Monitoramento e identificação numérico e experimental de danos em vigas e pontes de aço e concreto utilizando transformadas de wavelet

Tese (doutorado)—Universidade de Brasília, Faculdade de Tecnologia, Departamento de Engenharia Civil e Ambiental, 2015.

Evaluación de las propiedades mecánicas de diseños de mezclas de concreto hidráulico empleando granulometrías combinadas

En este trabajo se cuantifican los efectos de las combinaciones del agregado grueso en el concreto, introduciéndolo como variable para el diseño de las mezclas, para ello se elaboraron mezclas y se realizaron los ensayos requeridos. El procedimiento utilizado consistió en elegir dos granulometrías de agregados gruesos de diferente tamaño máximo nominal, elaborando cinco diseños de mezcla, un diseño de mezcla para cada tipo de granulometría en diferentes proporciones, manteniendo fijo: El tipo de concreto, contenido de concreto, y la relación agua-cemento. La investigación se inició con la recopilación de datos sobre el proceso de producción de los agregados, luego se seleccionaron los materiales y se determinaron sus propiedades físicas, una vez definido los diseños definitivos se realizaron las pruebas al concreto tanto en estado fresco como en estado endurecido

Estudio a nivel Colombia de la influencia del aditivo better mix en estado fresco, semi endurecido y endurecido del concreto estructural

Bogotá (Colombia): Universidad de La Salle. Facultad de Ingeniería. Programa de Ingeniería Civil

Nivelación dialectal: aspectos metodológicos y teóricos para el estudio de la convergencia lingüística a través de un caso concreto: los inmigrantes de Riogordo y Colmenar en Málaga

Convergencia y divergencia dialectales en los núcleos rurales Redes sociales Actitudes individuales y construcción de estilos personales Existe una tendencia bien conocida en las lenguas hacia la convergencia entre las variedades vernáculas regionales con las prestigiosas y de mayor estatus, propias de los núcleos urbanos y centros culturales. En las comunidades rurales, sin embargo, es más frecuente que tenga lugar una resistencia a la convergencia con el estándar y que se refuerce el uso de los rasgos vernáculos. Lo que ocurre es que el estudio de los procesos de convergencia en los centros urbanos está bien representado en la bibliografía y, sin embargo, son escasos los trabajos que se han ocupado de estudiar las tendencias divergentes en núcleos poblacionales más pequeños y en zonas rurales. De ahí que esta tesis pretenda dar respuesta a ese choque de tendencias convergentes y divergentes que tiene lugar en el ámbito rural. El estudio se centra en dos localidades de la provincia de Málaga, Colmenar y Riogordo, porque ambas reúnen las características idóneas para arrojar un poco de luz sobre este tipo de procesos de contacto dialectal: están cerca de la capital y bien comunicadas con el núcleo urbano, pero a la vez tienen una identidad muy marcada, lo que las convierte en un laboratorio ideal para investigar por qué sus habitantes se inclinan por una u otra variante impulsando, de esta manera, tendencias de convergencia o bien de divergencia con el estándar. Para crear el corpus en el que se basa esta investigación se establecieron cuotas de afijación uniforme basadas en tres variables de preestratificación: sexo, edad y nivel de instrucción. Las casillas de las cuotas se fueron completando por medio del procedimiento de bola de nieve. Para investigar los procesos de divergencia dialectal se han escogido tres variables dependientes, la fricativa velar /x/, la palatal africada /ʧ/ y las líquidas /r/ y /l/ en la distensión silábica. Son buenos indicios para estudiar las tendencias que aquí interesan y, por otra parte, su presencia en la bibliografía sociolingüística no está tan bien representada como la de, por ejemplo, el proceso de escisión de /θs/ en dos unidades, mate y estridente, o su variación en la coda silábica. En el capítulo correspondiente a la variación social se estudia la correlación entre variables dependientes y de preestratificación y también se presta atención a la influencia que ejercen otras variables de postestratificación, como el modo de vida y el grado de formalidad de la situación, porque aportan información relevante sobre la atribución de prestigio patente o encubierto en las localidades rurales. En relación con la variación reticular, se revisa de qué manera interactúan el rango de la red, el sexo y el nivel de estudios de los contactos con las variables dependientes, pues son estos precisamente los indicadores que más fuerza explicativa tienen en la muestra analizada. También interesa conocer qué influencia ejerce en los usos lingüísticos de los hablantes el grado de aceptación de los valores urbanos o su apego a las costumbres locales y su mentalidad rural. Con tal fin se ha construido una Escala de Orientación Urbana, ESORURB, que mide la interacción entre usos lingüísticos y mentalidad del hablante. La tesis se cierra con un estudio de la variación individual según las aportaciones de los trabajos de la tercera ola. Para el análisis se ha escogido a una integrante de una de las redes sociales que sobresale entre su grupo de edad (la segunda generación) y estudios (sociolecto superior) por el alto porcentaje de formas estigmatizadas que emplea. El objetivo del capítulo es detectar qué valor confiere esta hablante a las variantes vernáculas, estudiando los temas de conversación que favorecen su aparición y los marcos discursivos que sirven de contexto. A partir de estos datos se establecen dos estilos conversacionales concretos asociados al empleo de las variantes, y que ella adopta de forma consciente para mostrarse ante los demás y construir una imagen concreta de sí misma.

Estudo do comportamento plástico, mecânico, microestrutural e térmico do concreto produzido com resíduo de porcelanato

Population growth experienced in major cities, allied to society s need of infra-structure, especially ones related to habitational demands, increases the consumption of construction materials. As a consequence, consumption of natural resources itself. Thus, due to this process, concrete is one of the most produced materials in civil construction. This is also due to the great diversity of its application, easiness in its execution and adequate mechanical performance, as well as low production costs. Following the same tendencies in construction development, the ceramic industry has intensified the production of porcelain ceramic tiles and floors. These are achieved by a fine finishing and receive polishing at the end of the fabrication process. This work researched the use of porcelain residues in polishing for the production of concrete. All of which; due to economical and environmental issues. This process aims to prove adequate destiny for this type of residue, due to environmental issues, incorporating it to the concrete itself; all of which provides economy in consumption of the materials that constitute concrete. Thus, the main characteristics of concrete were investigated through the inclusion of different concentration of the porcelain residue as additional trait element. The residue rates incorporated to the trait varied from 10% to 50% in relation to the cement mass, in the traits with plastic additives and without plastic additives. It is observed that the inclusion of porcelain residue produced a meaningful alteration in the consistency of fresh concrete. This residue has a fine granulometry and it considerably absorbed the water used in the concrete spreading, influencing the way this material is dealt with. Thus, the value of cement striking decreases with the increase of residues present in trait. The maximal incorporation of the residue was of 50%, massively, for the same factor water/initial cement. The use of residues in concrete results in an 40% increase in the compression resistance. It is also proportional to residue concentration of porcelain in the trait. The microstructure was also favored once porosity and concrete absorption decreases with the use of this residue. The parameters demonstrate the quality and durability of the concrete produced with this residue. The use of porcelain residue in concrete composition has not produced meaningful thermal behavior changes. Thermal conductivity, heat capacity and thermal diffusivity have been maintained basically constant

Estudo de revestimentos inorgânicos com inibidor de corrosão aplicado na superfície do concreto

The corrosive phenomenon on reinforced concrete structures is one of the most founded pathologies on the coastal area. With the objective to prevent the process development, or even, retard its beginning, it was studied the application of inorganic covering over concrete surfaces, after its cure, as well as, evaluate the efficiency of the covering applied on the concrete in reducing its porosity of concrete preventing the entrance of aggressive agents to preserve the integrity of the existing armor inside it, comparing the result obtained with the body-of-proof reference, that didn´t receive covering protection. On the concrete production it was used Portland Cement CP II 32, coarse aggregate, fine aggregate and water from the local distributive. Two types of covering were used, one resin based of silicon and solvent and other white cement based, selected sands and acrylic resin. The concrete mixture adopted was 1:1,5:2,5 (cement, fine aggregate, coarse aggregate) and 0.50 water/cement ratio. With the concrete on fresh state was made the experiment test to determinate the workability. On the hardened state was made the concrete resistance experiment, absorption of water and electrochemical experiments, through polarization curves. Also was held optical microscopy and Scanning Electron Microscopy experiments to analyze the layer of the covering applied to the concrete surface and the interface between the concrete and the layer. The obtained results shows that the covering applied to the concrete surface didn´t affect the resistance towards compression. On the absorption of water occurred a diminution of the percentage absorbed, improving the concrete development by making it more impermeable towards the entrance of aggressive agents. The electrochemical experiment results confirmed the water absorption results; the body-of-proof covered presented larger protection towards the development of corrosives process and retarded the evolution of the corrosive phenomenon

Concreto celular polimérico: influência na adição de resíduo de poliéster insaturado termofixo

This work addresses the production of lightweight concrete building elements, such as plates, prefabricated slabs for pre-molded and panels of fencing, presenting a singular concrete: the Lightweight Concrete, with special properties such low density and good strength, by means of the joint use of industrial waste of thermosetting unsaturated polyesters and biodegradable foaming agent, named Polymeric Lightweight Concrete. This study covered various features of the materials used in the composition of the Polymeric Lightweight Concrete, using a planning of factorial design 23, aiming at studying of the strength, production, dosage processes, characterization of mechanical properties and microstructural analysis of the transition zone between the light artificial aggregate and the matrix of cement. The results of the mechanical strength tests were analyzed using a computational statistics tool (Statistica software) to understand the behavior and obtain the ideal quantity of each material used in the formula of the Polymeric Lightweight Concrete. The definition of the ideal formula has the purpose of obtaining a material with the lowest possible dry density and resistance to compression in accordance with NBR 12.646/92 (≥ 2.5 MPa after 28 days). In the microstructural characterization by scanning electron microscopy it was observed an influence of the materials in the process of cement hydration, showing good interaction between the wrinkled face of the residue of unsaturated polyesters thermosetting and putty and, consequently, the final strength. The attaining of an ideal formula, given the Brazilian standards, the experimental results obtained in the characterization and comparison of these results with conventional materials, confirmed that the developed Polymeric Lightweight Concrete is suitable for the production of building elements that are advantageous for construction

Estudio experimental del comportamiento de muros de mampostería confinada de bloques de concreto sometidos a cargas laterales cíclicas reversibles: caracterización de la respuesta y modelación analítica.

La mampostería confinada es uno de los sistemas constructivos más utilizados en el mundo. El estudio de su comportamiento ante cargas cíclicas es de vital importancia, ya que permite predecir su respuesta ante este tipo de solicitaciones. En este estudio se caracterizaron las respuestas asociadas al comportamiento cíclico y la inclusión en el rango inelástico de los muros de mampostería confinada, de bloques huecos de concreto.

Inicio de las obras de la torre de Rectoría: un edificio de acero, vidrio y concreto

Terminados los edificios para las facultades de Derecho, Ingeniería Mecánica e Ingeniería Civil y una vez determinado el plan para la siguiente etapa de Ciudad Universitaria, se anunció la construcción de los edificios de Arquitectura, Comercio, el Estadio Olímpico y el más importante como sede del gobierno universitario: la torre de Rectoría

Viabilidad en la elaboración de prefabricados en concreto usando agregados gruesos reciclados

49 p.

Estudo da substituição de agregados miúdos naturais por pó de pedra em concreto de cimento portland

The sharp consumption of natural resources by the construction industry has motivated numerous studies concerning the application of waste to replace partially or fully, some materials, such as aggregates, thereby reducing the environmental impact caused by the extraction of sand and crushing process. The application of stone dust from crushing process arising as an aggregate for the production of Portland cement concrete is a viable alternative in view of the high cost of natural sands, in addition to the environmental damage which causes its operation to the environment. The stone dust has reduced cost compared to natural sand because it is produced in the beds of their own quarries, which are usually located close to major urban centers. This study examined the feasibility of using stone dust from the crushing of rock gneisses in the state of Bahia, replacing natural quartz sand. In the development of scientific study was conducted to characterize physical and chemical raw materials applied and molded cylindrical specimens , using as reference values Fck 20, Fck 25 and Fck 30 MPa ( resistance characteristic of the concrete after 28 days) in following compositions stone powder: 10%, 30%, 50 %, 100% and 100% with additive. The specimens were cured and subjected to the tests of compressive strength and water absorption, then the samples were subjected to the tests of X-ray diffraction and scanning electron microscopy. The results obtained showed that the composition with 10% stone powder showed the best results regarding the physical and mechanical tests performed, confirming the reduction in compressive strength and increased water uptake increased as the content of the powder stone in the concrete composition

Efeitos do tratamento superficial da sílica ativa com soluções de ácidos nítrico e fosfórico em propriedades do concreto

The addition of active silica potentially improves the quality of concrete due to its high reactivity and pore refinement effect. The reactivity of silica is likely related to its charge density. Variations in surface charge alter the reactivity of the material consequently affecting the properties of concrete. The present study aimed at investigating variations in the charge density of silica as a function of acid treatments using nitric or phosphoric acid and different pH values (2.0, 4.0 and 6.0). Effects on concrete properties including slump, mechanical strength, permeability and chloride corrosion were evaluated. To that end, a statistical analysis was carried out and empirical models that correlate studied parameters (pH, acid and cement) with concrete properties were established. The quality of the models was tested by variance analysis. The results revealed that the addition of silica was efficiency in improving the properties of concrete, especially the electrochemical parameters. The addition of silica treated using nitric acid at pH = 4.0 displayed the best cement performance including highest strength, reduced permeability and lowest corrosion current

Estudo de inibidores de corrosão em concreto armado, visando a melhoria na sua durabilidade

This thesis has as objective presents a methodology to evaluate the behavior of the corrosion inhibitors sodium nitrite, sodium dichromate and sodium molybdate, as well as your mixture, the corrosion process for the built-in steel in the reinforced concrete, through different techniques electrochemical, as well as the mechanical properties of that concrete non conventional. The addition of the inhibitors was studied in the concrete in the proportions from 0.5 to 3.5 % regarding the cement mass, isolated or in the mixture, with concrete mixture proportions of 1.0:1.5:2.5 (cement, fine aggregate and coarse aggregate), superplasticizers 2.0 % and 0.40 water/cement ratio. In the modified concrete resistance rehearsals they were accomplished to the compression, consistence and the absorption of water, while to analyze the built-in steel in the concrete the rehearsals of polarization curves they were made. They were also execute, rehearsals of corrosion potential and polarization resistance with intention of diagnose the beginning of the corrosion of the armors inserted in body-of-proof submitted to an accelerated exhibition in immersion cycle and drying to the air. It was concluded, that among the studied inhibitors sodium nitrite , in the proportion of 2.0 % in relation to the mass of the cement, presented the best capacity of protection of the steel through all the studied techniques and that the methodology and the monitoring techniques used in this work, they were shown appropriate to evaluate the behavior and the efficiency of the inhibitors

Análisis comparativo entre el concreto simple y el concreto con adición de fibra de acero al 12% y 14%.

55 p.