Affects of Geometry on Weld Toe Stress Concentration of Socket Connection Details

Traffic signs and signals are often supported by flexible cantilevered structures that are susceptible to wind-induced vibration and fatigue. Following the collapse of a cantilevered structure in Michigan, research efforts were undertaken to better understand fatigue loading and resistance of welded details in these structures. However, minimal resistance testing was performed, and many of the details published in the AASHTO design code were untested and extrapolated from other design codes. In the past eight years multiple research programs have been undertaken to perform resistance testing of traffic signal structure details, most of which has been focused on socket connection details. The socket connection is an efficient tube-to-transverse plate connection by which a plate with a hole the same diameter as the outside diameter of the tube is cut into the plate. The tube is partially slid into the plate and circumferential welds join the plate and tube on the outside and inside of the connection. This paper will discuss a finite element parameter study that characterized how socket connection geometry affects the stress concentration factor (SCF) at the weld toe where fatigue cracks occur.