输电塔气动力系数和气动导纳风洞试验研究

输电塔结构的非定常抖振力与来流风速之间存在复杂的非线性关系,基于风洞试验得到的某1 000 k V格构式直线输电塔弹性模型的基底力以及参考高度处同步采集的风速时程,采用线性和高斯两种近似假定计算了非定常气动力系数并与试验值进行了比较;提出了包含结构气动阻尼效应在内的总气动导纳的概念,通过基底脉动力谱和来流脉动风速谱的比值对总气动导纳函数进行识别,并用基于频域相干函数对导纳函数的线性部分进行了估计。结果发现,风偏角线性近似所计算静气动力系数的偏差较高斯近似小;由于气动抖振力非定常性质明显,不考虑总气动导纳函数将高估输电塔模型的抖振响应;脉动风力与脉动风速间有较强的非线性关系,用线性导纳函数计算的抖振力谱将低估脉动风分量的影响。

Wind tunnel test for aerodynamic coefficient and aerodynamic admittance of a transmission tower

Buffeting forces of structures such as transmission tower usually have highly nonlinear relation to incoming wind fluctuations. Based on wind forces and simultaneous fluctuating wind speed measured from wind tunnel test on a model of 1000kV suspension transmission tower, aerodynamic coefficients and aerodynamic admittance functions are studied. Unsteady aerodynamic coefficients obtained in the test are compared with those estimated starting from linear and Gaussian assumptions. The concept of total aerodynamic admittance including structural aerodynamic damping effect is suggested, which is identified by ratio of power spectral density of wind force to that of fluctuating wind speed. The linear admittances, which represent correlated parts of the wind speeds and wind forces, are also calculated by employing frequency-domain coherence functions. Results show that linear assumption of relationship between time-dependent wind angle of attack and associated aerodynamic coefficient lends more accuracy than Gaussian assumption. Because of the unsteady nature of wind-speed-to-wind-force relation, neglect of aerodynamic admittances will lead to conservative estimation of buffeting responses of the structure. Moreover, effects of wind fluctuations will be underrated if linear admittances are adopted in spite of the prominent nonlinearity between wind speed and wind force.