A finite element study of welded aluminum shoe-base light pole details

Abstract

Cantilevered light poles are examples of lightly damped, slender structural systems subjected to wind (cyclic) loads making fatigue life analysis necessary. Experimental and numerical studies performed on welded aluminum shoe-base details often found on cantilevered light poles included thirty-five fatigue tested in the Structures Laboratory of the University of Akron that provided the basis for the analytical study described in this article. Twenty-two of the thirty-five specimens failed and the remainder taken as run-outs. In an attempt to understand the fatigue behavior of the welded aluminum details, parametric studies using ANSYS examined bolt circle diameter, fillet weld leg-size, socket depth, and tube thickness. An increase in the bolt circle diameter of 27% results in about a 50% increase in the local stress adjacent to the fillet weld, and a reduction in tip deflection. A 50% increase in the fillet weld leg-size from 6.35 mm (0.25 in.) to 9.5 mm (0.375 in.) corresponds to about a 14% increase in the local stress. Increasing the shoe-base socket depth by 51% leads to an increase of 36% in the local stress. An increase in the thickness of 40% from 6.35 mm (0.25 in.) to 8.9 mm (0.35 in.) reflects a 60% increase in local stress. The analysis demonstrated that the lowest factor of safety was observed adjacent to the toe of the fillet weld. Thermographic measurements confirmed the existence of a hot spot near the weld toe on the tube.