Structural vulnerability of power transmission line supports: development of fragility curves for snow avalanche loads

Snow avalanches pose a significant threat to power transmission lines in mountainous regions, where support structures are exposed to extreme dynamic forces. This study investigates the structural vulnerability of transmission line supports subjected to avalanche impacts, focussing on the development of fragility curves for wooden and steel poles as well as transmission towers. The analysis specifically considers both the dense snow avalanches and saltation and powder components as hazards, which exerts substantial dynamic loads on these structures. A simplified analytical approach is used for poles, while pushover FEM simulations assess the performance of transmission towers. The study evaluates the probability of failure under different avalanche flow conditions, considering a range of structural configurations with varying geometries and element sizes. The findings provide quantitative insights into the vulnerability of transmission line supports, offering a valuable tool for risk assessment, structural design, and land-use planning in avalanche-prone areas. The results emphasise the importance of incorporating avalanche-induced loads into the design of this type of infrastructure.