Facultad Regional Concep. del Uruguay

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    Estudio numérico-experimental del comportamiento mecánico-estructural de tubos de hormigón reforzado con fibras de acero
    (2024-03-22) Ferrado, Facundo Luis; Escalante, Mario Raúl; Rougier, Viviana Carolina
    La utilización de tubos de sección circular es la opción m ´ as difundida en la actualidad para aplicaciones de drenajes urbanos. La consideración de las fibras de acero como material de refuerzo en tubos de hormigón, en sustitución completa o parcial de la tradicional armadura, podrían tener un impacto positivo en la optimización del producto. Este impacto positivo esta relacionado con las propiedades mejoradas del hormigón reforzado con fibras (HRFA) en comparación con el hormigón tradicional reforzado con barras, entre las que se destacan un mejor comportamiento a tracción principalmente en estado pos-fisura junto con una mayor ductilidad y capacidad de deformación. Las dificultades actuales respecto a su uso están asociadas principalmente a la necesidad de un mayor conocimiento del comportamiento del HRFA aplicado a este tipo de estructuras y también a la escasez de modelos numéricos capaces de predecir aproximadamente el desempeño de los tubos. En este trabajo se investiga el comportamiento mecánico-estructural de tubos de HRFA elaborado con materiales y sistemas de fabricación utilizados por nuestra industria. Para ello, se plantea un modelo representativo de dos fases (hormigón-fibras) que considera la orientación y distribución aleatoria de las fibras dentro de la masa de hormigón y la influencia de dichas variables en la capacidad resistente del tubo. El modelo así propuesto tiene en cuenta también la proporción y geometría de la fibra. Para el hormigón se utiliza un modelo constitutivo desarrollado por el FIB MODELCODE 2010 mientras que para las fibras se utiliza un modelo de material que tiene en cuenta el fenómeno de arrancamiento de manera macroscópica. El modelo numérico desarrollado es implementado en un programa de elementos finitos, el cual reproduce el comportamiento mecánico de tubos de HRFA al someterlos a un ensayo de compresión diametral normalizado. Se llevo a cabo a su vez una campana experimental a escala real y los resultados ˜ obtenidos son comparados entre si. Finalmente se realizo una estimación teórica de los resultados obtenidos numérica y experimentalmente. La metodología propuesta permite analizar la influencia de la orientación y distribución de las fibras en la capacidad resistente del tubo. Del estudio numérico se concluye que dichas variables tienen una influencia significativa en el comportamiento de los tubos estudiados aquí. Por su parte, de la campana experimental se puede concluir que las fibras pueden utilizarse, en dosis adecuadas, como reemplazo de la armadura tradicional y que su utilización modifica tanto la capacidad de carga como el modo de falla en tubos.
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    Simulation of the three edge bearing test : 3D model for the study of the strength capacity of SFRC pipes
    (Asociación Argentina de Mecánica Computacional, 2018-11-06) Ferrado, Facundo Luis; Escalante, Mario Raúl; Rougier, Viviana Carolina
    The use of SFRC as building material, has been expanding its possibilities beyond conventional applications. Among its new applications, SFRC pipes appear as a new reliable alternative to the common pipes which use steel mesh as reinforcement, due to the structural benefits that mean the fiber addition. In spite of the advances achieved regarding the knowledge of the behavior of SFRC as a structural material, a numerical tool which allows to predict the mechanical response of SFRC pipes is needed,this is due to the complexity of the costly experimental campaigns. In this work the mechanical behavior of SFRC pipes is numerically assessed by means of the simulation of the three edge bearing test (TEBT) according to IRAM 11503 standard through a tridimensional model, which is implemented using a finite element analysis tool. SFRC is considered as an homogeneous material described for a damage-plasticity model which consider different behaviors in tension and compression by means of stress-strain uniaxial curves. These curves are obtained from equations arising from theoretical-experimental developments of other authors. Finally the results of the simulations are shown by means of load-deflection curves, ultimate loads charts and strength distribution diagrams, which are compared with those ones obtained in a experimental campaign carried out by the authors themselves. The results are complemented with some pictures depicting the experimental campaign mentioned above, with both the equipment used during the tests as well as the failure modes of the pipes are shown.
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    Numerical simulation of the three edge bearing test of steel fiber reinforced concrete pipes
    (Asociación Argentina de Mecánica Computacional, 2016-11-11) Ferrado, Facundo Luis; Escalante, Mario Raúl; Rougier, Viviana Carolina
    Historically, steel has been the material chosen to improve the tensile behaviour of concrete. Nowadays, the trending of replacing the traditional reinforcement bars with short and slender fibers randomly distributed in the mass concrete, is growing. This composite material made essentially of common concrete reinforced with discrete fibers is called steel fiber reinforced concrete(SFRC). In this work the mechanical behaviour of SFRC pipes is studied, simulating the diametral compression test called three edge bearing test by means of a 2d model in plane strain state. The SFRC is considered as a homogeneous material and its behaviour is represented through some damage - plasticity model (concrete damage plasticity) which takes into account the progressive reduction in the values of the elastic constants due to plastic strain and damage by means of a stiffness degradation variable. The model assumes that the main two failure mechanisms of the concrete are tensile cracking and compressive crushing, thus, the tensile and compression response is characterized through differentiated uniaxial stress-strain curves. This representation, although simplified, captures the most important features of the concrete response. The equations are solved with a commercial computational package. In addition, and as an alternative for the same problem, a case is addressed in which the SFRC is considered as an equivalent homogeneous material too, although a coupled plastic-damaged model is used where the coupling between plasticity and damage is achieved through a simultaneous solution of the plastic and the damage problem. Finally is presented a modified coupled damaged plasticity model that comes from a modification of the LublinerOller yield criterion from the adoption of a yield function of second degree in the components of the stress tensor. For the coupled damage plasticity the contribution of the fibers is considered through the classic mixture theory according to it is performed a modification of the elastic constants depending on the volumetric contribution of the fibers. Here, the problem is solved using the non-linear finite elements code PLastic Crack dynamic (PLCd) The validity of the numerical tool is performed comparing the results of the simulation with experimental data existing in the literature.
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    Finite element numerical analysis of the bearing capacity of hybrid fiber reinforced concrete pipes
    (2017-11-05) González, Federico Alejandro; Rougier, Viviana Carolina; Escalante, Mario Raúl
    Reinforced concrete with two or more types of fibers, rationally combined (hybrid fiber reinforced concrete,HFRC)may offer enhanced properties,especially in terms of ductility and crack control. The use of these concretes in drainage pipes, either partially or totally substituting steel meshes and bars of traditional reinforcement, might have a favorable impact on the optimization of the product in the precast industry from both technical and economic point of view. The HFRC can be prepared and placed into molds in a similar way as for plain concrete, where the fibers are added to the mix just like any other aggregate. In this paper, as part of an initial stage of an on going research, the mechanical behaviour of hybrid reinforced concrete pipes (steel and polypropylene) is numerically assessed by simulation of the threeedge bearing test (TEBT). The HFRC is modeled as a homogeneous material with equivalent properties (macro model), in which the characteristic parameters of the material, used in the simulation, are obtained through an experimental study. The problem is solved by a nonlinear finite element code in which a coupled damage and plasticity constitutive model is used.Finally, the results are compared with experimental data obtained by another author.