In 1931, the American Association of State Highway and Transportation Officials (AASHTO) published the first highway bridge design standard ever undertaken in the United States. During the more than 50 years that have passed since then, bridge engineering theory and technology have changed significantly. In recognition of these changes, in 1986, AASHTO Highway Subcommittee on Bridges and Structures requested that the AASHTO-sponsored National Cooperative Highway Research Program (NCHRP) initiate a study to assess current U.S. bridge design specifications and report to AASHTO with a series of options for improving the specifications and overall bridge design process.
The study found that the existing specifications had a number of major gaps and inconsistencies. In addition, the study reported a number of other countries that previously used the AASHTO specifications had adopted theitr own specifications based in most cases on a limit-states design approach. The report recommended that AASHTO develop completely new bridge design specifications, basing them on the limit-states design philosophy. It also recommended comprehensive commentary.
The third draft of the specifications and commentary was completed in April 1992 and widely circulated for review and evaluation. The draft specifications have so far received a positive reception by state and industry bridge engineers.