Shear and Longitudinal Modulus of Elasticity in Structural Lumber Beams

Abstract

This study aimed to present, with the aid of the four points static bending, conducted nondestructively, analytical methodology to determine the longitudinal (E) and shear modulus (G) of elasticity in lumber beams. The woods used were Manilkara spp and Pinus elliottii. Were used three different values to the form factor coefficient of the rectangular cross section, allowing evaluating the differences between the shear stiffness values obtained by wood species. The results of the analysis of variance indicated statistical equivalence between shear modulus of elasticity for the two wood species investigated, unless revealing significant the influence of the form factors used to determine the shear modulus of elasticity. The coefficients of the relationship between the modulus of elasticity (E=λ·G) obtained from the least squares method were equal to 37 and 33 to the woods Manilkara spp and Pinus elliottii, be revealing 85% and 65% higher respectively then the relationship (E=20·G) presented in the Brazilian standard ABNT NBR 7190. It is emphasized that these results may be different for the same or different wood species, justifying the use of this methodology in each work developed.