Fatigue Repair of the Arkansas River Bridge

Since the Kansas Department of Transportation (KDOT) started its fracture critical bridge inspection program around the mid-1980s, many welded steel bridge details at the diaphragm (or floorbeam) to girder connections were found to have developed fatigue cracks, often due to the cause of out-of-plane distortion. While proper fatigue design philosophy has been developed and incorporated into the current AASHTO bridge design specifications, repair of existing bridges with fatigue cracking remains a challenge to the bridge engineering community, especially when the repair details happen to reside in locations with geometrical complexity, or when cracking is compounded by corrosion or impact damage. Beginning 1996, a series of research studies were performed through the collaborative effort between the KDOT State Bridge Office and the University of Kansas (KU). Five candidate structures were selected to examine the overall fatigue problem experienced by the KDOT steel bridges, using state-of-art finite element (FE) modeling technique. Two of these five bridges were then strain gauged, both before and after the repair, to ensure that the fatigue details were eliminated and the chosen repair method was effective. This paper discusses the research and repair findings of the first case study sponsored by KDOT, the Arkansas River Bridge.