Comparison between monotonic and fatigue loadings responses of CFRP retrofitted RC beams

In the present study, a comparison between monotonic and fatigue loadings of CFRP strengthened RC beams is presented. The number of 3 control and 3 rerofitted beams are prepared for testing under transverse monotonic loading. In fatigue experiment, there are 2 control and 2 retrofitted RC beams considered. Dimensions of the tested beams are 150*150*1000 mm, and all of them are prenotched at the middle section. Considering the fatigue loadnig, the specimens are subjected to high cycle fatigue loading with a constant amplitude. The main contribution of this research is to identify the propagation of the cracks induces by fatigue loading and the assessment of produced interfacial stresses at the bond region between the FRP layer and the concrete substrate. An innovative experimental process is proposed in order to measure the interfacial stresses, which are crucial parameters in debonding mode of failure in FRP retrofitted RC beams. Strain guages are placed at the bond region between the FRP layer and the concrete substrate. When the specimens are subjected to the high cycle fatigue loading, changes of the stiffness properties of the beams and the interfacial stresses at the bond region near the cracked zone, could be detectable during the examination. The monotonoc loading was applied again to those specimens wchich were experienced under the fatigue loading. The comparison between responses of rerofitted and control RC beams for post fatigue loading static loading were explained in details and the effectiveness of the externsally bonded CFRP on controling of crack propagation and increasing the load capacity of RC beams are dicussed.