-This study evaluated the structural behavior of porticos made from eucalyptus glued boards, using wood of Eucalyptus sp and resorcinol formaldehyde adhesive. Three units, in real scale, of tri-articulated straight porticos, with a 5 meter porthole and a 26 º inclination, capable to support tiles covering placement were designed, constructed and subjected to load testing, until rupture. The amount of adhesive used in the construction of the porticos was 250 g/m 2 and the bonding pressure of 1.3 MPa. The Hankinson model was employed as an estimator of the glued joints strength, under different angles between the fibers. The average value for the last resistance of the structures was 4.63 times the design load, according to the criteria established by the ABNT, 1997. The structures showed satisfactory mechanical performance and deformations lower than the ones allowed by the standard. It was concluded there is technical feasibility to manufacture porticos fully bonded with small thickness veneers.
This study aimed to present a solution in glued laminated timber to replace frame structures built in reinforced concrete and metallic structure, which are common in agricultural buildings in western Paraná such as those destined to laying poultry house building by agricultural cooperatives. Structural behavior of frames build from Araucaria angustifolia glued boards and vegetable oil-based polyurethane adhesive was evaluated. Tests were carried out to characterize wood and adhesive to obtain verification/sizing parameters. Initially, a full-scale structural project was conducted to meet standard laying poultry house specifications. Afterwards, five units of straight three-articulated frames on a 1:2.5 reduced scale were designed, built, and subjected to strength tests until breaking. They were built with a 2-meter free span and a 15° slope, suitable for using metal roof tiles. The average for structure ultimate strength was 4.14 times the design load. Structures had satisfactory mechanical performance and displacements lower than those recommended by NBR 7190 (1997) standard (ABNT). Therefore, building glued frames with Parana pine boards and vegetable oil-based glue is technically feasible.
The objective of this study is to evaluate the effect of sugarcane bagasse ash on the compressive strength and water absorption index of soil-cement bricks. The ash was sieved without chemical and/or physical treatment to reflect the use of this material in real manufacturing processes. The addition of natural ash decreased the quality of the bricks, reducing the compressive strength and increasing the water absorption index.
This paper presents a methodology to obtain the shear strength of glued joints, at the torsion moment. In the current standards this strength is measured by compression tests. The device designed for this purpose are also presented. The motivation for this test is related to the possibility of execution of glued wooden structures with joints under bending moment, shear force and normal force simultaneously. It was admitted the hypothesis that the joint strength can be different depending on the test type. The methodology is relatively simple and in order to obtain the results classic equations from Mechanics of Materials were used. The strength results of 198 test specimens, tested by standard methodology, were compared, with an equal number of specimens made and tested with the proposed methodology, resulting in 396 tests. 208 specimens were glued with resorcinol-formaldehyde and 188 with castor oil-based adhesive. The wood used was Eucalyptus sp. The specimens were made according to seven series involving gluing with the following angles between the fibers: 0°, 15°, 30°, 45°, 60°, 75° and 90°. Regardless of the adhesive type, there was a significant difference for the strengths presented by the two methods. From the seven angles studied, it was noticed a difference in six of them, except for the 30° series. The compression shear strength was severely affected by the gluing angle, with increasing losses towards higher angles. On the contrary, the strength offered by the joints tested by torsion did not seem affected by the gluing angle.Keywords: wood; adhesive; characterization; procedure.
A indústria da construção civil é uma grande consumidora de recursos naturais, gerando muitos resíduos e sendo responsável por grande parte dos impactos ambientais mundiais. O emprego da madeira em estruturas ressurge como um material ambientalmente correto no setor da construção civil e agrícola por ser um material construtivo/estrutural renovável e seu uso de forma permanente contribui com a redução das emissões de carbono na atmosfera. Com isso, o presente estudo objetivou executar e ensaiar pórticos com tirantes, feitos em madeira laminada colada, de modo a avaliar sua aplicação estrutural em aviários. Foram confeccionados quatro pórticos em escala reduzida com tirantes de barras rosqueadas de 3/8”, com vão livre de 1,9 metros e altura de pilar de 1,83 metros. Os materiais utilizados para a confecção dos pórticos foram a madeira de Pinus sp. e adesivo bicomponente à base de óleos vegetais. As estruturas romperam para uma carga média de 1,37 vezes a carga de verificação estabelecida e exibiram deslocamentos próximos a linearidade mesmo para cargas elevadas. Ainda, obteve-se um coeficiente de correlação de 0,95 entre a densidade aparente da madeira dos pórticos com sua resistência. Desta forma, as evidências obtidas indicam que o emprego do tirante nas estruturas promoveu a melhoria do desempenho mecânico quanto à resistência e rigidez.
A fórmula de Hankinson estima propriedades de resistência da madeira quando o material está recebendo forças inclinadas em relação à direção das fibras. No Brasil, por força de orientação normativa, costuma-se usar o valor fixo igual a 2 para o expoente β dos seno e cosseno da fórmula, mas pode ocorrer melhores ajustes para expoentes β diferentes deste valor. O objetivo deste trabalho foi evidenciar, a partir de cinco experimentos independentes, a adequação da fórmula de Hankinson para estimar a resistência de juntas coladas à diferentes ângulos, quando rompidas sob compressão. Adicionalmente, procurou-se analisar a diferença de desempenho mecânico de juntas coladas quando o ensaio se dá por compressão ou por torção. Neste trabalho, os valores dos parâmetros β variaram entre 1,82 e 2,18, com média de 2,02, valor próximo ao adotado em norma. As juntas coladas rompidas por compressão apresentaram perda de resistência com o aumento do ângulo de colagem. Já no ensaio sob torção, a resistência sofreu pouca influência do ângulo de colagem. Verificou-se que a fórmula de Hankinson é adequada para estimar a resistência de juntas coladas à diferentes ângulos entre as fibras da madeira, quando a ruptura ocorre por compressão, mas não parece adequada para a obtenção da estimativa de resistência sob torção. As juntas coladas rompidas à compressão apresentaram resistência diferente de juntas coladas rompidas sob momento de torção. No conjunto, tanto a fórmula de Hankinson quanto os ensaios conduzidos à torção podem permitir a verificação de ligações coladas sujeitas simultaneamente a forças e momentos.
Este trabalho compila as produções científicas presentes na literatura, que fundamenta a proposta de uma metodologia para dimensionamento técnico de biodigestores tubular. A metodologia proposta apresenta uma rotina de cálculo simplificada e organizada que permite ao usuário, com base em duas informações básicas (quantidade e classe que pertence o animal), obter como resultados os parâmetros geométricos da fossa do biodigestor e das caixas auxiliares. Em geral, o desenho do biodigestor é baseado em parâmetros geométricos definidos que levam em consideração o volume de resíduos gerados diariamente e o tempo que esses resíduos devem ser retidos para que ocorra a biodigestão. Esse volume é estimado com base nas necessidades energéticas de cada propriedade (produção de biogás), pelo número de animais presentes e na área disponível para aplicação do biofertilizante. As dimensões da fossa estimadas na metodologia foram o volume (metros cúbicos), a largura (metros), o comprimento (metros) e a altura útil (metros). A metodologia de dimensionamento foi apresentada sintetizada em um fluxograma. Por ter como dados primários o tipo e número de animais, o procedimento para o cálculo demanda uma adaptação regional de cada produtor, considerando a literatura disponível, com dados do tempo de retenção hidráulica e quantidade estimada de dejetos por dia.
This paper aims to conduct an energy efficiency study in the tipping system of the unloading platform of a grain storage unit, based on the use of electrical devices to control the operation of the engine. For this purpose, two scenarios were established. The first scenario considers the platform in its current state, with engine start-up performed using a wye-delta switch. In the second scenario, wye-delta start is switched off, and a frequency inverter and a programmable logic controller (PLC) are coupled to control the electric motor. For both scenarios, the consumption of active and reactive energy in the discharge platform was measured, and the costs of the energy consumed were calculated over a period of one year. Finally, the discounted payback was calculated to evaluate the economic feasibility of installing the proposed equipment. The results obtained were as follows: For the current scenario, the energy consumed to tipping one metric ton of grain was 35.44.10-3 kWh; for the proposed scenario with the frequency inverter, the energy was 32.78.10-3 kWh. With an annual projection, the current scenario would consume the equivalent of 10 921.35 kWh, and the proposed scenario, 10 100.81 kWh, generating an annual savings, with the installation of the equipment, of R$721.49; the discounted payback found was approximately 31 years. It can thus be concluded that there is a reduction in electricity consumption from the use of the frequency inverter; however, the time of return of the invested capital is very long, making the proposal economically unfeasible.
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