Bridges that are classified as failure critical by AASHTO require more frequent inspections thanother types of bridges, resulting in greater costs for their design and operation. These higher
costs are justified if the use of such bridges does indeed pose a greater risk to the traveling public
in comparison to other bridge types. Several historical events involving the failure of main loadcarrying
members in steel bridges, however, have demonstrated the ability of bridges to have
significant reserve load carrying capability. For example, the girder failure of the I-79 ridge at
Neville Island in Pittsburgh in 1977 and the Hoan Bridge in Milwaukee in 2000 have shown that
severe damage can occur without necessarily resulting in bridge collapse. Consequently, research
is needed to characterize and define the different redundancies that can be safely incorporated
into the evaluation of failure critical bridges. With such information, it may be possible to
modify inspection procedures and bridge classifications so that costs are dramatically reduced.
This project addresses the behavior of steel bridges after failure of a critical component. The
research will include nonlinear structural modeling coupled with laboratory testing to validate
analysis predictions. Modeling guidelines will be developed that can be used by bridge engineers
to evaluate the behavior of steel bridges with critical structural components.