Research On Bending And Shearing Behavior Of Reinforced Concrete Beams Strengthened With FRP Under Composite Mechanical Anchoring

The use of externally bonded fiber-reinforced polymer is currently one of the most popular techniques for the rehabilitation of concrete structures.However,the efficacy of this technique is limited by the relatively weak adhesive interface it provides,which often causes premature debonding of the FRP materials from the concrete substrate and thus has definitely hindered the rapid application of the technique.In order to delay FRP peeling and improve the ductility and bearing capacity of reinforced members,many universities and scientific research institutions have developed various reinforcement technologies.Such as mechanical anchorage,FRP-ECC hybrid reinforcement,end anchorage and hybrid bonding(HB).In this paper,a new type of ductile end anchorage system is established based on the new ductile anchorage developed by our research group.At the same time,stiffeners are added to improve the hybrid bonding technology(HB)to solve the warpage problem of out-of-plane steel plate,and to establish a set of middle anchorage system.The purpose of these two reinforcement systems is to improve the ductility and bearing capacity of reinforced members,and ultimately realize the ductility conceptual design of composite mechanical reinforced concrete structures.Based on the above ideas,the flexural-shear behavior of reinforced concrete beams strengthened with FRP under composite mechanical anchorage is studied experimentally and theoretically,and the failure modes and ultimate bearing capacity prediction models based on the central anchorage system and the end anchorage system are established respectively,which have good accuracy compared with the test results.The main contents include:(1)The experimental beams of the anchorage system in the middle of the bending beams are treated by mechanical chiseling,and the flexural behavior of reinforced concrete beams strengthened by FRP is tested after reasonable stiffening ribs are added.The effects of different torques and thickness of FRP strips on failure modes,ductility,bearing capacity,FRP strain distribution and shear stress distribution of reinforced beams are studied.Based on the test results,a prediction model for the bearing capacity of reinforced concrete beams strengthened with HB considering the thickness of FRP strips and different confinement sizes of FRP strips is proposed.(2)A new type of ductile anchor developed by the research group for FRP end application of flexural beams is used to anchor reinforced concrete beams.The effects of different width of deformed section of anchor on failure mode,ductility,bearing capacity,FRP strain distribution and shear stress distribution of reinforced beams are studied.Based on the test results,a prediction model for failure modes of reinforced concrete beams and bearing capacity of reinforced concrete beams is proposed.(3)FRP reinforcement of reinforced concrete beams with end anchorage system of shear beams using a new type of ductile anchorage developed by our research group to anchor the end of FRP strips,the effect of different width of deformation section of anchorage on failure mode,ductility and bearing capacity of reinforced beams was studied.Meanwhile,the development of FRP along beam high strain and the strain development of FRP along main crack were analyzed by means of VIC-3D analysis software.The test results show that the end anchorage system can effectively improve the ductility and bearing capacity of shear beams and the utilization ratio of FRP materials.