Background: Fiber reinforced polymer (FRP) systems have been used for more than 15 years and are becoming a widely accepted method of strengthening concrete structures. FRP systems for strengthening reinforced or prestressed concrete girders consist of externally bonded laminates or near-surface mounted bars. These systems may contain either carbon or glass fibers. Extensive research has shown that FRP systems improve both short-term and long-term flexural behavior of concrete girders. ACI Committee 440 has developed guidelines for design and construction of externally bonded FRP systems for strengthening concrete structures.

In contrast to flexural behavior, there are less experimental and analytical data on the use of FRP systems for shear strengthening girders. The results of several experimental investigations have shown that FRP systems can be effective for increasing the shear strength of concrete girders, but there have been limited analytical studies of the shear behavior of concrete girders strengthened in this manner. Design of FRP strengthening systems has been based on system- or project-specific research. An AASHTO design method for FRP shear strengthening of concrete girders is needed.

Objective: The objective of this project is to develop design methods, specifications, and examples for design of FRP systems for strengthening concrete girders in shear. The proposed specifications should be in LRFD format and should be suitable for recommendation to the AASHTO Highway Subcommittee on Bridges and Structures for adoption.

Status: The project is complete. The final report has been published as NCHRP Report 678 and distributed to Program sponsors (state departments of Transportation).  The report is available at https://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_rpt_678.pdf