Extending Service Life through Pre-emptive Retrofits

Several hundred bridges are known to have developed one or more types of fatigue cracks. Often several types of fatigue cracks have developed in a single bridge because different details existed on the structure. Increasing demands on the aging infrastructure of the United States has resulted in accelerated deterioration of structural components. During the period between 1960 and 2000, a number of localized failures developed in steel bridge components due to fatigue crack propagation. In a few cases, brittle fracture resulted from crack instability without detectable fatigue cracking. The recent fracture of girder sections in the Hoan Bridge in Milwaukee, Wisconsin, is an example of an unexpected failure from a welded web detail.