Typhoon fragility analysis of transmission tower-line system considering wind-induced fatigue

In typhoon-prone areas, structures are vulnerable to typhoon loads. Compared to monsoon, the wind speed and turbulence intensity of typhoon are larger, which leads to structures being more prone to wind-induced fatigue. The degradation of material properties caused by fatigue damage makes towers more likely to fail, which seriously affects the safe operation of transmission lines. The existing researches on wind-induced fatigue analysis of transmission towers ignore the influence of typhoon. Therefore, this paper proposed a typhoon fragility analysis method of transmission tower-line systems considering wind-induced fatigue caused by typhoon and monsoon, and illustrated the application process through analyzing the fragility of a transmission tower-line system in Shanghai. Firstly, the historical wind speed and wind direction data in Shanghai were collected and categorized, and the joint probability distribution models of wind speed and direction for typhoon and monsoon were established, respectively. Then, the wind-induced fatigue analysis of the tower-line system was conducted to calculate fatigue damage caused by combined typhoon and monsoon loads of members. Subsequently, based on the material degradation model, the finite element models with fatigue damage in different service times were developed. Finally, the fragility analysis of the tower-line system subjected to typhoon was performed, and the influence of wind-induced fatigue damage on typhoon fragility of transmission lines was studied. The results revealed that wind-induced fatigue damage significantly increased the failure probability of transmission tower-line systems subjected to typhoon, and the influence of typhoon should not be ignored in fatigue analysis. This analysis method provides another approach for evaluating the structural performance in typhoon-prone areas.