输电塔脉动风荷载功率谱模型及时程模拟

Power Sprctra Model and Time-History Simulation of Fluctuating Windloading Acting on Tranmission Tower

基于风洞试验得到输电塔线性一阶广义荷载谱,推导了输电塔顺风向、横风向基本脉动风压功率谱公式,给出了输电塔顺风向、横风向任意阶广义荷载功率谱及分段脉动风荷载功率谱公式.基于此功率谱,应用谐波叠加法,建立了脉动风荷载时程数值模拟方法.脉动风荷载功率谱不仅与来流的风速、风速谱、气动导纳有关,还与地面粗糙程度、塔架构件的投影面积及沿高度分布情况、压力系数等有关,广义荷载谱还与振型有关.以一窄基输电塔为例,用Matlab语言编程,计算了广义荷载和分段风荷载功率谱,模拟了脉动风荷载时程.算例分析表明,输电塔抗风分析中,横风向脉动风荷载虽然比顺风向小,但远没有到可以忽略的程度,建议考虑横风向脉动风荷载功率谱或施加横风向荷载时程.

Expressions of power spectra of along-wind and cross-wind basic wind pressure of transmission tower are deduced based on the fundamental linear mode generalized force spectra obtained through a wind tunnel test.Power spectra of along-wind and cross-wind fluctuating wind load and generalized wind force acting on transmission tower are presented.Numerical simulation method of time histories of fluctuating wind load is developed based on these spectra and harmony superposition method.Power spectra of fluctuating wind load are influenced not only by wind velocity,wind spectra and aerodynamic admittance,but also by terrain types,projected area of members,distribution of projected area of member along height and drag coefficients.Power spectra of generalized wind force also are influenced by vibration mode.A transmission tower with a narrow foundation is taken as an example of this method.Matlab language is used for programming.The power spectra of generalized force and fluctuating wind load are computed.Time histories of wind load are simulated.The results show that,though the fluctuating wind load of cross-wind direction is smaller than the one of along-wind direction,but it can not be neglected.In the anti-wind analysis of transmission tower,either power spectra of cross-wind fluctuating wind load should be taken into account,or time histories of wind load of cross-wind direction should be exerted.