Research On Shear Behavior Of RC Beams Strengthened With NSN CFRP Strips

Fiber Reinforced Polymer / Plastic(FRP)has been widely used in the field of civil engineering reinforcement because of its advantages of light weight,high insulation,high mechanical strength,less recyclability and corrosion resistance.Embedded FRP reinforcement technology is a new reinforcement method proposed by foreign scholars in recent years,which slot in the surface of concrete structural components,put FRP slats or bars into them,bond both of them with cementing material to achieve the purpose of common force.At present,the embedded FRP reinforcement technology is mainly focused on the study of bending,there are still many problems to be solved for the shear reinforcement.In this paper,the finite element model is established by the four beams(one contrast beam and three test beams)of the existing experimental data,and the simulation results are compared with the experimental data to verify the reliability of the finite element model.Based on the same amount of CFRP slabs reinforcement,two contrast beams and 12 reinforced beams are established.The CFRP slab embedding angle,shear span ratio and slot spacing are used as the research parameters to analyze the failure mode and shear load Force,Stiffness,Stirrups and CFRP Strain of the reinforced beams.In this paper,based on the previous effective strain of the research results when NSM FRP peeling occurred.The formula of shear capacity of RC beams strengthened with embedded CFRP is deduced based on Truss Model.Through the finite element analysis,based on the same amount of CFRP slab reinforcement,the shear strength and rigidity of the strengthened beams strengthened by different reinforcement methods are improved in different degrees,but the increase of the crack load of the reinforced beam is not particularly obvious.In the same slotting mode,the increased range of shear capacity under 45°angle of embedding is the largest,and the 60°angle reinforcement effect is the second,and the 90°angle reinforcement effect is the worst.The greater the shear ratio,the more obvious the reinforcement effect;with multi-slot and multi-plate reinforcement,CFRP utilization is higher,the increased range of shear capacity is greater.Through the stirrups,the load strain curve of CFRP can well reflect the cracking load of oblique cracks.At the beginning of load loading,concrete,stirrup and FRP slab work together.At this time,the effect of CFRP slab is not obvious,tends to elastic stage.When the oblique cracks appear,the contribution of concrete is weakened,at this time,stirrups,CFRP entered the working state officially,strain increases dramatically.Through the comparison of the calculated and simulated values of the calculation formula of the shear capacity of the embedded CFRP strengthened beams proposed in this paper,it is found that the two data are in good agreement with each other.