The bending properties of Siberian spruce [Picea jezoensis], 2: The influence of moisture content on the bending properties
1999
Nakatani, H.(Toyama-ken. Forestry and Forest Products Research Center, Imizu (Japan)) | Sakai, T. | Hashimoto, A. | Hata, M.
In this report, the effect of moisture contents on the bending performance of Siberian spruce timber has been studied. We carried out bending tests of 10.5cm square timber under 3 moisture contents level (D15, D20, green). Numbers of specimens were 45 in each moisture levels, and were prepared having the same distribution of strength properties. Results are summarized as follows. 1) The bending properties of Siberian spruce increased 16% in their Young's modulus and 40% in bending strength in drying to MC 15% from green. This value in bending strength is very large compared with the value (23%) calculated from the adjustment formula in ASTM. 2) Young's modulus by longitudinal vibration method begins to change from 25% moisture content. 3) The nonuniformity of moisture distribution in a section has a small influence on Young's modulus. But the bending strength is influenced largely by moisture content of the outer layer. 4) We show following formulae like that in ASTM for adjustment of the effect of moisture content. E1/E2 = (1.4-0.015MC1)/ (1.4-0.015MC2), sigma1/sigma2 = (2-0.04MC1')/ (2-0.04MC2'): MC1, MC2: average moisture content in a section. MC1', MC2': moisture content of outer layer. E1, E2: Young's modulus with moisture content of MC1 or MC2. sigma1, sigma2: Bending strength with moisture content of MC1' or MC2'. These formulae can be used under 25% moisture content in Siberian spruce timber with the pith. If moisture content is over 25%, then it can change to 25%.
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