The project is proposed to investigate what improvements can be made to the base plate to pole connections for traffic structures, such as socket welds, to improve their fatigue life. Recent research on the fatigue life of traffic signal mast arm to pole socket welded connections has shown that the fatigue category of this detail is E¿ and sometimes less. The addition of stiffeners did increase the fatigue performance, but not to the level predicted by the AASHTO Specifications. This research has also shown that small changes in various connection details, such as plate thickness, bolt pattern, and stiffener pattern, can improve the fatigue life of the connection. More research is needed to develop a better understanding of the effect of these changes, and to provide a systematic way that this knowledge can be incorporated into the design process and the AASHTO specifications for signal poles, high mast illumination poles, and other traffic structures.

Objectives 1.Develop a comprehensive list of connection details that affect the fatigue life of various commonly used connection details 2.Determine which changes to these details could feasibly and most cost effectively be used to increase the fatigue life of base plate to pole connections, with and without stiffeners 3.Determine a quantitative relationship between the changes in the details and their effect on the fatigue life of the connection 4.Develop a fatigue design guide that would show designers how they could quantitatively use the various recommended changes for use in there fatigue designs 5.Develop language to incorporate the above guide into the AASHTO Standard Specifications for Structural Supports for Highway Signs, Luminaires and Traffic Signals

Phases 1)Literature review A review of literature and recent research in the field of fatigue to provide a good idea of what kind of tests have been performed, which ones are worth expanding on, and what factors effect the fatigue life of the connection. 2)Develop test plan After a list of fatigue life influencing factors has been put together, develop a test matrix. The matrix will show which factors or details are going to be tested, the range to test over, the number of tests required, and any combination of factors or details that should be tested together. The matrices shall then be reviewed by fabricators and contributing agencies to ensure that all tests are worthwhile and that other factors that may be important or useful will also be considered. This will help to ensure that the results from testing will yield feasible and cost effective solutions. 3)Testing Since the number of tests required to develop an in depth understanding of the wide gamut of connection possibilities would be quite large, and the costs and time required for such tests also quite large, Finite Element Models (FEM) may be used. These models will be correlated with actual tests, and they will allow an increase in the number of combinations and changes that can be evaluated with a fixed budget and in a reasonable amount of time. 4)Summarize Results The results should be summarized in three ways. 1. A final report detailing all of the tests, the test methods, literature review, results, and conclusions. 2. A fatigue design guide which outlines how to quantitatively include improvements in the connection detail in the design process. 3.A list of changes to the AASHTO Standard Specifications for Structural Supports for Highway Signs, Luminaires and Traffic Signals to recommend to the AASTHO T-12 Committee.

A suggested amount of $25,000 is needed from each study partner.