Evaluation of Fatigue Damage for Undamped Overhead Conductors Under Aeolian Vibration

The fretting fatigue of overhead transmission lines due to aeolian vibrations is a hazard that increases with the service life of such infrastructure. The aim of the paper is to introduce a comprehensive framework for assessing the residual life of Aluminum Conductor Steel Reinforced (ACSR) conductors to support optimal risk-informed decisions for planning their inspection, repair, or replacement. Utilizing wind and vibration data from a 450-meter undamped test line, a three-step methodology is developed. The first step is the estimation of the distribution of wind speed and direction at a specified non-instrumented location. The wind turbulence intensity is then estimated from the distribution while also considering local land surface characteristics. Next, a model is developed to estimate the amplitude and number of cycles of vibrations as a function of line and wind characteristics by using a proposed Energy Balance Principle (EBP) methodology. Finally, the probability of failure in fretting fatigue as a function of time is estimated by convolution of the distribution of predicted vibrations with the ACSR's Stress-Life (S-N) model. The Weibull S-N model is used to model the uncertainty in fretting fatigue resistance, and damage accumulation based on equivalent damage and Miner's law is used to define the limit state function. While the methodology is initially developed for ACSR Bersfort conductors, it is adaptable to other ACSR conductor types and line configurations.