Original paper(Vol.46 No.7 pp.839)
Effect of number of laminae on dynamic MOE of glued laminated timber composed of homogeneous grade MSR lumbers of Japanese larch
Takeda Takashi; Hashizume Takeo
Abstract: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 FFT 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 juvenile wood, some adjustment to the dynamic MOE values may be necessary for use.
In the present study, the relationship between static MOE (Es) and dynamic MOE (Ed) investigated, since it was expected that the variation of MOE in the craoss section of homogeneous-grade glulams would br\e relatively small. Two types of specimens were used: glulams laminated horizontally (H type) and vertically (V type). Dynamic MOE was measured by longitudinal vibration (El) and flexural vibration whose directions were horizontal (Eh) and vertical (Ev) in the direction of the adhesive face of the glulam.
The results indicated that Eh/Es in H type and Ev/Es in V type glulam were not influenced by the number of laminae. As it was supposed that El/Eh should be influenced by the number of laminae, the relationship between El and Eh was estimated by simple simulation for different numbers of laminae. The estimated ratios of El, Eh and Ev to Es were almost identical with the experimental data.
Key Words:homogeneous-grade composition, dynamic MOE, static MOE, vertically laminated timber, horizontally laminated timber