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In Brazil, some tile manufacturers have proposed a 10% (5.5°) slope between chords to minimize timber consumption. However, after simulating 21 slopes from 7% (4°) to 27% (15°), it was discovered that the axial strengths are inversely proportional to the slope, creating overly large dimensions for the bars competing for support. The results were obtained using software developed following the guidelines specified in the revised version of the ABNT NBR 7190 (2022) standard. Finally, it was found that the minimum slope until no reinforcement is needed for the string bars is 16% (9°).

Wood, a renewable source and a material with excellent mechanical properties, is one of the oldest materials used in civil construction. In Brazil, its use is widespread in roof structures in the form of plane trusses. Given the Brazilian context of the growing presence of wood in structural systems, in addition to the normative updating processes, this study presents a comparison between calculation methods and possible increases in material consumption of wood for roof structure. The design methods compared are according to the recently published standard ABNT NBR 7190-1 (2022) and its previous version ABNT NBR 7190 (1997). The results were obtained via iTruss software, which includes linear-elastic structural analysis by the finite element method (FEM). It was concluded that the ABNT NBR 7190-1 (2022) presents a conservative dimensioning in relation to the previous version of 1997, favoring safety. However, there were no significant increases in wood consumption, demonstrating the efficiency of the revised version.

RESUMO A caracterização dos elementos construtivos é um conhecimento essencial para garantir a estabilidade e resistência estrutural de qualquer construção. A resistência dos materiais é uma predição efetiva prescrita por normas técnicas, as quais delimitam comportamentos resistivos em diferentes condições. As propriedades físico-mecânicas da madeira permitem a aplicação racional desse biorrecurso em projetos estruturais. Porém, testes para determinar as propriedades mecânicas requerem equipamentos de grande porte e mão-de-obra capacitada, requerimentos os quais são encontrados em poucas instituições e centros de pesquisa específicos. Uma alternativa para entender as propriedades da madeira pode ser estabelecida pela microscopia e modelos de regressão. O presente artigo objetivou demonstrar a viabilidade de estimar as propriedades mecânicas da madeira de Eucalyptus em função de suas características anatômicas e da densidade aparente. Dez lotes de diferentes espécies de eucalipto foram selecionados para prever a tração paralela às fibras, tensão perpendicular às fibras e o módulo de elasticidade na tração paralela às fibras, bem como três diferentes parâmetros anatômicos (fibras, vasos e raios) das amostras de madeira de acordo com duas normas técnicas brasileiras. Na prática, os modelos de regressão propostos foram excelentes, pois os valores de R2 foram iguais a 90,55, 86,55 e 67,95% para estimar Et0, ft0 e ft90, respectivamente. ABSTRACT Characterization of construction materials is a piece of essential knowledge to ensure the structural stability and strength of any building. The strength of materials is an effective prediction prescribed by technical standards, which delimit the resistive behaviors in different conditions. Physical-mechanical properties of timber allow the rational application of this bioresource in structural projects. However, tests to determine mechanical properties require large equipment and a skilled workforce, found in few institutions and specific research centers. The microscopy and regression models may establish an alternative to understanding the properties of wood. The present paper aimed to demonstrate the feasibility of estimating the mechanical properties of Eucalyptus wood as a function of its anatomical characteristics and apparent density. Ten batches of different eucalypt species were selected to predict the tensile strength parallel to the grain, tensile strength normal to grain, and modulus of elasticity in tensile parallel to the grain, as well as three different anatomical parameters (fibers, vessels, and rays) of the wood samples according to two Brazilian standard documents. In practice, the proposed regression models were excellent, as the R2 values were equal to 90.55, 86.55, and 67.95% for estimating Et0, ft0, and ft90, respectively.

The development of standard methods and criteria for the stress grading of structural timber elements by non-destructive, fast and cheap bending tests, will allow producers, distributors and customers of such elements, have a better control of the marketed product. This paper analyzes the most suitable length of free span for stress grading of structural timbers, number of points to be assayed in each element, data precision and evaluation of cost of these tests for small business.

Shrinkage and coefficient of anisotropy are fundamental physical parameters in analysis of dimensional stability of timber structures members. In Brazil, properties of wood are obtained according to assumptions and calculation required by Annex B of ABNT NBR 7190: 1997 (Timber Structures Design). Among the physical properties, density appears as the easiest one to be experimentally obtained, defined by ratio between mass of the sample and its volume. To evaluate the possibility of estimating shrinkage (longitudinal, RL; radial, RR; tangential, RT; volumetric, RV; and coefficient of anisotropy, CA) of wood depending on density, this study aimed to test regression models (linear, exponential, logarithmic, geometric) using basic density (ρbas) and apparent density (ρ12) as independent variables. For this purpose, five wood species belonging to conifers: Pinus sp., Pinus oocarpa; and dicotyledonous: Parica (Schizolobium amazonicum), Jatoba (Hymenaea sp.) and Lyptus®, were employed. In all, 23 samples for Pinus sp.; 15 for Pinus oocarpa; 28 for Parica; 16 for Lyptus®; and 11 for Jatoba were produced, totaling 651 determinations. Results of analysis of variance for regression models indicated insignificance of the adjustments obtained by adopting densities as estimators of shrinkage and coefficient of anisotropy for this set of wood species. Only models involving basic density and apparent density were significant, wherein the optimal settings were from linear case, exhibiting coefficient of determination (R2) 91.72% (for softwoods) and 83.36% (for hardwoods).

The aim of this research is determining mechanical properties of Parica wood specie (Schizolobium amazonicum Herb) using structural and clear specimens, according to Brazilian standard ABNT NBR 7190 requirements. Parica wood specie in structural members, with moisture content of around 12%, were determined dynamic elasticity modulus (transverse vibration tests), static bending modulus (three point bending) and modulus of rupture in static bending test. In clear specimens, according to Brazilian standard were determined compression, shear, embedment and tension parallel to the grain, and the elasticity modulus in compression and tension parallel to the grain. It is concluded that the Parica wood specie present good strengths properties, although of low density, presenting potential for use in timber structures.

Glued laminated timber (glulam) is an engineered product that requires manufacturing precision in all its stages. The finished product can only be tested in laboratory conditions; however, it is necessary to provide the quality control in production to ensure that glulam properties are appropriate to the product specified requirements in accordance with proper codes. This research aimed to evaluate the proposed trials conducted with combinations of Parica (Schizolobium amazonicum, a tropical wood species coming from a certificate reforestation area), three adhesives (polyurethane, phenol resorcinol formaldehyde, melamine formaldehyde) and two types of treatment (CCA, CCB). The shear strength and delamination test results of all the treated samples showed the good performance of Parica glulam, which can be used to indoor and outdoor applications.

No Brasil, as últimas décadas foram marcadas pela crescente produção de paineis de madeira seguida pelo aumento do consumo nacional; isto descreve o quão promissora é a área devido à sua grande potencialidade quanto ao desenvolvimento de novos produtos e tecnologias; como exemplo disto existe a possibilidade de mistura entre materiais lignocelulósicos e os diversos resíduos produzidos pela sociedade. Entre tais resíduos o plástico é o que apresenta maior abundância nos descartes domésticos. Neste contexto, o presente trabalho objetivou determinar propriedades físicas de paineis aglomerados homogêneos confeccionados com partículas de madeira de Eucalyptus sp e Pinus sp e de embalagens de película de polipropileno biorientado tendo, como adesivo, a resina poliuretana à base de óleo de mamona. Foram avaliadas as propriedades: inchamento em espessura e absorção de água, com corpo de prova com e sem impermeabilização, e massa específica. Concluiu-se que, dos fatores investigados, apenas o uso do impermeabilizante foi significativo. De acordo com a ANSI A208.1 (ANS, 1999) os paineis produzidos são classificados como de alta massa específica (H). Relativamente ao inchamento em espessura por 2 h, os paineis atenderam ao exigido pela NBR 14810 (ABNT, 2013) para espessura de 8 a 13 mm. In Brazil, the last decades have been marked by increasing production of wood panels following increased domestic consumption. It describes how promising the area is due to its high potential for development of new products and technologies. As an example, the possibility of mixture of different lignocellulosic materials and residues produced by society. Among these, waste plastic is the one with the greatest abundance in domestic discards. In this context, the present study aimed to determine physical properties of homogeneous particleboards made of particles of Euycalyptus sp and Pinus sp wood and of bioriented polypropylene film packaging having as adhesive, polyurethane resin based on castor oil. The properties evaluated were: thickness swelling and water absorption, using specimen with and without waterproofing, and specific gravity. It was concluded that, of the investigated factors, only the use of waterproofing was significant. According to ANSI A208.1 (ANS, 1999), the panels produced are classified as high-specific gravity (H). Regarding the thickness swelling for 2 hours, the panels met the requirements included in NBR 14810 (ABNT, 2013) to thickness of 8 to 13 mm.

Although geometrical data describing structures are generally represented by their nominal values, practice has revealed that this is not the more appropriate for prestressed laminated wood plates, once the lamellae present significant size variability. The importance of this variability increases when it affects the height of plate cross sections, they also affect their moments of inertia which depends on the value of the height raised to the third power. Preliminary studies showed standard deviations of almost 10%. As far as stress-laminated plates are regarded, the variability of dimensions along the length of the length of the pieces introduces a new source of variability for the cross section moment of inertia. The obtained surfaces aren’t completely flat, presenting variability due the size variability along the length of the pieces. Consequently, the moment of inertia of the cross section of a stress-laminated plate is not obtained by summing up the individual moment of inertia of each piece. On the other hand, modulus of elasticity also presents a strong variability not only among the height of pieces, but also along their length. Preliminary experiments reveal a standard deviation of 23% for plates from Pinus taeda. The variability of moment of inertia of pieces and of the plate itself was determined, as well as the variability of the modulus of elasticity. The results show that rigidity just can be estimated probabilistically; that softwoods are suited for system of high redundancy; that the calculation of deformations and stress distribution along the structures are dependent on this variability and thus the referred calculations are nothing more than estimations with a certain level of confidence to be established according to the control procedures adopted; and finally that further research must be developed on probabilistic numerical factors to be incorporated to the calculation expressions of rigidity of the cross section of stress-laminated plates.

Schizolobium amazonicum is being much used in Brazil for several purposes because, besides being a native Brazilian wood specie, has important features such as low density and small incidence of natural defects. At this point, researches with the purpose of obtaining further knowledge of their properties are being conducted to better targeting their use. The aim of this research is to evaluate the modulus of elasticity of structural size pieces of Schizolobium amazonicum wood using the technique of transverse vibration. Tests were carried out using 30 pieces (standard moisture content 12%) with sizes of 3 cm x 15 cm x 2.5 m. The average value of elastic modulus determined for lumber of Schizolobium amazonicum was interesting to its low specific gravity.

Brazil is a continental size country with several rivers that creates a large demand for short and medium span bridges for which timber is a renewable and ecologically friend option for material for building, once resists well for quick loadings. Using Glued-laminated timber (glulam) allows the fabrication of large dimension pieces, resulting in good stability and high quality control providing safety and reliability for the structures. This work has the aim of providing criteria for the verification, based on ultimate state limit method, for bridges with glulam girders and transversal deck panels in glulam, applying procedures described by renowned researchers and adapting them for Brazilian Code conditions. Tables for pre-dimensioning for such kind of bridges with span ranging from 8 to 20 m for TB-30 and TB-45, as well as construction details.

A confecção e as características mecânicas e morfológicas de peças de madeira laminada colada (MLC) preparadas a partir de lamelas de Schizolobium amazonicum Herb, Paricá, coladas com três adesivos, Cascophen, Melamina e Pubond, após serem submetidas a dois tipos de tratamento químico preservante, arsanato de cobre cromatado (CCA) e borato de cobre cromatado (CCB) foram avaliadas. Após seleção visual das lamelas e seleção, foram determinados os módulos de elasticidade das mesmas visando a preparação de vigas com a distribuição mais uniforme possível deste parâmetro. A densidade aparente média da madeira de paricá determinada segundo a Norma NBR 7190:1997,usando todas as lamelas, após serem submetidas à seleção pela classificação visual foi igual a 370 kg/m3. As lamelas foram então coladas, prensadas e submetidas aos tratamentos CCA e CCB. A partir dessas peças foram cortados corpos de prova para ensaios de flexão estática, cisalhamento, delaminação e fluência, conforme a norma CSA 0112.9:2004. Os valores do módulo de elasticidade demonstraram que, vigas produzidas com Melamina, há aumento nos valores de MOE para as amostras tratadas por CCA (7656 ± 477 MPa) e CCB (8152 ± 570 MPa) em relação à amostra sem tratamento (7171 ± 519 MPa). No caso do CCA, esse aumento é menos significativo. No caso das amostras coladas com Cascophen praticamente não houve diferença estatística entre os módulos para as peças sem tratamento (9150 ± 672 MPa) e aquelas tratadas com CCA (8764 ± 908 MPa) e CCB (9822 ± 791 MPa), sendo a variação numérica maior no segundo tratamento. A mesma observação vale para as amostras coladas com Purbond sem tratamento (8119 ± 725 MPa), quando comparadas com aquelas tratadas com CCA (8154 ± 951 MPa) e com CCB (8331 ± 863 MPa). Nos ensaios de cisalhamento observou-se elevada incidência de eventos de compressão o que sugere que alta porosidade da madeira, tenha provocado a compressão do corpo de prova, em detrimento da ruptura do corpo de prova. Observou-se que a Melamina e o Purbond apresentaram a maior frequência de ruptura tipo 100% na madeira, sugerindo que esses apresentaram maior adesividade, não havendo diferença significativa entre os corpos de prova secos e saturados. Em relação à força de ruptura, notou-se, que os adesivos apresentam melhor desempenho quando secos (quando se apresentaram na ordem Melamina (3,7 ± 0,9 MPa), Purbond (3,5 ± 0,96 MPa) e Cascophen (3,4 ± 0,8 MPa).) Nenhum corpo de prova apresentou delaminação, todos permaneceram colados e praticamente intactos, o que sugere que os adesevos e os tratamentos químicos utilizados são adequados à preparação de MLC à partir de lamelas de Paricá. Os ensaios de fluência que a estabilização nos deslocamentos ocorreu em torno de 90 h, para os dois corpos de prova. Observou-se uma diminuição nos valores das linhas laterais e centrais, após ensaiadas, em relação aos valores antes do ensaio, o que pode estar relacionado com a porosidade e densidade da madeira, que permitiu a compressão irreversível do corpo de prova, sugerindo que as características da madeira são mais marcantes que o efeito do adesivo. Glued Laminated Wood timber samples were confectioned from Schizolobium amazonicum Herb, Paricá, using Cascophen, Melamine and Purbond adhesives, and submitted to preservative chemical treatment by cromated copper arsenate (CCA) and cromated copper bromated. These samples were characterized regarding their mechanical and morphological characteristics. After visual evaluation and selection of the lamellas they had their elasticity modulus measured in order to prepare timbers with the most uniform distribution as possible. The apparent density of Paricá wood had been determined as 370 kg/m3 according to the NBR 7190 Standard, using all the lamellas after submitted to the visual inspection. Then the lamellas were glued pressed and submitted to the CCA and CCB treatments. From these pieces specimens for the elasticity, shear, delamination and creep tests were cut. The elasticity modulus showed that for samples glued with Melamine there was an increasing in the MOE values for samples treated with CCA (7656 ± 477 MPa) and CCB (8152 ± 570 MPa) when compared with the untreated sample (7171 ± 519 MPa). In the CCA such increase is less remarked. For Cascophen practically the same values were found for untreated (9150 ± 672 MPa) and CCA (8764 ± 908 MPa) or CCB (9822 ± 791 MPa) treated specimens. Same conclusion is valid for the Purbond glue samples once untreated (8119 ± 725 MPa) and CCA (8154 ± 951 MPa) or CCB (8331 ± 863 MPa) samples presented statistically similar MOE values. Shear tests presented high incidence of compression events, suggesting that the porosity of the Wood facilitates this behavior instead of rupture of the specimen. Melamine and Purbond glued specimens presented higher frequency of 100% in-wood rupture, reveling higher adhesion in such glues, without differences in dry or saturated samples. Regarding the rupture force all the adhesives promoted more resistence when dry, in the order: Melamine (3,7 ± 0,9 MPa), Purbond (3,5 ± 0,96 MPa) e Cascophen (3,4 ± 0,8 MPa). Any specimens presented delamination, remaining all of them intact showing that the adhesives and chemical treatments are adequate for the preparation of Laminated Glued Wood from Paricá. Creep tests revealed that the stabilization in the displacements stabilized after 90h of pressure in both the specimens that resisted until the end of the test. There was a diminishing on the length of both central and lateral glue lines, at the end of the test which can be related to the porosity and density of the Paricá wood allowing the irreversible compression of the specimens, suggesting that such characteristics are more significant than the adhesive and chemical treatment used.

This research aims to study the shear strength of species-adhesive-moisture-waterproofing combinations and delamination of Glued Laminated Timber (Glulam) made with Parica (Schizolobium amazonicum Herb) and Lyptus Wood species, using two different adhesives, the bicomponent resorcinol-formaldehyde based adhesive (CASCOPHEN RS-216-M) with catalyst FM-60-M and the bicomponent melamine-urea based adhesive with catalyst AkzoNobel MUF 1242/2542, both in a proportion of 100 parts/adhesive mass and 20 parts/catalyst mass and waterproofed by the commercial product ProtectGuard. Shear strength tests in adhesion line were performed according to North American Standard AITC 190: 2007 and delamination tests were carried out obeying Canadian Code CSA 0177: 2006. The results show that average values of great shear strength were obtained in tests on the glue line of the specimens treated with the waterproofer, however, within them, the timber was dry. Lyptus Glulam beams did not present a performance in delamination that was compatible to external applications, but Parica beams are fit to this use, once they are previously treated.

Os resíduos provenientes das serrarias e da agroindústria, conhecidos como resíduos lignocelulósicos, têm a possibilidade de reutilização na fabricação de novos produtos, como os painéis compósitos de matriz polimérica reforçados/carregados com resíduos lignocelulósicos. O processo de fabricação desses painéis consiste na prensagem a quente da mistura do adesivo aglutinante, uma resina sintética ou natural, com as partículas/fibras lignocelulósicas utilizadas como reforço/carga. Esse processo de prensagem pode ser considerado um fator determinante no elevado índice de porosidade dos compósitos poliméricos, o que limita o desempenho físico-mecânico dos mesmos. Tendo em vista os benefícios do uso da infusão a vácuo na manufatura deste tipo de material em indústrias automobilísticas, a facilidade de automação, versatilidade, simplicidade e possibilidade de obtenção de um compósito com maior interação interfacial entre a fibra e a matriz e menor porosidade, este trabalho teve como objetivo analisar a influência da introdução da etapa da infusão a vácuo na confecção de painéis compósitos de matriz polimérica reforçados/carregados com resíduos lignocelulósicos. Para tal, foram fabricados os seguintes tipos de painéis com partículas de Caixeta e resina mista a base de óleos vegetais, classificados segundo a quantidade de resina (pré-polímero/poliol) e na utilização ou não da infusão a vácuo no processo: 48/48g sem vácuo; 48/48g com vácuo; 150/150g sem vácuo e 150/150g com vácuo. Foram realizadas as caracterizações físico-mecânica dos painéis e obtidas fotomicrografias de MEV para analisar e discutir os valores obtidos. Os resultados mostraram que a técnica da infusão a vácuo melhorou significativamente todas as propriedades dos painéis, exceto para as propriedades de densidade e no caso do MOE das amostras com 150/150g de resina. Waste from sawmills and agroindustry, known as lignocellulosic wastes, has the possibility of reuse in the manufacture of new products, such as reinforced / matrix composite panels loaded with lignocellulosic wastes. The manufacturing process of these panels consists of hot pressing the binder adhesive mixture, a synthetic or natural resin, with the lignocellulosic particles / fibers used as reinforcement / filler. This pressing process can be considered a determining factor in the high porosity index of polymer composites, which limits their physical-mechanical performance. Given the benefits of using liquid vacuum molding in the manufacture of this type of material in the automotive industry, the ease of automation, versatility, simplicity and the possibility of obtaining a composite with greater interfacial interaction between fiber and matrix and lower porosity, this work aimed to analyze the influence of the introduction of the vacuum infusion step in the manufacture of composite panels of polymer matrix reinforced/loaded with lignocellulosic residues. To this end, the following types of panels were manufactured with Caixeta particles and mixed resin based on vegetable oils, classified according to the amount of resin (pre-polymer/polyol) and whether or not the use of vacuum infusion in the process: 48/ 48g without vacuum; 48/48g with vacuum; 150/150g without vacuum and 150/150g with vacuum. Physical-mechanical characterizations of the panels were performed and SEM photomicrographs were obtained to analyze and discuss the values obtained. The results showed that the vacuum infusion technique significantly improved all the properties of the panels, except for the density properties and in the case of the MOE of the samples with 150/150g of resin.