Caracterización y diseño del homigón reforzado con fibras plásticas

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

Perfeccionismo individual y perfeccionismo estatal

La doctrina de la lesión enorme (en adelante DLE) es una herramienta utilizada por los tribunales de justicia para negarse a ejecutar contratos cuyas cláusulas sean notoriamente abusivas, favorezcan excesivamente a una de las partes, o configuren una situación de explotación. Existe un extenso debate entre quienes apoyan la validez de esta doctrina y quienes defienden la libertad contractual. Seana Shiffrin ha realizado una defensa novedosa de la DLE, intentando distinguirla de defensas pasadas, generalmente basadas en el paternalismo. En este ensayo me propongo mostrar de qué manera el argumento de Shiffrin implica que el estado se comporte en una manera perfeccionista, algo que tanto para liberales como para libertarios representa una amenaza más seria que el paternalismo a la autonomía individual. La estructura de este trabajo será la siguiente: en la parte (i) reproduciré el argumento de Shiffrin y delimitaré el ámbito de la discusión. En la parte (ii) presentaré mi crítica y contemplaré posibles objeciones. La parte (iii) contendrá las conclusiones más importantes

Nuevas formas de construcción en discursos interactivos : Una mirada sobre “The Stanley Parable”, un cambio radical en la cartografía de los videojuegos

El presente estudio hace referencia a un videojuego en particular denominado “The Stanley Parable” cual se constituye como un discurso interactivo con una naturalidad opaca. Es decir que en su estructura se podrán vislumbrar los hilos de la construcción generando de esta forma una suerte de distanciamiento. A pesar que no fue pionero este proyecto, la conjugación de una serie de recursos referidos al arte contemporáneo como la destrucción de la cuarta pared, la violencia que ejerce al espectador al romper con estructuras rígidas y clásicas que han dominado los videojuegos y la inclusión de un recurso que proviene de la televisión como lo es la metadiscursividad; estos elementos nutren a la obra ofreciendo una experiencia inusitada que tiene como primordial objetivo en el espectador generar una instancia reflexiva dado que este videojuego no establece un discurso transparente: el jugador sabe y es consciente que está participando en esta experiencia. En cuanto refiere al metadiscurso, esta modalidad permite al creador de la obra ofrecer una perspectiva reflexiva sobre el discurso que está creando, en la cual esta metadiscursividad se establece como un discurso mismo que se está construyendo sobre el mismo dispositivo. El poder inherente a las modalidades discursivas que hacen uso del extrañamiento genera choques dialécticos y violencias perceptivas con la finalidad de desarrollar una determinada consciencia y capacidad reflexiva en el jugador.Facultad de Bellas Arte

A hierarchical integration method under social constraints to maximize satisfaction in multiple criteria group decision making systems

Aggregating multiple opinions or assessments in a decision has always been a challenging field topic for researchers. Over the last decade, different approaches, mainly based on weighting data sources or decision-makers (DMs), have been proposed to resolve this issue, although social choice theory, focused on frameworks to combine individual opinions, is generally overlooked. To resolve this situation, a novel methodology is developed in this paper based on social choice theory and statistical mathematics. This method innovates by dividing the assessment into components which provides a multiple assessment analysis, assigning weights to each source regarding their position compared to the group for each considered criteria. This multiple-weighting process maximises individual and group satisfaction. Furthermore, the method makes it possible to manage previously assigned influence. An example is given to illustrate the proposed methodology. Additionally, sensitivity analysis is performed and comparisons with other methods are made. Finally, conclusions are presented.The first author acknowledges support from the Spanish Ministry of Education, Culture and Sports [grant number FPU18/01471]. The second and third author wish to recognise their support from the Serra Hunter programme. Finally, this work was supported by the Catalan agency AGAUR through its research group support program (2017SGR00227). This research is part of the R&D project IAQ4EDU, reference no. PID2020-117366RB-I00, funded by MCIN/AEI/10.13039/501100011033.Peer ReviewedPostprint (published version

A systematic review on multi-criteria group decision-making methods based on weights: analysis and classification scheme

Interest in group decision-making (GDM) has been increasing prominently over the last decade. Access to global databases, sophisticated sensors which can obtain multiple inputs or complex problems requiring opinions from several experts have driven interest in data aggregation. Consequently, the field has been widely studied from several viewpoints and multiple approaches have been proposed. Nevertheless, there is a lack of general framework. Moreover, this problem is exacerbated in the case of experts’ weighting methods, one of the most widely-used techniques to deal with multiple source aggregation. This lack of general classification scheme, or a guide to assist expert knowledge, leads to ambiguity or misreading for readers, who may be overwhelmed by the large amount of unclassified information currently available. To invert this situation, a general GDM framework is presented which divides and classifies all data aggregation techniques, focusing on and expanding the classification of experts’ weighting methods in terms of analysis type by carrying out an in-depth literature review. Results are not only classified but analysed and discussed regarding multiple characteristics, such as MCDMs in which they are applied, type of data used, ideal solutions considered or when they are applied. Furthermore, general requirements supplement this analysis such as initial influence, or component division considerations. As a result, this paper provides not only a general classification scheme and a detailed analysis of experts’ weighting methods but also a road map for researchers working on GDM topics or a guide for experts who use these methods. Furthermore, six significant contributions for future research pathways are provided in the conclusions.The first author acknowledges support from the Spanish Ministry of Universities [grant number FPU18/01471]. The second and third author wish to recognize their support from the Serra Hunter program. Finally, this work was supported by the Catalan agency AGAUR through its research group support program (2017SGR00227). This research is part of the R&D project IAQ4EDU, reference no. PID2020-117366RB-I00, funded by MCIN/AEI/10.13039/ 501100011033.Peer ReviewedPostprint (published version

Nuevas formas de construcción en discursos interactivos : Una mirada sobre “The Stanley Parable”, un cambio radical en la cartografía de los videojuegos

El presente estudio hace referencia a un videojuego en particular denominado “The Stanley Parable” cual se constituye como un discurso interactivo con una naturalidad opaca. Es decir que en su estructura se podrán vislumbrar los hilos de la construcción generando de esta forma una suerte de distanciamiento. A pesar que no fue pionero este proyecto, la conjugación de una serie de recursos referidos al arte contemporáneo como la destrucción de la cuarta pared, la violencia que ejerce al espectador al romper con estructuras rígidas y clásicas que han dominado los videojuegos y la inclusión de un recurso que proviene de la televisión como lo es la metadiscursividad; estos elementos nutren a la obra ofreciendo una experiencia inusitada que tiene como primordial objetivo en el espectador generar una instancia reflexiva dado que este videojuego no establece un discurso transparente: el jugador sabe y es consciente que está participando en esta experiencia. En cuanto refiere al metadiscurso, esta modalidad permite al creador de la obra ofrecer una perspectiva reflexiva sobre el discurso que está creando, en la cual esta metadiscursividad se establece como un discurso mismo que se está construyendo sobre el mismo dispositivo. El poder inherente a las modalidades discursivas que hacen uso del extrañamiento genera choques dialécticos y violencias perceptivas con la finalidad de desarrollar una determinada consciencia y capacidad reflexiva en el jugador.Facultad de Bellas Arte

Mives multicriteria assessment of urban-pavement conditions: application to a case study in Barcelona

© 2018 Informa UK Limited, trading as Taylor & Francis Group There are very few methods that can be used for the assessment of pavement conditions. Their application to urban networks tends to be complex, given the wide variety of urban pavement types (concrete, asphalt, and paving tiles) and their different functions (traffic, pedestrian, or both). A flexible method that can address the complexity of different areas is therefore proposed in this paper through a case study of pavement conditions. Hence the interest of this new approach for pavement management that employs a multi-criteria method adaptable to various urban environments: the Integrated Value Model for Structural Assessment (MIVES). It incorporates the Value Function (VF) concept in an Analytic Hierarchy Process (AHP), combining both Multi-criteria Decision Making and Multi-Attribute Utility Theory. The methodology is presented and its sensitivity is evaluated by means of a case study in the city of Barcelona. The quality index of various pavements is assessed through a survey of pavement distresses in a systematic categorisation of urban network pavement categories that is accurate, consistent, and repeatable

Influence of the type of fiber on the structural response and design of FRC slabs

Most codes for the design of fiber reinforced concrete (FRC) structures are based on the experience achieved throughout the years with steel fibers. Recent codes include the possibility of applying the same considerations for FRC structures with plastic fiber. However, the consequences of assuming identical design considerations regardless of the type of fiber is scarcely known in terms of the structural behavior of full-scale elements. The main goal of this paper is to assess the influence of the type of fiber on the performance of full-scale concrete slabs, emphasizing on the consequences of using a common design approach. For that, a comparative experimental study was conducted in order to expose differences regarding the crack pattern and load-deflection behavior. Then, finite element simulations were performed using the constitutive equations from the Model Code 2010. The results indicate distinct levels of overestimation of the structural behavior measured experimentally, confirming that specific design considerations are required depending on the type of fiber used. Based on the findings, correction factors are proposed for the design of FRC slabs with each fiber.Peer ReviewedPostprint (author's final draft

Compensación de la calidad del aire interior, el confort térmico y el consumo de energía para edificios educativos

In recent years, poor indoor air quality and thermal comfort have been widely reported in related studies on indoor environmental quality in classrooms. Improving indoor air quality through ventilation is common and effective. However, it compromises occupant’s thermal comfort and well-being, thereby consuming more energy to meet increased heating or cooling demand and challenging energy conservation for Sustainable Development Goal 7. The existing researches imply the significance of conducting an extensive review on the three domains mentioned above (indoor air quality, thermal comfort, and energy consumption) in educational buildings, as individual cases are of peculiarity due to the specific characteristics of buildings and occupants. In contrast, the standards for indoor air quality and thermal comfort in educational buildings are not explicit and unified for all countries. This paper summarizes relevant features from reviewed cases, including: the geographic and demographic characteristics, field investigation parameters, indoor air quality and thermal comfort standards, ventilation protocols, heating and cooling strategies, energy consumption, as well as important and valuable findings in order to investigate the progress on such a topic.Objectius de Desenvolupament Sostenible::3 - Salut i BenestarObjectius de Desenvolupament Sostenible::7 - Energia Assequible i No ContaminantPostprint (published version