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Abstract
Recent design requirements for traffic signal and sign structures incorporated fatigue load criteria related to wind that are producing significant increases in size and cost. The Fourth Edition of the AASHTO Luminaire and Traffic Signal Specification (2002 with interims) specification is a significant change to past practice and often results in much larger and more costly structures. Here conservative principles (envelope wind demands and infinite fatigue life) for design at increased cost even for those regions not adversely affected by wind-induced fatigue. The states that do not have steady, sustained winds and have not experienced significant fatigue failures have concerns with the larger and more costly structures. A rationale basis for lowering the fatigue design loads may be appropriate.
This study compares fatigue failures with respect to wind power (expressed as a function of average wind velocity). Inspection reports for approximate 2500 cantilevered traffic structures and 700 high-mast luminaires were collected and analyzed for suspected fatigue cracking. Each structure was located spatially and the associated wind power classification for that location was noted. (Wind power classifications are used to site wind generators.) This research is limited to traffic signal structures.
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