Fatigue Life Assessment of Traffic-Signal Support Structures from an Analytical Approach and Long-Term Vibration Monitoring Data

Wind-induced, large-amplitude vibrations of traffic-signal support structures are frequently observed. Such vibrations can result in a large number of stress cycles and substantial fatigue damage. This paper presents the characteristics of wind-induced vibration of a traffic-signal support structure observed in a long-term, full-scale measurement project, which are used as a basis to understand the vibration generation mechanism. Based on the measured structural response, conditional on mean wind speed, wind direction, and turbulence intensity, the fatigue damage is evaluated using a closed-form spectral method with consideration of narrowband, non-Gaussian response characteristics. The uncertainty in the structural response under given wind conditions is quantified and included in the fatigue damage evaluation. The effectiveness and accuracy of the proposed approach are illustrated by comparing the results of the spectral method with that from the time-domain rainflow counting method based on the long-term stress time histories. The core parameters that influence the fatigue damage analysis and fatigue life prediction of traffic-signal support structures are also examined through a parametric study. (C) 2016 American Society of Civil Engineers.