Longitudinal Forces on Transmission Towers due to Non-Symmetric Downburst Ground Wire Loads

摘要

Spatial localization of downbursts causes unique oblique load cases on long span structures such as transmission lines that do not occur during synoptic winds. This loading scenario causes an unsymmetrical wind loading along the spans of the cables resulting in an unbalanced longitudinal force acting on the transmission tower of interest. This longitudinal force is highly nonlinear; it depends on the material and geometrical properties of the cables. Therefore, a nonlinear analysis should be conducted considering the various possibilities of downburst-cable configurations and the cable material and geometrical properties. The current paper focuses on developing a simplified and manual approach to estimate this damaging longitudinal force, which develops in ground wires of transmission lines. A literature review regarding the downburst wind field and the oblique configurations that cause the peak longitudinal forces in the cables is provided. Then, the study systematically examined the effect of the variations of the ground wire parameters on their longitudinal response. Based on the findings of the assessment study, a set of charts is developed and linear interpolation equations are presented to estimate the power of such a force. This approach can address a current gap in the available transmission line standards.