Characterization of Joint Wind and Ice Hazard in Midwestern United States

Reliability-based design of infrastructure requires the probabilistic assessment of jointly occurring natural hazards. As infrastructure design practices evolve, it is important that multiple hazards be considered - for example, wind and storm surge in a hurricane, an earthquake generating a tsunami, or strong winds and high temperatures leading to wildfires. These jointly occurring hazards in some cases can be more devastating than a single hazard. This paper describes the assessment of two jointly occurring hazards: wind and ice. For locations in the United States, wind and ice [e.g., freezing rain (FR)] are hazards whose properties are of interest for the design of transmission lines and other energy infrastructure (e.g., wind turbines). Using archived meteorological data from measurement stations in the Midwest, occurrences of icing conditions and the wind speeds that accompany them were identified and input into a simple ice accretion model. Observations from wind speed and ice thickness were fit to probability distributions, and simulations using these distributions were constructed. These simulations were then compared with the observed data and with existing prescribed treatments of these two hazards in design loading guidelines, such as ASCE 7. It is shown that the ASCE 7 method is overly conservative when considering joint hazards.