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Development of Design Guidelines and Mitigation Strategies for Wind-Induced Traffic Signal Structure Vibrations

Project Summary

It has now been well-documented that mast-arm type structural supports for traffic signals can exhibit large-amplitude vibrations under wind excitation. Such vibrations can result in reduced fatigue life of the arm to pole shaft connection, and are believed to be the cause of many failures of traffic signal structures that have been reported in the state of Texas as well as in other states within the US. Extensive research has been conducted to study the causes of the vibrations and to develop corresponding mitigation strategies. To this date, however, the excitation mechanisms and the vibration characteristics are yet to be fully understood, and countermeasures that are both effective and efficient remain to be successfully developed. The objectives of this research project are: (1) to further understand the mechanisms of traffic signal structure vibrations and to develop analytical models that enable statistically assessing the failure risk of Texas standard traffic signal structures; (2) to develop guidelines for the design, fabrication, and implementation of traffic signal structures , such as limitations on placement and sizes of items placed on signal pole arms; and 3) to develop mitigation strategies for reducing or eliminating wind induced vibrations. We will conduct four phases of study to achieve the prescribed objectives. In phase I, we will conduct full-scale field measurements of representative traffic signal structures and wind tunnel tests of sectional models to further understand the excitation mechanisms and the vibration characteristics. In phase II, we will develop analytical models based on understandings from phase I for predicting wind-induced vibration characteristics and estimating fatigue loads of traffic signal structures of various configurations. In phase III, we will develop statistical methodologies for assessment of failure risk by integrating structure-specific vibration characteristics and fatigue capacity with site-specific wind climate data. In phase IV, we will use the combination of analytical simulation and full-scale measurements to develop guidelines for design, fabrication, and implementation of traffic signal structures, as well as to develop, test, and optimize mitigation devices for reducing or eliminating wind-induced vibrations of support structures for traffic signals.

Project Number

0-6649

Status

Completed

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