Experimental Examination of Intact and CFRP Retrofitted RC Beams under Monotonic and High-Cycle Fatigue Loadings

The aim of this research is to investigate the effect of Carbon Fiber Reinforced Polymer (CFRP) composite fabric on monotonic and fatigue behaviors of reinforced concrete beams. To control the failure occurrence, a small notch was induced at the middle span in bottom surface for all of the studied RC specimens. Totally 12 beams were tested out of which 6 beamswere tested under monotonic loading and the other 6 beams were tested under fatigue cyclic loading. Every group of 6 tested beams consisted of 3 intact and 3 CFRP retrofitted RC beams. Dimensions of the specimens were 150×150×1000 mm and a 150 mm-deep notch was cut at the center of all of the specimens. The experimental examination was conducted to study stresses distributed throughout the critical regions in reinforced concrete and carbon fiber reinforced plastic (CFRP) strengthened RC beams. Fundamentally, these critical regions were cracked zones in CFRP-retrofitted RC beams. Results from monotonic and fatigue tests were compared to each other. In the monotonic test, measurements of shear stress distribution and stiffness were carried out until the failure of the specimens. In the fatigue test, the ceiling of applied load was considered at the level of design service load for bridges. In addition, strain measurements led to the calculation of interfacial shear stresses between concrete substrate and the CFRP layer. The variation of such load cycles are presented and discussed. Load?deflection curves, strain responses and propagation of tensile cracks would provide an insight into the performance of the CFRP strengthened beams subjected to different cycles of fatigue loading.