Fatigue Life Investigation of Traffic Signal Mast-Arm Connection Details

This study investigated the fatigue performance of commonly used traffic signal mast-arm details. Prior research indicated that certain variables such as base plate thickness, connection weld type, external collars, and galvanizing had significant effects on the fatigue performance of traffic signal mast-arms. This study was initiated to investigate further the influence of these variables identified by previous researchers as being critical to the fatigue performance of traffic signal mast-arms as well as to investigate the fatigue performance of certain traffic signal mast-arms currently in use. A total of 20 full-size mast-arm specimens were tested for fatigue performance over the course of this project. The results indicate that increasing the base plate thickness as well as using full-penetration welded connections significantly improves the fatigue performance while galvanizing significantly decreases the fatigue performance. By using the Value Based Design Analysis Method, the external collars are also shown to improve the fatigue performance of traffic signal mast-arms. A numerical evaluation of the test data indicates that increased base plate rotational stiffness also improves the fatigue performance of traffic signal mast-arms.