Analytical Investigation of Repair Methods for Fatigue Cracks in Steel Bridges

Abstract

Numerous retrofits have been used to stop distortion-induced fatigue cracks from initiating and propagating in steel bridges. Some decrease stiffness in the web gap region to transfer the load path to an area of higher stiffness, while others increase the stiffness of the region to increase the capacity of the flexible web gap. The behavior of a bridge once a retrofit has been applied needs to be carefully considered because some retrofits may cause cracks to initiate in other locations or increase crack propagation rates. An analytical investigation of numerous retrofits is presented herein on a 2.7-m (9-ft) and a full bridge model with comparisons to configurations prior to retrofit application. This research is presented to extend the number of retrofit options to bridge maintenance engineers. This thesis is divided into three parts. Part I, "Evaluation of the Performance of Retrofit Measures for Distortion Induced Fatigue Using Finite Element Analysis" was presented at the joint conference of the National Steel Bridge Alliance and the World Steel Bridge Symposium in April 2012. The second part, "Finite Element Modeling Techniques for Crack Prediction and Control in Steel Bridge Girders" will be submitted for later publication. The final section, "Repair of Distortion-Induced Fatigue Cracks on 135-87-43/44 over Chisholm Creek" is a precursor to a final report that will be presented to the Kansas Department of Transportation.