Bending and shear properties of compressed Sitka spruce |
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Authors: | Hiroshi Yoshihara Shogo Tsunematsu |
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Institution: | (1) Faculty of Science and Engineering, Shimane University, Nishikawazu-cho 1060, Matsue, Shimane 690-8504, Japan |
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Abstract: | We examined the bending and shear properties of compressed wood using small and clear specimens of Sitka spruce (Picea sitchensis Carr.). For measuring the bending properties, three-point bending tests were conducted under the span/depth ratio of 14,
which is standardized in the American Society for Testing and Materials ASTM D143-94 (2005a)] and Japanese Industrial Standards
JIS Z2101-94 (1994)]. In the bending test, the load, deflection at the midspan, and strain at the bottom of the midspan were
simultaneously measured, and Young’s modulus and bending strength were obtained by elementary beam theory. For obtaining the
shear modulus and shear strength, asymmetric four-point bending tests were conducted using the specimens with rectangular
and side-grooved cross sections, respectively, and the influence of the compression ratio on the shear properties was examined.
The results are summarized as follows: (1) Young’s modulus increased with increasing compression ratio when it was determined
by the load–strain relation. Nevertheless, this tendency was rather obscured when Young’s modulus was determined by the load–deflection
relation. Hence, it is preferable that Young’s modulus is measured from the load–strain relation. (2) The shear modulus in
the longitudinal–tangential plane was maximum at the compression ratio of 50%, whereas that in the longitudinal–radial plane
was minimum at the compression ratio of 50%. (3) The influence of the compression on the bending and shear strength ratio
was not significant. |
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