Retrofitting Distortion-Induced Fatigue in Skewed Girders to Cross-Frame Connections

Distortion-induced fatigue is a serious problem faced by many aging steel bridges, and the problem is often exacerbated in skewed bridges. When distortion-induced fatigue cracks do occur in skewed systems, they can be especially difficult to repair. In situations where cross-frames are carried parallel to the skew, the connection to the cross-frame members is angled, presenting a geometric challenge during repair and non-symmetric loading of the detail. A retrofit called the angles-with-plate retrofit was previously developed at the University of Kansas for repairing distortion-induced fatigue damage in non-skewed steel bridges. The retrofit was subjected to a series of rigorous tests, and its good performance was the motivation to study the performance of the repair detail in skewed connections. This paper presents physical tests of the angles-with-plate retrofit conducted on girder subassemblies with 20 deg. and 40 deg.-skewed cross-frames. The tests were used to study the efficacy of the retrofit in mitigating fatigue crack propagation and localized deformations. It was found that crack propagation rates were drastically slowed while the retrofit was in place on the 20 deg.- and 40 deg.-skewed girder specimens, indicating good performance of the adapted angles-with-plate retrofit in this application.