Risk-Based Reliability and Cost Analysis of Utility Poles Subjected to Tornado Hazard

Tornadoes are hazards with low probability of occurrence and high consequences that cost the United States billions of dollars each year. Electric power distribution systems are susceptible to damage due to tornadoes, with utility poles being the most vulnerable components. Additionally, the reliability of power distribution systems can be affected by the deterioration of the strength of utility poles with age. Many utility companies nowadays are considering the use of steel and prestressed concrete poles instead of wood poles, which are the most widely used in the United States. To date, very few studies have been performed to study the behavior of power networks when subjected to tornadoes. This paper proposes a framework to compare the reliability of wood, steel, and prestressed concrete utility poles subjected to tornadoes through fragility analysis taking into account the deterioration of the strength of poles with age. In addition, fragility analysis is used to perform life cycle cost analysis and scenario-based cost analysis on utility poles subjected to tornadoes. The results show that utility poles are vulnerable to even weaker tornadoes of EF1 and EF2 scales. Because EF1 and EF2 tornadoes have a considerable probability of occurrence, especially in tornado-active regions, this supports the direction toward designing utility poles against those tornadoes. Moreover, the age of utility poles is shown to have a large impact on their resistance to tornadoes, with aging poles vulnerable to tornadoes that are much weaker than those that new poles can resist. (c) 2019 American Society of Civil Engineers.