Life-cycle assessment of transmission tower-line systems under coupled corrosion and wind fatigue

This study proposes a probabilistic life-cycle assessment framework for transmission tower-line systems (TTLSs) under coupled atmospheric corrosion and wind-induced fatigue. Based on atmospheric exposure data from Qingdao, a time-dependent corrosion model is established and incorporated into stage-wise finite-element models, while wind-induced fatigue damage is evaluated using dynamic time-history analysis and probabilistic wind-speed–direction information. Time-dependent fragility curves and a critical safety surface are subsequently developed, and the joint probability distribution of wind speed and wind direction is integrated to quantify failure probabilities at different service ages. The results show pronounced spatial and directional dependence of fatigue damage, with the upper cross-arm region generally exhibiting the highest fatigue demand. For the representative control member in Segment 11, the life-cycle model predicts a cumulative fatigue damage of 0.613, which is 51.36% higher than the 0.405 obtained from the conventional static model. Increasing service time causes the fragility curves and critical safety surface to shift toward lower wind speeds, while the 45° wind attack angle consistently produces the lowest safety margin. The complete-collapse probability increases markedly with service age and reaches 4.53 × 10 −6 at 50 years. These results demonstrate the importance of jointly considering corrosion, wind-induced fatigue, service age, and wind direction in the life-cycle reliability assessment of TTLSs.