Resumo O objetivo deste trabalho é avaliar o comportamento e a resistência de um sistema de lajes mistas de aço e concreto, considerando a influência do atrito na interface da fôrma de aço com o concreto na região dos apoios. Para isso foram utilizados os resultados de ensaios realizados no Departamento de Engenharia de Estruturas da Universidade Federal de Minas Gerais (UFMG). O sistema misto Steel Deck 60 foi considerado, o qual consiste em um perfil trapezoidal com mossas em forma de "V". As flechas, os deslizamentos de extremidades e as deformações das fôrmas de aço foram medidos, permitindo a análise do comportamento do sistema de laje mista e a determinação do seu modo de falha. A influência do atrito da região dos apoios na resistência longitudinal ao cisalhamento foi avaliada através do método da interação parcial, que também permitiu estabelecer critérios visando à determinação de expressões analíticas para o cálculo da carga última. As análises comparativas revelaram que a influência do atrito da região dos apoios na resistência ao cisalhamento longitudinal é mais significativa em lajes mistas com pequenos vãos de cisalhamento. São apresentadas expressões de cálculo incorporando o atrito, cujas aplicações em um exemplo permitiram mostrar a eficiência do método no cálculo da resistência ao cisalhamento longitudinal.

Abstract The aim of this work is to evaluate the behavior and strength of composite slabs considering the influence of the friction at the sheeting-concrete interface in the region of the support. Results from tests conducted in the Structural Engineering Department of Federal University of Minas Gerais (UFMG) were used. A Steel Deck 60 system was considered, which consists of a trapezoidal profile with “V” shaped embossments. Deflections, end slips and strains of the steel decks were measured, allowing for the analysis of the behavior of the composite slab system and for the determination of its failure mode. The influence of friction of the region of support in the longitudinal shear resistance was evaluated through the partial shear connection method, which also allowed for establishing criteria and determination of analytical expressions for calculating the ultimate load. Comparative analyses reveal that the influence of the friction of the region of support in the shear-bond resistance is more significant in composite slabs with short shear spans. Design expressions which incorporate friction will also be presented. Their application have demonstrated the efficiency of the method for evaluating the longitudinal shear resistance.

Apresentamos e comentamos o artigo homônimo de William Thomson, originalmente publicado em 1847, no qual o autor explora a analogia entre os estados de deformação em um sólido elástico e as configurações das linhas de força de Faraday. Nele Thomson introduz pela primeira vez o potencial vetorial magnético, associando-o à deformação rotacional de um sólido. Apresentamos também um apanhado histórico do contexto dentro do qual o original de Thomson foi concebido.

We present and comment the homonimous article originally published by William Thomson, in 1847, in which the author explores the analogy between the estates of deformation in an elastic solid and the configurations of Faraday's lines of force. In this article Thomson has introduced for the first time the magnetic potential vector, associated in this context with rotational deformations in the solid. We present as well, the historical context in which Thomson's original paper has been conceived.

Abstract Effects of phosphorus addition to HZSM-5 on ethanol conversion to propylene were evaluated. Catalysts were characterized by XRF, XRD, nitrogen adsorption, 27Al and 31P MAS NMR, n-propylamine and ammonia TPD. Increasing P content decreased the strength and density of acid total sites. Ethanol dehydration was carried out in a fixed bed reactor operating at atmospheric pressure. Conversion was around 100% for all catalysts. 1.2 wt% of P catalyst showed the highest propylene yield, and was used to evaluate temperature and ethanol partial pressure effects on the product distribution. The highest propylene accumulated productivity was obtained for an ethanol partial pressure of 0.4 atm. Propylene formation was favored in the temperature range 475-500 °C. Significant changes in the product distribution as a function of time on stream were observed at higher temperatures, suggesting stronger catalyst deactivation. The ethylene yield decreased up to 500 °C, rising significantly at 550 °C, possibly due to heavier product cracking reactions.