脉动风作用下基于Hilbert-Huang变换的附加质量及气动阻尼识别

An identification study on the added mass and aerodynamic damping based on Hilbert-Huang Transform under the action of fluctuating wind

自振频率低且自重较轻的大跨度屋盖等结构体系在脉动风作用下发生振动时,附加质量及气动阻尼对其振动特性有重要影响,需通过对实验数据的准确识别研究其变化规律。基于Hilbert-Huang变换,在IIR带通滤波的基础上对输出信号进行经验模态分解,并对各自由度方向同步作随机减量处理得到所需模态阶次的自由衰减信号,进而求解频率、阻尼比及振型。数值算例表明,该方法可以有效抑制噪声影响,并准确提取不同阶次的模态参数。在此基础上,根据振型相似的原则对一肋环型索穹顶结构的附加质量及气动阻尼进行了识别,得出了这两个参数相比于静止空气环境以及随风速的变化规律。

For the long-span roof structures which have relatively low frequency and light mass, the vibration property under the action of fluctuating wind is significantly influenced by the added mass and aerodynamic damping. The changing rule of these two parameters should be ex- tracted from exact identification method. Based on Hibert-Huang Transform theory, empirical mode decomposition method is applied on the output signal after IIR band pass filter. Then the random decrement technique is used synchronously on all the components of degrees of freedom to obtain the free decay signal of required mode, so the frequency, damping ratio and mode shape can be identified. The results of numerical example show that this method can restrain noise ef- fectively and extract the modal parameters of different order accurately. Taking the Geiger type cable dome as example, the added mass and aerodynamic damping under the action of fluctuating wind are identified according to the principle of highly similar mode shape, and the change law of these two parameters is also obtained compared with stationary air environment.