Determination of shear modulus on construction size timber

Shear modulus determination of construction size timber was examined. Three different Techniques were used: torsional vibration, simultan E&G, and variation of span technique. We found that the simultan E&G technique is quite sensitive to the error of natural frequency determination and provides only an estimate for G. Better shear modulus determinations are the static and torsional techniques, but the torsional technique is most precise. The torsional vibration technique can be a good solution for shear modulus determination in an industrial environment because it provides quick and precise etermination, but standardization of the method would first be necessary. We found a high correlation coefficient (0.80) between the screw withdrawal resistance and shear modulus of 2 by 4 timber. Based on this result it is possible to estimate the shear modulus of timber even if the timber is installed in a structure.