The brittle fracture of the Hoan Bridge in December 2000 highlighted the fracture susceptibility of details containing intersecting welds in steel bridges. Though it is now known that details with intersecting welds should be avoided, many existing bridges in Indiana contain details with intersecting welds. Little experimental data on the fatigue performance of these details exists. The purpose of this study was to evaluate the fatigue strength of several details commonly found in steel bridges in Indiana that contain intersecting welds. Large-scale experimental fatigue testing were performed using nine steel beams to study the behavior of three basic types of welded details: a vertical stiffener, a horizontal stiffener terminating near a vertical stiffener, and a horizontal gusset plate coped to fit around a vertical stiffener. The welded details in this study were fabricated with varying degrees of web gap, defined as the distance between perpendicular weld toes. The results of the experimental testing were examined and compared to prior testing to determine if the size of the web gap affected the fatigue strength. Furthermore, the performance of drilled hole retrofits used to extend the fatigue life of these details was studied. Within the scope of the fatigue testing program, the presence of intersecting welds was not found to significantly affect the fatigue strength of vertical stiffener and horizontal gusset details. However, the size of the web gap may have had an effect on the fatigue strength of details where a horizontal stiffener terminated near a vertical stiffener. Further experimental testing is needed to more clearly define the relationship between web gap and fatigue strength for this case. Drilled hole retrofits were successful at prolonging the lives of these details to varying degrees, but it should be noted that the stress redistribution resulting from these holes may cause fatigue cracking at nearby weld toes.
