Mechanical Grading of Round Timber Beams
Publication: Journal of Materials in Civil Engineering
Volume 18, Issue 1
Abstract
Current procedures used to sort round timber beams into structural grades rely on visual grading methods and property assignments based on modification of clear wood properties. This study provides the technical basis for mechanical grading of 228 mm (9 in.) diameter round timbers. Test results on 225 round Engelmann spruce–alpine fir–lodgepole pine beams demonstrate the conservative nature of current timber strength assignments. A good correlation was obtained between static bending strength and static modulus of elasticity (MOE), and between bending properties and dynamic MOE determined in transverse vibration. Relationships were also developed between compressive strength parallel to grain, bending strength, and MOE by transverse vibration. The property relationships developed in this study were used to propose grading criteria consistent with procedures used with mechanically graded softwood dimension lumber. Estimated grade yields obtained using the proposed criteria show that significant increases in yield might be obtained for a specified set of allowable properties than is currently possible by visual grading alone.
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Acknowledgments
The writers acknowledge the interest and assistance of Rocky Mountain Log Homes (Hamilton, Mont.) and Timber Products Inspection (Conyers, Ga.) in the completion of this research. The cooperation of the Wood Materials and Engineering Laboratory at Washington State University (Pullman) in conducting the static bending tests is also appreciated. Thanks are due Cherilyn Hatfield of the Forest Products Laboratory Statistics Unit for assistance in the MSR simulations. This study was funded by the USDA Forest Service, Forest Products Laboratory, Madison, Wis.
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Information & Authors
Information
Published In
Journal of Materials in Civil Engineering
Volume 18 • Issue 1 • February 2006
Pages: 1 - 10
Copyright
© 2006 ASCE.
History
Received: Dec 2, 2003
Accepted: Aug 5, 2004
Published online: Feb 1, 2006
Published in print: Feb 2006
Notes
Note. Associate Editor: Roberto Lopez-Anido
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