Design of FRP Systems for Strengthening Concrete Girders in Shear

Abstract

Fiber-Reinforced Polymer (FRP) systems have been used on a project-specific basis for the last two decades. They are now becoming a widely accepted method of strengthening concrete structures. The acceptance and utilization of these new strengthening techniques depend on the availability of clear design guidelines, installation procedures and construction specifications. Standard specifications exist for all commonly used traditional materials in civil engineering structures. At this time, design specifications for FRP use are still under development. The results of several experimental investigations have shown that FRP systems can be effective for increasing ductility and strength to structural members such as columns and girders. As most of the research focused on strengthening of axial members of flexural members, there are less experimental and analytical data on the use of FRP systems for shear strengthening of girders. Shear strengthening with FRP is still under investigation and the results obtained thus far are scarce and sometimes controversial. Even in traditional reinforced concrete members without FRP, the shear design is a complex challenge and uses more empirical methods as compared to axial and flexural design methods. Adding FRP to the equation, with its specific design issues, would bring another level of complication in the design. These FRP-related shear design issues and lack of comprehensive analytical and experimental models are the main motivation for this research project. Thus, a thorough understanding of the shear design problem along with the development of an American Association of State Highway and Transportation Officials (AASHTO) design method for FRP shear strengthening of concrete girders is needed. As such, 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 will be in Load and Resistance Factor Design (LRFD) format and will be suitable for recommendation to the AASHTO Highway Subcommittee on Bridges and Structures for adoption.