臺灣每年汛期出現的豪大雨、強風，除了水災之外，還有可能會伴隨出現的樹木落葉、斷枝甚至倒塌。都市裡的路樹倒伏問題已嚴重造成了人傷財損之安全疑慮，讓國內林業產官學界開始加強樹木安全的管理措施檢核。於此，林業學術界及林試所積極進行樹木腐朽與危木評估之研究，期盼能對校園、公園、人行道樹木的安全評估及危木處理技術提供可行的方法，藉以保障大眾的安全，提升生活品質。本研究以拉伸試驗的方式進行樹木評估，希望透過絞盤施予樹木的力量，模擬風荷載，分析其拉力、傾斜角大小，從樹木力學的角度，能提出傾倒評估的方案，藉以減低樹倒的風險。
本研究參考國外學者 Wessolly 的廣義傾倒曲線，以電動絞盤進行拉伸試驗，繪出屬於臺灣樹種的傾倒曲線，發現黑板樹、阿勃勒及小葉欖仁的傾倒曲線與Wessolly 的廣義傾倒曲線並不太符合，推測原因為Wessolly 的廣義傾倒曲線多以針葉樹種於天然林中進行試驗，而臺灣樹種多為闊葉樹種，且本研究的試驗樹種多為都市環境中的人工種植樹木。
一般認知中，當傾斜角小於0.25 度時，拉力不會對根系造成損害，拉力與傾斜角會呈正相關。透過手動絞盤施予樹木的力量，模擬風荷載，並將傾斜角0.25 度設定為極限值，分析其拉力、傾斜角大小，從結構學的角度，計算出該樹木的樹根盤剛度，與同樹種之間進行比較，判斷其大小是否有安全性不足的問題。本研究之試驗結果得出健康的樟樹、羊蹄甲、鳳凰木、臺灣欒樹與大葉桃花心木與對應之枯立木樹根盤剛度大約相差1.5 個標準差以上，而不健康樹木的樹根盤剛度大小分佈不似枯立木明顯的偏小，若其樹根盤剛度與平均值相差1.5 個標準差以上，建議能先治療、補強。

Trees in urban environment may fall, break branches and even collapse to threaten our life and finance safety during Taiwan's annual flood season, which raised awareness of tree risk management. To reduce risk, the forestry academia and government started researching dangerous tree assessment, hoping to provide feasible plans for tree risk assessment in campuses, parks, and sidewalks to protect public safety. As a result, this study aims to propose an improvement plan to reduce the risk of trees collapsing.
Based on the generalized tipping curve of Wessolly, L., by using an electric winch to conduct pulling tests to draw the tipping curve of the Taiwanese tree species. Results show that the tipping curves of Alstonia scholaris, Cassia fistula, and Terminalia mantaly aren't similar to the generalized tipping curve. The speculated reason may be that most of the Taiwanese tree species in urban environment are broad-leaved tree species, while the generalized tipping curve is mostly tested with coniferous tree species in natural forest.
Therefore, by applied load to the trees to simulate wind load with winch and set the limit inclination at 0.25 degrees, we can analyze pulling load and inclination for the root plate stiffness, and make a comparison between the same tree species. Results of this study show that the root plate stiffness of dying trees correspond to the healthy ones has less than 1.5 of standard deviations (SD) with the average of healthy root plate stiffness. We suggest the root plate of unhealthy trees with lower stiffness than 1.5 SD should be treated or strengthened.

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