Pedro Gutemberg de Alcântara Segundinho

Evaluation of glued laminated timber beams of cedrinho (Erisma uncinatum Warm.)

Glued laminated timber (glulam) is assembled layers of bonded pieces of timber. In Brazil, the use of native species timber to produce structural elements of glulam does not occur in satisfactory technological conditions. This is because the properties and performance of native species of wood, under various service conditions, are not entirely known. This study aims at determining and to relate the dynamic modulus of elasticity (E Mvt ) and the static modulus of elasticity (E M ), the modulus of rupture (f M ), the compression parallel strength (σ cp ) and the parallel elastic modulus (E cp ), and evaluating the performance of the native species Cedrinho (Erisma uncinatum Warm.) in the construction of glulam beams. Glulam beams were produced with random and nonrandom distributions of graded pieces of bonded lumber by using adhesives of phenol resorcinol formaldehyde (RFF) and polyurethane (PUR); the intensity of pressures used was 0.8 MPa and 1.2 MPa. The evaluation of these glulam beams was also performed using samples of compression parallel to glue lines and delamination. It was found that the E Mvt obtained by transverse vibration dynamic testing revealed a correlation coefficient with the E M obtained on static bending test (R 2 = 0.86) and significance level of 1% probability (P < 0,01). Thus, it can observed that the E Mvt is a good estimator of E M. It was found that this wood species may be used for glulam, and that the hardwoods species is in strength class C30.

Avaliação do módulo de elasticidade de peças de madeira laminada colada (MLC) obtido por meio do ensaio de vibração transversal

O controle da qualidade e fundamental no processo de fabricacao de pecas de madeira laminada colada (MLC), e uma das formas desse controle pode ser por meio da avaliacao nao destrutiva do modulo de elasticidade. O objetivo deste trabalho foi comparar os valores de modulo de elasticidade das pecas de MLC obtidos por meio do ensaio de vibracao transversal livre e do ensaio de flexao estatica, ambos feitos antes e apos tratamento preservativo (contra a acao de agentes biologicos), realizado pelo processo de Celula Cheia. No total, foram produzidas 54 pecas de MLC de dimensoes nominais de 9 cm x 9 cm x 200 cm, com tres especies de madeira de reflorestamento coladas com dois adesivos de aplicacao estrutural e tratadas com tres preservantes. Foi obtida uma correlacao significativa entre os valores do modulo de elasticidade obtidos pelos dois metodos (r variou entre 0,85 e 0,99). Concluiu-se que o ensaio de vibracao transversal livre pode ser utilizado para avaliacao do modulo de elasticidade de pecas de MLC, sendo uma alternativa ao ensaio de flexao estatica.

Aplicação do método de ensaio das frequências naturais de vibração para obtenção do módulo de elasticidade de peças estruturais de madeira

There are several techniques to characterize the elastic modulus of wood and those currently using the natural frequencies of vibration stand out as they are non-destructive techniques, producing results that can be repeated and compared over time. This study reports on the effectiveness of the testing methods based on the natural frequencies of vibration versus static bending to obtain the elastic properties of reforested structural wood components usually employed in civil construction. The following components were evaluated: 24 beams of Eucalyptus sp. with nominal dimensions (40 x 60 x 2.000 mm) and 14 beams of Pinus oocarpa with nominal dimensions (45 x 90 x 2.300 mm) both without treatment; 30 boards with nominal dimensions (40 x 240 x 2.010 mm) and 30 boards with nominal dimensions (40 x 240 x 3.050 mm), both of Pinus oocarpa and with chromate copper arsenate (CCA) preservative treatment. The results obtained in thiswork show good correlation when compared to the results obtained by the static bending mechanical method, especially when applying the natural frequency of longitudinal vibration. The use of longitudinal frequency was reliable and practical, therefore recommended for determining the modulus of elasticity of wood structural elements. It was also found that no specific support is needed for the specimens using the longitudinal frequency, as well as no previous calibrations, reducing the execution time and enabling to test many samples.

Thermo-mechanical analysis of Corymbia citriodora wood subjected to thermal gradients

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.

VARIAÇÃO DOS MÓDULOS DE ELASTICIDADE E RUPTURA EM MADEIRA DE CEDRO-AUSTRALIANO POR MEIO DE ENSAIOS NÃO DESTRUTIVO E DESTRUTIVO

The elastic of modulus is an important mechanical property in the design of timber structures, so obtaining it through several methods needs to be evaluated. This study aimed to evaluate the use of an efficient technique for determining the apparent longitudinal modulus taking into account the relationship range/height ( L/h ) and the influence of the shear modulus by comparing non-destructive tests with static bending tests. The wood used in paper was Toona ciliata M. Roemer (Australian cedar). Non-destructive tests were performed with the techniques of longitudinal and transverse vibration. It was concluded that the assay of longitudinal vibration is most suitable method to obtain the apparent longitudinal elasticity modulus, because the shear forces that occur due to the shear stresses are not significantly influenced by the variations of the ratio L/h . It was also possible to conclude that the relationship range/height, currently 21 in ABNT’s standards, may be replaced by 20, when determining apparent longitudinal elasticity modules and modulus of rupture, through the static bending and free transverse vibration tests.

Influências do Diâmetro e Umidade da Madeira na Qualidade do Tratamento Preservativo

Were evaluated the effects of moisture content and diametric class in industrial treatment quality of Corymbia torelliana and Eucalyptus grandis x Eucalyptus urophylla fence posts. 108 fence posts were used, 36 treated and 18 non-treated, with 2.20m long and moisture content of 15 to 20%; 20 to 30%; and 30 to 40% and diameters of 8 to 10cm; 10 to 12cm; 12 to 14cm. For treatment, were used 2% active ingredients of CCA-C, initial and final vacuum 550 mmHg (30min), pressure of 11 kgf cm-2 (1h). The fence posts were evaluated by electric meter that was adequate to estimate the moisture. Satisfactory penetrations were obtained and the biggest retention was reached in fence posts with moisture of 15 to 20% (8.23 kg m-3), however, the moisture content of 30 to 40% was also suitable for the treatment of wood, getting values higher than 6.5 kg m-3.

BIOLOGICAL RESISTANCE OF THERMALLY TREATED Corymbia citriodora (Hook.) K.D. Hill & L.A.S. Johnson E Pinus taeda L. WOODS AGAINST XYLOPHAGOUS TERMITES

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.

Proposta para estimar curva carga-recalque e capacidade de carga em estacas de madeira

Este trabalho teve como objetivo propor um metodo para estimar a curva carga-recalque e a capacidade de carga de estacas de madeira a partir do ajuste de equacoes de regressao nao lineares utilizando o metodo de Gauss Newton modificado. Para isso, foram utilizados dados experimentais obtidos para 12 estacas de madeira, curvas carga-recalque durante a cravacao e capacidade de carga determinada no ensaio de carregamento dinâmico, utilizando modelo teorico. Nesta pesquisa, realizada de forma pioneira no Brasil, fez-se a analise do comportamento de estacas de madeira imersas no solo durante a cravacao delas. As medias do erro percentual absoluto medio foram 4,0% e 29,3%, obtidas a partir das equacoes nao lineares ajustadas via metodo de Gauss Newton modificado e proposto por Van Der Veen respectivamente. Concluiu-se que as equacoes ajustadas via metodo de Gauss Newton modificado conduziram a uma maior exatidao nas estimativas, apresentando boa concordância com os dados experimentais obtidos nos ensaios de carregamento dinâmico, indicando sua utilizacao para estimar a curva carga-recalque e a capacidade de carga em estacas de madeira.