Fire Testing of Concrete and Steel Electric Utility Poles

A great threat to our nation, costing billions of dollars annually, are wildfires. These wildfires result from tinder-dry vegetation and conditions consisting of strong winds, low humidity, and warm temperatures. The 2018 Camp Fire in Northern California is currently the costliest, deadliest, and most destructive wild fire, having killed 88 people, destroyed more than 18,500 structures, and resulted in costs of approximately $15 billion. Over the years, utilities around the nation have had to deal with wildfire-related damage to their transmission and distribution lines, especially those that traverse wilderness areas. Moreover, there is growing evidence that, in some instances, the power lines themselves could trigger the wildfire due to vegetation into electrical distribution lines. The paper presents a summary of the performance of full-scale electric distribution poles when subjected to fire. The evaluation reported here addresses poles made of two materials: spun prestressed concrete and galvanized steel. The testing protocol, developed by Ackerman and RS Technologies in Canada, was adopted as it exposes the test articles to conditions that would be considered severe to extreme in terms of actual wildfire conditions occurring in the field. After exposure and cool down the poles were removed from the ground and transported to a test facility for strength evaluation. At this facility the pole was held in a fixture and loaded to failure. The intent of this strength evaluation was to gain some insight into the remaining strength after a simulated severe wildfire exposure. The paper also provides an overview of wildfire conditions and the basis for developing the test apparatus and procedure.