Study On The Influence Of Anchoring Methods On Mechanical Properties Of FRP Flexural Strengthening Beams

Due to environmental erosion,design defects or the use of increased load and other reasons,resulting in some active bridge with structure or functional defects,then the current use of functional requirements can not be satisfied.Due to low cost and short duration,reinforcement for defect Bridges become a solution to the above problems.Because of its high strength,light weight,corrosion resistance and other advantages,fiber reinforced polymer/plastic(referred to as FRP)has been applied to concrete structure,steel structure and other structures in the strengthened field in recent years.Compared with the traditional strengthened method,such as increasing cross-section method,externally bonded steel plates method,changing structural system method,and external prestressing method,FRP strengthening method has a series of advantages of short construction period,no large machinery,almost no increase in the original volume and weight and so on.But the method still has some shortcomings for instance premature debonding.And anchoring is an effective technique to solve this problem.Anchorage measures can not only effectively improve the bonding strength of FRP-concrete interfacial and delay or prevent FRP sheet from premature debonding failure,but also improve the mechanics characteristics of the strengthened structure and enhance the reinforcement structure of the bearing capacity,stiffness,ductility and other mechanical properties.Therefore,it is of great significance to apply the FRP strengthening method to the actual engineering.In this paper,the reinforced concrete simply-supported beams are strengthened by three kinds of anchoring methods,such as steel plating anchorage,FRP U-wrap anchoring and hybrid bonding anchoring.Compared with the traditional FRP strengthening beams and unstrengthened beams,the flexural test is used to analyze and explain the influence of the beam strengthened by the externally bonded FRP(EB-FRP)and the unstrengthened beam on the bearing capacity,the mid-span deflection and the failure mode.In addition,the influence of anchoring methods on mechanical properties of FRP flexural strengthening beams is analyzed and compared.The experimental results show that the traditional FRP strengthening method can effectively improve the ultimate bearing capacity and stiffness of the beam compared with the unstrengthened beam.Compared with EB-FRP,the anchoring method can significantly improve the ultimate bearing capacity,the overall stiffness,ductility and strength utilization of FRP,more effectively to play the function of FRP.Through the comparison of the three anchoring methods,FRP U-wrap anchoring method is simpler and more effective.In addition,based on the design formula of the bond strength model and the ultimate bearing capacity of the existing FRP strengthening method,a formula for calculating the bearing capacity of the FRP U-wrap strengthened beam was put forward.