FRP Tension Ties: State-of-the-Art Review of Existing Design Guidance for Debonding Capacity and Applicability to Concrete Diaphragm Seismic Strengthening

Fiber-reinforced polymer (FRP) ties can be used to provide tensile capacity to seismic-deficient concrete diaphragms, but there are no existing research or design provisions and guidance on how to design such ties is limited. Three commonly used design guidelines, ACI 440.2R, CNR-DT 200, and fib bulletin 90, have various provisions for calculating the axial tension capacity of FRP ties. These provisions have been summarized and their predictive ability compared with two databases, one for unanchored FRP ties and another one for FRP-anchored FRP ties. The unanchored tie data, compiled previously by others, consist of 855 test results from 135 documents; however, the range of parameters is limited, reporting primarily short, thin, and narrow FRP ties that are not representative of real practice. The second database was compiled by the authors and consists of 213 test results from eight papers; although it too is limited to short, thin, and narrow FRP ties anchored with small and shallowly anchored FRP anchors. Nevertheless, the behavior of anchored FRP ties from the database is described and guidance is provided to shape future research, necessary to confirm the suitability of FRP for diaphragm retrofits and develop design guidance.