Study On Seismic Performance Of Assembled Integral Reinforced Concrete Frame Beam-Column Joints

The development of precast concrete structure is the significant way for the for the future development of China's construction industry.The frame structure is a widely used structural system in the field of construction engineering,and its assembly method and seismic performance are the focus of current research.Based on the two connection methods of grouting sleeve and extruding sleeve,this paper proposes a new connection method of beam-column joints of assembled frame.In this paper,the middle joints with this type of connection is taken as the research object,and the quasi-static experiment is carried out on the test piece to study its mechanical performance,which provides a theoretical basis for the engineering application of the joints in the new assembly frame.The main contents are as follows:(1)By studying the existing connection methods of various assembly nodes,a new type of assembly frame beam-column joint structure is proposed,the construction process of this type of joint is introduced,and the mechanical mechanism and damage form are theoretically analyzed.three fabricated frame beam-column joint specimens and one cast-in-place reinforced concrete frame beam-column joint were made for comparison;(2)Three joint specimens in the assembled monolithic frame and one joint specimen in the cast-in-situ frame were produced as a comparison.Through repeated low-cycle load tests under the same axial pressure on each specimen,through quasi-static experiments on various specimens,the failure morphology,hysteretic characteristics,bearing capacity,deformation capacity,ductility,stiffness,energy dissipation capacity and other indicators of different types of specimens under low-cycle repeated loading were studied.The test results indicate that the new assembled beam-column joint specimen can basically achieve the bearing capacity of thecast-in-situ concrete joint specimen.Increasing the joint coupling rate can increase the ultimate shear bearing capacity of the joint,enhance the energy dissipation capacity of the joint,and increase ductility coefficient,post-cast steel fiber concrete in the core area of the joint can improve the load-carrying capacity of the joint specimen;(3)Based on the experimental research,the finite element software ABAQUS is used to establish a finite element model of the fabricated frame beam-column test piece,and the numerical simulation results are compared with the experimental results.A numerical analysis based on the changes of key parameters was carried out to analyze the influence of the reinforcement ratio at the beam,the concrete strength at the core area,and the axial compression ratio on the seismic performance of the new fabricated joint specimens.The analysis results show that the reinforcement rate of the beam is not obvious for the initial stiffness and initial bearing capacity;after entering the elastoplastic stage,the peak load capacity of the specimen increases with the reinforcement ratio;the higher the concrete strength level,the more ductile the worse,the easier the brittle failure occurs.As the axial compression ratio of the test piece increases,the load of the test piece at each stage of the stress increases accordingly,and the displacement ductility coefficient decreases.