脉动风作用下塔架结构的风振响应分析

 简述了应用线性滤波法中的自回归模型(AR)模拟出给定风速功率谱的风速时程序列,并验证其与目标谱(Davenport谱)的一致性,再通过规范公式推导脉动风载与风速之间的关系,从而得到作用在各节点的脉动风荷载时程样本。以某42m高的通信塔架为原型进行了模拟计算分析,用有限元分析软件ANSYS建立其有限元模型,并用Matlab获取了塔架迎风面各节点上的风荷载时程信号作为动力输入。利用ANSYS对结构进行了模态分析,结果显示结构的前几阶振动均是平面振动,第3阶振动开始出现扭转模态和局部振动模态;同时,基于ANSYS时程分析方法计算了结构在脉动风载作用下的风振响应。结果表明,在仅考虑脉动风作用的情况下,本塔架结构顶部的水平位移低于规范规定的位移限值,但塔架截面变化拐点处的弦杆在风载作用过程中会产生较大应力,在塔架设计中予以注意。

Wind-induced Response of a Tower Structure Under Fluctuating Wind Load

In this paper, an autoregressive model (AR model) is used to simulate the wind speed time series. The spectrum of the simulated wind speed time series is found in agreement with the target spectrum, i.e., Davenport wind speed spectrum. The relationship between the wind load and the wind speed is derived according to the related Chinese codes. Samples of the fluctuating wind load on the nodes of a structure are obtained. Simulations with the Finite Element Method (FEM) are carried out for a 42m-high communication tower. The tower is made of Q235 steel. ANSYS software is used to build the FEM model. 188 elements of beams are applied for the main members of the tower structure, while link elements are applied for the web members. The wind load time history series are simulated by using Matlab software and are used as the input loads. The modal analysis shows that the first several modes of the structure are all plane vibration modes, and after the 3rd mode one may find torsional vibration modes and local vibration modes. Meanwhile, the time history analysis is used to determine the structural responses under wind loads. Results show that, under fluctuation wind loads, the horizontal displacement is much smaller than the value suggested by the code for the design of high-rising structures. However, it should be noted that the transmission tower experiences a large stressing in the chords where the section of the tower changes.