Abstract: Engineered wood products need alternatives of raw materials to their production. The hybrid Eucalyptus urograndis has great potential to supply the demand of this industrial sector. In this context, the present paper aims to analyse the feasibility of using Eucalyptus urograndis in glued laminated timber (glulam) production. To this end, four groups with ten glulam beams each, were produced and tested. An extensive experimental program was performed in order to determine: the stiffness and bending strength of the beams; and the compression strength parallel to grain of the beams. The performance of structural adhesives was verified based on shear tests of glue lines. The experimental mean of stiffness was higher than 14675 MPa and the characteristic value of compression strength parallel to grain achieved a value above 40 MPa. Nevertheless, failure mode of the glulam beams showed that finger-joints reduced bending strength. The glulam beams produced with Eucalyptus urograndis proved to be a feasible alternative due to their mechanical properties. However, this material presents difficulties in finger-joints adhesion.

ABSTRACT CLT (Cross Laminated Timber) is a pre-fabricated engineered wood panel, generally made from conifer woods, mainly pine and spruce. Due to the low natural resistance of this species to deteriorating organisms attack, the Brazilian standard ABNT NBR 7190:1 (2022) orients the treatment of structural elements before being used. This study aimed to evaluate the resistance of woods from Pine and Spruce species, with different preservative treatments and retentions, against wood termite (Cryptotermes brevis) attack. Different species of Pine and Spruce (Pinus abies, Pinus sylvestris, Pinus elliottii e Pinus taeda) were evaluated, as well as different preservatives such as Impralit KDS-B, CCA (Chromated Copper Arsenate), CCB (Copper Borate Chromated), MCA-C (Micronized Copper Azol type C) and HQC 791 (fire retardant for wood), usually used in Brazil, the United States and Europe. The results demonstrated that the fire retardant induced greater resistance to attack by xylophagous organisms, with total insect mortality and no surface deterioration after 45 days of testing. The CCA preservative also demonstrated efficiency in wood treatment with high resistance to termite attack, high mortality and only superficial wear of the specimen. It was concluded, therefore, that preservative treatments are recommended to guarantee the durability of the constructive system so that the so-called engineered wood elements can be used as structural systems.

RESUMO CLT (Cross Laminated Timber) é um painel de madeira engenheirado pré-fabricado, geralmente feito de madeiras de coníferas, principalmente pinus e abeto. Devido à baixa resistência natural desta espécie ao ataque de organismos deteriorantes, a norma brasileira ABNT NBR 7190:1 (2022) orienta o tratamento de elementos estruturais antes de serem utilizados. Este trabalho teve como objetivo avaliar a resistência de madeiras das espécies Pinus e Spruce, com diferentes tratamentos conservantes e retenções, ao ataque do cupim xilófago (Cryptotermes brevis). Diferentes espécies de pinus e abeto (Pinus abies, Pinus sylvestris, Pinus elliottii e Pinus taeda) foram avaliadas, bem como diferentes conservantes como Impralit KDS-B, CCA (Chromated Copper Arsenate), CCB (Copper Borate Chromated), MCA- C (Azol de Cobre Micronizado tipo C) e HQC 791 (retardante de fogo para madeira), normalmente utilizados no Brasil, Estados Unidos e Europa. Os resultados demonstraram que o retardante de fogo induziu maior resistência ao ataque de organismos xilófagos, com mortalidade total dos insetos e sem deterioração da superfície após 45 dias de teste. O conservante CCA também demonstrou eficiência no tratamento da madeira com alta resistência ao ataque de cupins com alta mortalidade e desgaste apenas superficial do corpo de prova. Concluiu-se, portanto, que para garantir a durabilidade do sistema construtivo são recomendados tratamentos preservativos para que os chamados elementos de madeira engenheirada possam ser utilizados como sistemas estruturais.

Created in the 1940s, the splice finger-joint type for wood has now been more used to compose structural materials wood base as Glued Laminated Timber (Glulam) and Cross Laminated Timber (CLT). The main advantage of this amendment is to provide a simple and economical way to join timber parts on segments. This study evaluated by means of tensile tests the capacity of this type of joint (structural dimension of 21mm) to bond together Lyptus® wood beams (a Eucalyptus grandis and Eucalyptus urophyla hybrid) using Jowat polyurethane glue (Model 680.20) as compared to similar seamless beams. The results indicate that the seamless beams are 47.72% more resistant to traction (in characteristic values) than those with finger joints. However, to form structural elements where there is redundancy overlapping parts, such as Glulam and CLT, the values obtained can be considered satisfactory. Also noted is that denser samples have better traction results due to better bonding of the densest parts. The use of finger-joint and polyurethane adhesive o bond hybrid eucalyptus, although more brittle than wood without seams, enable the use of shorter wood sections for the composition of major structural elements, optimizing better forest material.

RESUMOO módulo de elasticidade na compressão paralela às fibras (Ec0) é um dos parâmetros de referência para estimar o desempenho da madeira. O Anexo B da Norma Brasileira ABNT NBR 7190:1997 estabelece, nos ensaios para determinação do Ec0, que seja tomada a medida de deformações em pelo menos duas faces opostas dos corpos de prova. O objetivo deste trabalho foi verificar a influência dessas condições de ensaio nos valores de Ec0. Tal propriedade foi determinada a partir das deformações de duas faces opostas dos corpos de prova e, em seguida, a partir das deformações obtidas nas faces complementares. Foram utilizadas espécies de madeira de forma a abranger todas as classes de resistência assumidas pela citada norma. Os resultados indicam significativa variação de Ec0determinado nos ensaios referidos, evidenciando que tal situação deve ser considerada para futura revisão dos métodos de ensaio para determinação de propriedades da madeira para aplicação estrutural.

ABSTRACTThe modulus of elasticity in compression parallel to the grain (Ec0) is a reference parameter to estimate the performance of the timber. Annex B of the Brazilian Code ABNT NBR 7190:1997 establishes, for determining the Ec0, to measure deformations at least on two opposite sides of the specimens. The aim of this study was to assess the influence of these test conditions in Ec0 values. This property was determined based on two opposite sides deformations of the specimens, and then, from the deformations obtained in complementary sides. Wood species were used to cover all strength classes assumed by this standard. Results showed a significant variation of Ec0 determined in mentioned tests, demonstrating that such a situation should be considered for future revision of the test methods for the determination of wood properties for structural application.

Wood is a natural material and so many factors interfere in estimation of its physical and mechanical properties. Consequently variability in properties should be taken into account to rationalize its application. Longitudinal modulus of elasticity is one of the main mechanical properties of the material, and its value can be obtained via standardized tests. The aim of this study is to evaluate the influence of test conditions compatible with ABNT NBR 7190:1997 Code requirements to determine modulus of elasticity in static bending. For each of eight species, eight specimens were tested, all of them four times, with the sample oriented on each of its four faces related to load application. Data analysis was performed independently of species and their respective strength class, using hypothesis testing to evaluate influence of specimens’ orientations to determination. It was concluded that specimen orientation is significant in determining modulus of elasticity in static bending according to ABNT NBR 7190:1997. This aspect can lead to a future normative review by the National Committee responsible by redaction of this Code. To represent natural variability of wood in specimens’ volume by only one bending test, values of the modulus of elasticity should be lessened in 8%.

A utilização da madeira em estruturas está vinculada a condições que permitam sua utilização por muitos anos sem a perda de suas propriedades de resistência e de rigidez. Entretanto, por se tratar de material natural, as estruturas em madeira projetadas podem estar sujeitas ao ataque de agentes biológicos, ação de intempéries, entre outros fatores, requerendo soluções na forma de reparo ou reforço. O presente trabalho objetivou investigar a influência do uso de resina epóxi como agente reparador em vigas danificadas de madeira de Pinus elliottii no cálculo do produto de rigidez à flexão. Para tanto, foi realizado um planejamento experimental completo, tendo a posição dos defeitos provocados (central ou laterais), o uso ou não da resina nos defeitos, e a posição desses defeitos (superior - compressão ou Inferior - tração) como fatores. Os resultados da análise estatística revelaram que o uso da resina epóxi nas regiões danificadas das vigas apresentaram valores do produto de rigidez na flexão significativamente superiores quando comparados com as vigas da condição com defeito e sem a resina epóxi. Mesmo sendo significativo o uso da resina nas regiões danificadas, o produto de rigidez à flexão das vigas reparadas foi inferior ao produto de rigidez à flexão das vigas sem defeito (referência), evidenciando a necessidade de outros estudos com outras resinas e outros materiais visando à recuperação total da rigidez da peça de madeira danificada.

The use of wood in structures is linked to conditions that allow its use for many years without losing its strength and stiffness properties. However, since it is a natural material, wood engineered structures may be subject to attack by biological agents, and weathering action, among other factors, requiring solutions for repair or reinforcement. The aim of this research study is to investigate the influence of using epoxy resin as a healing agent for damaged Pinus elliottii wooden beams in the calculation of bending stiffness for the product. Therefore, a comprehensive experiment was performed, considering the position of caused defects (central and sides), the use or not of resin in the damaged regions, and the position of these damages (superior - compression or inferior - tensile) as factors. The results of the statistical analysis revealed that the use of epoxy resin in the beam damaged regions provided a bending stiffness significantly higher when compared to damaged beams without the epoxy resin. Despite being significant the use of the resin in the damaged regions, the bending inertia of the repaired beams was smaller compared to the beams without damage (reference), pointing out the need for further studies with other resins and materials in order to obtain full recovery of the stiffness in the damaged wood.