Tree breakage from torsional wind loading due to crown asymmetry

Abstract

Data that were originally collected to study systematic asymmetries in the canopies of Scots pines were used as input in previously developed models. These models predict whether a tree will break due to bending loads or torsional loads during critical wind exposure. Data from four pine stands were used in the study, two lowland stands and two mountainous stands. For each of the stands there were large amounts of both categories of trees: those predicted to break due to bending and those predicted to undergo torsional failure. Moreover, there was no significant difference between any of the stands when it came to the distribution of predicted failure modes. These two facts suggest that the risk of bending failure and torsion failure is balanced so that neither is more likely than the other. The fact that torsion may be as critical as bending is a new finding.