Development of a Fatigue Design Load for High-Mast Lighting Towers

Abstract

Fatigue cracking has caused a number of high-mast lighting tower (HMLT) failures throughout the United States. Both buffeting and vortex shedding have been shown to contribute to the failures observed. To increase HMLT safety, an investigation of the loading spectrum and response was conducted. The study included multiple goals; the primary deliverable was the development of a rational wind load for the fatigue design of HMLTs. Long-term remote monitoring was used to collect wind and strain data from 11 HMLTs distributed throughout the United States over the course of 2 years in order to investigate the effects of buffeting, vortex shedding, and associated dynamic oscillations. Data obtained from the field monitoring led to the development of a notional load model for HMLT fatigue design. The combined wind effect concept for fatigue design, which accounts for the effects of a variety of wind-induced loads, is introduced. Results from the research have been implemented into current design practice.