基于气弹模型风洞试验的输电塔气动阻尼研究

输电塔挂线和不挂线情况下的气动阻尼比是精确进行其风振响应评估的重要参数。基于完全气弹模型风洞试验测试得到的位移与加速度响应时程,结合使用经验模态分解法(empirical mode decomposition,简称EMD)、小波分析和随机减量方法(random decrement technology,简称RDT)以及Hilbert变换识别了输电塔在挂线和不挂线情况下各阶振型结构阻尼比和气动阻尼比,分析输电塔在挂线和不挂线情况下结构阻尼比和气动阻尼比的变化规律。结果显示,输电塔挂线时的结构阻尼比比不挂线情况要大;输电塔的气动阻尼比随各阶振型频率的增加而减小,随着风速的增加而增加。最后,采用最小二乘法拟合得到了在试验风速条件下气动阻尼比的经验公式。

Analysis of Aero-Dynamic Damping of Transmission Tower Based on Aero-Elastic Model Wind Tunnel

Aero-dynamic damping ratios are significant parameters with which to accurately evaluate the wind dynamic responses of a transmission tower with and without lines. Based on the displacement and acceleration time series obtained by the full aero-elastic model wind tunnel, the first and second mode shape structural and aero-dynamic damping ratios of the electrical transmission tower with and without lines are evaluated respectively, by combining the empirical mode decomposition (EMD) method, wavelet analysis, random decrement technology (RDT) and Hilbert transform. In the meantime, the change rules of the structural and aero-dynamic damping ratios are analyzed. The results show that the structural damping ratios of the transmission tower with lines are larger than those without lines, and the aerodynamic damping ratios of the tower decrease with frequency while increasing with wind speeds. Furthermore, the empirical formulae to evaluate the aero-dynamic damping ratios of towers under the test wind speed are proposed based on the least mean square method.