Evaluation of Stiffness in Compression Perpendicular to Grain of Brazilian Tropical Wood Species

It is essential to have full knowledge of wood properties, such as strength and stiffness, for the preparation of reliable structural designs. The Brazilian Code ABNT NBR 7190 (1997) establishes that the modulus of elasticity in compression perpendicular to grain (Ec90) can be obtained in a simplified way, in the absence of experimental determination, by means of a correlation with the modulus of elasticity in the direction parallel to grain (Ec0 = 20 Ec90). In order to verify the adequacy of this expression, the results obtained for five species of wood, covering the strength classes assumed by the mentioned Code were analyzed: Cambará Rosa (Erisma sp.), C20; Cedro Amazonense (Cedrella sp.), C30; Cupiúba (Goupia glabra), C40; Itaúba (Mezilaurus itauba), C50; Roxinho (Peltogyne sp.), C60. For each species, from the tests prescribed by ABNT NBR 7190, the elastic moduli were obtained in the directions parallel and normal to grain. In the evaluation of the precision of the proposed estimation, the least squares method was used to determine the coefficient α of the investigated relation. For the data set involving the five species studied, the coefficient resulted in α = 20.64. This value is compatible with the correlation proposed by the Brazilian standard, evidencing its reliability.