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| Registros recuperados: 22 | |
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| Lahr,Francisco A. R.; Nogueira,Marta C. de J. A.; Araujo,Victor A. De; Vasconcelos,Juliano S.; Christoforo,André L.. |
| ABSTRACT Over the years, the species of eucalyptus has become a multipurpose raw material. In addition, the most relevant aspect of the use for various purposes is related to the production of a high quality wood, coming from short duration plantations, which is fundamental to the current demand of the industries. However, its use in civil construction has not yet reached a level of importance, due to the low knowledge of many of its resistance properties and the consequent popular fear in the use of reforestation woods, in particular the Eucalyptus grandis. This research investigated its main mechanical properties, aiming to reinforce its constructive applications in wood structures. For this, two physical properties and fourteen mechanical properties, in... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Rose Gum; Eucalypt; Mechanical properties; Bulk density. |
| Ano: 2018 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-69162018000500642 |
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| Christoforo,André L.; Arroyo,Felipe N.; Silva,Diogo A. Lopes; Panzera,Tulio H.; Lahr,Francisco A. R.. |
| ABSTRACT: Wood is a material that for years has been used by man for a variety of purposes, particularly in rural and civil constructions and furniture industry. The possibility of shortages of some wood species, the characterization of other unfamiliar species is an alternative source for use in civil and rural construction. This study aimed to determine, with the aid of Brazilian standard NBR 7190, physical and mechanical properties of Castelo (Calycophyllum multiflorum) wood specie. Twelve determinations were obtained by property, totaling 204 experimental values. In the characterization of wood, regression models were used to estimate the values of timber strength and stiffness as a function of apparent density, being density the physical property more... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Calycophyllum multiflorum; Physical-mechanical properties; Hardwood; Regression model. |
| Ano: 2017 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-69162017000400637 |
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| Christoforo,André L.; Couto,Natalia G.; Almeida,João P. B.; Aquino,Vinicius B. de M.; Lahr,Francisco A. R.. |
| ABSTRACT The use of new wood species in construction requires knowledge of their properties for safer and more economical structural sizing. In Brazil, structural projects are carried out according to the standard document ABNT NBR 7190:1997. Tests required by this standard for the complete characterization of species require large machines with high costs, which are present only in large research centers. Considering the lack of experimental determination, this study aimed, with the help of analysis of variance of regression models, to investigate the possibility of estimating, through apparent density, wood properties obtained in tests where failure is considered fragile, allowing the estimation of properties of species still little used. Ten wood... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Hardwoods; Fragile failure; Regression models; Analysis of variance. |
| Ano: 2020 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-69162020000100105 |
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| Christoforo,André L.; Aftimus,Bruno H. C.; Panzera,Tulio H.; Machado,Gilmara de O.; Lahr,Francisco A. R.. |
| ABSTRACT In Brazil, the characterization of wood is carried out in accordance with the premises established by ABNT NBR 7190standard; however, the determination of wood properties requires the use of equipment, which hinders the wood characterization for the construction professional. To circumvent this problem, the properties of wood strength and stiffness can be estimated through regression models using the apparent density as estimator, being the density a physical property of easy determination. This study aimed to determine 4 physical and 13 mechanical properties of “Angico Branco” wood (Anadenanthera colubrina), and with the aid of regression models based on analysis of variance, estimate the strength and stiffness properties as a function of... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Anadenanthera colubrina; Physico-mechanical characterization; Apparent density; Regression models; Analysis of variance (ANOVA). |
| Ano: 2017 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-69162017000200376 |
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| Christoforo,André L.; Panzera,Tulio H.; Neto Junior,Carlito Calil; Demarzo,Mauro A.; Ribeiro Filho,Sérgio L. M.; Toniolo,Luiz E.; Amstalden,Rogério A. S.; Lahr,Francisco A. R.. |
| This study aims to present an alternative calculation methodology based on the Least Squares Method for determining the modulus of elasticity in bending wooden beams of structural dimensions. The equations developed require knowledge of three or five points measured in displacements along the piece, allowing greater reliability on the response variable, using the statistical bending test at three points and non-destructively, resulting from imposition of measures from small displacements L/300 and L/200, the largest being stipulated by the Brazilian norm NBR 7190:1997. The woods tested were Angico, Cumaru, Garapa and Jatoba. Besides obtaining the modulus of elasticity through the alternative methodology proposed, these were also obtained employing the... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Wood; Beam theory; Modulus of elasticity; Least Squares Method. |
| Ano: 2014 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-69162014000100016 |
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| Christoforo,André L.; Almeida,Tiago H. de; Almeida,Diego H. de; Balanco,Giovana G.; Lahr,Francisco A. R.. |
| ABSTRACT Wood is one of the main materials used in the constructing of covering structures (roofs) because of its versatility. Under this situation, due to solar radiation incidence, the temperature can exceed 60 °C and, such as other environmental conditions, influence the mechanical properties of the wood in use. The aim of this research was to study the influence of exposure time of the wood of four different hardwood species at a temperature of 60 °C on the shear strength parallel to fibers. The wood of the following species was used: Cupiúba (Goupia glabra), Eucalyptus (Eucalyptus saligna), Garapeira (Apuleia leiocarpa), and Jatobá Tamarindo (Hymenaea sp.). In order to investigate the effect of exposure time (0, 168, 456, 720, and 2160 hours) of the... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Hardwoods; Mechanical properties; Roofs; Temperature. |
| Ano: 2019 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-69162019000300365 |
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| Christoforo,André L.; Nascimento,Maria F. do; Panzera,Tulio H.; Ribeiro Filho,Sérgio L. M; Lahr,Francisco A. R.. |
| ABSTRACT This study aimed to evaluate the mechanical performance of laminated composite materials (fiberglass, carbon, sisal, palm fiber) in epoxy matrix as reinforcement in wood particleboards of Pinus sp. with bicomponent polyurethane resin from castor oil. Modulus of elasticity (MOE) and modulus of rupture (MOR) were investigated using a three-point bending test. Single-layered laminated plates were used to reinforce traction of specimens obtained from boards. MOE and MOR of materials developed without reinforcements exceeded limits in ABNT standards both NBR 12810-2:2002 and A208.1:199, proving therefore their feasibility. In all investigated cases, inclusion of reinforcements led to higher values for both MOE and MOR. Composites in fiberglass... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Particleboard; Laminated composites; Structural reinforcement. |
| Ano: 2016 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-69162016000300558 |
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| Christoforo,André L.; Panzera,Tulio H.; Lahr,Francisco A. R.. |
| ABSTRACT According to the ABNT NBR 7190: 1997 standard, tensile strength of wood samples shall be defined as the ratio between the ultimate strength from a stress test and the specimen cross-sectional area (350 mm2). However, due to the complex wood anatomy and experimental difficulties, the fractured surface in tested samples are not perpendicular to the loading direction; therefore, such fractured surface becomes larger than the sample cross section, overestimating tensile strength by this method. Using an alternative approach, we aimed to determine the approximate fracture surface of wood specimens subjected to tensile test. For this purpose, we used the least square method to estimate tensile strength of four hardwood species, which were equally... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Tensile Strength; Wood; Hardwood; Least Square Method. |
| Ano: 2019 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-69162019000400533 |
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| Christoforo,André L.; Almeida,Diego H. de; Varanda,Luciano D.; Panzera,Tulio H.; Lahr,Francisco A. R.. |
| ABSTRACT Wood has been used for several purposes such as in civil and rural construction. Knowing wood mechanical behavior under short-term loading is essential for safer structural designs. However, wood toughness is a mechanical property little investigated for this purpose. Thus, this study aimed to evaluate, using exponential and polynomial regression models (linear, quadratic, and cubic), the possibility of estimating toughness as a function of apparent density, compression parallel to grain strength, and modulus of rupture in static bending. Thirty-six Brazilian tropical wood species from south of Roraima, Mato Grosso do Sul, and north and northeast of Mato Grosso were tested. Our results showed the significance and representativeness of all... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Apparent density; Tropical wood species; Modulus of elasticity; Compression parallel to grain strength; Toughness. |
| Ano: 2020 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-69162020000200232 |
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| Christoforo,André L.; Zangiácomo,André L.; Panzera,Túlio H.; Silveira,Márcio E.; Lahr,Francisco A. R.. |
| Vigas são elementos estruturais encontrados na maioria das construções civis. Dentre os materiais de engenharia, destaca-se a madeira, por ter resistência mecânica satisfatória aliada a baixa densidade. A madeira roliça apresenta-se como boa solução na confecção de vigas, uma vez que não precisa ser processada, como é o caso da madeira serrada. O projeto de elementos estruturais de madeira requer o conhecimento de suas propriedades físicas e mecânicas, obtidas segundo as premissas de documentos normativos. Em se tratando da madeira roliça, os documentos normativos nacionais que tratam da determinação das propriedades de resistência e rigidez estão vigentes há mais de vinte anos sem revisão técnica. De forma geral, tanto as normas nacionais como as... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Madeira roliça; Método dos Elementos Finitos; Método dos Mínimos Quadrados. |
| Ano: 2012 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-69162012000500016 |
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| Lahr,Francisco A. R.; Nogueira,Marta C. De J. A.; Araujo,Victor A. De; Vasconcelos,Juliano S.; Christoforo,André L.. |
| ABSTRACT: Eucalyptus urophylla consists in a wood-producing species, which offers a natural multiple raw material of good quality for applications in rural and civil constructions. However, Eucalyptus urophylla still has a small utilization as building parts and elements, resulting from the possible ignorance and low diffusion of its structural possibilities. Thereby, the present research aims to measure the main thirteen mechanical properties of Eucalyptus urophylla wood for two different moisture contents, 12% and 30% (green wood). Furthermore, in these two conditions of moisture content evaluation, volumetric mass densities were also evaluated. At the end of this evaluation, which included 2688 determinations, all the obtained results were statistically... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Timor White Gum; Strength modulus; Cracking; Shear stress; Hardness; Density. |
| Ano: 2017 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-69162017000500900 |
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| Zangiácomo,André L.; Christoforo,André L.; Lahr,Francisco A. R.. |
| ABSTRACT This research aimed at estimating both longitudinal (E) and shear (G) elasticity moduli of round structural-sized beams made of Pinus caribaea timber, verifying thus the validity of the G = E/ 20 relationship established by the Brazilian standard ABNT NBR 7190: 1997 (Designing of Wooden Structures). We tested twenty pieces of green wood with average length, diameter and conicity of 750 cm, 30 cm and 4%, respectively. Two static bending tests were applied at three points of each piece, being nondestructive and using different distances between supports. In the first trial, the length and diameter relationship (L/ d) was set as being equal to 24; yet in the second test, it was set at 12. The elasticity moduli were estimated by a successive use of... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Stiffness; Bending; Beam theory; Least square. |
| Ano: 2016 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-69162016000300566 |
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| Christoforo,André L.; Barbosa,Thaina Q.; Almeida,Diego H. de; Panzera,Tulio H.; Lahr,Francisco A. R.. |
| ABSTRACT This research aimed to evaluate the effect of the number of fatigue cycles (NC, 0 – reference, 450, 4500, 45000, and 90000) for frequencies (Fr) of oscillation equal to 0.5 and 1.0 Hz on the modulus of elasticity (Em) and operating stress (σm) in the static bending of Pinus caribaea wood. Em and σm were determined taking into account three specimens (SPEC) manufactured for reference condition and another three for each of the four NC levels and each Fr level, resulting in 27 SPEC. Sixty experimental determinations were obtained, being the approximate total time of sample exposure to fatigue of 350 hours. The same specimens used to determine Em and σm for the reference condition were also used (via non-destructive tests) to obtain these properties... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Fatigue; Pinus caribaea; Static bending; Analysis of variance; Regression models. |
| Ano: 2020 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-69162020000200238 |
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| Christoforo,André L.; Almeida,Andrea de S.; Lanini,Tamiris L. S.; Nogueira,Rodrigo de S.; Lahr,Francisco A. R.. |
| ABSTRACT For safety reasons, wood strength values, essential for structural dimensioning, are calculated based on the characteristic value, which corresponds to the 5% percentile of a given probability distribution model. For small samples, the Brazilian normative document ABNT NBR 7190 establishes an estimator of the characteristic wood strength, which can provide a significantly different result from the characteristic value coming from a suitable model of probability distribution. The main objective of this study was to evaluate the best probability distribution model (normal, lognormal, Weibull, and exponential) and the subsequent calculation of the characteristic value indicated by ABNT NBR 7190 (1997), allowing to evaluate its accuracy, being also... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Wood; Compression; Traction; Shear; Probability distribution; Characteristic value. |
| Ano: 2019 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-69162019000100127 |
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| Christoforo,André L.; Romanholo,Giuliano A.; Panzera,Túlio H.; Borges,Paulo H. R.; Lahr,Francisco A. R.. |
| Trusses are structural systems commonly used in projects, being employed mainly in roof structures, present in most rural buildings. The design of trusses, as well as other structural systems, requires the determination of displacements, strains and stresses. However, the project is developed from an ideal model of calculation, considering free rotation between the elements of a connection. This paper presents a computer program for the analysis of bidimensional wooden trusses with connections formed with two screws per node. The formulation is based on the flexibility method, taking into account the influence of the effect of semi-rigid connections formed by two screws. An example of a structure is presented and analyzed by the program developed here,... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Trusses; Semi-rigid connections; Flexibility method; Rural buildings. |
| Ano: 2011 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-69162011000500017 |
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| Registros recuperados: 22 | |
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