稳定风速和阵风交错作用下的林木风倒分析

风倒是形成林隙的主要原因, 是发生频率较高、波及范围较广、造成损失较严重的一种自然灾害。因此, 研究风倒具有重要的理论和实践意义。针对相关理论模型的不足, 利用动力学理论建立了林木风倒的非线性动态模型, 分别从稳定风速作用和阵风作用2个方面对林木的风倒机理进行了研究, 通过严格的数学推导获得了林木发生风倒的判断条件。结果表明:稳定风速和阵风作用下林木发生风倒的条件不同, 且互为补充。基于理论分析, 以西加云杉Picea sitchensis为例进行数值计算, 得到了风倒的标准风速值, 研究结果可以应用到其他树种的风倒问题中。同时, 稳定风速和阵风交错作用下发生风倒的标准风速值与还与风荷载的作用时间有关。研究结果为后续的理论研究和工程应用提供了指导。

Tree windthrow with stable winds and gusts

A major reason for gaps in forests is windthrow, which is a kind of natural disaster with high frequency, broad cope and much wastage making it very important to understand the theoretical and practical aspects of windthrow. In this study, a nonlinear dynamic model of windthrow was established using dynamics theory to improve the shortcomings of the related theoretical model. The windthrow mechanism for Picea sitchensis was studied from two aspects: stable winds and gusts. The judgment conditions of tree windthrow were obtained through strict mathematical deductions. Results showed that windthrow condition with stable winds and gusts was different, which are complementary each other. Also, the standard wind speed value was related to action wind load time for the interaction between stable winds and gusts. These research results could be applied to windthrow problems of other species and could provide guidance for subsequent theoretical research and engineering applications.［Ch，7 fig. 18 ref.］