Evaluation of member and structural redundancy on the US-421 bridge over the Ohio River
After several historical bridge failures, the fracture critical bridge classification was implemented for bridges in which the failure of a single member would probably lead to failure of the structure. This designation requires special inspection and bridge monitoring guidelines to be met increasing the lifetime cost of the bridge. As such, most bridge owners do not build new fracture critical bridges today. However, there is a very large population of older bridges that are deemed fracture critical. In order to reduce costs to state departments of transportation, it would be beneficial to remove the fracture critical designation from some bridges. This may be accomplished by considering the redundancy of the structure. Currently, there is no provision to allow bridge owners to make use of redundancy in the structure. In older, built-up, riveted structures, there may be significant capacity present in both member and structural redundancy. This capacity could be significant enough that, even in a failed state, there may be ability for load redistribution to prevent failure of the bridge. This research is focused on the use of a simple modeling technique to predict structural redundancy. The proposed modeling seems to have acceptable correlation to the controlled load testing using field instrumentation. Destructive testing will be performed to confirm the ability of the program accurately predict redundancy in a damaged state. Such models may be the first step toward proving adequate bridge redundancy in order to remove entire bridges or specific members from the fracture critical designation.
Connor, Purdue University.
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