Innovative retrofit technique for distortion-induced fatigue cracks in steel girder web gaps

Cracking in web gaps of steel girder bridges is often difficult and expensive to repair, especially at the top web gap. A commonly-used retrofit technique involves creating new load path between a transverse connection plate and the top flange of the girder, by means of bolted angles on both sides of the transverse connection plate. This technique often requires removing portions of the bridge deck to create the bolted connection at the top flange, which is an approach that can incur significant expense and inconvenience to the traveling public. This study was aimed at evaluating the effectiveness of a newly-developed retrofit technique, in which connection is made between the transverse connection plate and the girder web, through use of bolted angles on both sides of the transverse connection plate and a backing plate on the opposing face of the girder web. The retrofit was evaluated through extensive structural testing and finite element modeling. Testing was performed on a 9.1-m [30-ft] long test bridge system, comprised of three 910-mm [36-in.] deep girders and a concrete deck. The systemwas loaded to produce distortioninduced fatigue cracking, and then the bridge was retrofitted with the newly-developed stiffener-to-web repair technique. Results of the testing were compared to findings from finite element analyses, as well as findings from structural tests performed on 2.7-m [9-ft.] long segments of similar girders tested under distortion-induced fatigue. Results have indicated that the newly-developed retrofit technique has significant potential for effectively controlling distortion-induced fatigue cracking in web gaps of steel girder bridges without requiring disruption to the concrete deck.