Analysis On The Ultimate Load Capacity Of Large-span Transmission Towers

Transmission towers are a form of highly indeterminate space structures which are being used extensively. A lot of large span transmission towers appear recently with the climax of electricity power construction. The height of transmission towers becomes higher and higher, and the span of two towers becomes larger and larger. Therefore, the ultimate load capacity analysis of transmission tower structure is important both in theory and engineering practice.In this dissertation, on the basis of reviewing the study and design data available, the structural theory of transmission tower is discussed, and the mechanical behaviour of transmission tower is systematically studied.At present, most mechanical behavior analysis for transmission towers are in the domain of elasticity, using finite element method to establish the computer analysis model, The stress , displacements and other mechanical parameters are obtained by analyzing the model. The studies for transmission towers in the domain of plasticity are very few. The transmission towers sometimes are over loading and most transmission towers have already worked for many years. Varieties of damages and distortions have appeared inevitably, which made the towers in-use have different mechanical characteristics as contrasted with their ideal status.A method of double nonlinear analysis is presented in this thesis to study the mechanical behavior of tower structures. Analytical software ANSYS is used. The large deformation of structures is considered by geometric nonlinearities analysis. The mechanical characteristics of tower structures in the domain of plasticity are considered by material nonlinearity analysis. Contrasted with the results that come from linearity and nonlinearity analysis, it is concluded that to analyze transmission tower structures is feasible with linearity theory in the condition of light load and small deformation.The ultimate load of tower structure has been studied by using double-nonlinear buckling analysis in this thesis. And based on this theory, a computing model of 500kV large span transmission tower was established, and several working conditionswere considered. The effects of computing modek material nonlinearity and geometric nonlinearity were discussed . finally, the simulative results are compared with the real tower trial results, and some useful conclusions are found out. Finally, the function and ultimate load capacity of flange joint is studied.