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林业科学 ›› 2017, Vol. 53 ›› Issue (5): 170-178.doi: 10.11707/j.1001-7488.20170520

• 研究简报 • 上一篇    

风灾害下树木强度分析的理论、方法及应用

邵卓平, 吴贻军, 黄天来, 王福利   

  1. 安徽农业大学林学与园林学院 合肥 230036
  • 收稿日期:2015-10-30 修回日期:2017-02-25 出版日期:2017-05-25 发布日期:2017-06-22
  • 基金资助:
    国家自然科学基金项目(31570715)。

Theory and Method of Tree Stem Strength Analysis Under Wind Disaster and Its Application

Shao Zhuoping, Wu Yijun, Huang Tianlai, Wang Fuli   

  1. College of Forestry and Gardening,Anhui Agricultural University Hefei 230036
  • Received:2015-10-30 Revised:2017-02-25 Online:2017-05-25 Published:2017-06-22

摘要: [目的] 研究风灾害下树木强度分析的理论和方法,建立树干最大应力与风速平方之间的关系,预测树木能够承受的最大风力。[方法] 设计一套新的树木组合变形测试方法,通过将2个位移传感器沿轴向安装在树干的正交直径上,另2个位移传感器分别与轴向呈+45°、-45°交叉叠放安装,即能够测量立木在风载荷作用下树干因弯扭组合变形所产生的最大弯曲线应变(应力)和扭转切应变(应力),并且最大应变(应力)与风向无直接关系。[结果] 选择4株香樟树作为研究对象,采用可知力值的拉力试验对新方法进行验证,结果证明试验所测得的最大应变仅取决于传感器的测值而与拉力方向无关,并且通过虎克定律转换的应力值与理论计算值相符合。应用该方法与风速仪相连,在大风环境下对1株香樟树进行实际测试,建立树干应力与风速平方之间的关系,并预测该树发生断裂的临界风速以及破坏方式,测算结果符合实情。[结论] 本文提出的树木强度分析理论和方法,可对在风载荷作用下处于弯扭组合变形状态下的树干应变(应力)进行测试分析,并可预测树木能够承受的最大风速。该方法不需要估算树冠面积、透风率以及树冠中心的高度、偏心距等许多难以确定的量,可以为林区或城市园林评估树木抗风害能力提供一种直接、有效的方法。

关键词: 风灾害, 树木强度

Abstract: [Objective] The theory and method of tree stem strength analysis under wind disaster is studied. The strongest wind that tree could resist is predicted by building the relationship between tree stem strain and square of wind speed. [Method] A new method to measure the combined deformation of tree stem was designed: two strain meters were attached to the stem in orthogonal direction, and another two strain meters were attached to the trunk in the ”X“ pattern with 45° and -45°, then the maximum bending linear strain(stress) and maximum torsional shearing strain(stress) caused by combined deformation of bending and torsion of tree stem can be measured. The maximum strain(stress) had no direct relation to wind direction. [Result] Four spicy camphor trees(Cinnamomum camphora) were selected to perform pulling tests under measurable load to verify the new method, and the results indicated that the measured maximum strain only depended on the output values of the sensors and in no relation with the direction of load. Moreover, the stress transformed by Hooke’s law coincided with the theoretical results. Practical test was carried out on a spicy camphor tree in Hefei, China by combining the technique with anemograph under strong wind. The relationship between tree stem strain and square of wind speed was established, due to which the critical wind speed when tree fractured and the failure mode were predicted, and they conformed to the actual situation.[Conclusion] The tree stem strength analysis method proposed here could be applied to measure and analyze the strain(stress) of tree stem subjected to bending and torsion combined deformation under wind load, and predict the maximum wind speed that tree could bear. As crown area, ventilation rate, height of crown center and eccentric distance of crown and some other parameters that difficult to measure did not need to estimate, the new tree stem strength analysis method could provide forest and city garden trees a direct and effective method to assess the resist ability to wind disaster.

Key words: wind disaster, stem strength

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