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Project: T163700 #33/109
 

The structural design of overhead lines accounts for extreme climatological events, including wind and ice loads, properly combined to provide adequate reliability of components. Apart from direct climatological loads (transverse and vertical), the line is also exposed to longitudinal loads arising from differential ice loads. These arise from ice shedding, a phenomenon that occurs when ice sheds and creates unbalanced longitudinal loads on adjacent structures. This work presents reviews of literature and standards regarding ice and ice shedding loads in the structural design of transmission lines. A finite element code is implemented based on a co-rotational formulation for 3D beams. Two models are presented: a full model, where the towers, transmission lines, and ground wires are simulated in the same mesh, and a simplified model, where only one transmission line is simulated and the tower stiffness is considered in a simplified manner. The full model is applied to a sensitivity analysis. Three different towers are addressed: a truss steel tower, a steel pole, and an H-frame wood pole. Results allow the proposition of prediction formulas and dynamic impact factors to estimate dynamic loads from the correspondent static loads. The conductor cable tension and unbalanced forces of cables acting on towers are addressed.

Keywords:

Ice shedding, Finite element method, Sensitivity analysis.