柳树风致响应的实测分析与预测

Analysis and Prediction of Wind-induced Response of Willow

为探究在不同时距和不同风速条件下树干各个高度的风致加速度响应的分布规律,对单棵柳树的树前风场及其树干加速度响应进行了现场实测.结果表明:树前顺风向脉动风速与风致树干加速度响应的概率分布特性有显著区别,树前顺风向脉动风速近似高斯分布,树干顺风向加速度响应的概率分布为明显的尖峰非高斯概率分布;柳树的风致响应为一个强迫振动的过程;采用广义Pareto极值算法计算其极值加速度响应,当时距为180 s时树前平均风速与树干顺风向极值加速度响应的相关性最高;对树前不同平均风速下树干不同高度的极值加速度响应进行拟合分析与预测,发现其树干顺风向极值加速度与树前平均风速呈二次非线性关系.关于柳树的风致响应规律特性的探究,对于研究树木抗风具有重要的意义.

In order to investigate the distribution law of wind-induced acceleration response at various heights of the trunk,different time distances and different wind speeds,field measurements were made on the front wind field and trunk acceleration response of a single willow tree.The results show that there are significant differences between the probability distribution characteristics of wind-induced tree trunk acceleration response and wind-downwind pulsating wind speed.The wind-downwind pulsating wind speed approximates the Gaussian distribution,and the probability distribution of wind-downwind acceleration response of tree trunk is a sharp non-Gaussian probability distribution.The wind-induced response of willow is a process of forced vibration.The generalized Pareto extremum algorithm was used to calculate the extremum acceleration response.When the distance was 180 s,the correlation between the mean wind speed in front of the tree and the extremum acceleration response in the downwind direction was the highest.The response of extreme acceleration at different height of the trunk under different mean wind speed in the front of the tree was analyzed and predicted by fitting.It was found that the downwind extreme acceleration of the trunk had a quadratic nonlinear relationship with the mean wind speed in the front of the tree.The study of wind-induced response characteristics of willow is of great significance to the study of wind resistance of tress.