Analysis On The Mechanical Behavior Of Reinforced Concrete Frame Joints Strengthened By Sprayed GFRP

Joints are an important part of the reinforced concrete frame structure,but also the force transmission hub.The damage in joints will lead to the overall structure collapse and cause serious harm,which has been confirmed by the earthquake disaster history.In recent years,the advantages of pasted fiber material has been widely recognized,which are the light weight,high strength,corrosion resistance,and the effective for beam,column and slab reinforcement.But when the pasted FRP is used to reinforce joints whose surface morphology and stress are more complex,the construction process will be very complicate and the reinforcement effect is poor.It is simple and with good bonding effect to use Sprayed GFRP reinforcement construction technique which is particularly applicable to the joints surface where the beams and columns are arranged in a crisscross pattern.The Sprayed GFRP can form a good overall constraint layer on the joint too.But the research of this technology applied to the joints is still in the initial stage.Therefore,this paper carried out research on mechanical properties of Sprayed GFRP reinforcing frame joints,in order to promote the development of the technology and provide the basis for application in reinforcement of the joint.First of all,this paper conducts the numerical simulation to an existing test of fiber material reinforced joints in the middle layer,and discusses the effectiveness of the fiber reinforcement;On this basis,the establishment of 7 dimensional cross joints and 7 T –joints which respectively analysis on mechanical behavior and influence factors that the Sprayed GFRP reinforced different types of joints;Finally,this paper proposes Sprayed GFRP reinforced joints shear bearing capacity calculation formula.The main work and research results are as follows:(1)This paper conducts the analysis with numerical simulation on the pseudo-static test of the joints in the middle layer strengthened by pasted FRP,and discusses the failure patterns and bearing capacity of reinforced joints.It is verified that the model can better reflect the mechanical characteristics of the actual component by comparingthe experimental data with the finite element simulation data.(2)The comparative analysis on the joints strengthened of mechanical behavior and bearing capacity that the Sprayed GFRP reinforcement length,thickness,and chopped glass fiber length and axial compression parameters,which through the finite element numerical analysis results of different types of joints that through strengthened by Sprayed GFRP.The results show that the joints with Sprayed GFRP reinforced can effectively limit the crack development,reduce the joint deformation,reduce the maximum stress of the concrete,and improve the ultimate bearing capacity and limit displacement.(3)Summarize and analyze with the current codes and the formula for the shear bearing capacity of FRP reinforcement joints,this paper proposed the calculation formula of shear capacity with Sprayed GFRP strengthened joints in the core area through the numerical analysis.And comparing the calculation formula of the theoretical results with the finite element analysis results which show that a good agreement between them.(4)Based on the numerical analysis and theoretical analysis results,this paper summarizes the influence factors of the mechanical properties of the Spayed GFRP reinforced joints,and puts forward the corresponding construction measures.