Rejane Costa Alves

Resistência natural da madeira de Tectona grandis em ensaio de laboratório

This research aimed to evaluate the natural resistance of teak wood (Tectona grandis) to xylophagous fungi and termites in laboratory conditions. It was used trees with fifteen years old, from a plantation of the Forest Enterprise Celulose Nipo Brasileira - CENIBRA S.A., located in Belo Oriente, Minas Gerais State, Brazil. To determine the natural resistance of teak wood in laboratory were employed the Postia placenta, Neolentinus lepideus, Polyporus fumosus and Fomes connatus fungi and to termites resistance was employed the feeding preference assay with subterranean termites Nasutitermes sp. Samples were taken from four positions in the stem (heartwood near the pith, heartwood intermediate, outer heartwood and sapwood) at 1,30m to soil level and submitted to the action of fungi for thirteen weeks and termites for 45 days. It was found that the heartwood of teakwood from the Vale do Rio Doce, Minas Gerais State, Brazil was highly resistant. The internal heartwood was less resistant than the other portions of the heartwood to action of wood decay agents, while the sapwood was classified as moderately resistant (Polyporus fumosus) or resistant (Postia placenta and Neolentinus lepideus).

Propriedades Físicas da Madeira de Eucalyptus cloeziana F. Muell

We analyzed the wood physical properties of 70 Eucalyptus cloeziana trees, approximately 10 years old, from forests located in the Midwestern region of Minas Gerais. Moisture, basic and apparent density and shrinkage were determined. The samples showed mean values of 703 kg/m3, 843 kg/m3 and 916 kg/m3 for basic density, dry bulk density and apparent density at 12% moisture, respectively. Concerning the radial, tangential and axial shrinkage were found with average values of 7.08; 11.16 and 0.26%, respectively. The average volume shrinkage was 19.68%, and the anisotropic ratio of 1.60, thus the timber is considered stable dimensionally.

A Study of Adobes Made with No Usual Soils Concerning Grain Size Distribution Test

This article presents and discusses an adobe production with shows a clay/silt/sand proportion that is completely different from that recommended by most authors and construction associations. The main objective was to improve comprehension of earth behaviors as building material by studying these two atypical cases of adobe production. The soil was analyzed by different tests as the grain size distribution test and Atterberg limits. Adobe resistance was tested using a methodology proposed by Proterra network which was created by a group of researchers from different Iberian American laboratories. This methodology was used in Ph.D. thesis, too. The results show a soil with 1% clay and 65.1 silte and an average of resistance of 2.11 MPa for the adobes. These results show the importance of the clay mineral structure and the complexity of the soil behavior, indicating the need for additional studies.

Influences of Scarf-Joint of the Laminae in the Strength and Elasticity of Glued Laminated Timber Beams

The objective of this work is to determinate the influence of the scarf-jointed in the strength and the modulus of elasticity of the glued laminated timber beam. To determine this influence, several tests with the outer laminae with scarf-joint and the bevel with different inclinations has been made. The models were made of Parana Pine, Araucaria angustifolia. For the tests were performed three points bending. With the load values and the deflection at mid-span and by linear regression were determined the effective elastic modulus. The results indicate that the performance is reduced considerably in the presence of a scarf-joint in the external laminae and also the reduction is greater when the scarf angle increases.

Influência da densidade na velocidade de propagação da onda em sete espécies de madeira tropicais

A tomografia acustica aplicada em pecas de madeiras permite que seja determinada sua secao transversal por meio do principio fisico de emissao e de percurso de ondas acusticas. No entanto os valores da velocidade de propagacao sofrem influencia de alguns fatores, dentre eles, a densidade da madeira. Foram avaliadas sete especies de madeiras tropicais por meio do equipamento tomografo acustico Fakopp 3D. Toda a metodologia destrutiva experimental seguiu as prescricoes da NBR 7190/97, tendo sido realizados os ensaios de densidade e teor de umidade. O trabalho tem como objetivo analisar a influencia da densidade aparente na velocidade de propagacao de onda em sete especies de madeiras tropicais, com densidade variando de 650 a 1150 Kg.m-³. Como resultado foi verificado que os valores de velocidade de propagacao da onda nas madeiras diferenciaram-se entre si. Isto foi verificado pelo teste de Tukey a 95% de probabilidade. Os maiores valores foram encontrados para a madeira de garapa e os menores valores para a madeira de muiracatiara. O coeficiente de determinacao entre a velocidade de propagacao da onda e a densidade aparente dos corpos-de-prova foi 58%.