| Rebar corrosion is one of the reasons for the premature damage of the reinforced concrete structure and the failure to reach the design life.It is difficult to achieve good results with traditional methods of preventing corrosion.The use of FRP(Fiber Reinforced Polymer)bars to replace or partially replace steel bars in concrete structures can effectively solve the corrosion problem of steel bars.Therefore,the research on the performance of FRP bar concrete structures has important application value.At present,domestic and foreign researches on FRP-reinforced concrete structures are mainly focused on the structural performance of components(such as beams and columns),while there is relatively little research on the seismic performance of FRPreinforced concrete frames.Frame joint is the most important part of the structure in seismic energy consumption.Once the joint fails,it will lead to the failure or collapse of the overall structure.The research on the seismic performance of the joint is an important part of the research on the overall seismic performance of the frame structure.Therefore,based on the research on the structural performance of FRP-reinforced concrete beams and column members in the early stage,the seismic performance of FRP-reinforced beam-column joints is further studied.In this paper,six 1/2-scale frame beam-column joint specimens are designed and fabricated.The component types are T-shaped edge joint and cross middle joint.The reinforcements are ordinary steel bars,full BFRP(Basalt Fiber Reinforced Polymer)bars and full GFRP(Glass Fiber Reinforced Polymer)bars.Through the low-cycle reciprocating load test,record the test phenomena and data of the deformation,cracking and destruction of the test piece under the low-cycle repeated load.The hysteretic performances of the failure form,energy dissipation capacity,stiffness degradation and ductility of different types of reinforced frame-column joints are analyzed.The numerical simulation software ABAQUS was used to perform finite element analysis on the beam-column joints,and the simulation results were compared with the test results to verify the effect of different factors on the seismic performance of the joints by changing different parameters.The main research results are summarized as follows:(1)FRP bars have high strength,light weight,and corrosion resistance.Replacing steel bars as stress bars is used in concrete structures.It has good stress deformation performance and unloading reset performance,and can exert its own excellent material advantages.(2)The beam-column joint specimens made of FRP bars combined with concrete showed good deformation and load-bearing performance.Even in the late loading stage,the bearing capacity of the FRP bar concrete joint samples did not decrease significantly.The main failure mode occurs at the inner beam end of the joint,which is mainly reflected by the bending failure of the beam end.The cracks first appear on the inner beam end,and then develop uniformly outward,and are evenly distributed on the entire beam.Since the elastic modulus of FRP bars is lower than that of steel bars,the initial stiffness of FRP bar concrete joint specimens is less than that of reinforced concrete joints,but the rate of stiffness degradation is relatively slow,which is similar to that of reinforced concrete joints.Its energy dissipation capacity and ductility ratio are slightly lower than reinforced concrete,but it has excellent deformation recovery capacity,and the overall seismic performance of the joint still has certain advantages.(3)Through analysis and research on the field test process,test phenomena,test data,hysteresis curve,skeleton curve,etc.,we can see that because the FRP bar has no obvious yield point,it has been in the elastic stage throughout the process.The ability to work with concrete is good,stress can be transmitted evenly from the middle to the outer end of the beam,and the cracks are densely and evenly distributed.Unlike reinforced joints mainly concentrated in the beam-column plastic hinge area,the seismic performance of the structure is improved to some extent.(4)Simulation and analysis of FRP reinforced concrete frame beam-column joints through ABAQUS numerical simulation finite element analysis software,and comparison with field test results.The simulation results are in good agreement with the field test results.The data model can be used for the earthquake resistance of FRP reinforced concrete frame joints Performance analysis.Then,the parameters were changed to simulate the calculation of the FRP-reinforced concrete beam-column joints.The results show that the axial compression ratio of the frame joints and the reinforcement ratio at the beam ends have increased,and the bearing capacity of the beam-column joints has been improved to some extent. |
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