Analysis of relations between the moduli of elasticity in compression, tension, and static bending of hardwoods (original) (raw)
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In Brazil, standard ABNT NBR 7190 (1997) prescribes the determination of strength (fM) and modulus of elasticity (EM) in static bending from specimens measuring 5 cm × 5 cm × 115 cm. Thus, the relationship between the test span (L) and the specimen height (h) greater than or equal to 21 (L/h ≥ 21) is respected, ensuring that the effect of shear in the calculation of displacements is negligible (Euler Bernoulli Theory). Considering the expressive number of tree species cataloged in the Brazilian Amazon Forest, any procedure that aims to facilitate the realization of experimental tests is highly desirable because it provides the knowledge of unusual species. These wood species may potentially replace woods that have been traditionally used and historically exploited. Using five hardwood species, this research aimed to verify, while maintaining constant L/h ≥ 21 ratios, the influence of specimens dimensions in the determination of fM and EM. For all species studied, the statistical ana...
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International Journal of Agriculture and Forestry, 2013
The obtaining the modulus of elasticity in compression of the wood with the use of dial gauges, fixed on opposite faces of the specimens, may lead to deformation values and consequently to different elastic modulus as a function of the faces chosen for its attachment, being the timber an anisotropic material. This study aimed to evaluate the influence of two distinct positions for setting the dial gauges (A and B) in wood specimens tested in compression, using the assumptions of the test methods and calculation of the Brazilian standard ABNT NBR 7190: 1997. The woods evaluated in trials were the Pinus elliottii and Corymbia citriodora, being used seven specimens per species. A specimen was taken to the rupture, obtained the values of the ma ximu m stress and strain (references) needed to obtain the elastic moduli of the six remaining specimens per species, certain non-destructively (two tests per piece). The results of analysis of variance revealed the equivalence between modules elasticity in compression parallel to the grain for both wood species investigated, resulting not significantly arrangement of dial gaugesto determine the properties of stiffness. However, the anisotropy of wood, these results cannot be extrapolated to other woods of the same or d ifferent species, justifying the setting of dial gauges in two different positions, allo wing for judging whether or not the equivalence between the modulus of elasticity.
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International Journal of Materials Engineering, 2018
The modulus of elasticity is among the main properties required for the dimensioning of a wood structure. It can be calculated using different test methods, the most commonly used are the 3 and 4 points bending tests. The Brazilian standard, ABNT NBR 7190: 1997, recommends the 3-point static bending test. Studies about the influence of testing methods to determine the bending modulus of elasticity are always relevant, since can improve its reliability. Thus, the aim of this study is to examine the bending modulus of elasticity of samples of nine Brazilian wood species: Cambará Rosa (Erisma uncinatum Warm), Caxeta (Tabebuia cassinoides), Tatajuba (Bagassa guianensis), Itaúba (Mezilaurus itauba), Branquilho (Termilalia spp), Cedro Amazonense (Cedrelinga catenaeformis Ducke), Roxinho (Peltogyne spp.), Cumaru (Dipteryx odorata) and Cambará (Gochnatia polymorpha). The results of the confidence intervals have showed that the moduli of elasticity for both test methods were equivalent at 5% significance level.
Periodically, when necessary, standard documents are revised in order to analyze inconsistencies and to include considerations according new realities verified. In this sense, aiming to quantify the wood moisture content influence on modulus of elasticity, it was applied tension tests parallel to the grain for six specimens of different strength classes of wood, considering nominal moisture of 12, 20, 25, and 30% in Brazil. The present paper examine the adequacy of the current Brazilian standard ABNT NBR7190:1997, in review, about the adoption of a first degree equation to describe the influence of wood moisture content for timber structures design. It was obtained a new first degree equation which leads to statically equivalent estimations when compared with results by ABNT NBR7190:1997 equation. However, as recommendations it could be maintain the current expression for the next text of the referred document review, without prejudice to statistical significance of the estimates.
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This paper presents the results obtained in a series of tests on Pinus Pinaster Ait. timber specimens, using the prEN408: 2000, to estimate the local and global Young's modulus and strength both in bending and compression parallel to the grain. The results obtained are compared with the values presented in the Portuguese Nationally Determined Parameters of Eurocode 5, for the quality classes assign by Portuguese Standard NP4305: 1994 by visual grading.
BioResources, 2023
Tropical species are widely used in construction, and their physical and mechanical properties have been important characteristics with direct impact on the design of structures, especially the strength and stiffness of wood applied in them. Tests to obtain both parameters are conducted under ABNT NBR 7190 (1997) guidelines in Brazil, being rarely found in some research centers because of the higher costs of testing equipment. For instance, the toughness test depends on equipment with a pendulum, whose device requires accuracy and maintenance for reliable analyses. This paper aims to estimate toughness through another property more easily found, given by the compression strength parallel to the grain. For this, 20 tropical wood species of the South American region were used to obtain initial values of these properties. The characteristic values of the compression strength parallel to the grain as well as linear and quadratic regression models were obtained. Statistical analysis was performed and confirmed that a linear model gave better predictions than a quadratic model.
Models to estimate longitudinal compressive strength of Brazilian hardwood based on apparent density
BioResources, 2021
As wood is an orthotropic and natural material, there are several properties required for its use in civil construction. The apparent density has been used to estimate physical and mechanical properties of wood, as it is easy to determine experimentally, unlike other determinations, which involve the use of equipment available only in large research centers. Using the Brazilian standard ABNT NBR 7190 and linear and non-linear regression models, this research aimed to evaluate their accuracy in estimating the compressive strength parallel to the fibers (fc0) as well as their characteristic value (fc0,k). This study considered 72 tropical wood species from native forests that were divided into the 4 strength classes of this standard. For the set formed by all species, the linear polynomial model was the best fit, resulting in a determination coefficient of just over 70%.
Advanced Materials Research, 2015
Periodically, when necessary, standard documents are revised in order to analyze inconsistencies and to include considerations according new realities verified. In this sense, aiming to quantify the wood moisture content influence on modulus of elasticity, it was applied tension tests parallel to the grain for six specimens of different strength classes of wood, considering nominal moisture of 12, 20, 25, and 30% in Brazil. The present paper examine the adequacy of the current Brazilian standard ABNT NBR7190:1997, in review, about the adoption of a first degree equation to describe the influence of wood moisture content for timber structures design. It was obtained a new first degree equation which leads to statically equivalent estimations when compared with results by ABNT NBR7190:1997 equation. However, as recommendations it could be maintain the current expression