Effect of CFRP-spacing on fracture mechanism of CFRP-strengthened reinforced concrete beam identified by AE-SiGMA

One of the most efficient techniques for improving the shear strength of deteriorated reinforced concrete (RC) members is bonding external carbon fiber-reinforced polymer (CFRP) composites to them. However, the stresses at the end region of CFRP or on the edges of cracks cause to exceed the shear strength of concrete and epoxy, resulting in the separation of CFRP from the concrete surface. Sudden failure of RC members after the separation of CFRP is unavoidable. In order to understand the interaction between CFRP and concrete, the unit strain values obtained from strain gauges situated on the top of CFRP have been utilized. Strain increments can only identify the crack existence, but the real size of cracks cannot be determined by the strain values. AE-SiGMA method has been developed to define the orientation of crack as well as its source location, and type. In this study, it is aimed to identify the effect of CFRP-spacing on fracture mechanism of CFRP-strengthened RC beams by AE-SiGMA Method. Accordingly, three specimens one of which was the reference were tested in the laboratory. Locations, types and directions of cracks were identified and discussed.