The main spans of this Mississippi River bridge consist of continuous steel two-girder system spans with cantilevered floorbeams. The Illinois DOT discovered cracks in the top flanges of various cantilevered floorbeams during a routine inspection. Modjeski and Masters was contracted to perform emergency services to investigate, repair, and rehabilitate the cause of the cracking.
Field testing included the installation and monitoring of gages and sensors at critical floorbeam overhang locations. Finite element analysis, refined to simulate the actual behavior of the structure based on field testing results, was performed to determine the cause of the cracks, the susceptibility of the current details to future cracking, and the appropriate repair. Repair plans were prepared for the replacement of all cantilever floorbeams at expansion dams and stringer relief joints; in addition, repairs included replacement of the stringer ends supported at these locations. Rehabilitation details were developed to correct the fatigue prone details and prevent future cracking.
Illinois DOT’s immediate response to the discovery of cracks was to remove all traffic above the overhangs, limiting the four-lane structure to two lanes. M&M worked under an extremely compressed design schedule of four months to allow construction to begin as soon as possible to restore full traffic to this structure.
|Length of Main Span||370 feet|
|Total Project Length||2,692 feet|
|Lanes on Structures||4 Lanes|