Analysis Of Force Performance Of Prefabricated Concrete Beam And Column Joints Connected By Double Sleeve

Under the background of industrialization of construction,the assembled structure has been vigorously supported and widely used by the state.As the main form of assembled building,the assembled concrete structure has the advantages of fast construction,high labor efficiency,and clear node stressing.At present,there are two forms of assembled concrete connection: wet connection and dry connection.Wet connection nodes,i.e.,through the postcast concrete to achieve the connection of each member,although this method can be equivalent to cast-in-place,but the construction is complicated and the project cycle is long;dry connection nodes prefabricated components through pre-stressing tendons,welding or bolts and other forms of connection,construction is convenient,good force performance and nodes easy to achieve post-earthquake repair and replacement,but The overall stability of the structure is poor.At the same time,as the transmission hub of the frame structure,the core area of the concrete beam-column node needs to bear the joint action of axial force,shear force and bending moment transmitted by the beam end in the process of stressing,and is in a complex stress state of pressure-bending-shear,and the concrete in this area is prone to "X" shaped shear cracks.This paper designs an assembled concrete beam-column node based on "outer steel sleeve connector + inner grouting sleeve" with double sleeve connection,the plastic hinge of the node is transferred to the middle of the span by the outer steel sleeve connector,and the inner grouting sleeve makes the beam-column node connection in the form of rigid connection,so as to improve the node bearing capacity:Firstly,the finite element software ABAQUS was used to load the double sleeve connection node,single sleeve connection node and cast-in-place node with low circumferential reciprocal loading to observe the response characteristics of the nodes such as damage morphology,hysteresis performance,skeleton curve,energy dissipation capacity,stiffness degradation and strain.Under the action of outer steel sleeve connection,the core zone concrete deformation of assembled nodes is small,and the damage is mainly concentrated in the intersection area of prefabricated beams and outer steel sleeve connection,and the nodes are bending damage,while the cast-in-place nodes are shear damage of core zone concrete,which is in accordance with the design principles of "strong column and weak beam" and "strong node and weak member".The design principle of "strong column and weak beam" and "strong node and weak member".The external steel sleeve connection is involved in the energy dissipation of the node during the stressing process,so the hysteresis curve of the assembled node is more saturated and "shuttle-shaped",which has good energy dissipation capacity.Compared with the single sleeve connection node,the double sleeve connection node is rigid under the action of the inner grouting sleeve,which effectively improves the node bearing capacity and reduces the shear force of the connection surface.Secondly,on the basis of beam-column nodes connected by double sleeves,the damage morphology,ductility capacity,stiffness degradation capacity and energy dissipation capacity of the nodes under the action of different axial pressure ratios,different beam end reinforcement ratios,and different arm lengths and wall thicknesses of the outer steel sleeve connectors were investigated.The results show that different axial compression ratios have a small effect on the force performance of the node;increasing the reinforcement ratio at the beam end of the node can significantly improve the node bearing capacity,but reduces the ductility capacity of the node;changing the arm length of the outer steel sleeve connector can transfer the plastic hinge to the span and improve the bearing capacity and energy dissipation capacity of the node;when the thickness of the outer steel sleeve wall connector is 12 mm,the node shows better stiffness degradation capacity and bearing capacity.Therefore,the wall thickness can be chosen to be about 12 mm when designing the double sleeve connection node.Finally,the static pushover analysis of concrete frames with double sleeve connections and cast-in-place concrete frames was carried out using SAP2000 software.The base shearvertex displacement curves of the two frame structures under uniform and inverted triangular loading modes were compared and analyzed to obtain the performance points of the two frames at different seismic levels and to determine the stress conditions of the structures according to the magnitude of the inter-story displacement angle.The results show that the plastic hinge and the maximum inter-story displacement angle of both structures appear first on the prefabricated beams at the ground floor under the seismic action,which satisfy the requirement of "strong nodes and weak members".