Dynamic excitation and FE analysis to assess the shear modulus of structural timber

A total of 99 Silver fir lumbers were tested by means of torsional vibration, to calculate the shear modulus; and free–free flexural vibration, to calculate the Modulus of Elasticity. The first five frequencies of vibration in bending were recorded and used to evaluate the shear modulus by finite elements approach. The present work shows that, thanks to flexural vibration test, it is possible to predict the torsional shear modulus using the Modulus of Elasticity and the first five frequencies of vibration deduced from flexural vibration tests (r2 = 0.66, with high significance level). At present this work is the first one able to predict the shear modulus on structural lumber instead of small specimens, and the work is validated by comparing the results to the shear modulus calculated using another technique (torsional vibration test). This work has an important practical significance since it is carried out on structural lumber. The proposed method offers the possibility to predict the shear modulus with higher accuracy if compared to theEuropean standard EN338, suggesting that flexural excitation test can be used in practice for more accurate shear modulus prediction.