The Reliability Of Transmission Tower Under The Environmental Load

Transmission lines is an important lifeline and takes huge investment, its damage can result in power interruption and fire disaster and great economic losses.Transmission tower is a major component of transmission lines and has lots of characteristic such as high rise,slim shape and gentle weight and so on. These characteristics of structure decide the structure to be sensitive to wind loads and ice loads and seismic loads. With the rapid development of transmission project in China, to ensure transmission tower in various environmental loads safety and reliability has a great significance.In this paper, take the transmission tower in an area of Hunan for example, the finite element model of a tower and two lines were established. According to measured data of the thickness of covering ice in south in 2008, the reliability analysis and calculation was carried out using the Monte Carlo method on the model at four different ice conditions by considering the uncertainty of the size of transmission tower angle steel, angle steel material properties with time of aging and load randomness of ice and wind。Through calculation result, do a comparative analysis of the same conditions the intensity of transmission tower failure probability and stiffness failure probability.The paper analyzes the dynamic characteristics of transmission tower, obtained its bending and twisting of the top three order modes. The adjustment method of seismic waves was introduced and the Tianjin seismic wave was adjusted respectively to seven degrees, eight degrees and nine degrees, and then put the seismic load on the tower, the time history curve of vertex displacement, vertex acceleration, the tower bottom main material stress, the tower inclined material stress and the support reaction force in three seismic condition was obtained.Finally, this paper describes the development of the structural dynamic reliability and introduces the first-passage failure mechanism and fatigue failure mechanism. Adopting the first-passage failure mechanism and considering the action of wind loads and seismic loads and using the PDS module of ANSYS, obtained the response surface equation. Based on the strength of the transmission tower failure criterion and the stiffness failure criterion, and then can respectively obtained strength and stiffness function failure function. Then by using JC method and Monte Carlo method respectively, calculate and get the reliability.