Use of Adhesives to Repair out of Plane Bending at Stiffener to Web Connections

Project summary:

Since 1989, AASHTO Specifications require a positive connection (bolted or welded) between a diaphragm or floorbeam connection plate and both flanges of welded girders. However, it used to be standard to weld or attach the connection plate to the tension flange, due to an unfounded reluctance to weld to tension flange. Unfortunately, there is a gap between the stiffener and the tension flange. Out-of-plane distortion of the web in this gap area is probably the single largest cause of fatigue cracking of steel bridges across the country. Typical repairs include rigidly attaching the connection plate to the girder flange or cutting back the stiffener to increase the flexibility of the gap and accommodate the limited out-of-plane distortion. Rigidly attaching the connection plate to the flange, usually through a pair of half-inch-thick angle sections, is the preferred solution. However, bolting through the top flange requires access from the deck and it may be prudent to avoid field welding. The steel angles could be bolted to the connection plate and adhesively bonded to the flange. This alternative will be fatigue tested in the structural laboratory under conditions including induced out-of-plane displacement and field tested on Bridge 9340 TH I35W over the Mississippi River..