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Arboriculture & Urban Forestry Online
Volume 38, Issue 4 — July 2012

Determining if Lateral Imbalance Exists in First-order Branches Leading to a Potential Development of Torsional Stress    (View PDF)

Gregory A. Dahle and Jason C. Grabosky

Abstract: The management of urban trees requires an ability to appraise the stability of trees to select where and when a maintenance task is required to increase the functionally useful period of the tree. Torsion is often ignored during static bending trials and the goal of this study was to determine if first-order branches on open grown trees are laterally balanced. It is not known if lateral branch development leads to a parent branch that is evenly balanced. Second-order branch mass and center of gravity were measured and used to estimate the load acting on first-order branches. It appears that development can lead to imbalance in branches, because more than 60% of the firstorder branches were imbalanced. Furthermore, 80% of the first-order branches in this specific study had more loading to the left side of the branch. Researchers should consider whether it is appropriate to ignore torsion when predicting how branches will behave during loading exercises. Additionally, the data suggests that it is possible to develop a strong predictive equation between branch length and the center of gravity (r2 = 95%) which, tied with predicted branch mass, could be useful when modeling self-loading and later balance in branches.

Keywords: Biomechanics; Branches; Center of Gravity; Mass; Stress, Tilia cordata; Torsion.

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