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  • Enginyeria de la construcció

     Molins Borrell, Climent
    Date of publication: 2014-02-01
    Book chapter

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  • Characterization of the properties of steel fiber reinforced concrete by means of the generalized Barcelona test

     Carmona Malatesta, Sergio; Aguado De Cea, Antonio; Molins Borrell, Climent
    Construction & building materials
    Date of publication: 2013-11
    Journal article

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  • Effect of variations in thermal-curing cycle on the cracking risk of precast segmental tunnel lining

     Crespo, Maria D.; Molins Borrell, Climent; Mari Bernat, Antonio Ricardo
    Construction & building materials
    Date of publication: 2013
    Journal article

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    This paper analyzes, both experimentally and numerically, the effect of thermal curing on the evolution of temperatures, rate of temperature rise and cooling, stresses and strengths in reinforced concrete elements. It also describes the experimental program carried out to characterize thermally and mechanically the high strength concrete used in the precast segments of the Pajares Tunnel lining. The thermo numerical analysis allows verifying whether a given cycle complies with rules of good practice with regard to maximum temperatures reached within the segment and maximum rates of heating and cooling. The mechanical analysis allows evaluating the cracking risk by comparing the evolution of stress and effective strength at the points of the segments that have higher risk of cracking. The developed computational tool can be used as a virtual laboratory to determine the curing cycle that is most appropriate for each type of segment

  • Comportamiento resistente de revestimientos de túnel de anillos de dovelas prefabricadas de hormigón

     Arnau Delgado, Oriol; Molins Borrell, Climent
    Revista de obras públicas
    Date of publication: 2013
    Journal article

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    This article presents the results of research carried out in the field of the structural response of tunnel linings made of precast concrete segments. The investigation began with the realization of a load test on a site located within an experimental section line 9 of the Barcelona Metro. The conclusions drawn about its behavior allowed the development of numerical models, both 2D and 3D, validated with the experimental results. This research also includes the study of the longitudinal behavior of the lining in order to determine the extent to which longitudinal compression initially introduced by the TBM is dissipated over time due to the influence of lining creep, which determines the longitudinal interaction between adjacent rings. Finally, the effect on the segmental lining design of taking into account its 3D response subjected to both, typical distributed design loads, or localized actions that would occur in special or accidental conditions is appraised.

  • Enginyeria de la Construcció

     Molins Borrell, Climent
    Date of publication: 2013-01
    Book chapter

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  • Study of the sensitivity of different building structures to tunneling induced settlements

     Molins Borrell, Climent; Camos Andreu, Carles
    International Conference on Structures and Architecture
    Presentation's date: 2013-07-24
    Presentation of work at congresses

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    The sensitivity of urban buildings to tunneling induced settlements can vary according to the structural types and building materials. Very few studies deal with this particular field and, for design purposes, heuristic approaches are applied based on the studies developed in UK in the 1970's. From the statistical results of a sample of buildings located over the influence zones of the L9 metro line in Barcelona, three types of structures were devised to include most of them: (1) pure masonry buildings, (2) buildings combining masonry bearing walls and RC slabs and (3) buildings with RC structural frame with masonry infill. The paper discusses the numerical simulation of such structural types in service conditions and presents the particular phenomena (cracking of masonry and concrete, gapping between masonry walls and the RC beams or columns) that should be taken into account to assess the sensitivity of these buildings to tunneling settlements.

    he sensitivity of urban buildings to tunneling induced settlements can vary according to the structural types and building materials. Very few studies deal with this particular field and, for design purposes, heuristic approaches are applied based on the studies developed in UK in the 1970's. From the statistical results of a sample of buildings located over the influ- ence zones of the L9 metro line in Barcelona, three types of structures were devised to include most of them: (1) pure masonry buildings, (2) buildings combining masonry bearing walls and RC slabs and (3) buildings with RC structural frame with masonry infill. The paper discusses the numerical simulation of such structural types in service conditions and presents the particular phenomena (cracking of masonry and concrete, gapping between masonry walls and the RC beams or columns) that should be taken into account to assess the sensitivity of these buildings to tunneling settlements.

  • Studies and repair of the railway bridge of Soller in Mallorca

     Molins Borrell, Climent
    International Conference on Arch Bridges
    Presentation's date: 2013-10-03
    Presentation of work at congresses

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    The studies and the repair works that were carried out on the railway bridge of Monts Reials in Sòller, which is the main city in the north-west coast of Mallorca , are described. The bridge presents five barrel vaults spanning eight meters with a width of 3.6 m and a depth of 0.60 m. The bridge was in a general good condition except for the first arch which presented some significant cracks, including very wide transversal cracks close to the abutments and spalling of the brick fabric just under the key of the arch. The assessment of the arch included the review of design documentation, full geometrical characterization of the arch, dynamic load tests and finite element analysis to check the capacity of the arch and interpret the causes of the damage. Repair works consisted of grouting of the arch ring, particularly in the cracks, repointing of the intrados of the barrel vault and the voussoirs and a watertight layer on the extrados.

    The studies and the repair works that were carried out on the railway bridge of Monts Reials in Sòller, which is the main city in the north-west coast of Mallorca , are described. The bridge presents five barrel vaults spanning eight meters with a width of 3.6 m and a depth of 0.60 m. The bridge was in a general good condition except for the first arch which presented some significant cracks, including very wide transversal cracks close to the abutments and spalling of the brick fabric just under the key of the arch. The assessment of the arch included the review of design documentation, full geometrical characterization of the arch, dynamic load tests and finite element analysis to check the capacity of the arch and interpret the causes of the damage. Repair works consisted of grouting of the arch ring, particularly in the cracks, repointing of the intrados of the barrel vault and the voussoirs and a watertight layer on the extrados.

  • A 3D temporal evolutionary numerical model of a masonry building in Barcelona subjected to tunnelling subsidence

     Camos Andreu, Carles; Molins Borrell, Climent
    International Conference Computational Methods in Tunneling and Subsurface Engineering
    Presentation's date: 2013-04-17
    Presentation of work at congresses

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    The aim of this work is to deepen the knowledge of the numerical simulation used in the prediction of building damage produced by tunnelling subsidence. This paper analyzes the structural response of a one-storey building subjected to real ground movements experienced during the construction of the L9 Metro line tunnel in Barcelona, bored by a Earth Pressure Balance Machine (EPB) Tunnel Boring Machine (TBM). A 3D temporal evolutionary numerical model is used to predict the damage in the building resulting from tunnelling subsidence. The real structural damage presented is compared with the predictions of the numerical model. This last task can be done since the measures of real ground movements given by the monitoring instruments, such as retro-reflective prisms and total stations, are available for this research. Main model parameters have been determined by means of characterization experiments developed on the site and in the laboratory, thus giving a higher significance to the analysis.

    The aim of this work is to deepen the knowledge of the numerical simulation used in the prediction of building dam age produced by tunnel ling subsidence. This paper analyzes the structural response of a one-storey building subjected to real ground movements experienced during the construction of the L9 Metro line tunnel in Barcelona, bored by a Earth Pressure Balance Machine (EPB) Tunnel Boring Machine (TBM). A 3D temporal evolutionary numerical model is used to predict the damage in the building resulting from tunnelling subsidence. The real structural damage presented is compared with the predictions of the numerical model. This last task can be done since the measures of real ground movements given by the monitoring instruments, such as retro -reflective prisms and total stations, are available for this research. Main model parameters have been determined by means of characterization experiments developed on the site and in the laboratory, thus giving a higher significance to the analysis.

  • Micro-modeling of stack bond masonry in compression using a plasticity law

     Drougkas, Anastasios; Molins Borrell, Climent; Roca Fabregat, Pedro
    International Conference on Computational Plasticity Fundamentals and Applications
    Presentation's date: 2013-09
    Presentation of work at congresses

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    A set of experimental tests to determine the compressive strength of masonry stack prisms has been numerically simulated using a combined plasticity-smeared crack constitutive law employed in three-dimensional analysis. Supported by an experimental campaign for the mechanical characterization of lime mortar masonry, a series of finite element analyses was performed in an attempt to assess the capacity of the model to reproduce the results obtained in terms of capacity, failure mode and global stiffness. The constitutive law used for the non-linear analysis of the masonry is a combination of a smeared cracking model in tension and a pressure dependent plasticity model in compression, which is capable of accounting for all failure mechanisms that may arise in concentric compression of masonry, both in the units and in the mortar. The purpose of this investigation is to establish whether a numerical approach based on the micro-modeling method is suitable for the simulation of the salient features encountered in masonry under compression as well as highlighting the main material properties necessary to be determined in order to properly model such experiments. The results are expanded upon through a parametric investigation.

  • Ensayo de doble punzonamiento para concreto reforzado con fibra: efecto del tamaño y origen de la probeta

     Aire, Carlos; Molins Borrell, Climent; Aguado De Cea, Antonio
    Concreto y cemento: investigación y desarrollo
    Date of publication: 2013
    Journal article

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    Traditionally, to characterize the behavior of reinforced concrete with fiber (CRF) flexural tests are performed on beams. However, in accordance with various studies on FRC, it has been seen different variation coefficients of the order of 20 % for the results of flexural test beams. Recently, it has been developed a new method based on the double punching, called Barcelona test, as an alternative to determine the resistance to the indirect traction of the FRC. It is a test of easy execution over which a cylinder of 150 mm of diameter and 150 mm of height, undergoes double punching test, which allows to obtain the resistance to indirect tension of the FRC, with coefficients of variation less than those obtained by methods which employ beams. This article shows the results of a comparative study between results of resistance and toughness applying the Barcelona test obtained in molded test cylinders of 100 and 150 mm and cores of 93 and 153 mm.

  • Caracterización y diseño del homigón reforzado con fibras plásticas  Open access

     Pujadas Alvarez, Pablo
    Defense's date: 2013-03-22
    Department of Construction Engineering, Universitat Politècnica de Catalunya
    Theses

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    En esta Tesis Doctoral se abordan aspectos de gran interés en relación a la caracterización del HRFP, la definición de una ecuación constitutiva considerando la orientación de las fibras, y el comportamiento diferido del material. Con ello se pretende contribuir a abrir el camino definitivo del HRFP como posible material de refuerzo frente a las tracciones en elementos con clara responsabilidad estructural y superar, de este modo, las barreras que existen en la actualidad. En primer lugar se analiza la validez de las metodologías de diseño propuestas en las distintas normativas y se evalúan los modelos constitutivos que en ellas se proponen. Para ello se han realizado dos campañas experimentales a escala real: la primera sobre elementos tipo vigas de hormigón reforzados con armadura mixta, es decir macro-fibras plásticas y armadura convencional y la segunda sobre losas hiperestáticas reforzadas únicamente con macro-fibras plásticas. En dicho análisis se ha observado que los planteamientos de análisis inversos tradicionalmente utilizados en dichas normativas conducen a una clara sobreestimación de los resultados experimentales para elementos únicamente reforzados con fibras plásticas. Ello es debido a que la configuración de los ensayos de caracterización a flexotracción y la geometría y orientación de las fibras en las probetas prismáticas utilizadas no son representativas de los elementos tipo losa. Así mismo, las ecuaciones constitutivas de EHE y RILEM (trilineal y multiilineal), son excesivamente optimistas para el cálculo de elementos únicamente reforzados con fibras plásticas. Todo ello pone de manifiesto la necesidad de revisar los modelos constitutivos propuestos en las normativas para el HRFP y proponer una nueva ecuación constitutiva para el diseño basada en una filosofía diferente. Como pasos previos hasta la definición de la nueva ecuación constitutiva con la que superar los inconvenientes de los enfoques actuales, se ha desarrollado un modelo analítico para convertir el desplazamiento de pistón (delta ) en TCOD, eliminando la necesidad de emplear la cadena extensométrica en el ensayo Barcelona. Adicionalmente, se ha propuesto un nuevo ensayo de caracterización (MDPT) con el que determinar la resistencia a fisuración, tenacidad y resistencia residual a tracción del HRF teniendo en cuenta de manera indirecta la orientación de las fibras según tres direcciones principales. Ambas propuestas se han validado en base a campañas experimentales con probetas y testigos de HRFP. Finalmente, se presenta y valida un nuevo planteamiento directo para predecir la respuesta postfisuración del HRFP a partir del ensayo MDPT. La nueva filosofía tiene sentido físico y refleja de forma fidedigna el comportamiento a tracción del material, considerando la orientación de las fibras bajo las condiciones reales de puesta en obra y geometría de la estructura. El comportamiento diferido del HRFP no debe convertirse en un inconveniente para el uso de este material siempre y cuando la consideración de sus efectos sea contemplada en el diseño estructural. Por ello, la Tesis se completa con el estudio de las deformaciones diferidas que se producen en elementos fisurados de HRFP cuando están sometidos a cargas de larga duración. Para ello se ha realizado un campaña experimental con la que se evalúa la influencia del nivel de carga y fisuración en el rendimiento a largo plazo del material bajo cargas mantenidas en el tiempo y se propone un modelo para predecir el comportamiento diferido de los HRFP en base a los resultados obtenidos.

    This thesis discusses issues of great interest for the design of PFRC regarding its characterization, the definition of a constitutive equation for PFRC that takes into account the orientation of fibers and its long-term behavior. First, in addition to reviewing the key technical papers on the definition of constitutive equations, a detailed analysis of the main regulatory models proposed Europe-wide for the use of structural fibre-reinforced concrete is done. The intention is to provide an overview of the most relevant aspects of these models and the conceptual grounds on which they were developed. A detailed comparative study was conducted to determine the capacity of each model analyzed to predict PFRC structural behaviour. In this part, two real scale experimental campaigns are conducted: the first one with beams reinforced with both, macro-plastic fibers and conventional reinforcement and the second on hyperstatic slabs only reinforced with macro- plastic fibers. The results of the experimental campaigns are compared to the numerical results obtained with the constitutive equations analyzed. The inverse analysis approaches traditionally used for design of FRC lead to a clear overestimation of the experimental results in the case of the real-scale slabs, which were only reinforced with plastic fibres.This may be attributed to the characterization tests (flexural tests on small beams), whose test setup, geometry of the specimens and the fiber orientation are not representative the real-scale slabs. Likewise, the constitutive equations proposed by RILEM and EHE (trilinear and multilinear, respectively) are overly optimistic for the design of PFRC elements. This highlights the need to review the existing constitutive models for PFRC and propose a new constitutive equation, based on a different philosophy. As the first step to obtain a constitutive equation that overcomes the drawbacks of the existing approaches, an analytical model to transform the axial displacement (d) into TCOD in the Barcelona test is developed (eliminating the need to use in the chain gage). In addition to that, a new characterization test (MDPT) is proposed to determine the cracking strength, toughness and tensile residual strength of the PFRC indirectly considering the fiber orientation in three main directions. Both proposals are validated with experimental results. Finally, a new direct approach to predict the PFRC postcracking response by means of the MDPT test is presented and validated. The rational and comprehensive new approach provides physical insight that may be gathered into a straightforward procedure, in which the real orientation of the fibers (according to the casting method and the geometry of the structural application) is considered to obtain the tensile behavior of the material. Creep behavior of PFRC must not become an inconvenience for the use of this material as long as the its effects areconsidered in the structural design. Thus, this thesis includes the study of long-term deformations occurring in cracked specimens of FRCP when subjected to long-term loading. An experimental campaign iscarried out in order to evaluate the influence of load and cracking levels in the long-term performance of the material under maintained load over time. Based on the results, a simple model to predict the creep behavior of PFRC is proposed.

  • Método de doble punzonamiento de tracción indirecta para concreto reforzado con fibra: Ensayo Barcelona

     Aire, Carlos; Aguado De Cea, Antonio; Molins Borrell, Climent
    Date of publication: 2013-12-10
    Book

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    The present work describes the results of an experimental investigation on the performances of concrete specimens reinforced with steel fibers using the double punch test (DPT). The DPT is an indirect tensile test based on the configuration of double-punch test, named, Barcelona test that was developed for the systematic control of fiber reinforced concrete. DPT can be carried out by testing 150 × 150 mm concrete cylinders subjected to double punching test. Previous experimental results have showed that DPT gives significantly lower variability compared to other test methods. In the test performed, indirect tensile strength and fracture toughness result obtained by DPT were compared using molded cylinder and core concrete specimens.

  • Influence of fibre orientation on the performance of steel fibre-reinforced concrete

     Grünewald, Steffen; Laranjeira de Oliveira, Filipe; Walraven, Joost; Aguado De Cea, Antonio; Molins Borrell, Climent
    RILEM International Symposium on Fibre Reinforced Concrete
    Presentation's date: 2012-09-19
    Presentation of work at congresses

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    The performance of fibre-reinforced materials in the hardened state depends on the material behaviour, the production method and influences related to the structure. The position and the orientation of fibres in a structure can differ from the homogenous distribution and the random orientation in a mixer. Due to the flow of the concrete, fibres are able to orient which makes the prediction of the structural behaviour of fibre-reinforced concrete more complex, but it also offers the potential for an improved structural performance. Synergetic effects were observed with regard to flowable concrete related to the fibre efficiency. This paper discusses two studies on the effect of fibre orientation on the performance of steel fibre- reinforced concrete. The first study discusses the relation between fibre orientation and the distribution of fibre orientation. The analysis indicates that the variation of fibre orientation follows a Gaussian law and the distribution of fibre orientation can be predicted from the average fibre orientation. The second study on tunnel segments discusses the influence of production on the fibre orientation and how this affects the splitting tensile strength. The fibre orientation affects the fibre efficiency and the structural performance of steel fibre-reinforced concrete.

  • Ensayo de doble punzonamiento (ensayo Barcelona) para caracterizar el comportamiento del hormigón reforzado con fibra

     Aire, Carlos; Aguado De Cea, Antonio; Molins Borrell, Climent
    Congreso Internacional y Reunión Técnica Asociación Argentina de Tecnología del Hormigón
    Presentation's date: 2012-11-07
    Presentation of work at congresses

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    Tradicionalmente, para caracterizar el comportamiento del hormigón reforzado con fibra se realizan ensayos de flexotracción en vigas. Sin embargo, existen otros procedimientos que debido a la complejidad y variabilidad de sus resultados no son considerados como procedimientos sistemáticos de control. Recientemente, se desarrolló un nuevo método llamado ensayo Barcelona, como una alternativa para determinar la resistencia a tracción indirecta del hormigón reforzado con fibra. Es un ensayo de fácil ejecución mediante el cual un cilindro de 150 mm de diámetro y 150 mm de altura, se someten a ensayo de doble punzonamiento. El método permite obtener la resistencia a tracción del hormigón confinado con fibra con coeficientes de variación menor a los obtenidos por otros métodos. Este artículo presenta un estudio comparativo entre los resultados de resistencia y tenacidad aplicando el ensayo Barcelona y el de Flexotracción.

  • Numerical tool for modeling steel fiber reinforced concrete

     Molins Borrell, Climent; Pros Parés, Alba; Diez Mejia, Pedro
    RILEM International Symposium on Fibre Reinforced Concrete
    Presentation's date: 2012-09-20
    Presentation of work at congresses

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    Steel Fiber Reinforced Concrete (SFRC) allows overcoming brittleness and weakness in tension, the main drawbacks of plain concrete. The goal of the present presentation is to present an ad-hoc numerical strategy to account for the contribution of the fibers in the simulation of the mechanical response of SFRC. In the model presented, the individual fibers immersed in the concrete bulk are accounted for in their actual location and orientation. The selected approach is based on the ideas introduced in the Immersed Boundary (IB) methods. These methods were developed to account for 1D (or 2D) solids immersed in 2D (or 3D) fluids. Here, the concrete bulk is playing the role of the fluid and the cloud of steel fibers is acting as the immerse boundary (that is a 1D structure in a 2D or 3D continuous). Thus, the philosophy of the IB methodology is used to couple the behavior of the two systems, the concrete bulk and the fiber cloud, precluding the need of matching finite element meshes. In the proposed approach, the meshes of the concrete bulk and fiber cloud are independent and the models are coupled imposing displacement compatibility and equilibrium of the two systems. The concrete bulk is modeled using any nonlinear model. The constitutive model for the fibers is designed to account for the complex interaction between fibers and concrete. The fiber models are based on previous investigations describing the concrete-fiber interaction and its dependence on the factors identified to be relevant: shape of the fiber (straight or hooked) and angle between the fiber and the crack plane. 3D examples with fibers distributed and oriented randomly are reproduced using the proposed approach.

  • Use of double punching test (Barcelona test) for quality control of fiber reinforced concretes

     Carmona Malatesta, Sergio Alejandro; Aguado De Cea, Antonio; Molins Borrell, Climent
    International Conference: Concrete in the Low Carbon Era
    Presentation's date: 2012-07
    Presentation of work at congresses

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    Traditionally, flexural testing is used to characterize the strength and post–peak behavior of fiber–reinforced concretes (FRC). Nevertheless, these tests results exhibit a high dispersion, and therefore invalidate their use as tests for the systematic control of FRCs in works. Also, they have the disadvantage of being complex tests, which require heavy specimens and highly qualified staff. With the aim to solve these problems, an indirect tensile test based on double punching test set up, called the Barcelona test, has been proposed to control tensile behavior of FRC. This test requires smaller specimens, with a high specific surface of fracture, allowing obtain values representative of strength and toughness of materials, with considerably less dispersion than other experimental methodologies, and was recently standardized in Spain. This paper presents the results of an experimental program, which validate the use of Barcelona test as a suitable methodology to systematic characterization FRC in works.

  • An attempt to the determination of the partial safety factor for SFRC members subjected to bending forces

     Camos Andreu, Carles; Casas Rius, Joan Ramon; Molins Borrell, Climent
    RILEM International Symposium on Fibre Reinforced Concrete
    Presentation's date: 2012-09-20
    Presentation of work at congresses

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    In the last few years, research on techniques that permit the reduction or even the complete elimination of structural bar reinforcements has been intensified. The addition of steel fibres to the concrete matrix is proven to be an effective way of covering the deficiencies in this material when subjected to tensile stress. However, there still exists uncertainty surrounding some of the basis of design of structural members in ultimate condition. A clear example is the partial safety factor applied to the tensile strength. In this paper, a reliability-based analysis is carried out through the study of a particular application, such as the tunnel lining concrete segments built in an experimental section of the L9 Metro tunnel in Barcelona, solely reinforced with steel fibres. Specimens were extracted from three different segments and tested in tension by using the Barcelona test. Such a representative sample of tensile strength results made possible an assessment of the degree of the existing safety in this particular case by applying the reliability method FORM. The reliability analysis suggested a partial factor equal to 1.77. This would represent a first step to obtain the general material safety factor, which may involve a calibration in a wide range of tunnel segments and afterwards, other structural members and applications of SFRC.

  • Numerical simulation of the structural behaviour of buildings under tunnelling settlements: a case study in the L9 metro line (Barcelona)

     Camos Andreu, Carles; Molins Borrell, Climent; Arnau Delgado, Oriol; Gálvez, Javier
    International Conference on Structural Analysis of Historical Construction
    Presentation's date: 2012-10-15
    Presentation of work at congresses

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  • Fibre reinforced concrete pipes: new designing trends

     de la Fuente Antequera, Alberto; Domingues de Figueiredo, Antonio; Aguado De Cea, Antonio; Molins Borrell, Climent; Campos Escariz, Renata
    RILEM International Symposium on Fibre Reinforced Concrete
    Presentation's date: 2012-09-21
    Presentation of work at congresses

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  • A new approach on crushing strength test for fibre reinforced concrete pipes

     Domingues de Figueiredo, Antonio; de la Fuente Antequera, Alberto; Molins Borrell, Climent; Aguado De Cea, Antonio
    RILEM International Symposium on Fibre Reinforced Concrete
    Presentation's date: 2012-09-21
    Presentation of work at congresses

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  • A new design method for steel fibre reinforced concrete pipes

     de la Fuente Antequera, Alberto; Campos Escariz, Renata; Domingues de Figueiredo, Antonio; Molins Borrell, Climent; Aguado De Cea, Antonio
    Construction & building materials
    Date of publication: 2012-05
    Journal article

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  • Generalization of the Barcelona test for the toughness control of FRC

     Carmona Malatesta, Sergio; Aguado De Cea, Antonio; Molins Borrell, Climent
    Materials and structures
    Date of publication: 2012-07
    Journal article

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  • Numerical model for the analysis up to failure of precast concrete sections

     de la Fuente Antequera, Alberto; Aguado De Cea, Antonio; Molins Borrell, Climent; Armengou, Jaume
    Computers & structures
    Date of publication: 2012-09
    Journal article

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    Steel fiber reinforced concrete pipes. Part 2: Numerical model to simulate the crushing test  Open access

     de la Fuente Antequera, Alberto; Domingues de Figueiredo, Antonio; Aguado De Cea, Antonio; Molins Borrell, Climent; Chama Neto, Pedro Jorge
    IBRACON structures and materials journal
    Date of publication: 2012-01
    Journal article

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    This paper is part of an extensive work about the technological development, experimental analysis and numerical modeling of steel fibre reinforced concrete pipes. The first part (“Steel fibre reinforced concrete pipes. Part 1: technological analysis of the mechanical behavior”) dealt with the technological development of the experimental campaign, the test procedure and the discussion of the structural behavior obtained for each of the dosages of fibre used. This second part deals with the aspects of numerical modeling. In this respect, a numerical model called MAP, which simulates the behavior of fibre reinforced concrete pipes with medium-low range diameters, is introduced. The bases of the numerical model are also mentioned. Subsequently, the experimental results are contrasted with those produced by the numerical model, obtaining excellent correlations. It was possible to conclude that the numerical model is a useful tool for the design of this type of pipes, which represents an important step forward to establish the structural fibres as reinforcement for concrete pipes. Finally, the design for the optimal amount of fibres for a pipe with a diameter of 400 mm is presented as an illustrating example with strategic interest.

  • Framework to predict the orientation of fibers in FRC: a novel philosophy

     Laranjeira de Oliveira, Filipe; Aguado De Cea, Antonio; Molins Borrell, Climent; Grünewald, Steffen; Walraven, Joost; Pialarissi Cavalaro, Sergio Henrique
    Cement and concrete research
    Date of publication: 2012-06
    Journal article

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    Steel fiber reinforced concrete pipes. Part 1: technological analysis of the mechanical behavior  Open access

     Domingues de Figueiredo, Antonio; de la Fuente Antequera, Alberto; Aguado De Cea, Antonio; Molins Borrell, Climent; Chama Neto, Pedro Jorge
    IBRACON structures and materials journal
    Date of publication: 2012-01
    Journal article

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    This paper is the first part of an extensive work focusing the technological development of steel fiber reinforced concrete pipes (FRCP). Here is presented and discussed the experimental campaign focusing the test procedure and the mechanical behavior obtained for each of the dosages of fiber used. In the second part (“Steel fiber reinforced concrete pipes. Part 2: Numerical model to simulate the crushing test”), the aspects of FRCP numerical modeling are presented and analyzed using the same experimental results in order to be validated. This study was carried out trying to reduce some uncertainties related to FRCP performance and provide a better condition to the use of these components. In this respect, an experimental study was carried out using sewage concrete pipes in full scale as specimens. The diameter of the specimens was 600 mm, and they had a length of 2500 mm. The pipes were reinforced with traditional bars and different contents of steel fibers in order to compare their performance through the crushing test. Two test procedures were used in that sense. In the 1st Series, the diameter displacement was monitored by the use of two LVDTs positioned at both extremities of the pipes. In the 2nd Series, just one LVDT is positioned at the spigot. The results shown a more rigidity response of the pipe during tests when the displacements were measured at the enlarged section of the socket. The fiber reinforcement was very effective, especially when low level of displacement was imposed to the FRCP. At this condition, the steel fibers showed an equivalent performance to superior class pipes made with traditional reinforced. The fiber content of 40 kg/m3 provided a hardening behavior for the FRCP, and could be considered as equivalent to the critical volume in this condition.

  • Enginyeria de la construcció

     Molins Borrell, Climent
    Date of publication: 2012-01-31
    Book chapter

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    Tot i l'habitual creixement en potència i nuclis dels microprocessadors, l'any va tenir com a gran novetat l'estabilització del nou mercat dels telèfons intel·ligents (smartphones) i, sobre tot, de les "tauletes" (tablets), on diversos fabricants van començar a fer competència als iPhone i iPad d'Apple que ja van comercialitzar noves versions durant l'any 2011. També cal destacar que va crèixer de la idea de la "inf ormàtica verda" (green computing) respectuosa amb el medi ambient i, sobre tot, la força de les xarxes socials quasi ja del tot imprescindibles. Sense oblidar la desaparició, en poques setmanes, de tres personatges que han estat fonamentals en diversos aspectes de la informàtica moderna, ni els esforços d'Europa per estar al dia en el tema dels projectes de futur de les TIC. També és novetat l’arribada d’Amazon a Espanya, a partir de setembre d’enguany. Això suposa, entre d’altres coses, una empenta a la venda del seu lector de eBooks Kindle que es proposa com a regal nadalenc.

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  • Numerical Approach For Modeling Steel Fiber Reinforced Concrete  Open access

     Pros Parés, Alba
    Defense's date: 2012-02-06
    Universitat Politècnica de Catalunya
    Theses

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    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.

  • Structural Response of Precast Concrete Segmental Tunnel Linings  Open access

     Arnau Delgado, Oriol
    Defense's date: 2012-03-16
    Department of Construction Engineering, Universitat Politècnica de Catalunya
    Theses

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    The increasing use of the tunnel boring machines (TBMs) has entailed their own evolution and the improvement of the construction processes applied, allowing the construction of tunnels on more complex hydro-geological conditions. These new drilling facilities imply that higher ground and water pressures have to be resisted by the structural lining, turning its design into a key item in all current tunnel projects. TBMs construction process is mainly associated to precast concrete segmental tunnel linings, which are consisted of concrete rings sequentially placed as the tunnel drilling advances. Despite segmental tunnel linings are widely used, their structural response presents significant uncertainties due to the particular configuration on multiple precast pieces and the evolutionary construction process applied. The improvement and optimization of segmental tunnel linings, necessary to obtain safer structures at a lower cost, requires a significant advance in the knowledge of their structural response and about the appropriate techniques to properly reproduce it. This PhD thesis present the mechanisms and phenomena involved in the structural response of precast concrete segmental tunnel linings, detailing numerical modeling strategies to properly simulate them. The integration of all these techniques in a unique model allows the analysis of a real tunnel lining subjected to different scenarios, determining the influence and relevance of the main parameters defining a tunnel and its structural lining. Present research departs from an innovative in situ test carried out at Line 9 subway tunnel in Barcelona. The treatment and analysis of the obtained data provides experimental evidences about the structural response of segmental tunnel linings and the main involved mechanisms and phenomena. Different numerical simulation strategies are developed in order to properly reproduce such mechanism and phenomena, achieving a reliable simulation of an isolated ring response. The longitudinal response of the segmental concrete linings is obtained through the detailed study of the construction process applied and the ground-structure interaction mechanisms. The knowledge of the longitudinal force present at a segmental tunnel lining is of paramount importance in order to determine the interaction degree between adjacent rings and the consequent three-dimensionality of the lining response. Finally, the numerical simulation of a real tunnel section subjected to different scenarios of load and boundary conditions determines the influence of the three-dimensional effects on segmental concrete linings response, concluding about its structural implications in respect to the isolated ring approach usually employed in design processes.

  • AFOSP ¿ WP1: analysis of the state of the art

     Molins Borrell, Climent
    Date: 2012-12-17
    Report

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  • Q-00029

     Gironella i Cobos, Framcesc Xavier; Campos Hortigüela, Alexis; Molins Borrell, Climent
    Participation in a competitive project

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    Three dimensional structural response of segmental tunnel linings  Open access

     Arnau Delgado, Oriol; Molins Borrell, Climent
    Engineering structures
    Date of publication: 2012-11
    Journal article

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    The particular configuration of segmental tunnel linings produces that its structural response in front of usual design loads could present a significant three dimensionality due to the structural interaction between adjacent rings (coupling effects). The present paper studies the phenomena associated to coupling effects, determines the main involved parameters and analyzes their influence on a real lining structural response by means of a 3D numerical model. The comparison with the usual plane models currently employed in linings designs provide significant conclusions about the coupling effects implications and the conditions in which become more relevant.

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    Longitudinal time-dependent response of segmental tunnel linings  Open access

     Arnau Delgado, Oriol; Molins Borrell, Climent; Blom, C.B.M.; Walraven, Joost
    Tunnelling and underground space technology
    Date of publication: 2012-03
    Journal article

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    The longitudinal forces introduced by tunnel boring machines (TBMs) to the segmental tunnel linings influence their structural response. The analyses of the linings construction process and the ground-structure interaction mechanisms have shown the influence of the lining creep on the progressive loss of the initial longitudinal force. An analytical formulation to predict the remaining compression of the linings as a function of time is proposed, supported by means of a complete numerical model, which considers the effect of creep during the sequential construction process. An experimental program to determine the creep of plastic packers was developed, revealing its significant influence on the global lining creep factor and the evolution of the remaining compressive stresses.

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  • Proceso de sustitución o remoción de aerogenerador en estructuras flotantes monolíticas tipo SPAR

     Molins Borrell, Climent; Rebollo Pericot, Josep; Campos Hortigüela, Alexis
    Date of request: 2012-03-14
    Invention patent

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    Proceso de sustitución o remoción de aerogenerador en estructuras flotantes monolíticas tipo SPAR.

    La presente invención hace referencia al proceso de sustitución de un aerogenerador en una estructura flotante monolítica tipo SPAR fondeada.

    La invención se basa en la inundación controlada de la estructura flotante tal que la coronación de la estructura quede situada a una altura sobre el nivel medio del mar (NMM), entre 5 y 20 m, para que la coronación de la estructura y el aerogenerador sean fácilmente accesibles desde la cubierta de una embarcación tipo catamarán que se acople a la estructura y, mediante un sistema de puente grúa o similar, efectuar tareas de mantenimiento y/o sustitución sin necesidad de grúas flotantes. Finalizadas dichas tareas, la estructura se emerge mediante evacuación por bombeo del agua interior, permitiendo también reajustar la línea de flotación y la tensión en los amarres si las nuevas condiciones de masa lo requieren.

  • Procedimiento de instalación y mantenimiento de estructura flotante monolítica para soporte de aerogenerador

     Molins Borrell, Climent; Rebollo Pericot, Josep; Campos Hortigüela, Alexis
    Date of request: 2012-02-10
    Invention patent

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    Proceso de instalación de estructura flotante monolítica para soporte de aerogenerador en zonas marítimas de gran profundidad y alejadas de la costa que consiste en el fondeo de la estructura desde una posición horizontal de transporte hasta la vertical mediante la inundación controlada de su interior, de forma que el tramo emergente sobre la superficie marina sea mínimo, para que el montaje del aerogenerador a instalar en la coronación se realice a través de una embarcación tipo catamarán o similar y sin necesidad de medios complementarios de elevación. El emergido de la estructura se realiza mediante extracción del agua interior a través de diversas válvulas a lo largo de la altura que se equilibra parcialmente con el lastre tipo granular introducido a través de una apertura lateral. La fuerza en los amarres de sujeción se aplica mediante el ajuste de la línea de flotación de la estructura.

  • Nuevas tendencias para el refuerzo óptimo de tubos de hormigón

     de la Fuente Antequera, Alberto; Aguado De Cea, Antonio; Molins Borrell, Climent; de Figueiredo, Antonio; Campos Escariz, Renata
    Congreso de la Asociación Científico-Técnica del Hormigón Estructural
    Presentation's date: 2011-10-27
    Presentation of work at congresses

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    Este artículo tiene como objetivo presentar las últimas investigaciones realizadas en referencia al uso de fibras en tubos de hormigón. En la primera parte del trabajo se presenta un estudio de su comportamiento en el ensayo de aplastamiento, haciendo hincapié tanto en los aspectos técnicos de su ejecución como en cuestiones relacionadas con la simulación numérica. En la segunda parte, se presentan los resultados experimentales obtenidos en ensayos mecánicos de tubos de hormigón con fibras de 600 mm, 800 mm y 1000 mm de diámetro. Éstos han servido para validar el modelo numérico MAP, permitiendo concluir que ésta es una herramienta adecuada para el análisis el diseño de este tipo de tubos. Asimismo, se presenta un procedimiento para hallar la cuantía de fibras necesaria en función de la clase resistente exigida.

  • Clasificación de los tipos constructivos y estructurales de los edificios para el estudio de su sensibilidad frente a los efectos de la tunelación

     Serrà Martín, Isabel; Camos Andreu, Carles; Molins Borrell, Climent; Chirino Andalco, Mariel
    Congreso de la Asociación Científico-Técnica del Hormigón Estructural
    Presentation's date: 2011-10-26
    Presentation of work at congresses

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  • Efecto del ciclo de curado sobre el riesgo de fisuración de dovelas prefabricadas para revestimiento de túneles

     Crespo Garibay, María Delia; Mari Bernat, Antonio Ricardo; Molins Borrell, Climent
    Congreso de la Asociación Científico-Técnica del Hormigón Estructural
    Presentation's date: 2011-10-26
    Presentation of work at congresses

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    En esta ponencia se analiza el efecto del curado térmico sobre la evolución de las temperaturas, velocidades de calentamiento y enfriamiento, tensiones y resistencias de las dovelas de hormigón para revestimiento de túneles, a fin de determinar que ciclo de curado es el más ventajoso. Para la simulación numérica se utilizan los datos de caracterización térmica y mecánica obtenidos en base a resultados de ensayos del hormigón presentados con anterioridad [1]. El análisis térmico permite verificar si un ciclo determinado cumple con las reglas de buena práctica en lo que se refiere a temperaturas máximas alcanzadas dentro de la dovela, y velocidades máximas de calentamiento y enfriamiento. Finalmente, el análisis mecánico permite verificar hasta el riesgo que la dovela fisure, comparando la evolución de la relación tensión/resistencia efectiva en el punto que tiene mayor riesgo de fisuración. Ello permite determinar el ciclo térmico más adecuado para obtener una resistencia en un plazo dado.

  • Respuesta estructural de los revestimientos de túnel realizados a base de dovelas prefabricadas frente a cargas localizadas

     Molins Borrell, Climent; Arnau Delgado, Oriol
    Congreso de la Asociación Científico-Técnica del Hormigón Estructural
    Presentation's date: 2011-10-27
    Presentation of work at congresses

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    La presente comunicación tiene por objetivo evaluar la respuesta estructural presentada por los revestimientos de túneles a base de dovelas prefabricadas frente a cargas localizadas. La capacidad de interacción entre anillos determinará el grado de tridimensionalidad de la respuesta del revestimiento y, en consecuencia, su rigidez y resistencia. La contribución estructural entre anillos adyacentes se analiza por medio de un modelo tridimensional de elementos finitos de tipo lámina que reproduce adecuadamente la respuesta de las juntas existentes en un tramo real de 11 anillos. El estudio de distintas condiciones de terreno envolvente y de tensión de compresión longitudinal permiten obtener conclusiones prácticas sobre la respuesta de los revestimientos de dovelas frente a cargas localizadas.

  • Simulación de los daños estructurales producidos por la tunelación en estructuras de obra de fábrica

     Arnau Delgado, Oriol; Molins Borrell, Climent; Barbosa, Bruno; Alegre Heitzmann, Vicente
    Congreso de la Asociación Científico-Técnica del Hormigón Estructural
    Presentation's date: 2011-10-27
    Presentation of work at congresses

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    La perforación de túneles genera subsidencias en el terreno que pueden causar daños en los edificios existente en superficie debido a los asientos diferenciales. Los edificios cuya estructura portante está formada por elementos continuos de obra de fábrica son los que suelen presentar una mayor afectación frente a este tipo de solicitaciones. Además, el complejo comportamiento material que la obra de fábrica presenta dificulta significativamente la simulación y predicción de la respuesta del edificio ante dichas acciones. En esta ponencia se muestra el proceso de modelización empleado en la simulación de un edificio real de obra de fábrica afectado por el colapso del túnel del Carmel (Barcelona). Los resultados de la simulación han presentado una muy buena correlación con los registros de daños reales, lo que permite concluir sobre la capacidad de los modelos empleados.

  • Numerical simulation of steel fiber reinforced concrete: including fibers into plain concrete

     Pros Parés, Alba; Diez Mejia, Pedro; Molins Borrell, Climent
    Congreso en Métodos Numéricos em Engenharia
    Presentation's date: 2011-06-15
    Presentation of work at congresses

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  • Nueva metodología para la evaluación de la orientación de las fibras

     Laranjeira de Oliveira, Filipe; de la Fuente Antequera, Alberto; Aguado De Cea, Antonio; Molins Borrell, Climent
    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 esta comunicación se presenta una nueva filosofía para determinar la orientación de las fibras. En primer lugar, se evalúa la orientación de la fibra en el dominio espacial a través de un enfoque probabilístico que proporciona una visión más amplia que el análisis 2D recogido en la literatura. Posteriormente, se estudia el efecto pared sobre la orientación de las fibras y se anticipa una nueva aproximación para su cuantificación, tanto en condiciones isótropas como anisótropas. Por último se presenta la estrategia paso a paso propuesta en este trabajo para evaluar la orientación de las fibras.

  • Estudio de las cubetas de asientos producidas por la tunelación y simulación de la respuesta estructural de edificios afectados

     Camos Andreu, Carles; Arnau Delgado, Oriol; Molins Borrell, Climent; Alegre Heitzmann, Vicente
    Congreso de la Asociación Científico-Técnica del Hormigón Estructural
    Presentation's date: 2011-10-25
    Presentation of work at congresses

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    En el presente estudio se ha modelizado el comportamiento estructural de unos edificios afectados por los asientos producidos por la tunelación. Los valores reales de los asientos se comparan con los predichos mediante los métodos empíricos que estiman la forma y el área de la cubeta de asiento en función de las propiedades del terreno y de la supuesta pérdida de volumen inherente al método constructivo. Seguidamente se aplica el método de la viga equivalente para la predicción de los daños en los edificios afectados y se comparan con los daños reales. Finalmente se simula el comportamiento estructural de los edificios sometidos a los asientos medidos utilizando macro-modelos constitutivos ortótropos no lineales de obra de fábrica. De la comparación de los resultados numéricos con las lesiones y con las predicciones del método de la viga equivalente se extraen conclusiones relativas a la aplicación de dicho método simplificado.

  • Discrete meso-modeling of steel fiber reinforced concrete: simulation of flexural behavior

     Pros Parés, Alba; Diez Mejia, Pedro; Molins Borrell, Climent
    International Conference on Computational Plasticity
    Presentation's date: 2011-09-08
    Presentation of work at congresses

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  • Simulación numérica del hormigón reforzado con fibras de acero

     Pros Parés, Alba; Diez Mejia, Pedro; Molins Borrell, Climent
    Congreso de la Asociación Científico-Técnica del Hormigón Estructural
    Presentation's date: 2011-10-27
    Presentation of work at congresses

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    El Hormigón Reforzado con Fibras de Acero (HRFA) es una técnica que consiste en añadir fibras de acero en el hormigón. La forma, las dimensiones, la esbeltez, la orientación y la distribución de las fibras caracterizan el comportamiento del material. Para caracterizar y estudiar el HRFA, se han empleado distintos ensayos: de tracción directa e indirecta y de flexotracción. En esta ponencia se presenta un modelo simplificado para simular el acoplamiento fibra-hormigón mediante el cual es posible tener en cuenta el efecto real de cada una de las fibras individuales. Así, es posible obtener la respuesta resistente teniendo en cuenta el número real de fibras, su orientación y posición. Para poder tener en cuenta la interacción fibra-hormigón, las ecuaciones constitutivas de las fibras se basan en expresiones analíticas dependiendo del ángulo entre cada fibra y la fisura en el hormigón. El hormigón se modeliza considerando un modelo no lineal.

  • Comportamiento a tempranas edades de elementos de hormigón con restricción externa total

     Crespo Garibay, María Delia; Molins Borrell, Climent; Mari Bernat, Antonio Ricardo
    Congreso de la Asociación Científico-Técnica del Hormigón Estructural
    Presentation's date: 2011-10-26
    Presentation of work at congresses

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    Durante las primeras edades del hormigón se producen deformaciones termo-higrométricas las cuales, si son restringidas, sobre todo por coacciones externas, producen tracciones que pueden fisurar el hormigón. Un ejemplo típico es el caso de muros con empotramiento en su base. El objetivo del presente estudio es determinar las fuerzas que se producen en el momento de la fisuración en elementos con restricción total de las deformaciones a fin de poder analizar la exactitud de la hipótesis realizada en algunos códigos sobre el valor de los esfuerzos normales con los que se calcula la armadura mínima. Se realiza un estudio paramétrico a fin de distinguir la influencia que las diferentes variables (tipo de hormigón, tipo de encofrado, canto del elemento, edad de desencofrado) ejercen sobre el desarrollo de las temperaturas y tensiones dentro del elemento.

  • Diseño óptimo integral de tubos de hormigón

     de la Fuente Antequera, Alberto; Aguado De Cea, Antonio; Molins Borrell, Climent
    Hormigon y acero
    Date of publication: 2011-04-01
    Journal article

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  • Characterization of the orientation profile of steel fiber reinforced concrete

     Laranjeira de Oliveira, Filipe; Grünewald, Steffen; Walraven, Joost; Blom, C.B.M.; Molins Borrell, Climent; Aguado De Cea, Antonio
    Materials and structures
    Date of publication: 2011-07
    Journal article

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