Evaluation of drag force of trees damaged from storm and flood

通过试验和现场调查，对暴雨洪水对树木的拖曳力评估、树木倒塌和折断的机理进行了研究。从模型实验中检查了以下内容。在强风条件下，分支和树叶共同作用的阻力将分担90%，说明虽然树叶在低风速条件下为60%的分担效果，但冠层阻力的评价也很重要。从实地调查中审查了以下问题。在倒塌的树木中，树木的年龄约为20年，断裂与树木的年龄无关。通过对被撞树的拉倒试验，明确了被撞树的倒塌时刻。提出了树木年龄与树形结构的关系。此外，还进行了弯曲试验，研究了未干燥木材的抗弯承载力，通过模型分析，确定了未干燥木材的倒塌和断裂区域，阐明了未干燥木材的破坏机理。

Evaluation of drag force of trees damaged by storm and flood, the mechanism of collapse and the break were examined from the experiment and the field survey. The following were examined from the model experiment. The drag that combined the branch and the leaves would allot 90% at the strong wind, and it was clarified that the drag evaluation of the canopy was important though the leaves in the low wind was an effect of 60% allotment. The following were examined from the field survey. The age of a tree was about 20 years in the collapsing tree, and the breaking showed no relation to the age of a tree. The collapse moment of the struck tree was clarified from the pulling down examination of the tree. The relation between the age of a tree and the tree form structure was requested. In addition, the bending test was executed, the flexural capacity of unseasoned wood was examined, the region of the collapse and the break was shown from the model analysis, and the mechanism was clarified.