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Andre Luis Christoforo - One of the best experts on this subject based on the ideXlab platform.
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Pull Out Strength of Bonded-in Steel Rods Perpendicularly to the Grain in Corymbia citriodora and Pinus oocarpa Shiede Timber
International Journal of Materials Engineering, 2018Co-Authors: Julio César Pigozzo, Andre Luis Christoforo, Felipe Nascimento Arroyo, Diego Henrique De Almeida, Eduardo Chahud, Francisco Antonio Rocco LahrAbstract:The study of pull out strength of glued in rods perpendicularly to the grain is presented. Three types of resin were used in order to evaluate their efficiency. Additionally, the effects of the variation of the moisture content and of the glue line thickness were considered. The beams were made of wood from Corymbia citriodora, (ρ12% = 1000 kg/m3) and Pinus oocarpa Shiede (ρ12% = 550 kg/m3). The wood specimens (four samples for each type of test) were seasoned to the expected moisture contents of 12, 15, 18 and 22%. The anchorage length of the glued in rods was 80 mm, the hole diameters were 7.5, 8.5, 9.5 and 10.5 mm and their respective glue line thickness, 0.6, 1.1, 1.6 and 2.1 mm. The deformed reinforcing bars used as rods, with the minimum yield strength of 500 MPa, had nominal diameter of 6.3 mm. The obtained results confirmed the assumption that type of resin, moisture content, glue line thickness are strength determining factors, while density is less than others. The results are presented in a comparative form. The failure modes are discussed and the need of a broad understanding of resin behavior on wood was emphasized.
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aproximacao nao linear da geometria em vigas rolicas estruturais de madeira Corymbia citriodora na determinacao do modulo de elasticidade longitudinal
Engenharia Agricola, 2016Co-Authors: Andre Luis Christoforo, Andre Luiz Zangiacomo, Tulio Hallak Panzera, Marcio Eduardo Silveira, Francisco Antonio Rocco LahrAbstract:Os documentos normativos que tratam da determinacao das propriedades de rigidez e resistencia para elementos estruturais rolicos de madeira nao levam em consideracao em seus calculos e modelos matematicos a influencia das irregularidades existentes na geometria dessas pecas. Este trabalho objetivou avaliar a influencia das irregularidades da forma em pecas rolicas de madeira Corymbia citriodora considerando aproximacao quadratica por partes para a geometria segundo o ensaio de flexao estatica a tres pontos, permitindo comparar os resultados dos modulos de elasticidade encontrados pela metodologia numerica de calculo aqui proposta, fundamentada no Metodo dos Elementos Finitos e no Metodo dos Minimos Quadrados, com os fornecidos pela equacao proveniente da resistencia dos materiais com o uso de um unico valor de circunferencia, medido no ponto medio da viga. Pela equivalencia estatistica encontrada entre os valores dos modulos de elasticidade para os elementos rolicos da especie Corymbia citriodora segundo abordagem numerica e analitica, constata-se a boa aproximacao de calculo fornecida pela equacao da resistencia dos materiais. Este resultado e valido apenas para os elementos rolicos aqui estudados, podendo ser diferentes para outras madeiras com diferentes conicidades.
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biological resistance of thermally treated Corymbia citriodora hook k d hill l a s johnson e pinus taeda l woods against xylophagous termites
Revista Arvore, 2016Co-Authors: Juarez Benigno Paes, Pedro Gutemberg Alcântara Segundinho, Allan Ewerton Rezende Euflosino, Marcio Rogerio Da Silva, Carlito Calil, Andre Luis ChristoforoAbstract:This research aimed to evaluate the effect of the thermal-treated temperature to improvement of Corymbia citriodora and Pinus taeda wood resistance to the xylophagous termite Nasutitermes corniger, into forced feeding assay. The wood thermally treated was performed at temperatures of 160, 180, 200, 220, 240oC. For Pinus taeda, the temperature of 260oC was also used. Three boards of 6 × 16 × 56 cm (thickness × width x length) were used for each temperature. After being thermally treated, the boards were transformed into samples of 2.54 × 2.54 × 0.64 cm (longitudinal × radial × tangential). The experiment was kept in a climatized room (25 ± 2oC and 65 ± 5% of relative humidity), for 28 days. For Corymbia citriodora, the thermal treatment at 220 and 240oC improved the resistance to the termite. For Pinus taeda, the resistance improvement occurred at 240 and 260oC. The temperature of 160oC caused a decrease in the natural durability of both species.
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Chemical and Mechanical Properties Changes in Corymbia citriodora Wood Submitted to Heat Treatment
International Journal of Materials Engineering, 2015Co-Authors: Marcio Rogerio Da Silva, Andre Luis Christoforo, José Otávio Brito, Francisco Antonio, José Silvio Govone, Gilmara De Oliveira Machado, Carlito Calil Junior, Rocco LahrAbstract:The heat is important treatment in the wood processing. The changes are not significant in structural properties in some case, like wood drying. However, in other treatments, such heat treatment and carbonization the changes can be intense. The main purpose of this research is to investigate the influence of thermorectification process on the chemical and mechanical behavior of Corymbia citriodora (Hook.) K.D. Hill & L.A.S. Johnson. The heat treatment was performed in a laboratorial electric furnace at 160, 180 and 200 oC, under inert atmosphere, using boards measuring 6 × 16 × 56 cm 3 and the temperature in the wood pieces was controlled by thermocouples. The mechanical and chemical properties were determined to fresh and heat-treated wood. The mechanical properties were evaluated by Modulus of Rupture (MOR) and Modulus of Elasticity (MOE) in bending, and also tensile and shear strength parallel to the grain. The content of cellulose, hemicelluloses, lignin, extractives and ash were determined according to TAPPI Standard. The chemical analysis revealed that when the temperatures and time increase, the changes are ranged from 17.8 to 9.6% extractives; 30.4 to 44% lignin; 30.8 to 42.8% cellulose and 21.7 to 6% hemicelluloses. The ash content remains almost steady for all boards. The mechanical tests showed that the MOR and the tension parallel to the grain (ft0) decreased from 36% up to 55%, respectively. The stiffness properties (MOE) increased about 12%, improved during thermal treatment.
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Evaluation of the Shear Effect to Determine the Longitudinal Modulus of Elasticity in Corymbia citriodora Round Timber Beams
International Journal of Materials Engineering, 2014Co-Authors: Andre Luiz Zangiacomo, Andre Luis Christoforo, Decio Gonçalves, Francisco Antonio Rocco LahrAbstract:This study aimed to investigate, based on three points static bending tests, the influence of ratio between length (L) and diameter (d) in structural round timber of Corymbia citriodora to determine the modulus of elasticity (MOE) using equations that do not consider shear influence in beam displacements. Non-destructive tests were carried out in 24 round pieces, medium length 750cm and average diameter 30 cm, moisture content around 12%. Modulus of elasticity for six different ratios (L/d) between length and diameter (9, 12, 15, 18, 21, 24) were determined, providing obtains six distinct values of MOE for each structural elements. Hypothesis tests results indicated equivalence of modulus of elasticity only to ratios (L/d) 24, 21 and 18. This implies that for proper use of the simplified equation to obtain MOE, based on static bending tests over structural round timber, it is necessary to respect L/h≥18 ratio.
Francisco Antonio Rocco Lahr - One of the best experts on this subject based on the ideXlab platform.
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Pull Out Strength of Bonded-in Steel Rods Perpendicularly to the Grain in Corymbia citriodora and Pinus oocarpa Shiede Timber
International Journal of Materials Engineering, 2018Co-Authors: Julio César Pigozzo, Andre Luis Christoforo, Felipe Nascimento Arroyo, Diego Henrique De Almeida, Eduardo Chahud, Francisco Antonio Rocco LahrAbstract:The study of pull out strength of glued in rods perpendicularly to the grain is presented. Three types of resin were used in order to evaluate their efficiency. Additionally, the effects of the variation of the moisture content and of the glue line thickness were considered. The beams were made of wood from Corymbia citriodora, (ρ12% = 1000 kg/m3) and Pinus oocarpa Shiede (ρ12% = 550 kg/m3). The wood specimens (four samples for each type of test) were seasoned to the expected moisture contents of 12, 15, 18 and 22%. The anchorage length of the glued in rods was 80 mm, the hole diameters were 7.5, 8.5, 9.5 and 10.5 mm and their respective glue line thickness, 0.6, 1.1, 1.6 and 2.1 mm. The deformed reinforcing bars used as rods, with the minimum yield strength of 500 MPa, had nominal diameter of 6.3 mm. The obtained results confirmed the assumption that type of resin, moisture content, glue line thickness are strength determining factors, while density is less than others. The results are presented in a comparative form. The failure modes are discussed and the need of a broad understanding of resin behavior on wood was emphasized.
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aproximacao nao linear da geometria em vigas rolicas estruturais de madeira Corymbia citriodora na determinacao do modulo de elasticidade longitudinal
Engenharia Agricola, 2016Co-Authors: Andre Luis Christoforo, Andre Luiz Zangiacomo, Tulio Hallak Panzera, Marcio Eduardo Silveira, Francisco Antonio Rocco LahrAbstract:Os documentos normativos que tratam da determinacao das propriedades de rigidez e resistencia para elementos estruturais rolicos de madeira nao levam em consideracao em seus calculos e modelos matematicos a influencia das irregularidades existentes na geometria dessas pecas. Este trabalho objetivou avaliar a influencia das irregularidades da forma em pecas rolicas de madeira Corymbia citriodora considerando aproximacao quadratica por partes para a geometria segundo o ensaio de flexao estatica a tres pontos, permitindo comparar os resultados dos modulos de elasticidade encontrados pela metodologia numerica de calculo aqui proposta, fundamentada no Metodo dos Elementos Finitos e no Metodo dos Minimos Quadrados, com os fornecidos pela equacao proveniente da resistencia dos materiais com o uso de um unico valor de circunferencia, medido no ponto medio da viga. Pela equivalencia estatistica encontrada entre os valores dos modulos de elasticidade para os elementos rolicos da especie Corymbia citriodora segundo abordagem numerica e analitica, constata-se a boa aproximacao de calculo fornecida pela equacao da resistencia dos materiais. Este resultado e valido apenas para os elementos rolicos aqui estudados, podendo ser diferentes para outras madeiras com diferentes conicidades.
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Evaluation of the Shear Effect to Determine the Longitudinal Modulus of Elasticity in Corymbia citriodora Round Timber Beams
International Journal of Materials Engineering, 2014Co-Authors: Andre Luiz Zangiacomo, Andre Luis Christoforo, Decio Gonçalves, Francisco Antonio Rocco LahrAbstract:This study aimed to investigate, based on three points static bending tests, the influence of ratio between length (L) and diameter (d) in structural round timber of Corymbia citriodora to determine the modulus of elasticity (MOE) using equations that do not consider shear influence in beam displacements. Non-destructive tests were carried out in 24 round pieces, medium length 750cm and average diameter 30 cm, moisture content around 12%. Modulus of elasticity for six different ratios (L/d) between length and diameter (9, 12, 15, 18, 21, 24) were determined, providing obtains six distinct values of MOE for each structural elements. Hypothesis tests results indicated equivalence of modulus of elasticity only to ratios (L/d) 24, 21 and 18. This implies that for proper use of the simplified equation to obtain MOE, based on static bending tests over structural round timber, it is necessary to respect L/h≥18 ratio.
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Bending Strength and Stiffness of a Particulate Composite Material Manufactured with Epoxy Matrix and Corymbia citriodora Sawdust
International Journal of Composite Materials, 2013Co-Authors: Hélder Rafael Santos Pascoal, Francisco Antonio Rocco Lahr, Sergio Luiz Moni, Ribeiro Filho, Geraldo Roberto De Sousa, Andre Luis ChristoforoAbstract:This research had as objective the development of particu late co mposite materials in epo xy matrix reinforced with Corymbia citriodora sawdust. The evaluated properties were bending modulus of elasticity (MOE) and bendingstrength (MOR) . The resin volu met ric fraction over wood sawdust was the only variab le factor at experimental design, consisting 45% and 65% in fractions. The thickness of specimens for the bending test was 4mm, defined at preliminary studies. Were fabricated two panels by investigated fractions, with 200×200mm d imensions, under a press pressure of 3 MPa, and made at amb ient temperature, in d ifferent t imes. Fro m these panels, were extracted the specimens test with dimensions and specifications established by American Standard ASTM D790: 2010. Fro m results obtained from analysis of variance, concluded that variation of sawdust fraction present a significant behavior at response-variables, presenting the best results the materials manufactured with 45% of epo xy resin.
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modulos de elasticidade longitudinal e transversal em vigas rolicas de madeira de Corymbia citriodora
Revista Vértices, 2013Co-Authors: Andre Luiz Zangiacomo, Andre Luis Christoforo, Francisco Antonio Rocco LahrAbstract:This study aimed to evaluate, with the support of the three points static bending test, led nondestructively, the values of the shear (G) and longitudinal (E) modulus of elasticity in Corymbia citriodora structural round timber beams in order to verify the validity of the G=E/20 relationship established by the Brazilian standard ABNT NBR 7190:1997 (Design of Wood Structures). The specimens tested (20) have an average length of 750 cm, diameter of 30 cm, moisture content of 12% and 5% of average taper. There were two bending tests per element, with differences in the distances between supports. In the first trial, we used the L/D ratio between the length (L) and diameter (d) of the pieces equal to twenty-four, while the second was conducted in sequence, with L/d equal to fifteen. The elasticity modulus were obtained according to the successive use of the equation of Timoshenko’s beam theory, which takes into account the influence of the shear efforts to determine displacements. The results between the shear and longitudinal modulus of elasticity were related by the least squares method, the relationship G=E/56 was found, which demonstrates divergent results with the Brazilian standard for the structural round timber investigated.
David J. Lee - One of the best experts on this subject based on the ideXlab platform.
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Genetic variation in growth and wood-quality traits of Corymbia citriodora subsp. variegata across three sites in south-east Queensland, Australia
Southern Forests: a Journal of Forest Science, 2016Co-Authors: Tran D. Hung, David J. Lee, Jermey T Brawner, Roger Meder, Mark J. DietersAbstract:Ten growth or wood-quality traits were assessed in three nearby Corymbia citriodora subsp. variegata (CCV) open-pollinated family-within-provenance trials (18 provenances represented by a total of 374 families) to provide information for the development of a breeding program targeting both pulp and solid-wood products. Growth traits (diameter at breast high over bark [DBH], height and conical volume) were assessed at 3 and 7 years of age. Wood-quality traits (density [DEN], Kraft pulp yield [KPY], modulus of elasticity [MoE] and microfibril angle [MfA]) were predicted using near-infrared spectroscopy on wood samples collected from these trials when aged between 10 and 12 years. The high average KPY, DEN and MoE, and low average MfA observed indicates CCV is very suitable for both pulp and timber products. All traits were under moderate to strong genetic control. In across- trials analyses, high (>0.4) heritability estimates were observed for height, DEN, MoE and MfA, while moderate heritability estimates ...
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Genetic control of flowering in spotted gum, Corymbia citriodora subsp. variegata and C. maculata
Australian Journal of Botany, 2014Co-Authors: Myralyn Abasolo, David J. Lee, Carolyn A Raymond, Lyndon O Brooks, Mervyn ShepherdAbstract:Genetically controlled asynchrony in anthesis is an effective barrier to gene flow between planted and native forests. We investigated the degree of genetically controlled variation in the timing of key floral developmental stages in a major plantation species in subtropical Australia, Corymbia citriodora subsp. variegata K.D. Hill and L.A.S Johnson, and its relative C. maculata K.D. Hill and L.A.S. Johnson. Flowering observations were made in a common garden planting at Bonalbo in northern New South Wales in spring on 1855 trees from eight regions over three consecutive years, and monthly on a subset of 208 trees for 12 months. Peak anthesis time was stable over years and observations from translocated trees tended to be congruent with the observations in native stands, suggesting strong genetic control of anthesis time. A cluster of early flowering provenances was identified from the north-east of the Great Dividing Range. The recognition of a distinct flowering race from this region accorded well with earlier evidence of adaptive differentiation of populations from this region and geographically-structured genetic groupings in C. citriodora subsp. variegata. The early flowering northern race was more fecund, probably associated with its disease tolerance and greater vigour. Bud abundance fluctuated extensively at the regional level across 3 years suggesting bud abundance was more environmentally labile than timing of anthesis. Overall the level of flowering in the planted stand (age 12 years) was low (8–12% of assessed trees with open flowers), and was far lower than in nearby native stands. Low levels of flowering and asynchrony in peak anthesis between flowering races of C. citriodora subsp. variegata may partially mitigate a high likelihood of gene flow where the northern race is planted in the south of the species range neighbouring native stands
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Association genetics in Corymbia citriodora subsp variegata identifies single nucleotide polymorphisms affecting wood growth and cellulosic pulp yield
The New phytologist, 2012Co-Authors: Shannon Dillon, David J. Lee, Roger Meder, J. T. Brawner, Simon G. SouthertonAbstract:Wood is an important biological resource which contributes to nutrient and hydrology cycles through ecosystems, and provides structural support at the plant level. Thousands of genes are involved in wood development, yet their effects on phenotype are not well understood. We have exploited the low genomic linkage disequilibrium (LD) and abundant phenotypic variation of forest trees to explore allelic diversity underlying wood traits in an association study. Candidate gene allelic diversity was modelled against quantitative variation to identify SNPs influencing wood properties, growth and disease resistance across three populations of Corymbia citriodora subsp. variegata, a forest tree of eastern Australia. Nine single nucleotide polymorphism (SNP) associations from six genes were identified in a discovery population (833 individuals). Associations were subsequently tested in two smaller populations (130160 individuals), validating our findings in three cases for actin 7 (ACT7) and COP1 interacting protein 7 (CIP7). The results imply a functional role for these genes in mediating wood chemical composition and growth, respectively. A flip in the effect of ACT7 on pulp yield between populations suggests gene by environment interactions are at play. Existing evidence of gene function lends strength to the observed associations, and in the case of CIP7 supports a role in cortical photosynthesis.
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Relationships between early growth and Quambalaria shoot blight tolerance in Corymbia citriodora progeny trials established in Queensland, Australia
Tree Genetics & Genomes, 2011Co-Authors: Jeremy T. Brawner, David J. Lee, Craig M. Hardner, Mark J. DietersAbstract:The fungal pathogen Quambalaria pitereka can cause significant damage to spotted gum ( Corymbia sp. ) plantations in Australia. A series of seven progeny trials, involving seed from a range-wide collection from 527 individuals within 25 native populations of Corymbia citriodora sub-species variegata , were assessed for height growth and damage from Quambalaria around 1 year after planting. Infection at this young age has been found to detrimentally impact growth, form, and wood quality for many years. Genetic variance was found to be significant at both the provenance and family level. However, selection of families within provenances should lead to greater levels of genetic gain than what can be realized from selecting among provenances as estimates of additive genetic variance were consistently greater than estimates of variance among populations. Strong relationships between height and Quambalaria shoot blight (QSB) damage assessments in these trials were evidenced by very high genetic correlations between the traits; therefore, selection for any of these traits could be used to identify more productive and QSB-tolerant populations. While both provenances and families were found to interact with the trial environments at a similar level across traits, genetic correlations indicated that rankings for growth were be less stable than rankings for QSB tolerance across environments. Genetic parameter estimates derived from general and generalized linear models were very similar and either analytical method could be used to evaluate fungal damage.
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Reproductive biology of Corymbia citriodora subsp. variegata and effective pollination across its native range in Queensland, Australia.
Southern Forests: a Journal of Forest Science, 2009Co-Authors: Cecile F. E. Bacles, Jennifer Brooks, David J. Lee, Peer M. Schenk, Andrew J. Lowe, Antoine KremerAbstract:The spotted gum species complex represents a group of four eucalypt hardwood taxa that have a native range that spans the east coast of Australia, with a morphological cline from Victoria to northern Queensland. Of this group, Corymbia citriodora subsp. variegata (CCV) is widespread in south-eastern Queensland and northern New South Wales. It is currently the most commonly harvested native hardwood in Queensland. However, little basic knowledge of the reproductive biology of the species is available to inform genetic improvement and resource management programmes. Here we take an integrative approach, using both field and molecular data, to identify ecological factors important to mating patterns in native populations of CCV. Field observation of pollinator visitation and flowering phenology of 20 trees showed that foraging behaviour of pollinator guilds varies depending on flowering phenology and canopy structure. A positive effect of tree mean flowering effort was found on insect visitation, while bat v...
Andre Luiz Zangiacomo - One of the best experts on this subject based on the ideXlab platform.
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aproximacao nao linear da geometria em vigas rolicas estruturais de madeira Corymbia citriodora na determinacao do modulo de elasticidade longitudinal
Engenharia Agricola, 2016Co-Authors: Andre Luis Christoforo, Andre Luiz Zangiacomo, Tulio Hallak Panzera, Marcio Eduardo Silveira, Francisco Antonio Rocco LahrAbstract:Os documentos normativos que tratam da determinacao das propriedades de rigidez e resistencia para elementos estruturais rolicos de madeira nao levam em consideracao em seus calculos e modelos matematicos a influencia das irregularidades existentes na geometria dessas pecas. Este trabalho objetivou avaliar a influencia das irregularidades da forma em pecas rolicas de madeira Corymbia citriodora considerando aproximacao quadratica por partes para a geometria segundo o ensaio de flexao estatica a tres pontos, permitindo comparar os resultados dos modulos de elasticidade encontrados pela metodologia numerica de calculo aqui proposta, fundamentada no Metodo dos Elementos Finitos e no Metodo dos Minimos Quadrados, com os fornecidos pela equacao proveniente da resistencia dos materiais com o uso de um unico valor de circunferencia, medido no ponto medio da viga. Pela equivalencia estatistica encontrada entre os valores dos modulos de elasticidade para os elementos rolicos da especie Corymbia citriodora segundo abordagem numerica e analitica, constata-se a boa aproximacao de calculo fornecida pela equacao da resistencia dos materiais. Este resultado e valido apenas para os elementos rolicos aqui estudados, podendo ser diferentes para outras madeiras com diferentes conicidades.
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Evaluation of the Shear Effect to Determine the Longitudinal Modulus of Elasticity in Corymbia citriodora Round Timber Beams
International Journal of Materials Engineering, 2014Co-Authors: Andre Luiz Zangiacomo, Andre Luis Christoforo, Decio Gonçalves, Francisco Antonio Rocco LahrAbstract:This study aimed to investigate, based on three points static bending tests, the influence of ratio between length (L) and diameter (d) in structural round timber of Corymbia citriodora to determine the modulus of elasticity (MOE) using equations that do not consider shear influence in beam displacements. Non-destructive tests were carried out in 24 round pieces, medium length 750cm and average diameter 30 cm, moisture content around 12%. Modulus of elasticity for six different ratios (L/d) between length and diameter (9, 12, 15, 18, 21, 24) were determined, providing obtains six distinct values of MOE for each structural elements. Hypothesis tests results indicated equivalence of modulus of elasticity only to ratios (L/d) 24, 21 and 18. This implies that for proper use of the simplified equation to obtain MOE, based on static bending tests over structural round timber, it is necessary to respect L/h≥18 ratio.
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modulos de elasticidade longitudinal e transversal em vigas rolicas de madeira de Corymbia citriodora
Revista Vértices, 2013Co-Authors: Andre Luiz Zangiacomo, Andre Luis Christoforo, Francisco Antonio Rocco LahrAbstract:This study aimed to evaluate, with the support of the three points static bending test, led nondestructively, the values of the shear (G) and longitudinal (E) modulus of elasticity in Corymbia citriodora structural round timber beams in order to verify the validity of the G=E/20 relationship established by the Brazilian standard ABNT NBR 7190:1997 (Design of Wood Structures). The specimens tested (20) have an average length of 750 cm, diameter of 30 cm, moisture content of 12% and 5% of average taper. There were two bending tests per element, with differences in the distances between supports. In the first trial, we used the L/D ratio between the length (L) and diameter (d) of the pieces equal to twenty-four, while the second was conducted in sequence, with L/d equal to fifteen. The elasticity modulus were obtained according to the successive use of the equation of Timoshenko’s beam theory, which takes into account the influence of the shear efforts to determine displacements. The results between the shear and longitudinal modulus of elasticity were related by the least squares method, the relationship G=E/56 was found, which demonstrates divergent results with the Brazilian standard for the structural round timber investigated.
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modulos de elasticidade longitudinal e transversal em vigas rolicas de madeira de Corymbia citriodora shear and longitudinal modulus of elasticity in Corymbia citriodora round timber beams
2013Co-Authors: Andre Luiz Zangiacomo, Andre Luis Christoforo, Francisco Antonio, Rocco LahrAbstract:Este trabalho objetivou avaliar, com o auxilio do ensaio de flexao estatica a tres pontos, conduzido de forma nao destrutiva, os valores dos modulos de elasticidade longitudinal (E) e transversal (G) em pecas rolicas estruturais de madeira de Corymbia citriodora, de maneira a se verificar a validade da relacao G=E/20 estabelecida pela norma brasileira ABNT NBR 7190:1997 (Projeto de Estruturas de Madeira). As pecas testadas (20) possuem comprimento medio de 750 cm, diâmetro medio de 30 cm, teor de umidade de 12% e conicidade media de 5%. Foram realizados dois ensaios de flexao por peca, diferenciados apenas pelas distâncias entre os apoios. No primeiro ensaio, foi utilizada a relacao (L/d) entre comprimento (L) e diâmetro (d) das pecas igual a vinte e quatro, e no segundo, realizado na sequencia, com L/d igual a quinze. Os modulos de elasticidade foram obtidos de acordo com o emprego sucessivo da equacao da teoria de vigas de Timoshenko, que leva em consideracao a influencia dos esforcos cisalhantes no calculo dos deslocamentos. Os resultados obtidos entre os modulos de elasticidade longitudinal e transversal foram relacionados pelo metodo dos minimos quadrados, sendo encontrada a relacao G=E/56, evidenciando, para as pecas de madeira investigadas, a divergencia de resultados com a norma brasileira.
Pedro Gutemberg Alcântara Segundinho - One of the best experts on this subject based on the ideXlab platform.
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Nondestructive Evaluation of Corymbia citriodora Logs by Means of the Free Transverse Vibration Test
Journal of Nondestructive Evaluation, 2017Co-Authors: Marcelo Rodrigo Carreira, Antonio Alves Dias, Pedro Gutemberg Alcântara SegundinhoAbstract:The bending modulus of elasticity has been used as a wood quality predictor due to the good correlation between bending stiffness and strength. In recent years, there has been an increasing use of nondestructive testing techniques based on dynamic tests to assess wood quality. The objective of this study is to evaluate the results obtained with the application of transverse vibration test to measure the bending modulus of elasticity of Corymbia citriodora logs. The approach used estimated the log cylinders with the diameter equal to the diameter measured at half-length. A sample of 38 C. citriodora logs was tested in free transverse vibration and static bending tests, their diameter measured at half-length ranged from 13.6 to 20 cm and the length ranged between 4 and 4.4 m. A strong correlation ( $$\hbox {R}^{2} = 0.92$$ R 2 = 0.92 ) was found between static and dynamic bending modulus of elasticity. The transverse vibration test was faster than the static bending test. The results indicate that the free transverse vibration test provides accurate measurements of bending modulus of elasticity of C. citriodora logs.
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biological resistance of thermally treated Corymbia citriodora hook k d hill l a s johnson e pinus taeda l woods against xylophagous termites
Revista Arvore, 2016Co-Authors: Juarez Benigno Paes, Pedro Gutemberg Alcântara Segundinho, Allan Ewerton Rezende Euflosino, Marcio Rogerio Da Silva, Carlito Calil, Andre Luis ChristoforoAbstract:This research aimed to evaluate the effect of the thermal-treated temperature to improvement of Corymbia citriodora and Pinus taeda wood resistance to the xylophagous termite Nasutitermes corniger, into forced feeding assay. The wood thermally treated was performed at temperatures of 160, 180, 200, 220, 240oC. For Pinus taeda, the temperature of 260oC was also used. Three boards of 6 × 16 × 56 cm (thickness × width x length) were used for each temperature. After being thermally treated, the boards were transformed into samples of 2.54 × 2.54 × 0.64 cm (longitudinal × radial × tangential). The experiment was kept in a climatized room (25 ± 2oC and 65 ± 5% of relative humidity), for 28 days. For Corymbia citriodora, the thermal treatment at 220 and 240oC improved the resistance to the termite. For Pinus taeda, the resistance improvement occurred at 240 and 260oC. The temperature of 160oC caused a decrease in the natural durability of both species.
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Thermo-mechanical analysis of Corymbia citriodora wood subjected to thermal gradients.
Floresta e Ambiente, 2014Co-Authors: Marcos Oliveira De Paula, Gisele Rodrigues Moreira, Pedro Licio Loiola, Pedro Gutemberg Alcântara SegundinhoAbstract:Wood exposed to stress conditions, such as temperature gradients, may lead to collapse of installation structure. The rate at which wood becomes charcoal is crucial because of the reduction of the resistant section. This research aimed to evaluate the thermo-mechanical behavior of Corymbia citriodora wood subjected to temperature gradients and different exposure times, under different treatments (Varnish and CCB), in order to minimize the carbonization process. With respect to mechanical tests, it is possible to affirm that the increase in carbonization temperature and time of exposure of the samples resulted in a decrease in the compression strength parallel to the fibers of the material, causing brittleness. The treatments (Varnish and CCB) tested did not present satisfactory results with respect to combustion delay; therefore, they are not recommended for such purposes.
