This design memorandum describes WSDOT’s position in implementation of the new AASHTO Guide Specifications for LRFD Seismic Bridge Design. Beginning January 2008, WSDOT requires all new bridges, bridge widenings, and walls to be designed in accordance with the requirements of the AASHTO Guide Specifications for LRFD Seismic Bridge Design. The latest version (May 2007) of the AASHTO Guide Specifications for LRFD Seismic Bridge Design could be downloaded from: http://bridges.transportation.org/sites/bridges/docs/Seismic%20Guide%20Specification%20Ballot.pdf

The seismic provisions of the AASHTO LRFD Bridge Design Specifications 4th edition (force-based approach), as well as the seismic design provisions of the WSDOT Bridge Design Manual (BDM) chapters 4 and 7 will no longer be applicable. The WSDOT Bridge Design Manual will be soon updated to reflect the AASHTO Guide Specifications for LRFD Seismic Bridge Design.

The following items summarize WSDOT’s additional requirements and deviations from the AASHTO Guide Specifications for LRFD Seismic Bridge Design:

Background:

WSDOT requires the implementation of the AASHTO Guide Specifications for LRFD Seismic Bridge Design beginning January 2008. This design memorandum describes WSDOT’s position in implementation of this document. Some areas with obvious discrepancy with WSDOT design and construction requirements are identified and itemized in this memorandum. More requirements may be follows with the experience gained from the upcoming designs. The WSDOT Bridge Design Manual will then be updated to incorporate all these changes.

If you have any questions regarding these issues, please contact Chyuan-Shen Lee at 705-7441 or Bijan Khaleghi at 705-7181.

cc:   Mohammad Sheikhizadeh, Bridge Construction - 47354