Study On Seismic Performance Of Prefabricated Prestressed Frame Joints Of Buckle Mechanical Connection

In recent years,with the weakening and disappearance of the demographic dividend,and in the context of carbon peak and carbon neutrality,prefabricated buildings have gradually replaced traditional buildings,forming a modular,standardized and integrated system,which greatly reduces the wet work on site and significantly improves labor productivity.Compared with dry connection,wet connection has seismic performance equivalent to cast-in-place,but the existing wet node connection method has shortcomings such as difficult construction and difficult quality assurance,which hinders the development of prefabricated buildings.Based on the preliminary research of the research group,this paper proposes a buckle mechanical connection prestressed frame node,which is composed of a superimposed beam and a precast column,and the longitudinal ribs of the lower part of the beam and the longitudinal ribs of the column are connected by buckle mechanical connectors.The seismic performance of this node is tested and studied,and finite element simulation and parameter analysis are carried out.The main work is as follows:(1)The connection methods and seismic performance of prefabricated frame nodes of domestic and foreign scholars are summarized,and the nodes of different connection methods are compared.On the basis of the previous research of the research group,the prefabricated prestressed frame nodes of buckle mechanical connection are proposed.(2)Design and produce 5 new node specimens and 1 cast-in-situ comparison specimen,and introduce the characteristics,design scheme,construction points,test measurement content and loading scheme of the node in detail.Taking the effective prestress,axial compression ratio,etc.as variables,the low cycle reciprocating load test was carried out,and the hysteresis curve,skeleton curve,strength,stiffness degradation,ductility performance,energy dissipation capacity,deformation recovery performance and other parameters of each specimen were analyzed and compared.The test results show that the bearing capacity of the buckle mechanical connecting beam and column joints is similar to that of cast-in-place specimens,and the beam end is damaged,but the plastic hinge is externally shifted.Within the scope of experimental design,prestressed ribs were added,and the bearing capacity,stiffness,strength and deformation recovery performance of the node were improved while the energy dissipation capacity was slightly reduced.Within the scope of experimental design,the axial compression ratio is increased,the bearing capacity and energy dissipation capacity of the node are increased,and the residual displacement is increased.(3)The finite element software ABAQUS is used to establish a new node model,and the properties of each component are defined according to the data obtained from the material property test,and the interaction,boundary conditions and meshing between the components are set and calculated,and the simulation results are more consistent with the test results.The axial compression ratio,beam longitudinal reinforcement ratio and effective prestress were used as variables to analyze the expansion parameters.The results show that when the axial compression ratio does not exceed 0.4,the axial compression ratio has a significant effect on the bearing capacity and initial stiffness of the joint,and afer exceeding 0.4,the effect is small;the bearing capacity is improved by selecting small diameter steel bars under the similar reinforcement ratio;The effective prestress and the increase of concrete grade can improve the bearing capacity of the joint.(4)The test skeleton curves of specimens S2,S3 and S5 were selected for dimensionless processing,and the degenerate trifold line model was selected to fit the skeleton curve model of the node.The stiffness coefficient under different displacement loading is fitted to obtain the stiffness degradation formula,and the hysteresis point is increased with reference to the hysteresis characteristics of the test,and the hysteresis rule is formulated.Finally,the recovery force model of the prefabricated prestressed frame node of the buckle mechanical connection is established.It is found that the hysteresis curve calculated by the model is in good agreement with the experimental hysteresis curve,which can provide reference for subsequent theoretical research.