Different strategies can be used to repair, rehabilitate and strengthen existing structures. Techniques based on Fiber Reinforced Polymer (FRP) materials appear to be innovative alternatives to traditional solutions because of their high tensile strength, light, weight, and ease of installation. One of the most common and useful FRPs is Carbon Fiber Reinforced Polymer (CFRP) used in sheets and anchors attached on the concrete surface to strengthen the section through addition of tensile capacity. The purpose of this study was develop a technique for assesses the strength of anchors for quality control purpose. However, to transfer tensile capacity to a concrete surface, the sheets are bonded to the surface with epoxy adhesive. As tension increase, CFRP sheets lose adherence of the epoxy from the concrete surface and finally debond. To avoid this failure, CFRP anchors are applied in addition at the epoxy. The CFRP anchors allow the CFRP sheets to utilize their full tensile capacity and maximize the material efficiency of the CFRP retrofit. The number and size of anchors play a critical role. However the capacity of CFRP anchors has not been investigated extendedly. A methodology for assessing the quality of CFRP anchors was developed using plain concrete beams and reinforced externally with CFRP sheets attached with epoxy and CFRP anchors. Applying load to the beam, allowed the development a tensile force in the CFRP sheets and a shear force on the CFRP anchors. The shear forces in the CFRP anchors were defined by the load applied to the beam and compared with forces based on measured stress in CFRP sheets. / text

Most reinforced concrete (RC) structures are continuous in some way, and many of these structures are strengthened using fibre-reinforced polymer (FRP) materials as a routine basis. The problem of how to exploit moment redistribution in FRP-strengthened continuous RC structures is still unresolved. Reduction in ductility has been recognised in such structures. However, FRP-strengthening is introduced as an effective method to enhance the strength and load bearing capacity of RC structures. As a result, design guidelines worldwide employ conservative guidance for design, such that they limit the potential exploitation of moment redistribution in FRP-strengthened members. To date, limited research has been conducted into the redistribution of bending moment in such structures. Previous theoretical studies have not yet led to a reliable and rigorous solution for quantifying moment redistribution throughout the loading cycle. In addition, a wide scatter of moment redistribution percentage findings, from zero to 56%, has been reported in previous experimental studies. This demonstrates the need for further research to effectively characterise the circumstances under which moment redistribution can be relied on, both into and out of FRP-strengthened zones in continuous RC flexural members. This research aims to encourage the use of FRP for strengthening existing RC structures in a more efficient manner. The findings help to better understand restrictions on moment redistribution into and out of FRP-strengthened zones, effect of mechanical anchorage of the FRP on the degree of moment redistribution, and the extent to which moment redistribution can be relied on. A new analytical model, only based on structural mechanics, is developed in this research. A comprehensive set of large-scale structural testing is undertaken to validate the analytical model under various strengthening circumstances. The analytical and experimental results show that moment redistribution can occur into FRP-strengthened zones to full capacity without any limitation, even if the FRP is unanchored. Further, bending moment can also be redistributed out of strengthened zones to a considerable extent (up to 20%), depending on the quantity and stiffness of the FRP, and provided that the FRP is fully anchored. A set of parametric studies is conducted to investigate the effectiveness of different parameters on the level of moment redistribution. The major parameters include compressive strength of concrete, steel reinforcement proportion, steel yield strength, FRP quantity and stiffness, ultimate strain of the FRP, strengthening configuration, load position, beam shape, and curvature ductility. The outcomes demonstrate that it is not only the curvature ductility of FRP-strengthened sections that is important to the capacity for moment redistribution (out of such zones), but also the mode of failure, strength of the other critical zones, the ratio of stiffness between the critical zones, and the loading arrangement. It is concluded that moment redistribution in continuous FRP-strengthened concrete structures should be permitted both into and out of strengthened zones, provided that the criteria for such redistribution are met.