Fibre reinforced concrete column-supported flat slabs : from material and structural characterization to design and economic optimization

Tesi en modalitat de compendi de publicacionsFibre reinforced concrete (FRC) has proven to be a suitable material for statically indeterminate elements. The FRC column-supported flat slabs with partial or even total substitution of reinforcing steel bars constructed within the scope of this thesis provided the positive outcomes from both technical and sustainability perspectives, being a supporting evidence for this statement. Despite the successful experiences of FRC slab construction, the widespread use of this technology is still hindered because of a number of factors related to the general comprehension of the material’s properties, design procedure, and accurate assessment of both technological and economic aspects. In this context, further research is required to complement the current scope of knowledge, providing to practitioners and researchers a clear example of structural capacity of FRC column-supported flat slabs. Moreover, straightforward procedures focused on the design and following evaluation of the potential technological and economic benefits due to use of FRC should be de-rived. Therefore, a rather comprehensive doctoral thesis that covers the majority of the above-mentioned topics is proposed herein. The first part of the study focuses on the material characterization and analysis of the flexural behavior of FRC column-supported flat slab. A full-scale FRC slab was constructed and tested under different load magnitudes, assessing the structural response at both ultimate and serviceability limit states. The results derived proved the sufficient flexural strength at ultimate conditions along with the capacity of moment redistribution and the ductility of the system. Furthermore, the studied FRC slab evidenced the acceptable performance in terms of cracking and deflections. Subsequently, the straightforward design-oriented method is proposed to estimate the structural response of FRC column-supported flat slabs in terms of flexural strength, cracking control, and instantaneous deformations. The results derived were compared with a nonlinear analysis, highlighting a suitable accuracy and precision of the proposed approach. Finally, an industrial-oriented study was carried out with the main objective of elaborating a simplified method for the preliminary comparison of traditional and FRC solutions for column-supported flat slabs in terms of economic benefits. The results reflected an increment of direct costs for both fibre and hybrid (fibre + reinforcing steel bars, HFRC) solutions; however, these increments can be compensated by the reduction of the construction period and, as a consequence, time-dependent costs (i.e. preliminaries, equipment costs, overheads, and finance costs).El hormigón reforzado con fibras (HRF) ha demostrado ser un material adecuado para elementos sujetos a condiciones de contorno que conducen a hiperestaticidad. La construcción de forjados de HRF soportados por pilares ha proporcionado resultados positivos tanto desde el punto de vista técnico como de la sostenibilidad. A pesar de las experiencias de éxito en la sustitución parcial o incluso total del refuerzo tradicional (barras de acero) por fibras, el uso de esta tecnología todavía sigue siendo limitada debido a una serie de factores relacionados con la compresión general de las propiedades de HRF, los métodos de diseño junto con el análisis de los aspectos tecnológicos y económicos. En este contexto, se hace necesario continuar investigando el comportamiento de las losas bidireccionales de HRF con el objeto de complementar el marco actual de conocimiento, proporcionando a los profesionales evidencias de la capacidad estructural de este tipo de elementos. Además, la industria requiere los métodos de diseño prácticos junto con herramientas para llevar a cabo el análisis comparativo de diferentes soluciones en términos de beneficios tecnológicos y económicos. Por este motivo, se plantea una tesis doctoral generalista que abarca la mayoría de los temas mencionados en el ámbito de la tecnología de los forjados de losa maciza de hormigón reforzado con fibras. La primera parte del estudio se enfoca en la caracterización del material y posterior análisis del comportamiento a flexión de un forjado de HRF soportado por pilares. Para ello, se ha construido y ensayado una losa a escala real bajo diferentes magnitudes de carga, evaluando la res-puesta estructural del elemento en estado límite de servicio y último. Los resultados obtenidos han mostrado la suficiente resistencia a flexión bajo las cargas últimas junto con una elevada ductilidad y capacidad de redistribuir los esfuerzos en el sistema hiperestático. Asimismo, la losa de HRF analizada ha cumplido con los requisitos del estado límite de fisuración y de deformaciones. Posteriormente, se propone un método de diseño analítico para estimar la respuesta estructural de las losas de HRF soportadas por pilares en términos de resistencia a flexión, control de fisuración y de deformaciones instantáneas. Los resultados derivados se compararon con un análisis no lineal mediante el método de los elementos finitos, destacando una precisión adecua-da desde el punto de vista ingenieril del método propuesto. En la última parte se presenta un método simplificado para llevar a cabo un análisis comparativo de soluciones tradicionales y de HRF para las losas apoyadas sobre pilares en términos eco-nómicos. Los resultados del estudio comparativo demostraron un incremento de los costes directos para las soluciones con fibra (sustitución parcial o total del refuerzo tradicional); sin embargo, este incremento de los costes puede compensarse debido a la reducción del periodo de construcción y, como consecuencia, reducción de los costes indirectos (costes de maquinaria y herramientas, gastos de administración y dirección técnica, costes financieros).Postprint (published version

A limit state design approach for hybrid reinforced concrete column-supported flat slabs

Hybrid reinforced technology (combination of steel reinforcing bars and fibers) can be considered as a competitive alternative to the already existing solutions for the construction of column-supported flat slabs. Constructed hybrid-reinforced buildings prove that hybrid solutions have sufficient bearing capacity to maintain structural integrity despite being exposed to high stress levels, thereby providing a beneficial solution in terms of toughness, ductility, and sustainability performance. However, the lack of design-oriented recommendations based on the accepted limit state format for dealing with both serviceability and ultimate limit states slows down the wider implementation of this technology. Considering the above-mentioned, this article presents a simplified design-oriented method that covers the evaluation of the structural response of hybrid reinforced concrete column-supported flat slabs in terms of flexural strength, cracking, and instantaneous deformations. Two hybrid reinforced alternatives for a given flat slab are studied by means of the proposed approach. Furthermore, a nonlinear finite element analysis is carried out in order to evaluate the effectiveness of the developed simplified method. Based on the achieved results, its suitable accuracy and precision can be pointed out. This outcome may motivate current practitioners to consider hybrid reinforced concrete solutions as a possible alternative during the design of residential and office buildings.Departament d'Innovació, Universitats i Empresa, Generalitat de Catalunya, Grant/Award Number: 2018 DI 77; Ministerio de Ciencia e Innovación, Grant/Award Number: CREEF (PID2019-108978RB-C32)Peer ReviewedPostprint (published version

Systematic review on the creep of fiber-reinforced concrete

Fiber-reinforced concrete (FRC) is increasingly used in structural applications owing to its benefits in terms of toughness, durability, ductility, construction cost and time. However, research on the creep behavior of FRC has not kept pace with other areas such as short-term properties. Therefore, this study aims to present a comprehensive and critical review of literature on the creep properties and behavior of FRC with recommendations for future research. A transparent literature search and filtering methodology were used to identify studies regarding creep on the single fiber level, FRC material level, and level of structural behavior of FRC members. Both experimental and theoretical research are analyzed. The results of the review show that, at the single fiber level, pull-out creep should be considered for steel fiber-reinforced concrete, whereas fiber creep can be a governing design parameter in the case of polymeric fiber reinforced concrete subjected to permanent tensile stresses incompatible with the mechanical time-dependent performance of the fiber. On the material level of FRC, a wide variety of test parameters still hinders the formulation of comprehensive constitutive models that allow proper consideration of the creep in the design of FRC elements. Although significant research remains to be carried out, the experience gained so far confirms that both steel and polymeric fibers can be used as concrete reinforcement provided certain limitations in terms of structural applications are imposed. Finally, by providing recommendations for future research, this study aims to contribute to code development and industry uptake of structural FRC applications.This study has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 836270 and from BASF. This support is gratefully acknowledged. Any opinions, findings, conclusions, and/or recommendations in the paper are those of the authors and do not necessarily represent the views of the individuals or organizations acknowledged. A.d.l.F. has previously received research grants from BASF.Peer ReviewedPostprint (published version

Semantic Guidelines and Conceptual Basis of a Social Education Teacher Professional Mobility in the Pedagogical Science

The article is dedicated to enhancing urgent scientific problems, which is considered the formation of professional mobility of future teachers of professional training as one of the main components of the modernization of their professional training system. The purpose of the article is to show the results of the scientific search for semantic guidelines and the structure of professional mobility of future teachers of professional training in the conceptual basis of pedagogical science. The main goal of this research paper was a kind of report on the author's vision of the essence of professional mobility of future teachers in the structure of their professional readiness and scientific results, and acquaint readers with the opinion of scientists on the semantic guidelines and structure of professional mobility of future teachers based on a review of various information sources on selected topics; The leading idea of the publication of the article "Semantic guidelines and structure of professional mobility of a teacher in the conceptual basis of pedagogical science" is to share the experience of identifying the semantic guidelines and structure of professional mobility of future teachers of professional training. Then the concept of "the formation of professional mobility of future teachers of professional training" will be presented as a motivated, focused, and informed process of professional training, reflecting the dynamics of the development of its components and providing predicted changes, professional self-realization, and a quantitative increase in the indicators of the transition of subjects from a low level of mobility to a higher one by creating a system of pedagogical tools

Effects of low temperatures on flexural strength of macro-synthetic fiber reinforced concrete: experimental and numerical investigation

Fiber-reinforced concrete (FRC) is an attractive alternative to traditional steel bar-reinforced concrete structures, as evidenced by the constantly increasing market consumption of structural fibers for this purpose. In spite of significant research dedicated to FRC, less attention has been given to the effects of low temperatures on the mechanical properties of FRC, which can be critical for a variety of structural typologies and regions. With this in mind, an experimental program was carried out to assess the flexural behavior of macro-synthetic fiber-reinforced concrete (MSFRC) at different temperatures (from 20 °C to -30 °C) by means of three-point bending notched beam tests. The tested MSFRCs were produced by varying the content of polypropylene fibers (4 and 8 kg/m3). The results proved that the flexural strength capacity of all MSFRCs improved with decreasing temperature. Finite element analyses were then used to calibrate constitutive models following fib Model Code 2010 guidelines and to formulate empirical adjustments for taking into account the effects of low temperatures. The outcomes of this research are the basis for future experimental and numerical efforts meant to improve the design of MSFRCs subjected to low temperatures during service conditions.Peer ReviewedPostprint (published version

High-Performance Computational and Information Technologies for Numerical Models and Data Processing

This chapter discusses high-performance computational and information technologies for numerical models and data processing. In the first part of the chapter, the numerical model of the oil displacement problem was considered by injection of chemical reagents to increase oil recovery of reservoir. Moreover the fragmented algorithm was developed for solving this problem and the algorithm for high-performance visualization of calculated data. Analysis and comparison of parallel algorithms based on the fragmented approach and using MPI technologies are also presented. The algorithm for solving given problem on mobile platforms and analysis of computational results is given too. In the second part of the chapter, the problem of unstructured and semi-structured data processing was considered. It was decided to address the task of n-gram extraction which requires a lot of computing with large amount of textual data. In order to deal with such complexity, there was a need to adopt and implement parallelization patterns. The second part of the chapter also describes parallel implementation of the document clustering algorithm that used a heuristic genetic algorithm. Finally, a novel UPC implementation of MapReduce framework for semi-structured data processing was introduced which allows to express data parallel applications using simple sequential code

Hormigones autocompactantes reforzados con fibras para aplicaciones con alta responsabilidad estructural: campaña experimental en laboratorio

El desarrollo de fibras de acero con mayores prestaciones mecánicas ha abierto la posibilidad de sustituir total o parcialmente el armado tradicional en elementos estructurales con elevadas solicitaciones, tales como los forjados de edificación. En este caso, se requiere de un hormigón con alta resistencia post-fisuración (lo que puede conseguirse con elevados contenidos de fibra), y consistencia autocompactante, a fin de poder ser puesto en obra mediante bombeo. Para comprobar la viabilidad técnica del Hormigón AutoCompactante Reforzado con altas cuantías de Fibras de Acero (HACRFA), se ha llevado a cabo una extensa campaña experimental de caracterización del material. En total, se han realizado 15 dosificaciones de HACRFA, utilizando diferentes tipos y contenidos de fibra (60, 90 y 120 kg/m3). Para cada amasada se ha caracterizado el hormigón en estado fresco y en estado endurecido. Los resultados obtenidos han sido satisfactorios, poniendo de manifiesto que el material diseñado tiene propiedades adecuadas como para ser usado como material estructural en forjados de edificación.Postprint (published version

Fresh and hardened characterization of self-compacting fibre reinforced concretes with high amounts of steel macrofibres

El uso de HRF con responsabilidad estructural ha experimentado una creciente demanda en el sector de la construcción proporcionando beneficios económicos, tecnológicos y estructurales. Sin embargo, este material relativamente nuevo no ha mostrado su potencial pleno hasta el momento; lo que conduce al desarrollo continuo en términos de diseño y caracterización de HRF. Teniendo esto en cuenta, se realizaron 15 dosificaciones de hormigón autocompactante reforzado con fibras de mayores prestaciones mecánicas, utilizando diferentes tipos y contenidos de fibra con el objetivo de estimar propiedades mecánicas y reologicas del material; los resultados se presentan y analizan en esta comunicación.Los autores quieren agradecer el apoyo económico del Ministerio de Economía, Industria y Competitividad a través de la ayuda RTC-2016-5263-5 asociada al proyecto eFIB (optimización de procesos constructivos y de diseño de elementos estructurales empleando hormigones reforzados con fibras en sustitución de la armadura convencional), proyecto desarrollado conjuntamente con SACYR Ingeniería e Infraestructuras; en particular se agradece a Ángel Sánchez de Dios (ICCP); Patricia Díaz Martín (ICCP); Ramón Sánchez Fernández (ICCP); Antonio Ángel Ramirez Rodríguez (Dr. ICCP). El primer autor también da las gracias al apoyo del Plan de Doctorados Industriales de la Secretaría de Universidades e Investigación del Departamento de Empresa y Conocimiento de la Generalitat de Cataluña.Postprint (published version