NCHRP Report 595  documents research performed to develop recommended revisions to the AASHTO LRFD Bridge Design Specifications to extend the applicability of the flexural and compression design provisions for reinforced and prestressed concrete members to concrete strengths greater than 10 ksi. The report details the research performed and includes recommended revisions to the Specifications. The material in this report will be of immediate interest to bridge designers.  The report appendices are available HERE.

The AASHTO LRFD Bridge Design Specifications state: "Concrete strengths above 10.0 ksi shall be used only when physical tests are made to establish the relationships between the concrete strength and other properties." When the LRFD specifications were written, the data were insufficient to demonstrate that the provisions were applicable to concrete compressive strengths above 10 ksi (high-strength concrete). Nevertheless, recent research has started to address design issues with high-strength concrete, and the FHWA Showcase Projects are encouraging the use of high-strength concrete in bridge structures. There is a need to expand the LRFD specifications to allow greater use of high-strength concrete.

The objective of this research was to develop recommended revisions to the AASHTO LRFD Bridge Design Specifications to extend the applicability of flexural and compression design provisions for reinforced and prestressed concrete members to concrete strengths greater than 10 ksi. Companion NCHRP Projects 12-56 (published as NCHRP Report 579) and 12-60 (publication pending) address shear and transfer and development length, respectively.

This research was performed by North Carolina State University, Florida International University, Henry G. Russell, Inc., and Berger/ABAM Engineers. The report fully documents the research leading to the recommended revisions to Section 5 of the AASHTO LRFD Bridge Design Specifications.