Quantification of spatial variability for transverse elastic modulus of spruce wood

Different factors such as age, location of timber within the tree, structural imperfections, load history such as wind and snow etc. can affect the material properties of timber. Consequently, there is a high variability in the mechanical properties which is sometimes referred to as ‘random spatial variability’. In this work, the spatial variability of the transverse elastic modulus of clear spruce wood is quantified by conducting mechanical tests. Specimens of 120 mm nominal length with a small cross-sectional area were prepared and their quasistatic behavior was experimentally investigated under tensile loading. In addition to the global displacement monitoring, the local deformations along the length of each specimen were measured. Using these data, the spatial variability of the elastic modulus was experimentally characterized in both longitudinal and transverse directions. Variability coefficients were defined to quantify the variability in both directions. Also, the effect of the mesostructure of the clear timber on the local elastic modulus was examined. The results show a very significant spatial variability in the transverse elastic modulus, more 1000% within some specimens. The variability of the transverse elastic modulus is much higher in the transverse direction. The grain angle has the most important effect on the value of the local elastic modulus. The results of this work can be considered as part of establishing advanced stochastic models with ransom spatial variability for timber structures.