Design Memorandum

TO:                  All Design Section Staff

FROM:            Bijan Khaleghi
DATE:             April 30, 2007
SUBJECT:       AASHTO LRFD 4th Edition 2007

The AASHTO LRFD 4th Edition 2007 shall be used for all WSDOT bridges and structures. The General Notes of all Contract Plans printed on or after May 1, 2007 shall call for “The AASHTO LRFD Bridge Design specifications 4th Edition Dated 2007.”

The following Sections of the LRFD 4th Edition shall not be used in design of WSDOT bridges:


The LRFD Article allows for some degree of continuity for loads applied on the bridge after the continuity diaphragms have been cast and cured. This assumption is based on the age of the girder when continuity is established, and degree of continuity at various limit states. Both degree of continuity and time of continuity diaphragm casting may result in contractual and design issues. WSDOT will continue its conservative way of designing these types of bridges for the envelope of simple span and continuous spans for applicable permanent and transient loads as stated in BDM Table 5.2.2-1

If you have any questions regarding this issue, please contact Bijan Khaleghi at 705-7181.

cc:   Mohammad Sheikhizadeh, Bridge Construction - 47354

       F. Posner, Bridge and Structures – 47340