Project No. B371, Acoustic Emission and Strain Gage Monitoring of WIDOT Structure B-5-158, Tower Drive Tied Arch - Green Bay, Wisconsin. Technical Report #1Public Deposited
The in-depth inspection by WIDOT detected two sites that had visible cracks in the stiffener-to-hanger diaphragm welds, the east side of Hanger 6 in the north tie girder, and the east side of Hanger 4 in the south tie girder. Additionally, many ultrasonic indications were detected by WIDOT in the web-to-stiffener welds. On May 3, 1993, BIRL commenced testing. Test sites included Hangers 4 and 6 on both the north and south tie girders. A total of six sites were monitored (the west side of Hanger 4 on the north girder, the east side of Hanger 6 on the south girder, and the east and west sides of Hanger 6 on the north and Hanger 4 on the south girder). These sites included all of the known cracks, sites that were adjacent to known cracks but with no known cracks, and sites that had no known cracks present either in or adjacent to the test site. The acoustic emission setup monitored both the stiffener-to-diaphragm and stiffener-to-web welds at each test site. Two strain gages were monitored at each of the test sites. Testing continued through May 13, 1993. Traffic loading during the tests included many large obviously heavy loads. A wide range of environmental conditions were encountered, including high gusty winds and temperatures ranging from 37 degrees F to 80 degrees F. Test results showed no detectable crack-related activity from any of the six test sites and very small live loads (30 to 50 µin.fin. strain) from the strain gage tests. These test results imply that some mechanism other than fatigue is responsible for the visible cracks.
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