Effect of Number of Laminae on Dynamic MOE of Glued Laminated Timber Composed of Homogeneous-Grade MSR Lumbers of Japanese Larch

摘要

The tapping method to measure Young's modulus of wood is useful for non-destructive evaluation of sawn lumbers. The dynamic MOE values are calculated from the resonance frequency of the tap tone with a FVF spectrum analyzer. However, if a glulam is used for a bending member such as a beam, it is not certain that the static MOE value of the glulam is equal to the dynamic MOE value. In case of glulams composed of sawn lumbers from juvenilewood, some adjustment to the dynamic MOE values may be necessary for use.In the present study, the relationship between static MOE (E_s) and dynamic MOE (E_d) was investigated, since it was expected that the variation of MOE in the cross section of homogeneous-grade glulams would be relatively small. Two types of specimens were used: glulams laminated horizontally (H-type) and vertically (V-type). Dynamic MOE was measured by longitudinal vibration (E_l) and flexural vibration, whose directions were horizontal (E_h) and vertical (E_v) in the direction of the adhesive face of the glulam.The results indicated that E_h/E_s in H-type and E_v/E_s in V-type were not influenced by the number of laminae. As Ii was supposed that E_l/E_h should be influenced by the number of laminae, the relationship between E_l and E_h was estimated by simple simulation for different numbers of laminae. The estimated ratios of E_l, E_h and E_v to E_s were almost identical with the experimental data.