Analysis Of Off-Axis Tension Test Of Wood Specimens

Jen Y. Liu


This paper presents a stress analysis of the off-axis tension test of clear wood specimens based on orthotropic elasticity theory. The effects of Poisson's ratio and shear coupling coefficient on stress distribution are analyzed in detail. The analysis also provides a theoretical foundation for the selection of a 10° grain angle in wood specimens for the characterization of shear properties. The Tsai-Hill failure theory is then applied to derive a formula for predicting shear strength. Existing strength data for Sitka spruce (Picea sitchensis Carr.) were used in a numerical analysis. Because of the large discrepancies in published test data from different sources, the accuracy of the formula is limited to the data used to derive it. However, the procedures are believed to be accurate. The off-axis tension test is attractive mainly because of its economy and ease of application. This research promises to pave the way for the adoption of the off-axis tension test for characterizing the shear properties of clear wood by the practicing engineer once representative input data become available.


Off-axis tension test;orthotropic elasticity;shear strength;tensile strength;Tsai-Hill failure theory

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