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The National Academies

NCHRP 12-77 [Final]

Structural Concrete Design with High-Strength Steel Reinforcement

  Project Data
Funds: $600,000
Research Agency: University of Cincinnati
Principal Investigator: Bahram M. Shahrooz
Effective Date: 5/1/2007
Completion Date: 8/31/2010

NCHRP Report 679 provides an evaluation of existing AASHTO LRFD Bridge Design Specifications relevant to the use of high-strength reinforcing steel and other grades of reinforcing steel having no discernable yield plateau. The report also includes recommended language to the AASHTO LRFD Bridge Design Specifications, Sections 3, 5 and 9 that specifically permits the use of high-strength reinforcing steel with specified yield strengths not greater than 100 ksi when the specific article permits it. The material in this report will be of immediate interest to bridge engineers.

The AASHTO LRFD Bridge Design Specifications allow the use of reinforcing steel conforming to many different AASHTO and ASTM materials specifications, but limit the specified yield strength to 75 ksi. Reinforcement is now available that has yield strength in excess of 75 ksi. Typical steel reinforcement has well-defined yield plateaus whereas high-strength reinforcing bars generally do not. The higher strength and the lack of a well-defined yield plateau could alter structural behavior and do not satisfy some of the design assumptions in the AASHTO LRFD Bridge Design Specifications. Research was needed to evaluate the use of high-strength reinforcing steel in structural concrete.

The research was performed under NCHRP Project 12-77 by a team led by Dr. Bahram Shahrooz at the University of Cincinnati, Cincinnati, OH. Recommended revisions to the AASHTO LRFD Bridge Design Specifications to permit reinforcing bar yield strengths not exceeding 100 ksi were investigated and validated for concrete strengths up to 10 ksi and in some instances up to 15 ksi.

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