Study On Wind Effects Of Typical Transmission Tower Under Downburst

With the development of China’s electric power,the voltage level and capacity of overhead transmission lines are constantly increasing,which makes the height and span of transmission towers in the transmission tower line system also increase.In addition,in recent years,downburst have caused the transmission tower line system to occur damage,so it is of great significance to study the structural response of the transmission tower under the downburst.In this paper,based on the wind tunnel test of the aeroelastic model of the drum tower,the acceleration response,stress response and displacement response of the transmission tower under three types of wind fields such as category B wind field and downburst wind fields are compared,and then the numerical simulation method is used to study the stress of the transmission tower under different wind fields,and the difference between the experimental and numerical results of the wind vibration response of the drum tower is compared and analyzed.Due to the different structural response of different types of transmission towers under wind load,the structural response of the wine glass tower is also numerically analyzed and compared with the drum tower.The main contents of this article are summarized as follows:(1)Based on similarity theory and wind field debugging,wind tunnel test of aeroelastic model of transmission tower were conducted to study the acceleration response,stress response and displacement response of transmission tower in different wind fields.Through the wind tunnel test,two types of stable downburst wind fields with a maximum ratio of 1:50 were simulated,these are the downburst wind fields with maximum wind speed located at the height of 70m(downburst 1)and maximum wind speed located at the height of 90m(downburst 2).It can be seen from the test results of the transmission tower under each wind field: the acceleration pulsation response caused by downburst 1 is greater than downburst 2,the acceleration pulsation response of the transmission tower under the category B is between the two types of downburst wind fields.The average stress response and peak stress response of transmission tower members under the impact of downburst 1 tend to be equal with the impact of downburst 2,the average stress response and peak stress response of transmission tower members under the action of two types of downburst wind fields are greater than the average stress response and peak stress response under the action of category B;under the action of category B,the pulsation stress response of the transmission tower members is the largest,followed by the response of the downburst 1,and the minimum response under the downburst 2.The average response and peak response of the top displacement of the two types of downburst wind fileds tend to be equal and both are greater than the average displacement response of the category B;the pulsation response of the top displacement under the action of the category B is greater than the pulsation response of the top displacement under the action of the two types of downburst wind fields;the pulsation response of the top of the tower under the impact of downburst 1 is slightly greater than the pulsation response of the top of the tower under the impact of downburst 2.The displacement wind vibration coefficient at each height of the transmission tower under the category B is greater than the displacement wind vibration coefficient at each height under the two types of downburst wind fields,of which the displacement wind vibration coefficient at each height under the two types of downburst winds tends to be equal,and the wind vibration coefficients of the tower top displacement calculated by the experiment are all smaller than those calculated in the towering code.(2)The linear filtering method is used to simulate the wind speed time history at different heights and convert the wind load time history and then apply it to the transmisson tower structure of pulsating wind at different heights then the structural response of the transmission tower under different wind fields was analyzed and compared with the experimental values.The research and analysis of the transmission tower structure response under different wind fields are compared with the test values.According to the analysis results,the test value of the transmission tower and pulsation response of acceleration is less than the simulated value under the category B,the test values of the average stress response,pulsation stress response and peak stress response of the transmission tower memberss are significantly greater than the numerical simulation values;the test values of the average displacement response,pulsation displacement response and peak displacement response of the transmission tower are obviously larger than the numerical simulation value.Under two types of downburst wind fields,the test value of the peak stress response of transmission tower members is significantly greater than the numerical simulation value and the difference between the two fileds caused the relative response becomes larger as wind speed increases.The test value of the peak displacement response of transmission tower is obviously greater than the numerical simulation value and the difference between the two fileds caused the relative response becomes larger as wind speed increases.(3)The numerical results of two types of transmission towers show that he changes in height of the main materials stress and inclined materials stress of two types of transmission towers under category B are significantly different,the main materials stress of the drum tower increases along the height while the main materials stress of the glass tower gradually decreases along the height,the stress of inclined materials of the drum tower fluctuates along the height and glass tower has a greater stress at the leg and K-shaped node and the stress at the tower body gradually increases along the height.In addition,the peak response of the axial displacement of the drum tower changes linearly with the increase of height,while the peak response of the axial displacement of the wine transmission tower changes parabolically with the increase of height.With the increase of height in the range,the increase of the peak displacement value is greater than the increase of the peak displacement value in the height range of the drum tower head,indicating that the glass transmission tower head is more sensitive to the wind.