Research On Wind Loads Of Transmission Towers Under Flat Ground And Hilly Terrain Wind Field

Lots of long span transmission towers have been built in recent years, with the continuously development of electric power industries in our country. Meanwhile, hills in our country occupy about 65 percent of the land, resulting in plenty of transmission towers being built in the mountain area. Further research on the related problems on wind loads under flat ground terrain and hilly terrain has a significant effect on the structure design of transmission towers, because of the accelerating effect reduced by the complex hilly terrain.Taking a long-cross-arm tower and a custom tower as examples, wind-induced response on transmission towers under flat ground terrain is analyzed first by time domain method, frequency domain method and High Frequency Force Balance tests. Results show that by using the method of POD decomposition in time domain or the SRSS method in frequency domain a lot of calculating time will be saved. Wind-induced response based on the HFFB wind tunnel tests has the same tendency as that of time domain method and frequency domain method.Gust loading factor method and background-resonance method are used in order to get equivalent static wind loads of the two transmission towers, whose results are compared with those calculated by the data of HFFB wind tunnel tests. Analyses indicate equivalent static wind loads based on HFFB wind tunnel tests are smaller than those of gust loading factor method and background-resonance method.Last but not the least, two hill models with different diameters are made in a scale ratio of 1:500, by which wind tunnel tests of single hill and double hills are carried out. The characteristic of wind profile under single hill and double hills is studied and typical hill terrains are gotten. Wind-induced response and equivalent static wind loads of flat ground terrain, typical single hill terrain and typical double hill terrain are studied in detail. Research shows that results of single hill terrain and double hill terrain are very close, but bigger than those of flat ground terrain.