DECAT - Artigos publicados em periódicos

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Application of total quality management tools in the risk analysis of pathologies in steel-structured buildings.
(2022) Hofmann, Giane Alfenas Antunes; Souza, Henor Artur de
Structured steel construction is an interesting option to the already established concrete structure at a time when Brazilian civil construction seeks more efficiency. Encouraging the use of this material requires a better understanding of its characteristics and especially its possible pathologies to prevent degradation, costs, and even structural collapse. This study uses Total Quality Management tools are applied to analyze the pathologies present in five medium and large steel-structured buildings. The causative elements are identified with the information about the buildings’ pathologies, and the risk analysis of the pathologies is performed using, especially, the Ishikawa Diagram and the GUT Matrix. The most frequent pathologies highlighted in the study are corrosion in the structure, cracks in the closures, and infiltrations in the interface closure/structure. The main causes, according to the Ishikawa diagram and the GUT matrix, are related to construction technique, labor, environmental conditions, and raw material used. The results show that it is possible, through the tools of Quality Management, to establish the risk of each pathology and its origin and determine the degree of risk that each one offers.
Naturally ventilated industrial sheds : an investigation about the influence of wind direction in flow rate efficiency in continuous roof vents.
(2021) Camargos, Bruno Henrique Lourenço; Souza, Henor Artur de; Gomes, Adriano Pinto; Ladeira, Artur Hallack; Reis, Reinaldo Antonio dos; Mapa, Lidianne de Paula Pinto
Natural ventilation portrays an effective technique for lowering the internal temperature, without spending electricity, and directly contributes to the renewal of indoor air by establishing a healthy environment for workers. Given this, it is usual to have air vent openings located at the top of the roof (continuous roof vents), in addition to those present on the facades of sheds. In naturally ventilated buildings, it is recommended to give due importance to the provision of these openings, since depending on the proposed arrangement, the wind may or may not help in the effectiveness of this strategy. In this work, it is evaluated via computer simulation (EnergyPlus, version 8.7.0), for the climatic conditions of the city of Belo Horizonte/Brazil, the influence of the wind direction in the flow rate of indoor air through the ridge vents, of the longitudinal and transversal type, present in industrial sheds endowed with an internal source of high-intensity heat release. The results obtained show that the flow rate has a symmetrical behavior in the openings of the longitudinal continuous roof vent, that is, when an opening is with the maximum outflow of the internal air, the opening opposite the predominant wind direction is acting as an entry point for the air external. The transverse continuous roof vents are more sensitive about the wind direction since they are positioned perpendicular to the building. The best result found is for the wind situation occurring parallel to the shed, obtaining a reduction in the internal temperature of up to 1°C, an increase in the rate of air changes per hour, in the internal environment, at 1acph, and an increase of up to 10,7% in the volume of air infiltrated into the shed.
Variables of influence on thermal performance of buildings under transient conditions.
(2021) Ferreira, Camila Carvalho; Souza, Henor Artur de; Carlo, Joyce Correna
Residential buildings significantly increase electricity demand, especially in developing countries. In this case, the requirements addressed by the standards can ensure the climatic adequacy of the envelope, enhance thermal performance, and promote thermal comfort conditions while reducing energy consumption. However, the criteria for evaluating the thermal performance of a building’s envelope that is commonly adopted in energy performance standards and codes have proved to be inefficient in hot climates. The heat exchanges within buildings are dependent on solar radiation and ventilation. The purpose of this article is to establish the variables with the greatest influence on the thermal performance of naturally ventilated dwellings in hot climates (equatorial, tropical and subtropical). For this investigation, a factorial design was adopted for sensitivity analysis. The structure of the factorial experiment defined the simulations of four patterns of single-family and multifamily residential buildings. We varied the thermophysical properties of the external walls and roofs, the heat gain coefficient of the openings, and natural ventilation. Brazil was adopted as a basis for climate analysis, including equatorial, tropical and subtropical climates. The analyses were based on comfort hours in an adaptive model and statistically evaluated using Analysis of Variance (ANOVA) tests. In general, the absorption of the walls and cover, the thermal transmittance of the cover and the natural ventilation were the variables of greatest influence on thermal comfort in a hot climate.
Analysis of the influence of soil in the thermal performance of subterranean rooms in a ground-level building in São Paulo, Brazil, via EnergyPlus.
(2020) Resende, Bruna Cristina; Souza, Henor Artur de; Gomes, Adriano Pinto
Among the several factors that interfere with the thermal performance of buildings, soil temperature is not always considered in thermal performance evaluations. However, soil temperature is a factor that influences the result of heat exchanges in the environment, especially in ground-level buildings. Thus, it is necessary to evaluate this influence due to the interaction of the soil with the building. In addition, due to the three-dimensional and transient character of the heat exchange processes involving the ground, the numerical approach becomes an important tool in the thermal performance analysis of buildings. In this respect, the software EnergyPlus emerges as an alternative to obtain such results, especially through the Basement preprocessor. Results suggest that, when the soil effect is considered in thermal analyses, the internal temperature of subterranean rooms increases up to 8.9% in the summer and decreases to 5.4% in winter. These results were obtained when compared to the initial situation, where soil influence had been neglected. Such results provide an indication of the importance of considering the soil influence on the thermal performance analyses where an accurate assessment is requested.
Heat flow avaliation in closing system in light steel framing.
(2020) Muzzi, Thassiana Armond; Gomes, Adriano Pinto; Souza, Henor Artur de
The use of steel in construction appears as an alternative to change the overview of this sector, contributing to increase productivity, reduce waste and the running time of construction. The Light Steel Framing System (LSF) introduced in Brazil in the late 1990s is going through a process of technical development and acceptance in the domestic construction market, but there are still shortcomings in the design, detailing and implementation of complementary systems of closing and also in its thermal performance. This study covers an analytical approach in which simplified methods of calculating resistance and thermal transmittance and a numerical approach are presented, using the computer program ANSYS (version 15) for checking and comparing of these methods. It is considered the closing of multi-layer compound in the outer layer by cement board and the inner layer of gypsum board, brokered by fiber glass insulation, with studs formed by C-sections profiles in galvanized steel. Among the simplified methods discussed in analytical analysis, the method of Isothermal Plans showed the lowest value of thermal resistance and thus the highest thermal transmittance and heat flow. In relation to the numerical analysis, the results showed that the heat flow is equal to a value around 49% higher than the heat flux value for a closing without the presence of steel profile. The method of Modified Zone showed the smallest difference in the value of the equivalent thermal resistance in comparison of analytical and numerical analysis.
Influência de paredes verdes no desempenho térmico de habitações sociais.
(2020) Sousa, Luana Resende de; Souza, Henor Artur de; Gomes, Adriano Pinto
A utilização da vegetação como elemento de fachada ainda compreende uma prática bastante incipiente, mas tem se popularizado devido à promessa de melhoria no desempenho térmico das edificações, além de representar uma alternativa de ampliação da biodiversidade no ambiente urbano. Neste trabalho investiga-se a influência das paredes verdes, no contexto climático brasileiro, sobre o desempenho térmico de edifícios habitacionais de interesse social. Como metodologia, utiliza-se a simulação do comportamento termoenergético de um edifício habitacional multifamiliar, por meio do programa EnergyPlus, incluindo-se o modelo HAMT que leva em conta o processo de transferência de umidade através da envoltória, para três zonas bioclimáticas previstas na norma NBR 15.220-2005, clima extremo para inverno (ZB1), clima extremo de verão (ZB8) e para um clima considerado como intermediário (ZB3). Os resultados obtidos demonstram uma diferença na temperatura interna dos ambientes, decorrente dos dois arranjos de fachada analisados: com e sem vegetação. O uso da parede verde proporcionou uma redução na temperatura interna de até 2,8 °C no verão e um aumento de até 1,4 °C no inverno. Observa-se que a vegetação na fachada ajudou a manter a temperatura interna mais baixa durante o dia e amena durante a noite. Logo, as paredes verdes podem representar uma solução sustentável e de baixo custo a ser implantada às edificações, visando melhorar seu desempenho térmico.
Modelagem da transferência de calor de ambientes subterrâneos no programa de simulação EnergyPlus.
(2019) Resende, Bruna Cristina; Souza, Henor Artur de; Gomes, Adriano Pinto
A temperatura do solo é um dos fatores mais influentes nas avaliações de desempenho térmico de ambientes subterrâneos e quase sempre é desconsiderada. Por isso, é necessário avaliar essa influência devido à interação do solo com a edificação, pois a transferência de calor através de paredes e pisos subterrâneos tem uma extensão significativa na carga térmica total de uma edificação. Este trabalho compara e avalia o impacto de diferentes alternativas de modelagem presentes no programa de simulação EnergyPlus por meio da análise das trocas de calor entre o solo, o piso e as paredes de um ambiente subterrâneo de uma edificação unifamiliar de São Paulo, Brasil, não condicionada artificialmente e não isolada termicamente. A comparação das alternativas de modelagem por meio da análise recomendada pela NBR 15575 indicou grande variação nos resultados de temperatura interna do ambiente subterrâneo da edificação. Quando comparado ao pré-processador Basement, os modelos do objeto GroundDomain apresentaram variação de temperatura interna do ambiente subterrâneo de até 6 ºC no verão e de 5,2 ºC no inverno. Tais resultados fornecem indicações da influência e da variabilidade que o uso das diferentes opções de modelagem do EnergyPlus podem gerar em uma análise de desempenho térmico.
Residência em contêiner : comparativo de estratégias para a melhoria do desempenho térmico.
(2019) Viana, Françoíse Santana; Souza, Henor Artur de; Gomes, Adriano Pinto
A construção civil passa atualmente por desafios em construir de forma mais econômica e ambientalmente correta. Neste trabalho visa-se conhecer melhor o equipamento não convencional utilizado para edificações, o contêiner, avaliando seu desempenho térmico. O contêiner é escolhido como objeto de estudo pois é um módulo que pode ser adaptado para diversos tipos de climas, terrenos e construções. E como no Brasil sua utilização na construção é recente, torna-se necessário uma análise para entender como adaptá-lo de forma eficiente. Neste estudo, a avaliação do desempenho térmico do contêiner é feita via simulação numérica utilizando o programa Energyplus, analisando o impacto da ventilação natural e da massa térmica dos fechamentos no comportamento térmico da edificação. São consideradas as condições climáticas para as zonas bioclimáticas 2, 3 e 8, que englobam o litoral brasileiro, previstas na norma NBR 15.220-2005, observando também os requisitos mínimos da norma NBR 15.575-2013. Para o estudo, projetou-se uma casa com dois módulos de contêiner, totalizando uma área de 29,57 m². Os resultados obtidos mostram a necessidade de adaptações para que o contêiner possua habitabilidade em todas as zonas bioclimáticas analisadas. Constata-se que o uso de isolamento térmico nos fechamentos verticais, de uma cobertura termicamente eficiente, de uma fundação adequada e de cores com tons mais claros no fechamento externo proporcionam um melhor desempenho térmico à edificação, para os climas analisados.
A relação entre capacidade atencional, psicopedagogia e o conforto térmico em salas de aula.
(2019) Marçal, Viviane Gomes; Souza, Henor Artur de; Cristeli, Pablyne Sant’Ana; Marçal, Caio Cesar Sousa
A interferência do conforto térmico na capacidade de atenção dos estudantes em salas de aula já tem sido relatada em pesquisas nas áreas que desenvolvem os projetos de edifícios escolares. Entretanto, no campo da educação trata-se da temática da capacidade atencional e da aprendizagem sem relacionar ao ambiente construído. Desse modo, verifica-se o quanto é preciso trazer esse debate a fim de subsidiar e inter-relacionar as áreas. Assim, este trabalho teve por objetivo tratar das possíveis relações entre a capacidade atencional, a psicopedagogia e o conforto térmico no ambiente escolar a partir de seus percursos e da produção de conhecimentos, assim como dos dados coletados com os estudantes. Esta pesquisa tem natureza de abordagem qualitativa e quantitativa, com base em levantamentos de dados realizados em duas instituições públicas de educação superior, localizadas na cidade de Belo Horizonte e em Ouro Preto, Minas Gerais. Os resultados em Belo Horizonte indicaram que, a impaciência, dificuldade de concentração e sonolência foram mais percebidas pelos discentes, e ainda 70% têm a atividade de estudo prejudicada no ambiente de sala de aula. Em Ouro Preto ao serem perguntados sobre o prejuízo na atividade de estudo, 79% dos estudantes conseguem desenvolver a atividade de estudo normalmente no interior das salas de aula.
Simulação termoenergética e lumínica de fachadas com brises no clima tropical.
(2023) Dias, Luma de Souza; Souza, Henor Artur de; Gomes, Adriano Pinto; Caetano, Lucas Fonseca; Camargos, Bruno Henrique Lourenço; Tribess, Arlindo
O uso da luz natural em edificações é uma importante estratégia de projeto pois minimiza o consumo de energia com iluminação elétrica e proporciona maior qualidade visual para seus usuários. Porém, essa estratégia pode resultar em ganhos térmicos excessivos e ofuscamento, causando desconforto térmico em ambientes de trabalho. No intuito de buscar uma combinação entre qualidade visual e bom desempenho termoenergético e lumínico, analisa-se nesse estudo a influência do tipo de brise-soleil e tipo de vidro, aplicados a uma edificação comercial com fachada envidraçada, localizada em regiões de clima tropical. Incluise na análise a edificação sem o uso do brise-soleil, como referência. São realizadas simulações computacionais com os programas Daysim e EnergyPlus considerandose a fachada oeste da edificação. Ao considerar o parâmetro tipo de vidro, os modelos que apresentam melhor comportamento são aqueles com vidro comum. Comparando-se os resultados entre os tipos de brises percebe-se que os modelos com brise vertical possuem valores mais elevados de taxa de radiação solar do que os modelos com brise horizontal, trazendo benefícios de maior luz natural ao ambiente. Os resultados, considerando-se as horas de conforto do usuário, indicam que o modelo de brise horizontal com vidro laminado na cor verde apresenta-se como o mais adequado, visto que possui o menor consumo de energia e mais horas de conforto. Ressalta-se, como contribuição do presente trabalho, a obtenção de modelos de brises mais adequados para projetos de brises aplicados em fachadas envidraçadas em regiões de clima tropical.
Proposal of stainless steel roof structure and tiles for gymnasiums.
(2022) Oliveira, Géferson Diogo de; Souza, Henor Artur de; Ribas, Rovadávia Aline de Jesus; Caetano, Lucas Fonseca
This work proposed an architectural alternative project of a stainless steel roof structure that uses roof tiles also in stainless steel with emphasis on roofs for multi-sport gymnasiums. In the development of the work, two existing multi-sports gymnasiums are taken as a reference, but with ASTM (American Society for Testing and Materials) A36 steel roof structure. The proposed cover system uses cables and light gauge profiles, in commercial stainless steel, which reduces the weight and of course the final price of the roof structure. A structure that presents technical feasibility is obtained and analyzed by checking its behavior with respect to the efforts and displacements generated by the combinations of the acting loads, following the safety recommendations of the applicable standard. It is verified that using the stainless steel structure proposed in this work would cost 42% of the reference structure if this were in AISI (American Iron and Steel Institute) 304 stainless steel. And this cost tends to be minimized due to greater durability and consequent reduction in maintenance costs of this type of steel.
Identification of the origins and risks of pathologies in steel structure buildings using total quality management tools.
(2022) Hofmann, Giane Alfenas Antunes; Souza, Henor Artur de
The steel structure construction is an interesting option to the already established concrete structure at a time when the Brazilian civil construction seeks more efficiency. To promote the use of this material it is necessary to have a better understanding of its characteristics and, especially, of its possible pathologies, to avoid degradation, costs, and even the collapse of the structure. In this study Total Quality Management tools were applied to analyze the pathologies found in five medium and large steel-structured buildings. The most frequent ones were structure corrosion, cracks in the closures, and infiltrations in the interface closure/structure. The Ishikawa Diagram is used to identify the origin of the causes of pathologies and the Gravity Urgency Tendency Matrix (GUT Matrix) is used inthe risk analysis of each pathology. The results obtained show that it is possible, through these Quality Management tools, to understand the origin of the pathologies, establishing their dangerousness and the degree of risk each one offers.
Computer simulation of moisture transfer in walls : impacts on the thermal performance of buildings.
(2021) Araújo, Mariana Tonini de; Souza, Henor Artur de; Gomes, Adriano Pinto
In order to reduce electricity consumption in buildings, it is imperative to improve their thermal performance. Due to the many variables involved in thermal processes computer simulation is a consolidated method for thermal analysis. However, in many energy efficiency analyses calculus of heat conduction through the dwelling envelope does not consider moisture transportation and storage. The objective of this work was to evaluate the impacts of moisture transfer in walls on the thermal performance of naturally ventilated and artificially conditioned buildings using EnergyPlus computer simulation. This research contributed to the literature by showing the difference in thermal zone air humidity, temperature and annual energy demand (i.e. electricity consumption) when moisture effects are considered in walls. Buildings were composed of masonry and solid concrete envelopes and three numerical models were simulated: Conduction Transfer Function Model (CTF), Effective Moisture Penetration Depth Model (EMPD) and Combined Heat and Moisture Transfer Model (HAMT). The CTF model does not consider moisture effects. Results found a higher relative air humidity for the studied thermal zone by applying the HAMT model in the numerical simulation, and the envelope porosity was proven to affect HAMT humidity results. Comparing the HAMT and EMPD models with the CTF model, the annual energy demanded for cooling presented a 21% reduction for the EMPD model in the masonry and 9% increase for the HAMT model in the solid concrete. This article shows the importance of an accurate EnergyPlus heat transfer model for simulating a whole building to check edification attendance of minimum comfort parameters and select envelope materials aiming the reduction of electricity consumption.
Evaluation of the thermal performance in external vertical enclosures constituted of metal panels.
(2021) Faria, Marcela Assunção; Souza, Henor Artur de; Ferreira, Franciele Maria Costa
Brazil has a great climatic diversity, with different demands for the adequate thermal performance of buildings, where the variables that impact it have different influences depending on the location and the type of wrapping used. When a prior study of the thermal performance of a building is not done in the design phase, the unpleasant effects for the user appear after the building is ready, and bring with them problems such as internal temperatures that are too high in the summer or too low in the winter. Therefore, the objective of this study is to provide recommendations for the application of ACM (aluminum composite material) composite panels and thermoacoustic (sandwich) tiles for external enclosure in the single-family residential sector. A high standard two-story residence with approximately 162 m2 per floor is used as a model and through computer simulations, utilizing the Energyplus program and observing the requirements of the NBR 15.575 performance standard, the thermal performance is evaluated. The factorial experiment was applied encompassing thermal performance variables such as absorptance, natural ventilation and thermophysical properties of the “wrapping for three different climatic conditions: extreme winter climate, average climate and extreme summer climate. The results obtained show that the thermoacoustic roof tile keeps the internal temperature more stable independent of external oscillations, while the ACM panels follow the external oscillations, not meeting the expectations of thermal performance and needing passive treatments.
Effect of the exposed steel structure on the thermal performance of buildings.
(2022) Caetano, Lucas Fonseca; Souza, Henor Artur de; Gomes, Adriano Pinto
Depending on the building typology, the architectural characteristics and the materials used in a building, its interaction with the local climate can produce negative impacts on the energy consumption of the buildings. The presence of steel in the building structure characterizes a reduction in the thermal resistance of the building envelope, which causes an increase in energy costs for environment heating or cooling. In this context, simulation of the thermal performance of buildings using computer programs has generated several constructive advantages for the establishment of energy-efficient buildings. This paper’s main purpose is to evaluate the influence of the exposed steel structure area on the thermal performance of naturally ventilated and artificially conditioned environments using computational simulations. The results showed that in the numerical simulation of naturally ventilated environments, there were increases of about 3.0% and 2.0% in the environment indoor temperatures during the winter and summer periods, respectively. Considering the winter period, the heat losses through the steel structure were up to 4.1 times larger concerning those made for walls without steel, and the heat gains about 4.2 times higher in the summer period. The effects of thermal bridging were more evident in the evaluation of artificially conditioned environments. There was a maximum increase of 4.8% in the environment total cooling thermal load and, as a consequence, a maximum variation of 4.9% in the building energy consumption, evidencing that the larger the exposed steel area in the building closure system, the larger the effect caused by this thermal bridge.
Analysis of the perception of users of pre-hospital architecture in Light Steel Frame : a case study in Minas Gerais, Brazil.
(2019) Melo, Mirvane Vasconcelos Santos; Souza, Henor Artur de
The quality of many physical spaces can be achieved from the use of a flexible architecture. Understanding whether such a building has acceptable comfort conditions, adequate division of its internal spaces, efficiency of functionality, can be possible by consulting its own users/employees, analyzing and considering one of the basic concepts for architectural spatial design: people and environments are inseparable and cannot be thought out separately. Therefore, the purpose of this case study is to analyze the perception of users and managers of three USP (Unidades de Saúde Públicas) (Public Health Units), built in the LSF (Light Steel Framing) system, in relation to the built environment and thus contribute to a reflection on health care architecture based on identified gaps. These Public Health Units in LSF are located in 3 (three) different cities in the interior of the state of Minas Gerais, in the southeastern region of Brazil. To this end, the development of the work is carried out through on-site interviews with users and managers. The answers of the questionnaires are analyzed with the help of the software SPSS (Statistical Package for the Social Sciences), version 19.0. The results show that the buildings present project inadequacies related to the performance of self-supporting closures, extensive to the presence of cracks and infiltrations and to some aspects related to environmental comfort. However, the hospital architecture produced with the LSF can allow flexibility, modifications and probably possible solutions to these issues.
Impact of photovoltaic generation on the allowed revenue of the utilities considering the lifespan of transformers : a Brazilian case study.
(2021) Baroni, Bruno Randazzo; Uturbey, Wadaed; Costa, André M.G.; Rocha, Samuel P.
This paper investigates the effect of distributed photovoltaic (PV) generation on the aging of overhead dis- tribution transformers and on the allowed revenue of the utilities that defines tariff readjustments. A metho- dology based on the calculation of the depreciation rate of assets and replacement of transformers as a function of transformers’ aging is proposed. Different penetration levels of PV generation are considered by means of a probabilistic load flow using the Monte Carlo simulation method. Randomness of the load, solar irradiation, location of the PV systems and ambient temperature are modeled. Three indexes are defined to represent the effects and conduct the discussion. The network hosting capacity is analyzed in relation to overvoltage and overcurrent impacts. A realistic case study based on representative feeders of a distribution utility in the southeast of Brazil is conducted by computer simulations. Results indicate that the effect of distributed PV of increasing revenue readjustments occurs at PV penetrations higher than 40%. Overvoltages can limit the amount of distributed PV only at very high penetration levels and overcurrents are not a major problem.
The precautionary principle and the risk concept.
(2020) Gouveia, Antônio Maria Claret de; Gouveia, Alberto Frederico Vieira de Sousa; Serrano, Alessandra Marques; Soares, Melissa Manger; Versiani, Eduarda Veloso
Objectives: This work focuses on the Precautionary Principle, starting from its current position as a principle still extra-judicial until the delineation of a procedural routine that effectively includes it in the quarrels in which the precautionary nature is evidenced. The context is the duty of care towards the environment, introduced in the main section of Article 225 of the 1988 Constitution. Methods: descriptive, applying hermeneutic principles to analyze laws and literature; the notion of risk, associated with human affairs, is used in order to establish the basis for suggestion of a procedural routine for cases of precautionary nature. The concepts of civil liability without damage and of malice or negligence in face of risk exposure are discussed in parallel for their importance in sustaining the precautionary nature of a dispute. Results: the duty of care towards the environment stated in the main section of Article 225 of Constitution of 1988 makes evident that introducing a procedural routine proper to treat the cases of precautionary nature is a necessity of Brazilian Civil Processual Law. It is concluded that discussing the precautionary nature of the case the public audiences and amicci curiae roles is a first phase in this procedural routine. Next, the formation of Court's conviction in a context where there isn't scientific confidence about the consequences of someone's act or omission must be considered. The decision which may not be the end of the case may include the installation of an Observatory to follow and evaluate periodically the environmental consequences of the enterprise.
Influence of cooling methods on the residual mechanical behavior of fire-exposed concrete : an experimental study.
(2019) Carvalho, Espedito Felipe Teixeira de; Silva Neto, João Trajano da; Soares Junior, Paulo Roberto Ribeiro; Maciel, Priscila de Souza; Fransozo, Helder Luis; Bezerra, Augusto Cesar da Silva; Gouveia, Antônio Maria Claret de
This work reports the main conclusions of a study on the mechanical behavior of concrete under ISO 834 fire with different cooling methods. The aim of this research was to provide reliable data for the analysis of structures damaged by fire. The experimental program used cylindrical concrete test specimens subjected to ISO 834 heating in a furnace up to maximum gas temperatures of 400, 500, 600, 700, and 800 ◦C. The compressive strength was measured in three situations: (a) at the different temperature levels reached in the furnace; (b) after a natural cooling process; and (c) after aspersion with water at ambient temperature. The results indicate that the concrete residual compressive strength is fairly dependent on the maximum temperature reached in the furnace and revealed that concrete of a lower strength preserved relatively higher levels of strength. The cooling method significantly influenced the strength, albeit at a lower intensity. In all cases, the residual strength remained in the range of 38% to 67% of the strength at ambient temperature. The statistical analysis showed that the data obtained by the experimental program are significant and confirmed the influence of the conditions imposed on the residual strength.
A novel two degrees of freedom system for measuring iron ore water content on a conveyor belt.
(2021) Pinto, Érica Silva; Santos, Gabriel Almeida; Magalhães, Paulo Henrique Vieira; Rêgo Segundo, Alan Kardek
Water content or moisture of materials is a parameter widely used in the industry. In mining, it is an important variable to control in iron ore production. High moistures may cause instability of iron ore piles and may make transport by ship unfeasible. Therefore, this paper presents the development of a system for measuring iron ore moisture on a conveyor belt (laboratory-scale). The structure that supports the sensor has two degrees of freedom, which allow perpendicular and parallel movements. The parallel movement makes the relative velocity between the measurement cell and the ore almost zero. The vertical movement allows the sensor to be placed at different depths in the ore. These sets enable real-time and in situ measurements. The system uses the capacitive method to determine the dielectric constant of the iron ore located between the sensor electrodes and, consequently, the moisture. This system has a measuring range of 0 to 14% on a dry basis and presents an uncertainty up to 0.07 percentage points for a 2-standard-deviation confidence level. In the validation process, the absolute error was less than 0.34 percentage point in the mining interest range of 6 to 14%. The founded results achieve a significant advance in the development of real-time equipment for measuring ore moisture since there is no device capable of doing it with the necessary level of accuracy and precision. For mining, this kind of system represents a big step to take corrective and preventive decisions around iron ore moisture control.

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