Distortion-induced fatigue cracking of girder-to-crossbeam connection

Abstract

Oregon Department of Transportation’s bridge no. 9743b is a multi-span, two-girder steel deck bridge connecting the busy interstates 5 and 205. Vertical cracks have been detected in the welded girder-to-crossbeam connections at the bents. Distortion-induced fatigue is suspected to be responsible for the cracking. Linear elastic beam analysis, 2-D and 3-D finite element analyses, and fatigue analysis were performed to determine the fatigue life of the connection based on highway moving loads and actual truck traffic data. Results of the analyses are discussed, and insight about the possible causes of distortion-induced fatigue cracking is presented. In conclusion, the live truck loading is ruled out as the cause, and the problem is narrowed down to the thermal loads.