Although many tests have been conducted investigating strengthening reinforced concrete members with FRP materials, there are still many aspects of their use that remain to be investigated. The fatigue behavior of reinforced concrete beams strengthened with FRP composite sheets and strips, for instance, which is described in this paper, provides valuable information regarding the expected long-term performance of the FRP strengthening systems.
The present study examines the effects of one-dimensional FRP composite rehabilitation systems on the flexural fatigue performance of reinforced concrete bridge girders. Experiments are being conducted on reinforced concrete tee-beams with and without bonded FRP reinforcement on their tensile surfaces. The objective of this investigation is to determine whether such external FRP repair methods are able to resist fatigue loads and to establish the effect that these repair systems have on the fatigue behavior and remaining life of the girders.
Eight 508 mm deep reinforced concrete tee-beams having 5.6 m clear spans were tested with a concentrated load at midspan under constant amplitude cyclic loading. The details of these beams represent a 62% scaling of full-scale beams, removed from a 1961 Interstate, to be tested in 2002. Two commercially available CFRP repair systems were used to retrofit the stem soffits of the girders. The two retrofit systems were designed such that their stiffness was approximately equivalent.
Results from the fatigue tests are presented with particular attention paid to the FRP-concrete interface and its significant degradation and eventual failure under fatigue loading conditions.