【作者】 潘磊；

【导师】 陈勇；

【作者基本信息】 浙江大学 ， 结构工程， 2014， 硕士

【摘要】 雷暴冲击风(下击暴流)是雷暴过程中一股强烈的下击气流,在地面或接近壁面处产生极高风速,造成了大量建筑结构物的破坏。目前,雷暴冲击风的研究重点主要集中在稳态雷暴风的风场特性上,对于非稳态雷暴风风场、雷暴冲击风的风荷载及风致响应的研究则较少。论文对雷暴冲击风风场、雷暴冲击风下的铁塔风效应及输电线路风偏进行了相关研究。在风场研究中,通过雷暴冲击风试验设备,测试了不同地面粗糙高度下稳态雷暴冲击风风场以及地面粗糙高度为0.3679m时的非稳态雷暴冲击风的风场,得出了稳态雷暴冲击风水平风速及其湍流强度、竖向风速及其湍流强度沿竖向的剖面,研究了各参量随地面粗糙高度、径向位置的变化规律。获得了非稳态雷暴冲击风的不同高度处的水平风速时程曲线和最大风速剖面,并分析了水平风速时程曲线随高度的变化规律、两类雷暴冲击风最大风速剖面的异同。研究表明地面粗糙高度能提高水平风速出现的高度,非稳态雷暴冲击风的运动能形成风场加强区和减弱区。分析发现,经典的DSHM (Deterministic stochastic hybrid method, DSHM)在运用过程中有自身使用条件的限制,论文在此基础上提出了改进的DSHM,采用CFD或风洞试验获得的非稳态雷暴冲击风下的结构受力平均荷载时程,结合DSHM给出的脉动成分调制叠加方法,获得了结构在非稳态雷暴冲击风下的总风荷载时程。在对于具有横向结构特征的导线的非稳态雷暴风致风偏研究中,采用基于Fluent动网格技术的CFD数值模拟放,模拟了导线在非稳态雷暴冲击风运动过程中的平均风荷载时程,再采用改进的DSHM生成了总荷载时程,利用Ansys分析了导线在非稳态雷暴风场中的风偏,并据此与规范的风偏结果进行对比,发现,雷暴风下的结果大于规范的风偏结果,需对风压不均匀系数进行修正。在对于具有竖向结构特征的输电塔,由测力试验得到了稳态、非稳态雷暴冲击风下输电塔各段的风荷载。分析了在稳态雷暴冲击风中风荷载随径向位置以及高度的分布规律,得到了输电塔相应的静力响应特征；对非稳态雷暴冲击风下各工况下风荷载峰值随旋转角的变化规律进行了分析,通过改进的DSHM得到了非稳态雷暴风下的输电塔各段的风荷载时程,并据此分析了输电塔的准静态响应与风振响应。将考虑非稳态荷载时程的脉动成分影响后的风振响应最大值和非稳态雷暴风下的准静态响应最大值之比定义为风振系数。y,=0Djet位置0°旋转角位置,体轴x向的风振系数底部节段较大为1.51,塔顶较小为1.21,90°时,体轴y向的底部节段与塔顶风振系数相差不大,分别为1.41和1.47。规范下的位移响应要大于雷暴风的结果,但不能据此得出规范趋于安全。更多还原

【Abstract】 Thunderstorm downburst is a strong downdraft air impinging on the ground during the thunderstorm, with an extremely high velocity generated close to the surface, which leads to the destruction of quantities of structures. Currently, the research of the downburst mainly focused on the wind field characteristics of stationary downbursts, while little study have been done towards the wind field characteristics of non-stationary downburst, the loading and wind-induced response of downburst. In this article, the wind field of thunderstorm downburst, wind-induced response and windage yaw of the transmission lines were studied.In the process of wind field research, with the application of the downburst test equipment, the stationary downburst with various surface roughness and non-stationary downburst with a given surface roughness of0.3679m were obtained. Accordingly, vertical profile of both the horizontal and vertical velocity, together with their relevant turbulence intensity were improved as well as the dependent changing rules of which on the surface roughness and the radial distance. In addition, the maximum velocity profile and time histories of horizontal velocity of the non-stationary downburst at various height levels was gained, based upon which there is a detailed study of the dependent changing rules of the time histories of horizontal velocity on the height and the difference between the maximum velocity profiles of two analogies of downbursts mentioned above.In view of the fact that analysis found that classical deterministic stochastic hybrid method has some limitation and could not be used in all cases, a revised DSHM was imposed in this article. In combination the fluctuating component given by the revised DSHM with the time history of structural average force under non-stationary downburst obtained through CFD or wind tunnel test, the time history of total wind load could be presented.For the windage yaw research of conductors with a transverse structural feature under the non-stationary downburst, Fluent moving grid technique based CFD simulation was implemented to generalize the time history of conductor’s average load in the moving process of the non-stationary downburst. Then, the revised DSHM was used to gain the time history of total wind load. In contrast the results of the conductors’ windage yaw under the non-stationary downburst calculated by ANSYS with the code, it was revealed that the computation of the downburst exceeded the code by a large margin, thus the span reduction was appropriately amended.Regarding the transmission tower with a vertical structural feature, the wind load under stationary and non-stationary downburst was earned through force test. Accordingly, the radial and vertical distribution of the wind load under stationary downburst was analyzed to obtain the relevant static response characteristics of the transmission tower; moreover, the peak wind load as the change of the wind angles in various conditions under non-stationary downburst was analyzed and meanwhile the tower was divided into several segments, with the time history of wind load of every segment calculated by the revised DSHM, according to which the quasi-stationary and vibration response was figured up.The ratio of max wind-induced response and max static response under non-stationary downburst is defined as wind vibration coefficient.The former is obtained with considering the turbulent wind.At y=0Djet, wind vibration coefficient in x directionis under0°rotation angle is bigger in the bottom than that in the top.The values are1.51and1.21.But under90°rotation angle,wind vibration coefficient in y direction in the bottom is closed to that in the top.They are1.41and1.47.The displacement is bigger under the wind load based on the code than that in downburst,but it is not right to conclude that the wind load given by code is safe.更多还原