André Luiz Zangiácomo

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.

Emprego de ferramentas numéricas na avaliação do módulo de elasticidade em vigas roliças de madeira

Beams are structural elements used in the most of civil constructions. The wood can be found in several applications of engineering due to the moderate mechanical strength and low density. The use of round timber as a beam is very attractive, since it does not need to be processed, such as lumber. The design of structural timber elements requires the determination of its physical and mechanical properties in which are obtained based on the recommendations of engineering standards. In case of round timber, the national standards dealing with the determination of strength and stiffness properties are in term for more than twenty years with no technical review. Overall, both national and international standards consider truncated-cone geometry for cylindrical logs of wood, resulting in simplified equations unable to predict the effect of shape irregularities on the longitudinal modulus of elasticity. This paper aims to evaluate the effect of shape irregularity of round timber of Corymbia citriodora and Pinus caribaea to determine the longitudinal modulus of elasticity. The three-point bending test is used to determine the modulus, considering a simplified analytical model, with constant circular section for the element. The irregularities of the wood are considered in the numerical models based on a beam and three-dimensional finite elements. The results showed statistical equivalence between the modulus of elasticity for both methods of calculation, indicating that the constant circular section is a reasonable assumption for the wooden here evaluated.

Módulo de elasticidade aparente em vigas roliças estruturais de madeira Pinus elliottii

Este trabalho investiga, com o auxilio da norma brasileira ABNT NBR 7190:1997 (Projeto de Estruturas de Madeira) e do ensaio de flexao estatica a tres pontos, a influencia das medidas entre o comprimento (L) e o diâmetro (d) de pecas estruturais de madeira rolica da especie Pinus elliottii no calculo do modulo de elasticidade (MOE). Foram ensaiadas, de forma nao destrutiva, 24 pecas de madeira (verde) com comprimento medio de 750 cm e diâmetro medio de 30 cm. Para tanto, foram determinados os valores dos modulos de elasticidade para seis relacoes (L/d) distintas entre comprimento e diâmetro (9; 12; 15; 18; 21; 24), fornecendo seis valores distintos de MOE por peca utilizada. Os resultados da analise de variância indicaram equivalencias dos modulos de elasticidade apenas entre as relacoes L/d iguais a 24, 21, 18 e 15, revelando ser de 15 o menor valor da relacao responsavel por minorar significativamente o efeito das forcas cisalhantes. Isso implica que, para o uso adequado da equacao de calculo do modulo de elasticidade pela norma brasileira para as pecas de rolicas de madeira Pinus elliottii, faz-se necessario respeitar a relacao L/d≥15.