NCHRP Report 579 contains the findings of research performed to extend the applicability of shear design provisions for reinforced and prestressed concrete structures in the AASHTO LRFD Bridge Design Specifications to concrete compressive 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 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 shear design provisions for reinforced and prestressed concrete structures to concrete compressive strengths greater than 10 ksi. The research effort also included an article-by-article review of Section 5 of the Specifications to identify all provisions that directly or indirectly have the potential for preventing the extension of the specifications to high-strength concrete. Some findings from this project were used in developing the recommendations for simplifying shear design contained in NCHRP Report 549. Companion NCHRP projects 12-60 and 12-64 address transfer and development length, and flexure and compression, respectively; these projects are scheduled for completion in 2007.
This research was performed by The University of Illinois at Urbana-Champaign. The report fully documents the research leading to the recommended specifications.
