树木风荷载、风致响应的研究

China is affected mostly by typhoons and strong wind in the world, witnessing the situations that strong wind destroys the buildings and bridges, makes people lose lives and causes trees bent or broken. And it is of great importance to do research on wind resistance characters of the trees, because every typhoon landing in Hainan Island brings about fallen roots, bent branches and broken trunks in most rubber trees, which probably results in economic losses of several billion yuan. Thus, assisted by a series of mixed methods comprising field measurement, wind tunnel test, numerical simulation and theoretical analysis, this research mainly focuses on such aspects as wind field characters and relative simulation methods of tree regions, calculation methods about dynamic characteristis of tress under the consideration of material anisotropy, the interactions between soil and trees, tree morphology and its effects on wind effects , wind tunnel test method for wind effects of trees, numerical simulation about wind load and wind-induced response of trees, characteristics and rules of wind load on trees, and characteristics and rules of wind-induced response of trees. After that, this research determines the main factors affecting the wind-induced disaster of trees, and then proposes calculation methods about wind field near ground in the wooded areas, wind load of trees, wind-induced response of trees, performance evaluation about wind resistance of trees, and disaster prediction for wind-induced of trees. This research is to provide adequate theoretical basis and technical support for the wind resistance of trees in the forest region of China.

中国是世界上受到强、台风影响最多的国家，强风除了会造成建筑物和桥梁的破坏、人员的伤亡，还会导致树木被压弯或破坏。在海南岛每次登陆台风都会导致橡胶树林出现大量的根倒、弯曲和干折现象，可能造成数十亿元的经济损失，开展树木抗风的研究具有重要的意义。本项目将综合应用现场实测、风洞试验、数值模拟和理论分析等方法，对树林区域的风场特性与模拟方法、考虑材料各向异性的树木动态特性计算方法、土-树木相互作用、树木形态及对于风效应的影响、树木风效应的风洞试验方法、树木风荷载与风致响应的数值模拟方法、树木风荷载特征和规律、树木的风致响应特征和规律等开展系统研究。进而确定影响树木风致灾害的主要因素，提出树林区域近地风场的计算方法、提出树木风荷载的计算方法、提出树木风致响应的计算方法、提出树木抗风性能的评价方法，提出系统的树木风致灾害预测方法，为我国森林地区的树木抗风、减灾提供充分的理论依据和技术支撑。

本项目采用原型实测、风洞试验、数值模拟及理论分析等多种研究方法对树木流场和树木风荷载特性进行了系统深入地研究。建立了树木抗风实测基地，通过现场实测方法获得了内陆地区典型常态风和季风下树木前后的风剖面、平均风向、湍流强度、阵风因子、湍流积分尺度、脉动风速谱以及湍流相关性等风场特性；获得了环境激励、力锤激励等多种方式下香樟树、柳树等典型树种的树干前十阶模态。基于实测风场特性，在风洞中采用特定活树来模拟城市行道树，制作刚性和气弹风洞模型，研究了不同布置方式下树木风荷载与风速的关系，并将试验结果和现场实测结果进行了对比分析。研究了不同布置方式下树木风荷载与风速的关系，获取了特定模型树的迎风面积、疏透度、阻力以及阻力系数等反应模型树气动特性的因素与风速的关系，对单棵和一排布置下树后特定平面的流场特性进行了研究；在此基础上，通过风洞试验探究了模型树与房屋间距以及模型树高度对低矮房屋表面平均风压、脉动风压的影响；同时研究了树后的风沙流场特性，包括树木对风速、沙浓度和湍流度的影响规律。基于实测风场特性，采用数值模拟方法，建立 REV 尺度的树木多孔模型，由多松弛时间格式Boltzmann模型结合大涡模拟计算分析树木模型在风荷载下的流场。研究成果为树木的抗风、抗风沙设计提供了理论依据和技术支撑。