Fragility Analysis of Transmission Line Subjected to Wind Loading

Neither structural properties nor wind loads are deterministic; accordingly, a fragility analysis of overhead transmission towers can be employed to comprehensively evaluate their strength capacity. Here, a fragility analysis method for a transmission line under wind loading is developed that incorporates the uncertainties of structural parameters and wind loads into a numerical model. First, a simplified model with one tower and two span lines is presented to improve calculation efficiency; this model is validated via a comparison with a complete tower-line system under both static and dynamic conditions. Then the fragility analysis process for transmission towers subjected to wind loading is presented in three main steps: development of uncertainty models and wind loadings, nonlinear dynamic analysis, and regression analysis. Afterwards, the random variables and their corresponding probability distributions are determined. Finally, a case study of a real operational transmission tower under wind loading is carried out. The results indicate that the consideration of a greater number of uncertainty parameters leads to a greater dispersion of the fragility curve and that the wind attack angle has a significant influence on the fragility curve.