In recent years, electric power projects of our country has developed quickly. With regard to electric voltage, its class has risen from 110kv、 220kv to extra high voltage of 330kv、 500kv. Nowadays, our country's electric network line is launching the plan and research work of ultra high voltage of 1000kv. Compared with that of today, weight of one tower in this transmission line will increase about 4-5 times. Then it will call for higher requirement on steel intensity and structural design of electric tran...