Study On Seismic Behavior Of Prefabricated Concrete Beam-column Joints With Cantilever Beam Segments

The connection form is the key to the research in the field of beam-column nodes,and the design of a connection form that balances efficiency and high energy is the key research direction in this field.RCS combination node and tree column frame node are popular research in the field of assembled concrete beam-column node and assembled steel beam-column node respectively.This topic draws on the advantages of the above existing node connections,integrates and improves them,and proposes a new type of concrete beam-column assembly node with cantilevered beam segments,and carries out research on node loadbearing performance and seismic performance by means of experiments,simulations and theoretical analysis,the main contents and research results are as follows:(1)The load-bearing performance of the new nodes was investigated.Monotonic loading static tests and simulations were carried out with cast-in-place nodes as reference,and the similarities and differences between the two in terms of damage morphology and bearing capacity were compared.The results show that the bearing capacity of the new node is close to that of the cast-in-place node.(2)The seismic performance of the new nodes was investigated.The similarities and differences in damage morphology,hysteresis curve,skeleton curve,energy dissipation capacity,and stiffness degradation were compared by using cast-in-place nodes as a reference and conducting low circumferential reciprocal loading proposed static tests and simulations.The results show that the seismic performance of the new node is slightly lower than that of the cast-in-place node.(3)The force mechanism of the new node is studied,and the force transfer mechanism on the beam segment is analyzed and summarized.Based on the above test and simulation results,the interaction mechanism between the intersection of steel and concrete in the splicing area of the new node is revealed.The results show that the new node completes the transfer of bending moment and shear force through the extrusion of concrete by the steel sections.The pre-buried depth will change the contact area between the steel wing and concrete,thus reducing or intensifying the degree of extrusion in the pre-buried area,which affects the premature failure and normal bending damage of the node.(4)The factors influencing the bearing performance and seismic performance of the new node were studied.By establishing 26 groups of finite element models,the influence of the difference between positive and negative Z connection,pre-buried depth,cantilever beam length and beam longitudinal reinforcement diameter on the bearing performance and seismic performance of the node was investigated.The results show that: the influence of positive and negative Z connection difference is extremely limited;the pre-buried depth and cantilever beam length do not affect the node alone,but through the coupling of the two ratios,and the approximate critical ratio of its influence on premature failure and normal yielding energy dissipation of the node is0.375,and when the ratio is in 1～1.8,the load bearing capacity will be increased to1.14～1.24 times of the cast-in-place node.(5)The concept of conversion factor is introduced,and the design methods of new nodes with different section sizes are summarized.Based on the results of existing tests and simulations,the nodes are optimally designed to limit the range of section sizes of steel sections,and design suggestions are given to effectively transfer the plastic hinge to the section by adjusting the degree of weakening or strengthening the longitudinal reinforcement of the beam section.In order to prevent excessive extrusion of the beam section by the section,to make full use of the material properties and to reduce the economic cost,a design suggestion of simultaneous yielding at the root of the beam section,the pre-buried area of the section flange and the bone-type weakening of the new node is proposed.The research results of this thesis provide some reference value for the design of the connection form of concrete beam-column assembly nodes and the study of the mechanical properties of concrete-steel combination nodes.