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NCHRP 20-07/Task 193 [Completed]

LRFD Guidelines for the Seismic Design of Highway Bridges, Version 2
[ NCHRP 20-07 (Research for AASHTO Standing Committee on Highways) ]

  Project Data
Funds: 150000
Research Agency: Imbsen & Associates
Effective Date: 12/22/2004
Completion Date: 7/1/2006
Comments: Completed

Task 193, FY 2005
Development of LFRD Guidelines for the Seismic Design of Highway Bridges, Version 2

Consultant: Imbsen & Associates
Effective Date: December 22, 2004
Completion Date: July 1, 2006
Funds Allocated: $150,000

"Recommended LRFD Guidelines for the Seismic Design of Highway Bridges" (the Guidelines) were produced as an outcome of NCHRP Project 12-49. These Guidelines were submitted to the AASHTO Bridge Subcommittee for final review and possible adoption in May 2002. The Guidelines were evaluated through trial designs from the states of New Jersey, New York, Washington, Alaska, California, Georgia, Arkansas, Oregon, South Carolina, Tennessee, Missouri, Illinois and Nevada. Subsequent to this evaluation, unresolved issues have kept the Guidelines from being adopted by the Subcommittee.

Primary issues include the seismic hazard level, the increased seismic design effort required for bridges in some states, and complexity of the Guidelines for bridge engineers in the majority of states. Additionally, as NCHRP Project 12-49 was being completed, other new developments surfaced which should now be considered in any revision of the Guidelines.

Some work has been done during the past year under Federal Highway Project 094 to develop a road map for this effort (Task F3-4) and to begin to achieve a consensus on outstanding technical issues (Task F3-5). Nevertheless, the actual work to produce the updated document is outside the scope of Project 094.

Task 193 will build on the extensive technical studies completed under NCHRP Project 12-49 and reformat the guidelines that were produced under that project to have the "look and feel" of the current South Carolina Seismic Design Criteria in order to facilitate use by practicing engineers. Additionally, material from the Caltrans Seismic Design Criteria (SDC), ATC-32 and other state agencies will be integrated into the guidelines as appropriate. This project will provide user aids such as flowcharts, maps and charts. The road map and suggested approach developed under FHWA Highway Project 094 shall be used as a guide.

The project is complete. A number of states are performing trial design usign the recommended specifications. (NCHRP Staff: D. B. Beal)


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