Numerical approach for modeling steel fiber reinforced concrete

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

Un programa informático de habilidades visuoespaciales como recurso educativo

Este trabajo pretende presentar un programa informático como estrategia de apoyo para el desarrollo de las habilidades de visión espacial en niños pre-adolescentes. El programa informático 'Laber.exe' consiste en solucionar laberintos en 3 dimensiones, después de haber sido presentados en 2 dimensiones. Una vez realizada la tarea, el programa reproduce de manera exacta todo lo realizado por el sujeto en la solución o intento de solución del laberinto. El programa tiene un doble valor educativo: la adquisición de habilidades visuoespaciales y, la introducción de términos cómo: atención, percepción, memoria, etc.. y su posible optimización en situaciones parecidas del ámbito educativo (mapas, diagramas, esquemas, etc..) .This aim of this work is to present a computer program as a support strategy for the development of spatial awareness in pre-adolescent children. The computer program 'Laber.exe' consists of solving mazes in 3 dimensions after having first been presented in 2 dimensions. Once the task has been completed the program reproduces exactly what the subject produced in the solution or attempted solution to the maze. The program has a dual education value: The acquisition of visual-spatial abilities and, the introduction of terms such as attention, perception, memory etc. and their possible optimization in other sucheducational situations (maps, diagrams, sketches etc.

From analog to digital: study of Frei Otto's experimental models

The need to carry out experiments and physical tests with models is today questioned with the use of the computer; which constitutes an important optimization and a shape search tool. But to what extent? Frei Otto, a German architect born in 1925 in Siegmar, devoted much of his career to the study of shapes and materials from experimental models. Experimentation in architecture was the central axis of his work. Although the principles of these models cannot be applied directly to buildings, they served a pure research purpose and offered a theoretical point of view in the design of structures. He established an unprecedented working methodology. His experimental models allowed him a further understanding of how materials work at their best when they are under tension, the soap film minimal surface models for tensile membranes and the hanging chain catenary form models for compressive arch and shell structures. This allowed him not only to find an optimal lightweight structure, but also to have a more environmentally friendly approach to architecture. This research work interrogates, reads, interprets and reconstructs Frei Otto’s soap film models in order to find a method of working with digital tools that allows us to deepen the study of these forms. After this study, both methods, analog and digital, will be compared to see which one is better to work with nowadaysAward-winnin

Integrated management system of a transport company

Unaprjeđenjem proizvoda i usluga kao preduvjeta poslovnog uspjeha na tržištu, raste potreba za efikasnim sustavima upravljanja što rezultira intenzivnim razvojem normizacije. U interesu je vlastitog tržišnog položaja praćenje pomaka u razvoju normi i promjenama koje one donose. Sustav upravljanja kvalitetom, okolišem, zdravljem i sigurnosti na radu predstavlja moderan način organiziranja rada i upravljanja tvrtkom pa se menadžment svake organizacije, tako i prijevozničke tvrtke, susreće s problemom koji je ovdje postavljen kao zadatak. Predmet istraživanja ovog rada je analiza mogućnosti i načina, prednosti i nedostataka uvođenja sustava i organiziranja rada prema zahtjevima međunarodnih normi primijenjenih na prijevozničko poduzeće, a iz perspektive njegovog menadžmenta. Opisani su zahtjevi pojedinih točaka normi radi istraživanja konkretne primjenjivosti u prijevozničkom poduzeću. Rad je prezentacija dovoljnog broja jasnih i sažetih informacija na jednom mjestu a zamišljen je kao svojevrsna smjernica menadžmentu prijevozničkog poduzeća prilikom odluke o uvođenju sustava sukladno zahtjevima normi.The improvement of products and services as precondition for the business success on the market means an increase in the need for efficient management systems which in turn results in intensive development of standardization. It is in the interest of one’s own market position to monitor the shift in the development of standards and the resulting changes. Quality, environment, occupational health and safety management systems represent a modern way of organizing work and company administration so that the management of every organization, including transport companies, encounters a problem which is here set as a task. The subject of research in this paper is the analysis of the possibilities and methods, advantages and drawbacks of introducing the systems and organizing work according to the requirements of international standards applied to a transport company, from the perspective of its management. The requirements of single items of the standards have been described in order to study the concrete applicability in the transport company. The paper is a presentation of a sufficient number of clear and concise pieces of information in one place, and it has been conceived as kind of a guideline for the transport company management during decision-making about the introduction of the system pursuant to the requirements of the standards

Miniature Wideband stacked microstrip patch antenna based on the sierpinski fractal geometry

The main interest in the design of a miniature microstrip patch antenna (MPA) is its small size in conjunction with the well-known advantages of a MPA (cost, profile, weight). However there is a big constraint on the bandwidth limitation either in a miniature antenna or in a MPA. The proposed solution to overcome such problem is to couple a miniature parasitic resonator to the miniature active patch forming a wideband small stacked microstrip patch antenna.Peer ReviewedPostprint (published version

Efectos diferenciales de un prolongado entrenamiento en una tarea espacial entre hombres y mujeres

El objetivo de este trabajo es comprobar los efectos de un largo entrenamiento en la realización de una tarea espacial por ordenador, en el que uno de los procesos implicados es el de rotación mental. Para ello 63 sujetos universitarios, 44 mujeres y 19 hombres son sometidos a un conjunto de problemas espaciales durante 13 sesiones con un intervalo de una semana. De estas sesiones, sólo se computan los resultados de las sesiones 1, 7 y 13. Los resultados muestran que, aunque los hombres son más rápidos y cometen menos errores que las mujeres en todas las sesiones experimentales, las diferencias de tiempo y errores entre sexos se minimizan a medida que aumenta el entrenamiento. Un estudio más detallado de los resultados conduce a que están interviniendo factores de naturaleza social, cultural, y no tanto factores biológicos.This work is adressed to check the effect of a long training in a computarized task, where one of the main processes involved is mental rotation. 63 university students, 44 women and 19 men solved a set of computarized spatial problems during 13 weekly sessions. Only the results of the sessions 1, 7 and 13 were computed. Results show that, although in all the experimental sessions men are faster and they make less errors than women, differences of time and errors among sexes are minimized when the training increases. A closer view of the results provides some cues that point to factors of social, cultural nature, and not so much to biological explanations

Aportes y perjuicios de las TIC’s a la educación

Un uso normalizado e indiscriminado de las TIC en el contexto educativo queda reflejado en la hegemonía de las presentaciones en PowerPoint, puede obstaculizar más que facilitar el proceso de aprendizaje. Ciertas propiedades son una ganancia cualitativa en el proceso docente, pero otras inhiben recursos convencionales mucho más flexibles. Se debe entender la tecnología como un medio y no como un fin. Es un recurso a integrar en la gestión de la docencia por parte de buenos profesores, a los cuales no puede substituirThe overwhelming use of ICT in educational environments proves its normalization, although are often used without clear criteria, as the widespread occurrence of PowerPoint presentations shows. Part of technology properties are a qualitative gain in teaching process, but other properties interfere, or even inhibit, some flexible and efficient teaching resources. Technology should be represented as a tool, not as an end. It’s just a means that has to be embedded within good teachers’ assets, who cannot be replaced by technology alone

Efectos diferenciales de un prolongado entrenamiento en una tarea espacial entre hombres y mujeres

El objetivo de este trabajo es comprobar los efectos de un largo entrenamiento en la realización de una tarea espacial por ordenador, en el que uno de los procesos implicados es el de rotación mental. Para ello 63 sujetos universitarios, 44 mujeres y 19 hombres son sometidos a un conjunto de problemas espaciales durante 13 sesiones con un intervalo de una semana. De estas sesiones, sólo se computan los resultados de las sesiones 1, 7 y 13. Los resultados muestran que, aunque los hombres son más rápidos y cometen menos errores que las mujeres en todas las sesiones experimentales, las diferencias de tiempo y errores entre sexos se minimizan a medida que aumenta el entrenamiento. Un estudio más detallado de los resultados conduce a que están interviniendo factores de naturaleza social, cultural, y no tanto factores biológicos.This work is adressed to check the effect of a long training in a computarized task, where one of the main processes involved is mental rotation. 63 university students, 44 women and 19 men solved a set of computarized spatial problems during 13 weekly sessions. Only the results of the sessions 1, 7 and 13 were computed. Results show that, although in all the experimental sessions men are faster and they make less errors than women, differences of time and errors among sexes are minimized when the training increases. A closer view of the results provides some cues that point to factors of social, cultural nature, and not so much to biological explanations