Study of the Effects of Wind Power To Establish Fatigue Design Criteria for High-Mast Poles

Traffic signal poles and high-mast poles are used by transportation agencies to control and illuminate intersections; their structural design is governed by national specifications. Unfortunately, these flexible structures are susceptible to vibration from wind which leads to fatigue cracking near the welds. Recent changes to the requirements have called for expensive member size increases. However, for areas that have no problems with failures, such increases may be unnecessary and uneconomical. In a previous study conducted by the University of Wyoming, fatigue cracking of traffic signal poles was determined to be directly related to the average wind speed. However, high-mast data did not indicate the same behavior. The goal of this research is to gain a more complete understanding of the relation between wind speed and high-mast pole cracking through both the collection of more data and wind load modeling. It is hypothesized that the cracking is related not to the wind speed, but rather the wind that causes vortices to be shed at frequencies near a resonance. Through a database that will be created and a wind modeling sheet, it will be possible to make further recommendations to better predict where high-mast poles must be designed to be particularly fatigue resistant.