Thesis. 1975. Ph.D.--Massachusetts Institute of Technology. Dept. of Earth and Planetary Sciences. / Vita. / Includes bibliographical references. / Ph.D.

This investigation was involved with the combustion of 0.020" diameter aluminum in various mixtures of industrial oxygen and nitrogen at a total pressure of one atmosphere. A combustion chamber was constructed similar to that which was utilized in previous investigations involving titanium, zirconium, iron and molybdenum wires. Prior investigations of the combustion of metal wires were made using conventional high speed motion picture photography to burning rate data. Because combustion of aluminum evolves oxide smoke which obscures motion picture vision, a method utilizing an electronic counting circuit and infrared sensitive cadmium sulfide photo conductive cells in lieu of motion picture photography was developed. Burning rates of O.020" diameter titanium wire were determined for comparison with published information from the previous investigations. This data compared favorably with the published information. It was found that sustained combustion of the O.020" diameter aluminum test wire occurred only in an atmosphere of 90 per cent to 100 per cent industrial oxygen. Burning rates for this mixture range are presented. With mixtures between 70 per cent and 90 per cent industrial oxygen, it was found that the melting rate of aluminum exceeded the burning rate, drastically limiting sustained combustion and causing rapid extinguishing of any flame which did occur. Below an atmosphere mixture or 70 per cent industrial oxygen ignition could not be obtained. / Master of Science

Lam Lai-yee. / Thesis submitted in: November 2004. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (leaves 124-140). / Abstracts in English and Chinese. / Abstract --- p.i / Acknowledgement --- p.vii / Table of contents --- p.viii / List of Tables --- p.xi / List of Figures --- p.xiii / List of Plates --- p.xiv / Chapter CHAPTER ONE --- Introduction / Chapter 1.1 --- Introduction --- p.1 / Chapter 1.2 --- Background and ecological impact of hill fires in Hong Kong --- p.2 / Chapter 1.3 --- Conceptual framework of study --- p.4 / Chapter 1.4 --- Objectives of the study --- p.10 / Chapter 1.5 --- Significance --- p.11 / Chapter 1.6 --- Organization of the thesis --- p.12 / Chapter CHAPTER TWO --- The study area / Chapter 2.1 --- Introduction --- p.14 / Chapter 2.2 --- Geographical setting of Hong Kong --- p.14 / Chapter 2.2.1 --- Climate of Hong Kong --- p.14 / Chapter 2.2.2 --- Geology of Hong Kong --- p.15 / Chapter 2.2.3 --- Soils of Hong Kong --- p.16 / Chapter 2.2.4 --- Vegetation of Hong Kong --- p.17 / Chapter 2.3 --- Site selection --- p.18 / Chapter 2.4 --- Grassy Hill --- p.20 / Chapter CHAPTER THREE --- Heating effect on the properties of ash / Chapter 3.1 --- Introduction --- p.23 / Chapter 3.2 --- Experimental design and methodology / Chapter 3.2.1 --- Selection of simulation heating --- p.26 / Chapter 3.2.2 --- "Heating intensity at 200°-600°C for 1,5 and 15 minutes" --- p.27 / Chapter 3.2.3 --- Field work --- p.27 / Chapter 3.2.4 --- Heating method --- p.28 / Chapter 3.2.5 --- Chemical analysis --- p.28 / Chapter 3.2.6 --- Analysis of data --- p.32 / Chapter 3.3 --- Results and Discussion / Chapter 3.3.1 --- Heating effect on ash weight and pH --- p.33 / Chapter 3.3.2 --- "Heating effect on ash organic C, N and P" --- p.33 / Chapter 3.3.3 --- Heating effect on ash available cations --- p.40 / Chapter 3.4 --- Conclusion --- p.42 / Chapter CHAPTER FOUR --- The effect of heat and ash on soil / Chapter 4.1 --- Introduction --- p.44 / Chapter 4.2 --- Methodology / Chapter 4.2.1 --- Field work --- p.48 / Chapter 4.2.2 --- Soil heating methods --- p.48 / Chapter 4.2.3 --- Chemical analysis --- p.49 / Chapter 4.2.4 --- Statistical analysis --- p.52 / Chapter 4.3 --- Results and Discussion / Chapter 4.3.1 --- The effect of heat and ash on soil pH --- p.53 / Chapter 4.3.2 --- "The effect of heat and ash on soil organic matter, N and P" --- p.55 / Chapter 4.3.3 --- The effect of heat and ash on soil cations --- p.62 / Chapter 4.4 --- Conclusion --- p.65 / Chapter CHAPTER FIVE --- Nitrogen and phosphorus mineralization after heating / Chapter 5.1 --- Introduction --- p.67 / Chapter 5.2 --- Methodology / Chapter 5.2.1 --- Heating and incubation method --- p.70 / Chapter 5.2.2 --- Laboratory methods --- p.72 / Chapter 5.2.3 --- Statistical analysis --- p.72 / Chapter 5.3 --- Results and discussion / Chapter 5.3.1 --- Temporal changes of N mineralization in heated bare soils --- p.72 / Chapter 5.3.2 --- The effect of ash on N mineralization --- p.78 / Chapter 5.3.3 --- Comparison of N mineralization with other studies --- p.79 / Chapter 5.3.4 --- Temporal changes of P mineralization in the heated bare soils --- p.81 / Chapter 5.3.5 --- The effect of ash on P mineralization --- p.83 / Chapter 5.3.6 --- Comparison of P mineralization to other studies --- p.84 / Chapter 5.4 --- Conclusion --- p.85 / Chapter CHAPTER SIX --- Vertical movement of mineral N in ash-covered soil columns / Chapter 6.1 --- Introduction --- p.87 / Chapter 6.2 --- Methodology / Chapter 6.2.1 --- Package of soil columns --- p.89 / Chapter 6.2.2 --- Water addition and extraction of pore water --- p.90 / Chapter 6.2.3 --- Statistical analysis --- p.92 / Chapter 6.3 --- Results and Discussion / Chapter 6.3.1 --- Mineral N in the pore water --- p.92 / Chapter 6.3.2 --- The effect of ash on mineral N in pore water --- p.97 / Chapter 6.3.3 --- The leaching loss of mineral N --- p.98 / Chapter 6.3.4 --- Comparisons with other studies --- p.103 / Chapter 6.4 --- Conclusion --- p.105 / Chapter CHAPTER SEVEN --- Integrative discussion / Chapter 7.1 --- Summary of major findings --- p.107 / Chapter 7.2 --- Clarifying some misconceptions about the effect of fire --- p.110 / Chapter 7.3 --- Estimated losses of N and P from heating --- p.112 / Chapter 7.4 --- Nutrient supplying capacity of soils after heating --- p.115 / Chapter 7.5 --- Why are repeatedly burnt areas reduced to grassland? --- p.118 / Chapter 7.6 --- Implication on the restoration of fire-affected areas --- p.119 / Chapter 7.7 --- Limitations of the study --- p.121 / Chapter 7.8 --- Suggestions for future research --- p.122 / References --- p.124 / Appendices --- p.141

Thesis (MScEng)--Stellenbosch University, 2005. / ENGLISH ABSTRACT: The convection heat transfer coefficient between an infinite, horizontal surface and the natural environment is determined experimentally. It is shown that, during daytime, heat is transferred due to natural and forced convection, while during nighttime heat is transferred due to conduction and forced convection. Equations that correlate the daytime and nighttime convective heat transfer coefficients respectively, are presented. The results are compared with values obtained by other investigators. The equations for the convection heat transfer coefficient are then used to predict the surface temperature and the temperature at depth of asphalt pavement samples using a simulation model. It is found that there is good agreement between the measured and the predicted asphalt pavement sample temperatures. / AFRIKAANSE OPSOMMING: Die konveksie warmteoordrags-koëffisiënt tuseen 'n oneindige, horisontale oppervlak en die natuurlike omgewing is eksperimenteel bepaal. Daar word getoon dat warmte, tydens die dag, oorgedra word deur natuurlike en geforseerde konveksie, terwyl warmte tydens die nag oorgedra word deur geleiding en geforseerde konveksie. Die resultate word vergelyk met die resultate van ander navorsers. Vergelykings wat die konveksie warmteoordrags-koëffisiënt gedurende die dag en nag onderskeidelik korreleer word voorgestel. Die vergelykings vir die konveksie warmteoordrags-koëffisiënt word dan gebruik in 'n simulasiemodel om die oppervlaktemperatuur en die temperatuur onder die oppervlakte van asfalt-padoppervlakmonsters te voorspel.

As ondas de calor constituem sequências extremas de elevadas temperaturas que podem causar prejuízos biológicos, econômicos e sociais, desta forma demandando discussões em planejamentos estratégicos para a manutenção do funcionamento social. No entanto, inexistem trabalhos que as abordem historicamente em suas complexidades estatísticas, sinóticas e termodinâmicas em toda a extensão da América do Sul (AS), sendo os estudos ora restritivos no tempo, ora restritivos no espaço. Esta dissertação identifica e analisa as ondas de calor sobre a AS em suas distintas áreas de atuação regional, para um período de 30 anos, fazendo uso dos dados diários de reanálise do European Centre for Medium-Range Weather Forecasts (ECMWF), com resolução de 0,75° na área delimitadas pelas coordenadas (60°S15°N) e (8530°W). Para isto adota um critério de identificação objetivo e consistente com a variabilidade da extensão temporal e da intensidade das anomalias positivas de temperaturas, discutindo os aspectos metodológicos não consensuais presentes na literatura. As ondas de calor foram agrupadas segundo os padrões de variabilidade guiados por fenômenos atmosféricos específicos, em uma nova técnica alternativa ao uso das Funções Ortogonais Empíricas, derivada dos mapas de correlações espaciais. Os resultados mostram que as ondas de calor acontecem em qualquer época do ano, preferencialmente no período climatológico de maiores temperaturas; além disso, sua frequência está aumentando com o passar dos anos na AS. Para completar, os mapas de composições das climatologias sinóticas permitem identificar sistemas meteorológicos específicos para cada uma das dez regiões homogêneas identificadas, alguns deles relacionados ao fenômeno El Niño Oscilação-Sul e a padrões determinados de circulação atmosférica, precipitação e Temperatura da Superfície do Mar. Tendo em vista a possibilidade de inclusão da mesma técnica aos estudos globais e para as ondas de frio, este trabalho se insere no início de uma vasta gama de estudos inter-relacionados, dentro do contexto das mudanças climáticas e de considerável interesse socioeconômico envolvido. / Heat waves constitute extreme sequences of high temperatures that can cause biological, economic, and social damages, thus requiring strategic planning discussion for social functioning maintenance. However, there are no papers addressing them from a historical point of view in their statistical, synoptic, and thermodynamic complexities throughout South America (SA), being the studies sometimes restrictive in time, and sometimes restrictive in space. This dissertation identifies and analyses the SA heat waves over their regional areas, for a period of 30 years, making use of reanalysis daily data of European Centre for Medium-Range Weather Forecasts (ECMWF), with 0.75° resolution over the area delimited by the coordinates ranges (60°S15°N) and (8530°W). To do that, it adopts an objective identification criterion consistent with the variability of the temporal extension and the intensity of the positive anomalies of temperatures, discussing the nonconsensual methodological aspects present in the literature. The heat waves were grouped according to the variability patterns guided by specific atmospheric phenomena, in a new alternative technique to the use of the Empirical Orthogonal Functions, derived from the maps of spatial correlations. The results show that the heat waves happen at any time of the year, preferably in the climatic period of higher temperatures; in addition, its frequency is increasing over the years in AS. To complete, the correlation maps of synoptic climatology allow the identification of specific meteorological systems in each of the ten identified homogeneous region, some of them related with El Niño Southern Oscillation and with determined patterns of atmospheric circulation, precipitation, and Sea Surface Temperature. Considering the possibility of including the same technique in global studies and in the case of cold waves, this work is part of a wide range of interrelated studies within the context of climate change and considerable socioeconomic interest involved.

As ondas de calor constituem sequências extremas de elevadas temperaturas que podem causar prejuízos biológicos, econômicos e sociais, desta forma demandando discussões em planejamentos estratégicos para a manutenção do funcionamento social. No entanto, inexistem trabalhos que as abordem historicamente em suas complexidades estatísticas, sinóticas e termodinâmicas em toda a extensão da América do Sul (AS), sendo os estudos ora restritivos no tempo, ora restritivos no espaço. Esta dissertação identifica e analisa as ondas de calor sobre a AS em suas distintas áreas de atuação regional, para um período de 30 anos, fazendo uso dos dados diários de reanálise do European Centre for Medium-Range Weather Forecasts (ECMWF), com resolução de 0,75° na área delimitadas pelas coordenadas (60°S15°N) e (8530°W). Para isto adota um critério de identificação objetivo e consistente com a variabilidade da extensão temporal e da intensidade das anomalias positivas de temperaturas, discutindo os aspectos metodológicos não consensuais presentes na literatura. As ondas de calor foram agrupadas segundo os padrões de variabilidade guiados por fenômenos atmosféricos específicos, em uma nova técnica alternativa ao uso das Funções Ortogonais Empíricas, derivada dos mapas de correlações espaciais. Os resultados mostram que as ondas de calor acontecem em qualquer época do ano, preferencialmente no período climatológico de maiores temperaturas; além disso, sua frequência está aumentando com o passar dos anos na AS. Para completar, os mapas de composições das climatologias sinóticas permitem identificar sistemas meteorológicos específicos para cada uma das dez regiões homogêneas identificadas, alguns deles relacionados ao fenômeno El Niño Oscilação-Sul e a padrões determinados de circulação atmosférica, precipitação e Temperatura da Superfície do Mar. Tendo em vista a possibilidade de inclusão da mesma técnica aos estudos globais e para as ondas de frio, este trabalho se insere no início de uma vasta gama de estudos inter-relacionados, dentro do contexto das mudanças climáticas e de considerável interesse socioeconômico envolvido. / Heat waves constitute extreme sequences of high temperatures that can cause biological, economic, and social damages, thus requiring strategic planning discussion for social functioning maintenance. However, there are no papers addressing them from a historical point of view in their statistical, synoptic, and thermodynamic complexities throughout South America (SA), being the studies sometimes restrictive in time, and sometimes restrictive in space. This dissertation identifies and analyses the SA heat waves over their regional areas, for a period of 30 years, making use of reanalysis daily data of European Centre for Medium-Range Weather Forecasts (ECMWF), with 0.75° resolution over the area delimited by the coordinates ranges (60°S15°N) and (8530°W). To do that, it adopts an objective identification criterion consistent with the variability of the temporal extension and the intensity of the positive anomalies of temperatures, discussing the nonconsensual methodological aspects present in the literature. The heat waves were grouped according to the variability patterns guided by specific atmospheric phenomena, in a new alternative technique to the use of the Empirical Orthogonal Functions, derived from the maps of spatial correlations. The results show that the heat waves happen at any time of the year, preferably in the climatic period of higher temperatures; in addition, its frequency is increasing over the years in AS. To complete, the correlation maps of synoptic climatology allow the identification of specific meteorological systems in each of the ten identified homogeneous region, some of them related with El Niño Southern Oscillation and with determined patterns of atmospheric circulation, precipitation, and Sea Surface Temperature. Considering the possibility of including the same technique in global studies and in the case of cold waves, this work is part of a wide range of interrelated studies within the context of climate change and considerable socioeconomic interest involved.

The potential hazard of fire is one of the major concerning issues after the recent events of 9/11 and others. A lot of studies and research work is being carried out presently, to ensure the safety of buildings. But, there is no accurate method to estimate the fire endurance/resistance for a building due to the variability of fire characteristics, material properties of construction material, and other characteristics of a building. One can only provide guidelines and can adopt from the lessons learnt in the past to ensure better quality to make the buildings more fire proof, so that they can withstand high temperatures and stresses for a longer time, before collapse mechanism occurs. From a long time, live laboratory tests have been conducted to study the performance of assemblies by subjecting them to appropriate time-temperature histories that are derived from standardized fire curves. The performance-based approach is very time consuming and also involves high costs. In recent times, due to the advances in technology, computer models have been developed, that aid towards the simulations of assemblies and other components of a building that are subjected to a fire event. This approach helps in attaining reasonable results, thereby providing an alternative to the prescriptive and performance-based approaches. This project deals with the study of heat transfer mechanism that takes place in steel structures in case of a fire event. For proper and accurate simulation process, the use of software is a must along with the support of technical resources. Due to high thermal conductivity of steel the heat gets transferred rather fast in the steel section which creates non-uniform temperature distributions because of variable thermal properties, like thermal conductivity and specific heat. 3-D finite element software TAS (Thermal Analysis Software) was used to study the non-uniform temperature distributions in case of a W 12x27 beam protected with vermiculite coating. The results were compared with the studies done by Professor Bletzacker, which involved the furnace testing of a W 12x27 beam by subjecting it to ASTM E-119 curve time-temperature history. In addition to this, the sensitivity of results was evaluated based on the variation of thermal properties for concrete, vermiculite, and gypsum board. Different beam models for W12x27 section protected with vermiculite and gypsum board coatings were simulated to justify their performance based on temperature rise within the assembly. Also, simulations were performed for analyzing the behavior of the beam when subjected to different fire curves like ASTM E-119 and ENV. Analytical analysis was also carried out using the method of Lumped mass parameter method to provide a comparison of results from different models. Finally, conclusions and recommendations were made to ensure further development and understanding in the field of Structural and Fire Protection Engineering.

A alvenaria estrutural é um dos mais antigos sistemas construtivos existentes. Atualmente estruturas em alvenaria encontram uma vasta aplicação em construções residenciais, sobretudo em obras de interesse social. No entanto, ao contrário das estruturas de concreto, cujo comportamento durante exposição ao fogo e sua resistência residual tem estudos e resultados amplamente disseminados, pouco se sabe a respeito do comportamento de estruturas de alvenaria submetidas à ocorrência de sinistros dessa natureza. Com a intensificação das preocupações acerca da segurança das edificações e de seus usuários em situações de incêndio, faz-se cada vez mais imprescindível o conhecimento do comportamento dos sistemas empregados atualmente na construção civil perante a ação de altas temperaturas. Tendo isso em vista, o presente trabalho teve por objetivo a realização de uma análise dos danos e do comportamento apresentados por amostras de alvenaria com função estrutural ao serem expostas ao aquecimento excessivo. Foram avaliadas nesse estudo paredes de pequenas dimensões executadas com blocos estruturais cerâmicos. Visando simular condições mais próximas da realidade, foram restringidas, com o auxílio de macacos hidráulicos, as laterais das amostras, para que houvesse contenção da dilatação das mesmas. Com o intuito de verificar diferentes tipologias de alvenarias, foram utilizados três blocos distintos: de 14 cm de largura, com resistências de 7 e 10 MPa, e de 19 cm de largura, com 7 MPa de resistência à compressão. Também foram variadas as espessuras das juntas entre as unidades e a argamassa de assentamento das mesmas, a fim de compreender a importância desses fatores para o comportamento das amostras, e, por fim, foram ensaiadas amostras com revestimento na face exposta As miniparedes foram acopladas a um forno de resistências elétricas e submetidas a um aquecimento próximo à curva padrão determinada por norma, até a temperatura máxima de 950ºC, a qual foi mantida pelo período de 4 horas. Foram mensurados, além da temperatura dentro do forno, no interior da parede e na superfície das amostras, os deslocamentos transversais ocorridos durante o ensaio. Também se utilizaram transdutores de deslocamento para verificar a dilatação dos blocos e o esmagamento ou abertura das juntas. Imagens termográficas da face oposta ao aquecimento foram capturadas no decorrer da exposição. Ao final das análises, pôde-se inferir que as miniparedes ensaiadas apresentaram bom desempenho frente à ação das altas temperaturas, mantendo sua estanqueidade, isolamento térmico e resistência mecânica. A restrição lateral não ocasionou desplacamentos dos blocos, no entanto, pôde-se observar transferência de tensão para os mesmos quando utilizadas nas juntas argamassas pouco flexíveis. O deslocamento transversal apresentado pelas amostras indicou deflexão em direção ao forno durante o aquecimento, com posterior reversão do sentido. Tal deflexão foi atenuada pela redução da espessura das juntas, pelo uso de argamassas menos flexíveis e pelo aumento da resistência e largura dos blocos. As alvenarias de 19 cm de largura e, especialmente, as dotadas de revestimento apresentaram melhor desempenho térmico que as demais. / Structural masonry is one of the oldest existing building systems. Nowadays, masonry structures find a wide application in residential constructions, mainly in those with social interest. However, unlike concrete structures, whose behavior during fire exposure and its residual resistance have widely disseminated studies and results, there is a lack of knowledge about the behavior of masonry structures submitted to fire. Because of the spread of concerns about the safety of buildings and their users in fire situations, it becomes essential to know the behavior of the systems currently used in civil construction when exposed to high temperatures. With this in view, the present study intended to analyze the damage and the behavior of structural masonry samples exposed to heating. This study evaluated clay hollow-bricks small walls, and, in order to simulate real conditions, the boundaries of the samples were restrained, with the aid of hydraulic jacks, aiming to restrain the deformation. In order to verify different types of masonry, three different blocks were used: 14 cm wide, with nominal strength of 7 and 10 MPa, and 19 cm wide, with 7 MPa of compressive strength. The thicknesses of the joints and the mortar were also varied, in order to understand the importance of these factors in the behavior of the samples, and, finally, samples were tested with a mono-layer coating at the exposed face. The small walls were coupled to an electrical furnace and subjected to a heating approximately equal to the standard curve, up to the maximum temperature of 950ºC, which was maintained for 4 hours The deflections of the samples during the test were measured, beyond the temperature inside the furnace, in the center of wall and at the non-exposed surface. Clip gages were also used to verify the expansion of the blocks and the crushing or opening of the mortar joints. Thermographic images of the opposite face were captured during the testing. At the end of this research, it was possible to affirm that the walls had good behavior against the high temperatures, maintaining their integrity, thermal insulation and load-bearing capacity. The restriction of the boundaries did not cause the spalling of the blocks, however, it was possible to observe the stress transfer to them in samples with rigid joint mortar. The deflection of the samples increases towards the furnace during the heating, and, then, they show the phenomenon of “reverse bowing”, changing the direction of the displacements. Reducing the thickness and increasing the stiffness of the joint mortars, as well as the increase in block strength and width attenuated such deflection. The masonry 19 cm width and, specially, the ones with coating shows better thermal performance, comparing to the others.

Considerando as crescentes aplicações das ligas fundidas de alumínio-silício em altas temperaturas e seu importante papel relacionado a redução do consumo de combustíveis fósseis no setor automotivo, este trabalho de pesquisa tem como principal objetivo investigar os efeitos da adição combinada de cério e zircônio na microestrutura e propriedades mecânicas da liga 354.0, visando sua otimização em temperaturas de trabalho elevadas. Para atender a este objetivo, foram desenvolvidas três ligas experimentais com adições constantes de Ce (0,3%) e crescentes de Zr (0,16; 0,27 e 0,36% em peso). Observações microestruturais e medições de dureza foram realizadas em todas as etapas de processamento (condições bruto de fusão, solubilizado, envelhecido naturalmente e artificialmente) buscando caracterizar o efeito destes elementos e também otimizar as etapas de tratamento térmico. Adicionalmente, ensaios de tração foram executados a temperatura ambiente e também a 175, 210, 245 e 275 °C na condição T6. A análise microestrutural na condição bruto de fusão revela que as adições combinadas de Ce e Zr, levaram a formação de novas fases intermetálicas na matriz, além de influenciar de forma significativa a orientação da rede de partículas de silício, sendo estas características ainda remanescentes após o tratamento térmico de solubilização. Em relação a resposta das ligas modificadas nas condições T4 e T6, a adição de Ce e Zr conduz a comportamentos distintos em relação a cinética de endurecimento devido a reação Ce-Cu durante a solidificação das ligas, a qual reduz substancialmente a quantidade de cobre disponível para endurecimento por precipitação. Considerando o incremento de Zr na composição química das ligas, este tem apenas o efeito de endurecimento por solução sólida, não afetando de forma significativa o processo de envelhecimento. Os resultados obtidos dos ensaios de tração realizados em diferentes temperaturas mostraram um desempenho superior na condição T6, principalmente utilizando concentrações de 0,27%Zr em ensaios conduzidos a 210 °C, apresentando um aumento na tensão limite de resistência de aproximadamente 6,7% em relação a liga padrão. / In view of increasing in cast aluminum-silicon alloys for high temperature applications and it´s important role for reduce fuel consumption in automotive industry, the aim of this research is investigated the effects of cerium and zirconium additions upon the microstructure and mechanical properties 354 alloy, aiming to improve high temperature behavior. To this goal, was development three experimental alloys with fixed cerium (0.3%) and increasing zirconium content (0.16; 0.27 and 0.36 wt.%). Microstructural observations and hardness measurements were performed in all process steps (as cast, solutionized, natural and artificial aged), for characterize effects of these elements and also optimize the steps of heat treatment. In addition, tensile tests were performed at room temperature and also 175, 210, 245 e 275 °C in the T6 condition. Microstructural analysis as cast condition leads the formation of new intermetallic phases in the matrix, and significantly modification in silicon particle network, which are still remains characteristics after solution heat treatment. In regarding the response of modified alloys under T4 and T6 conditions, the addition of Ce and Zr leads to different behavior in hardening kinetics due to Ce-Cu reaction during alloys solidification, which substantially reduces amount available copper for precipitation hardening. In despite increase of Zr in the chemical composition of the alloys, considering an increase of zirconium content in alloys, the only effect is solid solution strengthening, does not affecting the age process. Tensile properties in different temperatures show an increase in T6 condition for modify alloys with 0.27 wt.%, particularly in 210 °C, exhibits an increase that 6.7% compared with the standard alloy.

Tradicionalmente, admite-se que o concreto é um material resistente ao fogo por ser incombustível e apresentar baixa condutividade térmica (elevada capacidade de isolamento térmico). No entanto, quando exposto a altas temperaturas, experimenta vários problemas: a deterioração das propriedades térmicas e mecânicas, o dano causado pela restrição às deformações térmicas e a possibilidade de ocorrência de desplacamentos. Neste contexto, as modelagens computacionais, especialmente através do método dos elementos finitos, têm adquirido cada vez mais importância. Através da simulação do comportamento das estruturas de concreto sob altas temperaturas um dado problema pode ser estudado em diferentes cenários, geometrias, propriedades dos materiais, carregamentos e condições de vinculação. Neste trabalho foi desenvolvido um programa computacional para a simulação do comportamento termomecânico não linear de estruturas planas de concreto armado sob a ação de altas temperaturas através do método dos elementos finitos. O programa realiza, em sequência, para cada incremento de tempo, as análises térmica e mecânica. O campo de temperaturas, determinado na análise térmica, é considerado na determinação das propriedades dos materiais, consideradas na análise mecânica. Na análise mecânica, utilizou-se o modelo de fissuras discretas para a representação do comportamento frágil do concreto sob a ação dos esforços de tração. O modelo de armadura incorporada foi empregado para a representação mecânica da armadura. Foi desenvolvida uma analogia térmica ao modelo mecânico de armadura incorporada para a consideração da contribuição do aço na transferência de calor. Os resultados do programa foram comparados com valores experimentais disponíveis na literatura. Primeiramente, realizou-se a análise térmica de seções de concreto de diferentes formas. Após, foi analisado o comportamento termomecânico de uma laje armada em uma só direção. As respostas obtidas tiveram boa aproximação em todas as comparações executadas. / Traditionally, it is admitted that concrete is a fire-resistant material due to its incombustible nature and low thermal conductivity (high insulating capacity). However, when exposed to high temperatures, it experiments a number of problems: deterioration of its thermomechanical properties; damage caused by the restricted thermal deformations; and the possibility of spalling. In this context, computational modelings, especially through the Finite Element Method, have gained increasing importance. Through the simulation of the behavior of concrete structures under high temperatures, a given problem can be studied in different scenarios, geometries, material properties, loadings, and boundary conditions. In this work a computational program for the simulation of non-linear thermo-mechanical behavior of reinforced concrete plane structures under the action of high temperatures through the Finite Element Method was developed. The program executes, in a sequence, for each time increment, thermal and mechanical analyses. The temperature field, determined in the thermal analysis, is considered in the determination of the material properties that are considered in the mechanical analysis. In the mechanical analysis, the smeared cracking model to represent the fragile behavior of concrete under the action of tension stresses was used. The embedded model was used in the mechanical representation of the reinforcement. A thermal analogy of the mechanical embedded model for reinforcement bars to the steel contribution in the heat transfer was developed. The program results were compared with experimental values available in the literature. Firstly, a thermal analysis of the concrete sections was carried out in different ways. Next, the thermo-mechanical behavior of a one-way reinforced slab was analyzed. The obtained responses had a close agreement in all comparisons conducted.