Safety of power transmission line structures under wind and ice storms

The extreme events that are likely to occur for poles and towers of power transmission lines during severe wind and ice storms are discussed. Extreme wind storm, ice deposit and broken conductor events and relevant loads of structures are considered. The structural performance of prestressed spun (centrifugally cast) concrete poles of annular cross-section and metal towers are analysed. The time-dependent performance processes of particular members (sections or angle bars) are presented in terms of their random safety margin sequences. The survival probability of poles and towers as autosystems representing their multicriteria failure mode is analysed. It is recommended that their survival probabilities are calculated using the analytical method of transformed conditional probabilities. The target reliability index of poles and towers is considered.