Background: A Load and Resistance Factor Design (LRFD) code for bridges, the LRFD Bridge Design Specifications (hereafter referred to as the LRFD Specifications), has been adopted and published by the American Association of State Highway and Transportation Officials (AASHTO). Historically, AASHTO has relied on committee volunteers to maintain its bridge design specifications. The new code is a comprehensive document incorporating many new engineering concepts and design criteria, and it will be difficult to maintain properly in a timely manner using solely committee volunteer effort. As the LRFD Specifications are put into use by the states and others, there will be technical areas requiring additional research for their refinement. Additionally, as new information becomes available from research and practice, it should be considered in a manner consistent with the philosophy and calibration of the LRFD Specifications. To supplement its own volunteer activities in a timely manner, the AASHTO Subcommittee on Bridges and Structures will require outside professional assistance. An NCHRP project will be initiated to ensure comprehensive, coordinated improvement and implementation of the LRFD Specifications.

Objective: The objective of this project is to provide timely assistance to the AASHTO Subcommittee on Bridges and Structures (the bridge committee) in interpreting, implementing, revising, and refining the new AASHTO LRFD Specifications.

Tasks: This assistance will be provided by professionals who will perform, at a minimum, the following tasks: (1) Identify and discuss areas in the LRFD Specifications requiring modification, clarification, or interpretation in the near term. Specific areas that may need to be addressed include live load distribution, application of shear reinforcement design criteria based on compression field theory, temperature gradients, live load deflections, and substructure design. (2) Evaluate research findings that are recommended for adoption in the LRFD Specifications, as directed by the project panel. (3) Perform special studies, as directed by the project panel, for elements of the LRFD Specifications needing additional development. (4) Prepare and submit recommended revisions or new provisions for the LRFD Specifications, based on the work performed under Tasks 1 through 3, in a format suitable for consideration for adoption by the bridge committee. (5) Develop and submit reports to substantiate any recommended revisions or new provisions. (6) Present recommended revisions or other findings to the bridge committee or other groups as directed by the project panel. These presentations probably will be made at the annual meetings of the bridge committee. (7) Assist the technical committees of the bridge committee with special interpretations of the LRFD Specifications. This assistance will be provided directly to the chairs of the technical committees, and reports detailing the guidance given to the technical committees will be submitted to the project panel. (8) Develop research problem statements for areas needing additional study. (9) Perform other tasks as defined by the project panel. (10) Submit periodic reports detailing the work conducted in the project as well as anticipated activities. Submit a project final report documenting the entire research effort. Each of these reports must include a breakdown of expenditures for each project task and subtask.

Status: This project is complete.

A new project to provide continuing support to the AASHTO Highway Subcommittee on Bridges and Structures in interpreting, implementing, revising, and refining AASHTO load and resistance factor documents has been established by AASHTO.

Product Availability: An electronic copy of the research agencies final report is available on request.


The revisions to the AASHTO LRFD Bridge Design Specifications were incorporated into the recently published 2nd edition and are based largely on material developed in NCHRP Project 12-42. This specification is available from AASHTO.