LRFD Minimum Flexural Reinforcement Requirements

NCHRP Research Report 906 presents proposed revisions to the AASHTO LRFD Bridge Design Specifications minimum flexural reinforcement provisions with detailed design examples illustrating the application of the proposed revisions. The proposed revisions are based on comprehensive analytical and large-scale testing programs for investigating the minimum flexural reinforcement requirements with consideration to scale effects. The material in this report will be of immediate interest to bridge engineers. According to the AASHTO LRFD Bridge Design Specifications, minimum reinforcement provisions are intended to reduce the probability of brittle failure by providing flexural capacity greater than the cracking moment. There was a concern with the current AASHTO LRFD minimum flexural reinforcement requirements, especially when applied to pretensioned or post-tensioned concrete flexural members. Increasing the nominal capacity of a member can result in increasing the cracking moment of the same member. This makes the design process iterative, and the current minimum reinforcement requirement for post-tensioned segmentally connected members is difficult to satisfy. This also may lead to less efficient design of pretensioned/post-tensioned concrete flexural members. Provisions for the design of minimum flexural reinforcement must be suitable for all structure and reinforcement types covered by the AASHTO LRFD Bridge Design Specifications and should be consistent with the LRFD design philosophy. Under NCHRP Project 12-94, Iowa State University was asked to propose revisions to the AASHTO LRFD Bridge Design Specifications minimum flexural reinforcement provisions. The research considered reinforced, pretensioned, and post-tensioned concrete flexural members (e.g., bonded and unbonded tendons for segmentally and other than segmentally constructed bridges).


  • English


  • Status: Completed
  • Funding: $550000
  • Contract Numbers:

    Project 12-94

  • Sponsor Organizations:

    Federal Highway Administration

    1200 New Jersey Avenue, SE
    Washington, DC  United States  20590

    American Association of State Highway & Transportation Officials (AASHTO)

    444 North Capitol Street, NW, Suite 225
    Washington, DC  United States  20001

    National Cooperative Highway Research Program

    Transportation Research Board
    500 Fifth Street, NW
    Washington, DC  United States  20001
  • Project Managers:

    Dekelbab, Waseem

  • Performing Organizations:

    Iowa State University, Ames

    Ames, IA  United States  50011
  • Principal Investigators:

    Sritharan, Sri

  • Start Date: 20130930
  • Expected Completion Date: 20180930
  • Actual Completion Date: 20180930
  • Source Data: RiP Project 38351

Subject/Index Terms

Filing Info

  • Accession Number: 01547641
  • Record Type: Research project
  • Source Agency: Transportation Research Board
  • Contract Numbers: Project 12-94
  • Files: TRB, RiP
  • Created Date: Dec 12 2014 1:00AM