| The transmission tower has the characteristics of light,high,soft and hollow.At the same time,the tower-line system has the characteristics of long coverage distance,different terrain and large environmental impact.As a result,transmission lines are particularly sensitive to wind loads.In recent years,the frequency of typhoons and other wind disasters in China has increased,which makes the collapse of transmission lines under wind loads occur frequently.This requires us.The failure mechanism and the rationality of structural design are deeply studied.In order to facilitate the follow-up study on the failure mechanism of transmission tower-line system,a method considering the similarity of stability stress is proposed to design and fabricate the aeroelastic model of transmission tower.At the same time,the damage of transmission towers also reveals that we need to further study the wind-resistant design of transmission towers.At present,the wind-resistant design of transmission towers is to consider the effect of wind-induced vibration through the wind-induced vibration coefficient.Therefore,the accuracy and rationality of the calculation of wind-induced vibration coefficient is of great significance to the design of transmission towers.The wind-induced vibration coefficient is studied by finite element method and wind tunnel test.The main contents are as follows:1)The models of transmission tower,transmission line and tower line are established in ANSYS and the dynamic characteristics are analyzed.It is found that after the tower-line system is coupled,the transmission tower has little influence on the dynamic characteristics of the transmission line,but the transmission line has great influence on the dynamic characteristics of the transmission tower and has directionality.The tower-line coupling system presents dense low-frequency modes.2)Aiming at the ultimate stress state and yield characteristics of transmission tower under wind load,a method considering the similarity of stable stress is proposed to design and make the aeroelastic model of transmission tower.Through validating the rationality of the model in the aspects of wind field environment,dynamic characteristics and wind damage mode of transmission tower,it can be concluded that the design of the model is more reasonable.Based on the test data and results of the model,the structural prototype can be deduced,which can provide a certain model design basis for the follow-up study of the damage mechanism of transmission tower.3)Based on the finite element analysis and wind tunnel test,the wind-induced vibration coefficient is studied,and it is found that the wind-induced vibration coefficient increases with the increase of wind speed;with the increase of wind direction angle,the wind-induced vibration coefficient of the upper and middle parts of the tower body first decreases and then increases,which indicates that the influence of the cross-arm on the wind-induced vibration coefficient of the upper and middle parts of the tower body can not be neglected;It is found that the wind-induced vibration coefficients of the upper and middle parts of the tower increase significantly with the presence of transmission lines at wind direction angles of 45 to 90 degrees,which indicates that the influence of transmission lines on the wind-induced vibration coefficients can not be neglected,and the closer to the location of transmission lines,the greater the influence.The influence of transmission lines can be considered in the design of transmission towers.4)Comparing the wind-induced vibration coefficients calculated by test,finite element method and three codes.It is found that the sudden change of mass and windward area at the crossbar is not taken into account in the load code and the high-rise code,and the wind load at the crossbar position contributes significantly to the displacement of the tower and the internal force of the main material,which makes the safety degree of wind-resistant design of the wind-induced vibration coefficients calculated by the two codes low.It is suggested that when calculating the wind-induced vibration coefficients of transmission towers by the two codes,the position of the crossbar should be taken as a value.The load code of overhead transmission line takes into account the vertical correlation of fluctuating wind,the mass of cross-arm and the sudden change of windward area.This method is safer than time history analysis and is suitable for the calculation of wind-induced vibration coefficient of transmission tower structures.It is suggested that the influence of transmission line on complex transmission lines should be considered. |
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