida en función de tres parámetros (energía de fractura, máxima tensión tangencial y deslizamiento asociado a dicha tensión).La formulación de un caso de corte puro se ha extendido a un caso general de una viga bajo cargas transversales en el Capítulo 4. Se ha estudiado la evolución del desprendimiento del laminado en dos casos específicos: un elemento entre dos fisuras contiguas, y un elemento entre el extremo del laminado y la siguiente fisura. Se han obtenido las distribuciones de tensiones para las distintas fases del proceso. Cabe mencionar que la fuerza transferida entre dos fisuras alcanza su máximo valor cuando la tensión tangencial máxima llega a la fisura menos cargada. En este instante, ya se puede haber iniciado o no la formación de una macrofisura. El elemento entre el extremo del laminado y la siguiente fisura es similar al caso de corte puro.Las distribuciones de tensiones presentadas en el Capítulo 4 nos ayudan a comprender el comportamiento de un elemento reforzado con laminados adheridos en su cara traccionada, sin embargo, resultan complejas en la práctica. En el Capítulo 5 se describe un nuevo método de dimensionamiento y verificación basado en la obtención de una relación entre el máximo cortante antes de que se produzca el desprendimiento prematuro del refuerzo y el momento aplicado. Esta relación está asociada a la fuerza máxima transferida entre fisuras. A partir de la predicción del valor máximo de cortante, se verifica el desprendimiento del extremo del laminado evaluando la fuerza transferida entre dicho punto y la siguiente fisura. Se ha verificado la fiabilidad de esta propuesta mediante la base de datos de ensayos a flexión.Finalmente, en el Capítulo 6 se resumen las principales conclusiones del trabajo presentado en esta tesis y se sugieren futuras líneas de investigación.

    The strengthening of aging infrastructures is in most cases required because of the necessity for increased levels of service loads or because of the degradation of structural materials. The technique of strengthening by externally bonding steel plates has been in practice since the late 1960's. However, steel plates present some disadvantages in terms of weight and corrosion that can be solved by replacing them with fiber reinforced polymer (FRP) laminates. FRP laminates provide benefits such as high strength-to-weight and stiffness-to-weight ratios, corrosion resistance as well as reduced installation costs due to their easy-handling.Existing experimental work has shown that the application of externally bonded laminates can result in a catastrophic brittle failure in the form of a premature debonding of the laminate before reaching the design load.The main aim of this research has been the development of a simple effective method to design and verify the strengthening of an existing structure with an externally bonded plate while preventing the premature peeling failure that causes the laminate to debond. Special attention has been drawn on to transfer of stresses from laminate to concrete through the interface, which is the main key in the correct performance of externally reinforced concrete structures.After a historical overview of the existing experimental and theoretical lines of research, the suitability of using existing theoretical models to forecast and prevent peeling failures is evaluated in Chapter 2 by means of an experimental bending test database. This database includes results from the existing literature and results from an experimental program conducted by the author at the Structural Technology Laboratory of the Technical University of Catalonia.To solve the weaknesses of the existing theoretical models, in Chapter 3, Non-Linear Fracture Mechanics theory is applied in a pure shear case to model the interface behavior and its premature failures. The stress distributions, together with the maximum transferred force are obtained as a function of three model parameters (the fracture energy, the maximum shear stress and the sliding associated to this stress).The formulae of a pure shear specimen are then extended to a general case of a beam under transverse loads in Chapter 4. For this purpose, the evolution of the debonding process is studied for two specific cases: a beam element between two cracks, and a beam element between the laminate end and the nearest crack. The stress distributions are obtained for the different stages observed in the debonding process. A specific highlight observed was that the transferred force between cracks is at maximum when the maximum shear stress reaches the less-loaded crack. In this instance, a macrocrack may or may not have already initiated. Another point observed is related to the beam element between the laminate end and the nearest crack, which is similar to the pure shear specimen.The stress distributions derived in Chapter 4 allow us to understand the behavior of an externally reinforced element, but are awkward for design purposes. Chapter 5 describes both a new design and verification method based on a maximum shear force-bending moment relationship associated to the theoretical maximum transferred force between two consecutive cracks before peeling occurs. After calculating the predicted value for the maximum shear force from the peeling relationship, the developed method verifies the debonding at the laminate end by checking the transferred force between the laminate end and the first crack in the laminate. The reliability of this proposal is verified by means of the assembled bending test database.Finally, the main conclusions drawn from the work presented in this dissertation are summarized in Chapter 6. Future work and research lines are suggested as well.

  • Refuerzo a flexión de vigas de hormigón armado con materiales compuestos: Estudio de la zona de anclaje

     Oller Ibars, Eva; Cobo Del Arco, Diego; Mari Bernat, Antonio Ricardo
    Hormigon y acero
    Date of publication: 2004-04
    Journal article

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  • Refuerzo a flexión de vigas de hormigón armado con laminados CFRP

     Oller Ibars, Eva; Cobo Del Arco, Diego; Mari Bernat, Antonio Ricardo
    Congreso de Puentes y Estructuras de Edificación de la Asociación Científico-Técnica del Hormigón Estructural
    Presentation of work at congresses

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  • Flexural strengthening of reinforced concrete beams with externally bonded CFRP laminates

     Oller Ibars, Eva; Salcedo, J; Cobo Del Arco, Diego; Mari Bernat, Antonio Ricardo
    International Conference Composites in Construction
    Presentation of work at congresses

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  • Refuerzo a flexión de vigas de hormigón armado con laminados de fibras de carbono

     Oller Ibars, Eva; Salcedo, J; Cobo Del Arco, Diego; Mari Bernat, Antonio Ricardo
    Colloquia 2001
    Presentation's date: 2001-04-23
    Presentation of work at congresses

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  • Utilización de materiales compuestos avanzados en estructuras de ingeniería civil

     Cobo Del Arco, Diego; Oller Ibars, Eva; Salcedo, J; Mari Bernat, Antonio Ricardo
    Colloquia 2001
    Presentation of work at congresses

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