BACKGROUND
The state departments of transportation (DOTs) have been investigating alternative reinforcement materials such as fiber reinforced polymers (FRP) to extend the service life of highway structures especially in aggressively corrosive environments. In the effort to further facilitate the use of these materials, the American Association of State Highway and Transportation Officials (AASHTO) adopted the AASHTO Guide Specification for the Design of Concrete Bridge Beams Prestressed with Carbon Fiber-Reinforced Polymer (CFRP) Systems and the AASHTO LRFD Bridge Design Guide Specifications for GFRP-Reinforced Concrete. Herein, both are referred to as AASHTO FRP guide specifications.
The current AASHTO specifications do not address the design of FRP auxiliary (non-prestressed) reinforcement in prestressed concrete girders. The behavior and the mechanical properties of FRP reinforcement (including carbon, glass, and basalt FRP reinforcement) are different from the traditional steel reinforcement, which is the basis of the current design specifications. Bridge owners, fabricators, designers, and contractors need specifications and guidelines for the design of prestressed concrete girders using FRP auxiliary reinforcement.
OBJECTIVES
The objectives of this research are to (1) propose modifications to the AASHTO FRP guide specifications for the design of prestressed concrete girders using FRP auxiliary (non-prestressed) reinforcement and (2) develop guidelines for the design of prestressed concrete girders using FRP auxiliary reinforcement including design examples and training materials to demonstrate the application of the proposed AASHTO FRP guide specifications modifications and guidelines.
Accomplishment of the project objectives will require at least the following tasks.
TASKS
Task descriptions are intended to provide a framework for conducting the research. The NCHRP is seeking the insights of proposers on how best to achieve the research objective. Proposers are expected to describe research plans that can realistically be accomplished within the constraints of available funds and contract time. Proposals must present the proposers' current thinking in sufficient detail to demonstrate their understanding of the issues and the soundness of their approach to meeting the research objectives.
PHASE I—Planning
Task 1.Conduct a literature review of relevant research considered to be the state-of-the-practice related to the design of prestressed concrete girders using FRP auxiliary reinforcement. The review shall include published and unpublished research conducted through the NCHRP; FHWA; and other national, international, state, and pooled-fund sponsored research.
Task 2. Synthesize the literature review to identify the knowledge gaps for the design of prestressed concrete girders using FRP auxiliary reinforcement. In addition, identify the current available FRP reinforcement and their applicability to this research from material and mechanical properties perspective. These gaps should be addressed in the proposed modifications or in the recommended future research as budget permits.
Task 3. Propose analytical and full scale testing programs, to be executed in Phases II and III, to achieve the project objectives. At a minimum, the programs should consider the following:
-
anchorage zone, confinement, and splitting reinforcement;
-
transverse shear reinforcement;
-
interface shear reinforcement;
-
longitudinal non-prestressed reinforcement;
-
pre-tensioning and post-tensioning of concrete bridge girders (excluding segmental bridges); and
-
three different fiber materials.
Task 4. Identify areas of the current AASHTO FRP guide specifications, AASHTO LRFD Bridge Design Specifications and AASHTO LRFD Construction Specifications that will be modified in Phase III.
Task 5. Provide an annotated outline of the proposed guidelines for the design of prestressed concrete girders using FRP auxiliary reinforcement including a list of design examples to demonstrate the application of the proposed specification modifications and the guidelines.
Task 6. Prepare Interim Report No. 1 that documents Tasks 1 through 5 and provides an updated work plan for the remainder of the research. This report must be submitted no later than 4 months after contract execution. The updated work plan must describe the process and rationale for the work proposed for Phases II though IV.
Note: Following a 1-month review of Interim Report No. 1 by the NCHRP, the research team will meet in person with the NCHRP project panel to discuss the interim report. Work on Phases II though IV of the project will not begin until authorized by the NCHRP. Phase I shall be limited to $40,000.
PHASE II—Analytical Program
Task 7. Execute the analytical program according to the approved Interim Report No.1.
Task 8. Finalize the full scale testing program work plan including a matrix of specimens and the design and construction drawings. Describe how the testing results will be utilized to achieve the research objectives.
Task 9. Provide a matrix of the design examples to demonstrate the application of the proposed modifications and guidelines.
Task 10. Prepare Interim Report No. 2 that documents the results of Tasks 7 through 9 and provides an updated work plan for the remainder of the project. This report is due no later than 8 months after approval of Phase I. The updated plan must describe the work proposed for Phases III and IV.
Note: Following a 1-month review of Interim Report No. 2 by the NCHRP, if necessary, the research team will meet in person with the NCHRP project panel to discuss the interim report. Work on Phases III and IV of the project will not begin until authorized by the NCHRP. Phase II shall be limited to $100,000.
PHASE III—Testing Program and Specification Modifications
Task 11. Execute the testing program according to the approved Interim Report No.2.
Task 12. Validate the analytical program based on the testing results and update accordingly.
Task 13. Develop the draft proposed modifications to the AASHTO FRP guide specifications.
Task 14. Prepare Interim Report No. 3 that documents the results of Tasks 11 through 13 no later than 12 months after approval of Phase II. The updated work plan must describe the work proposed for Phase IV.
Note: Following a 1-month review of Interim Report No. 3 by the NCHRP, If necessary, the research team will meet in person with the NCHRP project panel to discuss the interim report. Work on Phase IV of the project will not begin until authorized by the NCHRP. Phase III shall be limited to $300,000.
PHASE IV—Guidelines Development and Final Products
Task 15. Develop the draft guidelines for the design of prestressed concrete girders using FRP auxiliary reinforcement including the design examples, and prepare the training materials and illustrations (e.g., flowcharts, graphs). These deliverables are due no later than 4 months after approval of Phase III.
Task 16. Present draft final deliverables to appropriate AASHTO technical committees for comments and propose any revisions to NCHRP. Revise the proposed modification and guidelines, design examples, and training materials considering the NCHRP’s review comments and prepare ballot items for AASHTO Highway Subcommittee on Bridges and Structures consideration. The draft final deliverables are due no later than 6 months after approval of Phase III.
Task 17. Prepare final deliverables including: (1) the proposed modifications to the AASHTO guide specifications, (2) guidelines for the design of prestressed concrete girders using FRP auxiliary reinforcement with the design examples, (3) the training materials, (4) a final report that documents the entire research effort, and (5) a stand-alone technical memorandum titled “Implementation of Research Findings and Products.” See Special Note D for additional information.
Note: Following receipt of the draft final report, the remaining 3 months shall be for NCHRP review and comment and for research agency preparation of the revised final report. Phase IV shall be limited to $100,000.
STATUS: Research in progress
