Windthrow risk diagnosis for park trees based on the drag coefficients of tree crowns and the measurement of tree form

探讨了公园树木抛风风险的定量评价方法，提出了公园树木抛风的诊断方法。利用风速和树干挠度的实测数据，提出了一种估算树木阻力系数的田间试验方法。利用得到的阻力系数，可以计算出作用在树干和根-土板上的力矩作为风速的函数。为了评估树干折断时的抗风抛性能，发展了一种确定树干横截面形状的无损方法。此外，还进行了公园树木的下拉测试。

Methods of quantitative evaluation for windthrow risk of park trees were discussed in order to propose a procedure for windthrow diagnosis. A field test method was developed to evaluate drag coefficients of trees, using measured data of wind speed and stem deflection. The moment acting on stem and root-soil plate can be calculated as a function of wind speed, using the obtained drag coefficients. To evaluate windthrow resistance with respect to stem breakage, a nondestructive method for determining the shape of a trunk cross section was developed. Furthermore, pull-down tests of park trees were conducted