Aspects of the Difference between the Local and Global Modulus of Elasticity of Structural (hardwood) Timber

The modulus of elasticity of structural timber (MOE) may be determined by 2 methods according to the European standard EN 408 [1]. The ratio between the so-called local and global MOE that is found from tests according to these two methods, cannot be explained by the ratio between the MOE and shear modulus G that is assumed in the strength class tables of EN 338 [2]. The relationship between MOE

local

and MOE

global

from EN 384 [3] is not consistent with the shear values given in [2]. In this study the shear modulus for samples of the tropical hardwood species massaranduba and of softwood species spruce was determined. The shear modulus G was found to be not related to the MOE and was shown to be constant at around 550 N/mm

2

for massaranduba and 190 N/mm

2

for spruce. With these values, the ratios between MOE-local and MOE-global that were found in the test series could be explained. The found values for the shear moduli differ from previous research. The study concludes that it is unclear which parameters determine the magnitude of the shear modulus of a single piece of timber and that this needs to be investigated.