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风载荷作用下树木干折规律研究

Trunk break rule of tree under wind loads

  • 摘要: 为更好地保护树木树干健康,降低其干折风险,该文探究树木在不同风载荷作用下的干折规律。利用树木自相似和自仿射的特点,基于参数化建模思路,构建多样化结构形态的树木地上部分几何模型。在风载荷作用下,运用流固耦合原理和有限元理论对3种东北典型树种(白杨Populus tomentosa Carrière、榆树Ulmus pumila L.和云杉Picea koraiensis Nakai)进行干折模拟。结果表明:树木的抗干折能力受结构形态、胸径和树种的影响;对于同一树种,与树木结构形态相比胸径对树木抗干折能力的影响较显著,树木胸径越大,抗干折能力越强;不同树种的抗干折能力具有显著差异;当风速达到15 m/s时,胸径小于18 cm的白杨易发生干折倒伏;风速增至20 m/s时,胸径小于15 cm的榆树具有一定的干折风险。通过拉伸试验获得的形变及倾斜度数据表明,当施加压力在0~0.6 kN范围内,白杨形变值为17.65~32.47 µm,倾斜度为0.046°~0.101°;榆树形变值为8.67~22.34 µm,倾斜度为0.008°~0.04°;云杉形变值为0.93~2.46 µm,倾斜度为0.031°~0.061°,拉伸试验数据验证了数值模拟结果。

     

    Abstract: To better protect the health of tree trunks and reduce their risk of wind breakage, this paper explores the break rule of tree trunk under different wind loads. Using the characteristics of tree self-similarity and self-affinity, a geometric model of the above ground part of trees with diversified structural morphology is constructed based on the idea of parametric modeling. Under the action of wind load, three common trees (Populus tomentosa Carrière, Ulmus pumila L. and Picea koraiensis Nakai) in Northeast China were simulated by using the principle of fluid-structure coupling and finite element theory. The simulation results show that the resistance of trees to trunk break is affected by structural form, diameter at breast height (DBH) and tree species, For the same species, DBH is the most significant factor. The larger the DBH, the stronger its resistance to trunk break. And the resistance to trunk break of the different tree species is different. When the wind speed reaches 15 m/s, Populus alba with a diameter at breast height of less than 18 cm is prone to trunk break and collapse; U. pumila with a diameter at breast height of less than 15 cm is at risk of trunk break when wind speed increases to 20 m/s. Deformation and tilt data are obtained by tensile testing in field. When the applied tension force is in the range of 0-0.6 kN, the deformation value of P. tomentosa is 17.65-32.47 μm, and the tilt is 0.046°-0.101°; the deformation value of U. pumila is 8.67-22.34 μm, and the tilt is 0.008°-0.04°; and the deformation value of Picea asperata is 0.93-2.46 μm, and the tilt is 0.031°-0.061° . The accuracy of the simulation results was verified.

     

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