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Arboriculture & Urban Forestry Online
Volume 34, Issue 5 — September 2008

Failure Mode and Prediction of the Strength of Branch Attachments    (View PDF)

Brian Kane, Robert Farrell, Shepard M. Zedaker, J.R. Loferski, and D.W. Smith

Abstract: Predicting the strength of branch attachments is important for arborists and urban foresters because branch failure can cause damage and injuries. Previous studies have shown that the ratio of branch to trunk diameter is a better predictor of strength than the angle of attachment. Aside from these two factors, however, few other morphological measures of the attachment have been investigated with respect to predicting the strength of attachments. Many branch attachments from three species were broken on a testing machine and breaking stress was calculated. Prior to breaking, various morphological measures and ratios describing the attachment were made. Breaking stress varied by form of the attachment (u-shaped or v-shaped), failure mode, and the presence of included bark. The best predictor of breaking stress was the ratio of branch to trunk diameters. Results are discussed in the context of previous studies and with respect to tree risk assessment.

Keywords: Branch attachment; breaking stress; included bark; tree risk assessment

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