Detailing of Carbon Fiber Reinforced Polymer Anchorage for Shear Strengthening

Abstract

Carbon Fiber Reinforced Polymers (CFRP) have increased in popularity in the repair and strengthening of reduced shear capacity of concrete bridges. Significant design challenges arise when using CFRP to repair or strengthen bridge girders as the top faces of girders are in contact with decking (i.e. the members cannot be fully wrapped). A full wrap laminates all faces with CFRP and ensures that the failure mode is governed by shear fracture combined with, or followed by, fracture of the CFRP. The Florida Department of Transportation (FDOT) Structural Design Manual permits three-sided wrapping schemes (i.e. U-wraps), but the CFRP must be anchored to the girder to prevent debonding, an unfavorable failure mode. The primary anchorage method utilized in Florida is the installation of spike anchors. Although FDOT projects show that spike anchors provide sufficient strength, the anchors are invasive and impractical; hence, there exists a need to explore alternative anchoring solutions. The first objective of the research is to synthesize existing research on CFRP anchorage design and detailing with a focus on externallybonded shear strengthening and other externally-bonded end anchorage applications. The second objective is to provide recommended modifications to current design and detailing guidance of CFRP anchorage. Based on the synthesis, more tests are needed to better understand the failure mechanism of various anchors for prestressed concrete applications. Given the limited test data, the three most promising CFRP anchor details are spike anchors, mechanical anchors, and CFRP strips. The performance of all anchor systems should be experimentally validated prior to application.