Effect of bond degradation on fire resistance of FRP-strengthened reinforced concrete beams

FRP-strengthened reinforced concrete (RC) members experience significant loss of strength and stiffness properties when exposed to fire. At elevated temperatures, the rate of loss of such properties is influenced considerably by the bond degradation at the FRP-concrete interface. This paper presents a numerical approach for modeling the bond degradation in fire exposed FRP-strengthened RC beams. The numerical procedure is incorporated into a macroscopic finite element model which is capable of accounting high temperature material properties, different fire scenarios, and failure limit states in evaluating fire response of FRP-strengthened RC beams. The validity of the model is established by comparing predictions from the program with data from full scale fire resistance tests on FRP-strengthened RC beams. The validated model is applied to evaluate the effect of bond degradation on fire response of FRP-strengthened beams. Results from the analysis indicate that significant bond degradation occurs close to glass transition temperature of the adhesive leading to initiation of FRP delamination. The time at which bond degradation occurs depend on the fire insulation thickness and glass transition temperature of the adhesive. However, variation of adhesive thickness does not significantly influence fire resistance of FRP-strengthened RC beams.