Predicting Tensile and Compressive Moduli of Structural Lumber

Abstract

Nondestructive bending modulus of elasticity (MOE) of lumber is commonly used as input data to estimate mechanical properties of glued lumber or laminated timber components. Many standard and nonstandard test methods exist to determine MOE. However, when glued components are loaded, the stresses imposed on the lumber subcomponents are quite different from stresses used in determining MOE of the lumber. It is well known that the bending MOE of lumber is somewhat different from its tensile and compressive moduli. Therefore, defining the differences and relationships between bending MOE and tensile and compressive moduli is important. This study predicted the tensile and compressive modulus from dynamic and static bending MOE of major softwood structural lumber in Korea. The measured MOE and tensile and compressive moduli from the same specimens by various test methods were found to differ. In particular, the tensile modulus was twice the compressive modulus for the same specimen. Edgewise bending MOE, which showed the highest correlation with tensile and compressive moduli, was suggested as a suitable input parameter for predicting tensile and compressive moduli. Predicting tensile and compressive moduli from dynamic or flatwise bending MOE of structural lumber is also possible, although with a different relationship. With better prediction of tensile and compression moduli, it is expected that the properties of engineered wood or timber structures can be more accurately estimated.