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Developing Endurance Characterization Curves for GFRP Reinforcing Bars


Expanding the American Association of State Highway and Transportation Officials (AASHTO) Load and Resistance Factor Design (LRFD) Bridge Design Guide Specifications for glass-fiber reinforced plastic (GFRP)-Reinforced Concrete Bridge Decks and Traffic Railings (BDGS for GFRP) to include all reinforced concrete members will require developing endurance limits that meets the AASHTO design needs. Also, BDGS for GFRP identifies areas where further work is needed. These areas include the creep rupture due to sustained tension load. This project should identify the appropriate endurance limits that would match the AASHTO LRFD Bridge Design Specifications reliability.

As part of the GFRP specifications, it is necessary for owners to require the manufacturers to certify, based on testing, that their product meets certain endurance limits. However, it is impractical to require each manufacturer to develop their own endurance curves. Therefore, new industry wide endurance limit characterization curves would allow manufacturers to assure that a product meets the endurance limits through simple short duration verification testing.


The objective of this research is to develop endurance limits that would meet the AASHTO LRFD Bridge Design Specifications reliability requirements. This work should include developing the applicable resistance factors.

Related Research:

The literature search did not provide sufficient information to indicate definite endurance limits for GFRP bars. Existing research points toward fatigue and creep rupture information specific to materials and environmental conditions and largely related to aerospace and marine applications.


This work would involve the following tasks:

  1. Literature search of test methods and accelerated testing.

  2. Develop testing procedures for both the creep rupture and fatigue.

  3. Develop testing program to produce the endurance characterization curves.

  4. Preform the testing.

  5. Review and analyze test results.

  6. Recommend endurance limits.

The testing and recommended results should cover products from multiple manufacturers.


Developing endurance limits would facilitate the development and implementation of efficient and effective GFRP reinforced concrete specifications.

Sponsoring Committee:AKB10, Innovative Highway Structures and Appurtenances
Research Period:24 - 36 months
Research Priority:High
RNS Developer:Sam Fallaha, P. E. (Sam.Fallaha@dot.state.fl.us)
Source Info:The currently proposed ASTM specification prepared under Subcommittee D30.10 does not provide tests methods or acceptance criteria for creep rupture or cyclic loading (fatigue). While there are standard test methods (ASTM D3479 for Fatigue properties; ASTM D7337 for Creep properties), the need for updated acceptance criteria remains outstanding. Also, ACI 440.1R-15 Guide for the Design and Construction of Structural Concrete Reinforced with Fiber-Reinforced Polymer (FRP) Bars recommends maximum sustained tension limits and maximum fatigue stress of 0.2ffu for GFRP reinforcement. This ACI limit was developed based on limited experience and early-generation GFRP bars. The new endurance design limit should be linked to a maximum time for creep and number of cycles for fatigue (e.g., a 125-year service life and 3 million cycles).
The current AASHTO LRFD Bridge Design Specifications is calibrated for a 75-year service life and a 2-million cycle fatigue threshold. However, GFRP is expected to lengthen and extend the service life, so a 125-year service life and 3 million cycles are more appropriate for GFRP specifications.
Date Posted:03/18/2017
Date Modified:03/20/2017
Index Terms:Glass fiber reinforced plastics, Load and resistance factor design, Performance based specifications, Durability tests, AASHTO LRFD Bridge Design Specifications, Creep,
Cosponsoring Committees: 
Bridges and other structures

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