Seismic Performance Of A New Precast RC Frame Joints

The beam-column joint is a key component of prefabricated structures,and its form and load-bearing mechanism have a significant impact on the overall seismic performance of the structure.Traditional prefabricated concrete frame joints mainly rely on on-site secondary pouring,which not only requires a large amount of wet work on-site but also has difficulty ensuring construction quality.Exploring joint forms that are reliable in transmitting forces,easy to construct,and easy to control construction quality is particularly necessary in prefabricated concrete frame structures.This article proposes a new type of prefabricated RC frame beam-column joint form,conducts experimental research and finite element analysis,and provides practical seismic design methods.The main research work and conclusions of this article are as follows:(1)A new type of prefabricated RC frame beam-column joint form was proposed,and a full-scale quasi-static test was conducted to study it.The research found that the area where cracks first appeared in the joint was mainly at the end of the embedded H-shaped steel beam(at the junction of the later-poured section and the prefabricated beam),and then developed outward continuously.The final failure still occurred at the end of the embedded H-shaped steel beam,and the plastic hinge moved outward,but the connection in the core area of the joint did not fail,which meets the requirements of "strong joint,weak member" in seismic design.The hysteresis curve of the joint as a whole shows a shuttle-shaped form.Through hysteresis curve analysis,the ductility coefficient of the joint is 2.67,and the equivalent viscous damping coefficient is 0.252.Therefore,the joint has good plastic deformation capacity and energy dissipation capacity,and has good seismic performance.(2)Finite element simulation of the new type of prefabricated RC frame beam-column joint was carried out using ABAQUS software.The failure mode,hysteresis curve,and skeleton curve of the simulation results were compared with the experimental results to effectively verify the reliability of the modeling method proposed in this paper.Based on the experimental joint,a cast-in-place joint model was established and compared with the prefabricated joint model proposed in this paper.The results show that compared with the traditional cast-in-place joint,the new type of prefabricated joint has a 11.56% higher ultimate bearing capacity,significantly increased initial stiffness,and better energy dissipation capacity.(3)On the basis of the experimental node,the influence of axial compression ratio,beam concrete strength,beam stirrup diameter,and beam longitudinal reinforcement strength on the bearing capacity,stiffness,and energy dissipation capacity of the node was studied by variable parameter analysis.The study shows that the axial compression ratio has a relatively small effect on the node,and it is not recommended to exceed 0.6.Increasing the concrete strength of the beam can significantly improve the bearing capacity and energy dissipation capacity of the node,with less impact on stiffness degradation.Increasing the diameter of the beam stirrups can slightly improve the bearing capacity and energy dissipation capacity of the node,with less impact on stiffness degradation.Improving the longitudinal reinforcement strength of the beam can increase the bearing capacity of the node and delay the stiffness degradation of the assembly-type node,but it will reduce the energy dissipation capacity of the node.(4)Following the seismic design principle of "strong node,weak member," this paper summarizes the design of the steel reinforced concrete column-to-square steel tube connection,the reinforced concrete beam-to-square steel tube connection,and the node area bearing capacity.Relevant design formulas are proposed.