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

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.