Instability Analysis Of Transmission Tower Under Tornado

Transmission tower are generally built in the field,struck by various natural disasters frequently.Tornado damage to transmission tower is particularly serious.At present,there are a lot of researches on transmission tower against surface wind.The research on transmission tower against tornado is relatively few.Therefore,it is of great significance to research the stability of transmission tower under tornado.At present,the calculation method for wind load at tower section are adopted by every country’s specification.Actually,the transmission tower is consisting of angle steel component calculates the wind load distribution of transmission tower accurately.Speed component of tornado wind filed is simulated based on model of Wen and taking typical 5AJ1 500 kV power transmission tower for a research objective.The calculation method for wind load at each angle steel component is adopted.The author research dynamic and static stability analysis of transmission tower by the method of Incremental Dynamic Analysis combining with Budiansky-Roth criteria and displacement equivalency criteria.The thesis is divided into such part as follows:(1)The advantages and disadvantages of the most widely used Rankine vortex model and Wen model are compared and analyzed.A more comprehensive Wen model is selected to simulate the wind speed of three dimensional tornado wind field.(2)Finite element simulation of 5AJ1 transmission tower is carried out by using beam and rod hybrid unit and modal analysis of finite element model.(3)The static stability analysis of transmission tower is carried out by using the F3 level tornado load under the maximum load angle.It includes eigenvalue buckling analysis and nonlinear buckling analysisfor finite element models.The results of the two kinds of analysis are compared.(4)The dynamic stability analysis of transmission tower is carried out based on the load time history of F3 tornado under each attack angle.It includes time history analysis and dynamic stability analysis of finite element models.The results of dynamic stability analysis and nonlinear buckling analysis are compared.