RESEARCH PAYS OFF: MODERN AND COMPREHENSIVE BRIDGE DESIGN SPECIFICATIONS

Efforts to compile highway bridge design specifications began in 1921. The first edition of the Standard for Highway was published by the then American Association of State Highway Officials in 1931. Since that time the specifications have evolved through 16 editions. Although the specifications initially incorporated only an allowable-strength design philosophy, an approach that considers load variability was introduced in 1970. In 1986 state bridge engineers from California, Colorado, Florida, Michigan, and Washington submitted a letter to the American Association of State Highway and Transportation Officials (AASHTO) Highway Subcommittee on Bridges and Structures expressing their concern that the AASHTO Standard for Highway was falling behind the times, and that the 13th edition contained many gaps and inconsistencies. In addition, the specifications did not incorporate the load and resistance factor design (LRFD) philosophy used in Canadian and European bridge design codes and in other areas of structural engineering. This article discusses the response to these concerns, which led to the publishing of the AASHTO LRFD Bridge Design Specifications in 1994, and the benefits from the new specifications.