Analytical identification of bond-slip relationship of EB-FRP joints

Bond-slip relationship of externally-bonded (EB) fiber reinforced polymer (FRP) joints can be determined by either directly or indirectly from a pull-off test. The indirect analytical method is gaining popularity and has been recommended in recent literature because of the more consistent and accurate results it yields. To date, loaded end slip vs applied load curve is used for indirect identification of the bond-slip relationship, ignoring the free end slip. This work shows that ignoring free end slip may result in significant errors in measuring the bond-slip relationship. The analytical method is used in this work to derive closed form solutions for FRP strain, interface slips, and bond strength of EB-FRP joints. The analytical solutions are validated by experimental results. Using the analytical solution, it is clearly shown in the paper that free end slip affects results and should be considered in deriving bond-slip relationship of EB-FRP joints, especially when bond length is short.