Bridge Design Manual
The Bridge Design Manual (BDM) M 23-50 is a guide for those who design bridges for the Washington
for experience, good judgment, and common sense
State Department of Transportation (WSDOT). This manual supplements the AASHTO LRFD
Specifications. It explains differences where it deviates from the AASHTO LRFD Specifications.
It contains standardized design details and methods, which are based on years of experience.
The Bridge Design Manual is a dynamic document, which constantly changes because of the creativity
and innovative skills of our bridge designers and structural detailers. It is not intended for the design of
unusual structures or to inhibit the designer in the exercise of engineering judgment. There is no substitute
This manual and the following AASHTO Specifications are
the basic documents used to design highway
bridges and structures in Washington State:
• AASHTO LRFD Bridge Design Specifications (AASHTO LRFD)
• AASHTO Guide Specifications for LRFD Seismic Bridge Design (AASHTO SEISMIC)
The Bridge Design Manual is not intended to duplicate the AASHTO Specifications. This manual
supplements the AASHTO Specifications by providing additional direction, design aides, examples, and
information on office practice. The Bridge Design Manual takes precedence where conflict exists with
the AASHTO Specifications. The WSDOT Bridge Design Engineer will provide guidance as necessary.
References are listed at the end of each chapter.