Embolia pulmonar quase fatal, um modelo experimental: variáveis hemodinâmicas, gasométricas e capnográficasNear-fatal pulmonary embolism in an experimental model: hemodynamic, gasometric and capnographic variables Abstract Introduction: Experimental studies on pulmonary embolism (PE) are usually performed under mechanical ventilation. Most patients with suspicion of PE enter the Emergency Services in spontaneous breathing and environmental air. Thus, under these conditions, measurements of hemodynamic, gasometric and capnographic variables contribute largely to a more specific comprehension of cardiopulmonary and gasometric alterations in the acute phase of the disease. Studies which evaluated animals under conditions are lacking.Objective: This study aimed to submit animals under spontaneous ventilation and without supplemental oxygen to PE.Methods: PE was induced in six pigs using autologous blood clots, and cardiorespiratory and gasometric records were performed before and after PE. The values of "near fatal" mean pulmonary arterial pressure (MPAP) were previously determined.Results Conclusion: In this model, the near fatal MPAP was from 2 to 2.5 times the basal MPAP; and the capnographic variables, associated with arterial and venous gasometry, showed effective in discriminating an acute obstructive profile.Descriptors: Pulmonary embolism. Hypertension, pulmonary. Capnography. Models, animal. Swine. ResumoIntrodução: Estudos experimentais de embolia pulmonar (EP) são habitualmente realizados sob ventilação mecânica. A maioria dos pacientes com suspeita de EP adentra os Serviços de Emergência em respiração espontânea e em ar ambiente. Assim, medidas das variáveis hemodinâmicas, gasométricas e capnográficas, nessas condições, em muito Universitária "Zeferino Vaz"
This article analyzes sleeve connections between circular hollow sections. This type of connection is composed of two tubes connected by bolts to an inner tube with a smaller diameter, and explores the efficiency, aesthetics and resistance of hollow sections subjected to tension and compression. In previous researches, sleeve connections with aligned and crossed bolt dispositions and under axial tension were studied. Herein, the behavior of sleeve connections with aligned bolts and under compression was analyzed. A model to represent the connection using the finite element method was developed, which allowed a numerical analysis with geometric property variations. In the numerical/parametric results, bearing failure was observed in all cases, either in the outer or inner tube. Limiting the number of bolts to 6 and considering that connections have a lower outer thickness than the inner tube, a formulation was proposed to determine the ultimate bearing capacity of sleeve connections under compression and with bearing failure.
Tubular joints with thin-walled sections could have a wide range of applications in the construction industry, possibly providing light structures with high structural efficiency. However, current design prescriptions do not recommend their use and more studies are needed to attest their viability. In this context, the effect of the size of fillet welds on cold-formed T-joints consisting of thin-walled rectangular hollow section chords and circular hollow section braces under axial compression loading was analysed. Experimental and numerical analyses were conducted and the results were compared with current design prescriptions. Three experiments were performed, with different weld sizes, in a machine that provided displacement-controlled testing with data acquisition from strain gauges and displacement transducers. Finite-element models were developed to replicate the general experimental setup and the results showed good correlation with the experimental data, indicating that the size of the weld influences joint resistance.
This article presents a theoretical and numerical study of an innovative joint using cold-formed steel sections. The motivation for the study of this connection is the ease of manufacturing and assembly that it provides. The profiles are made of coldformed lipped channel sections, which are welded to form closed built-up sections on the columns and open built-up lipped sections to the beams. The beams use endplates connected by bolts (threaded bars) to the columns. The study evaluates the connection's initial stiffness of 19 models, where the following parameters were varied: the thickness of the profiles and endplates, the height of the column sections and the diameter of the bolts. A theoretical and a numerical study were developed: the numerical study was performed using finite elements through the commercial software ANSYS, whereas the theoretical study was made based on the component method, prescribed by Eurocode 3, that does not include the design of the connection analyzed herein. Thus, aiming to enable the design of joints composed of cold-formed lipped channel sections, the analysis results were compared and an adjustment coefficient, proportional to the slenderness of the column's plates, was proposed. The coefficient was introduced to the stiffness component that represents the column web in compression in the mechanical model. The ratio between the coefficients' numerical and theoretical values presented a maximum variation of 11%, which was considered satisfactory.
Hollow steel sections are widely used in the construction industry due to their mechanical properties. Joints used in these structures are the subject of research because of their singular and critical behavior. Joints containing chords with more slender cross-sections and axially loaded are still a challenge for design, especially in joints with circular hollow sections (CHS) in the braces and rectangular hollow sections (RHS) in the chords. In this context, this work aimed to study joints formed by a combination of CHS braces subjected to compression loads and RHS chords axially loaded with tension, welded as T-joints. Experimental tests, a numerical model using finite elements, and a parametric analysis were developed. A new equation for the chord stress function was proposed, including joints containing chords with semi-compact sections in tension. The joint resistance values obtained through the numerical models were compared with the equations from ISO 14346:2013 and with the proposed equation. It was observed that, for the numerical models with geometric properties inside the normative validity ranges of ISO 14346:2013, the mean rate of analytical by numerical joint resistance results was equal to 68%, using either the normative or the proposed equation. In the same way, for models outside the current validity ranges, either the proposed equation or the modified equation from ISO 14346:2013 could be used to design CHS-RHS T-joints with the geometric and material properties analyzed.
RESUMO:Em uma edificação, a escolha do sistema de fechamento adequado é determinante para o seu desempenho e o conforto dos usuários. Devido a isso, essa escolha deve ser feita de maneira correta ainda na fase de projeto, pois uma seleção indevida pode comprometer seu desempenho global. No mercado nacional, há vários sistemas de fechamento industrializados, aplicados em edificações estruturadas em aço, que necessitam de mais conhecimento quanto às suas propriedades térmicas e acústicas. Nesse trabalho, faz-se uma avaliação do desempenho térmico e acústico de alguns sistemas de fechamento aplicados em edificações estruturadas em aço, compostos por painéis aplicados em multicamadas. Esses sistemas de fechamento são constituídos por placa cimentícia, gesso acartonado, pré-moldado de concreto, concreto celular autoclavado e poliestireno expandido. O estudo é realizado determinando-se a temperatura no interior dos ambientes de uma edificação, por meio do software ESP-r, para as condições climáticas da cidade de Belo Horizonte-MG, e o tempo de reverberação, por meio de formulação empírica, que aplica nos cálculos os valores de temperatura e umidade obtidos na simulação. Os resultados explicitam os parâmetros relevantes na definição de sistemas de fechamento, que sejam adequados ao clima e ao entorno, e mostram que os sistemas em multicamadas, quando recheados com material isolante, em geral, apresentam-se como solução eficiente capaz de proporcionar desempenho térmico e acústico adequados.
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