© 1995 Oxford University Press
RESEARCH-ARTICLE |
Twist-to-bend ratios of woody structures
Department of Zoology, Duke University Durham, NC 277080325, USA
1+ 1 91968461688. E-mail: svogel{at}acpub.duke.edu
Flexural rigidity (El), or resistance to bending loads, and torsional rigidity (GJ), or resistance to twisting loads, were measured on a variety of woody structures-bamboo culms, three kinds of hardwood trunks, two softwood trunks, two vines, and pine roots. The ratios of these rigidities, EI/GJ, was highest and relatively constant for bamboo and hardwoods, slightly lower for softwoods, and lower still for vines and roots. All values were substantially above those for circular cylinders of ordinary isotropic materials; since all specimens were nearly circular in cross-section, the high values reflect the elastic moduli of wood rather than geometric factors. While all material showed substantial creep under torsional loading, only the vine, Wisteria, crept appreciably under flexural loading as well.
Key words: Wood, trees, flexural rigidity, torsional rigidity, biomechanics
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