Wind Load And Wind-induced Effect Research Of Guyed Portal Tower Under Terrain B Wind Field And Downburst

Guyed portal tower with the advantage of low cost,light weight,convenient construction and so on is widely used in high voltage transmission lines in China.But the downside of guyed portal tower is the horizontal load mainly undertaked by the prestressed anchor and two columns,vulnerable to external force at greater risk of damage and collapse.At present,the transmission tower structure design code of wind resistance is based on atmospheric boundary layer wind which is different from the downburst wind filed,resulting in the transmission line tower system which has enough safety coefficient under atmospheric boundary layer wind is easily collapsed by the downburst wind filed.This paper takes a certain 220 kv transmission line guyed portal tower which was collapsed by downburst wind filed as the research object,based on wind tunnel test and time history response analysis method,comparative studying on response and characteristics of the typical lattice guyed portal tower under atmospheric boundary layer wind and downburst wind filed.The main research work from the following several aspects:(1)The current research status of wind vibration response of transmission tower line system have been introduced,and then from the field measurement,physical simulation and numerical simulation these three aspects introduced the research status of downburst.At last,introducing the the application and research situation at home and abroad of guyed portal tower.Based on concrete engineering instance,the research object and the research target object are confirmed.(2)Based on the harmonic synthesis method,the average wind speed and fluctuating wind speed of the tower-line system under the normal wind field and downburst are simulated by the program compiled by MATLAB.The difference between the mean wind and fluctuating wind in the two types of wind field is compared.Calculated static load value on the guyed portal tower by the wind load specifications.(3)The guyed portal tower rigid scale model wind tunnel test carried on wind engineering research center of Hunan University HD-2 large boundary layer wind tunnel,in order to get the shape coefficient of calculation and analysis needs.And analyzed the change law of guyed portal tower model and wire model shape coefficient.(4)A guyed portal tower-transmission line system space finite element model was established and the dynamic characteristics was analysed,compared with dynamic characteristics of single tower and transmission tower-line system;In accordance with the relevant design codes,the static load effect on the guyed portal tower-transmission line system under different wind directions is calculated.The response characteristics of single tower and tower-line system under the two types of wind fields,such as the normal wind field and the downburst wind field,are analyzed.The basic theory of dynamic time history calculation is introduced.Based on the method of Newmark-beta,the response of guyed portal tower under fluctuating wind load was analysed,comparative analysis the wind effect of the tower.(5)Based on Budiansky-Roth criterion and incremental dynamic analysis(IDA),analysed the static stability and dynamic stability of single tower and transmission line system under normal wind field and downburst wind field.Get the guyed portal tower instability occurred in the corresponding condition.