Experimental Researches On Mechanical Properties Of RC Defective Beams Of Hybrid-Bonding Of FRP

Since fiber reinforced polymers (FRP) have the advantages such as their high tensile strength-to-weight ratio, good corrosion resistance and the moderate cost, strengthening, transforming and repairing of reinforced concrete structures using FRP composite materials has become an accepted engineering practice in recent years. The external bonded FRP (EB-FRP) has emerged as one of the most popular methods, and the most flexible operation for structural rehabilitation in recent years. However, in this reinforced method, the poor bonding strength between the FRP and the beams' surface usually induces the premature failure which is interfacial bonding which reduces the strengthening effect. In order to solve these problems, the domestic and foreign scholars developed different method such as plate end bonded FRP, mechanically fastened FRP, near surface mounted, fiber anchor bonded FRP and so on. However these methods could raise bonding strength of FRP in a certain extent, they wouldn't prevent premature failure completely, intermediate bonding and improve the utilizing rates of the tensile capacity of FRP. So new methods are needed to solve these problems.A New hybrid bonding FRP (HB-FRP) that combines EB-FRP and mechanically fastened FRP were developed by the Department of Building and Construction in city University of HK in 2008. This new technique used particular and simple mechanical fasteners which can be placed along the length of beams at certain spacing to prevent the separation between FRP and the beams' surface. Researches showed that the interfacial bond strength of FRP in HB-FRP is about 7.5 times greater than which in EB-FRP, indicating that this method is simple and efficient. However, more comprehensive investigation is needed to establish design models and guiding formula. Research findings whether could be directly applied to RC defective beams that needs to be studied further. Meanwhile, also a new anchor device with more safety and better stability will be developed. Thus, this thesis presents experimental studies on anchoring parameter, bonding behavior, flexing resistance and resisting shear of HB-FRP strengthened RC beams. The results show that HB-FRP system could prevent premature bonding of FRP compared with EB-FRP system. The HB-FRP strengthened RC beams have greater improvement in flexural capacity, ductility and utilization ratio of FRP. Function mechanism and failure mode of HB-FRP system were analyzed and corresponding design guidelines and formula were given on the base of date analysis.