As of December 2013, there were 607,751 bridges in the U.S. national bridge inventory, and 181,095 of those bridges have steel superstructures.   Fatigue cracking in steel bridge members is an issue that must be addressed in all structure maintenance programs. If a fatigue crack is allowed to grow and reach a critical length, fracture may occur with the possibility of structural failure of the member. Fatigue cracks may be caused by both in-plane and out-of-plane effects.

 

The vulnerability of a steel bridge superstructure to further damage depends on the loading conditions and crack locations. Immediate replacement of superstructure components with fatigue cracks is often not possible due to funding priorities, access, traffic, and environmental issues. Repair of fatigue cracking has been performed on numerous bridges.

 

Substantial research effort has previously been devoted to understanding the sources of fatigue-prone details and developing engineering solutions to prevent such cracking through enhanced design and construction practices. However, a significant portion of the existing bridge inventory comprises steel structures and systems that contain fatigue-cracked or fatigue-prone elements. 

 

Bridge Preservation and Bridge Maintenance Engineers and Practitioners would benefit from a  summary of current transportation agency and industry practices and procedures used to repair fatigue cracks in existing steel bridges, and the effectiveness of the various repair methods in mitigating further growth of existing fatigue cracks.

 

The objective of this project was to develop proposed AASHTO guidelines for maintenance actions to address fatigue cracking in steel bridges. The proposed guidelines covers as a minimum: repair procedures and detailing, and includes maintenance and preservation actions to mitigate further growth of existing fatigue cracks in steel bridges.