Long-Term Fatigue Behavior of Aluminum Shoe Base Details Top Mounted Luminaries

With increased use of welded aluminum light poles along highways and in industrial service applications such as parking lots, harbors, stadiums, etc., it is important that they are sustainable and resist fluctuating wind induced stresses or fatigue loading. Forty-one welded aluminum shoe base light poles were fatigue tested in the structures laboratory of the University of Akron. The fatigue life of the test specimens was considered and used to develop a design S-N curve for the specific shoe base details used on the light poles. The proposed S-N curve derived from the test results, including the endurance limit in high cycle regime, was compared to the Aluminum Design Manual’s (2015) category F1.Among forty-one aluminum shoe base light poles, twenty-six specimens failed (63.4%) and the remaining survived (run-outs). Crack development in the specimens was observed on the surface primarily along the weld toe between the tube and cast shoe base. The lower bound S-N curve was extracted and provides approximately 97.5 percent probability of survival for the shoe base detail and is in a good agreement with category F1 of Aluminum Design Manual (2015). Additionally, the run-out data for the fatigue test results, which is taken to be 10 million cycles for the older tests and 20 million cycles for new test group, is in good agreement with the British Standard Institute 8118 and the Aluminum Design Manual (2015). The S-N curve is useful for investigating the fatigue behavior of the light poles during analysis for wind induced loadings.