Modeling Wind Damage for Japanese Cedar (Cryptomeria japonica D. Don) Trees Using Cantilever Beam Theory

Abstract

Japanese cedar (Cryptomeria japonica D. Don) clones, called kawaidanisugi, planted in western forests of the Toyama prefecture suffered severe wind damage from typhoon No. 23 in 2004. A dynamic model of kawaidanisugi, based on “cantilever” theory, was built to examine the mechanics of wind damage for this cedar tree. The stem form, elasticity data and necessary for construction of the model was collected from the forests in Toyama. Overturning moments at the tree stem was investigated in three different forests throughout the prefecture. Given tree size, the model can estimate the failure type (uprooting or stem breakage). To verify the model’s accuracy, actual tree size and failure type in kawaidanisugi forests were compared to predicted values. This comparison revealed that stem breakage could be predicted with a relatively high level of success, while the ability to predict uprooting was poor. As for the height of stem breakage, observed values corresponded well with estimated values. Assuming equal diameter at breast height, taller trees were more likely to suffer stem breakage, while shorter trees were more likely to uproot.