Study On Seismic Behavior Of Assembled Square Steel Tubular Recycled Concrete Column Steel Beam Joints

The seismic design of a building requires that the beam-column joints have sufficient bearing capacity and ductility to ensure the safety of the building under earthquake.As a new building material,recycled concrete is often used in non-load-bearing structures due to its nature of the material,limiting the use of recycled concrete.The combined use of steel pipe and recycled concrete can theoretically improve the bearing capacity of recycled concrete.In order to explore whether it can be used for beam-column joints with stringent seismic requirements,this paper studies the seismic performance of prefabricated square steel-reinforced concrete columns and the impact of external partitions on the seismic performance of joints.Firstly,this paper adopts the method of theoretical analysis to analyze the stress mechanism of prefabricated square steel tube regenerated concrete column beam joints,the stress state of recycled concrete in the core area of the joint,and calculate the shear capacity of the joint core area.Then use ABAQUS software to calculate the finite element model of the low-cycle repeated loading test of the completed four fabricated square steel tube reclaimed concrete column steel beam joint specimens.The finite element model is consistent with the experimental conditions,and the numerical simulation results are compared with the test results.The hysteretic behavior,energy dissipation capacity,skeleton curve,and bearing capacity of the two are less different,indicating that the finite element model calculation is feasible.Due to the limitation of test conditions,there are only one set of control tests for the two control variables,the outer baffle thickness and the outer baffle extension,and the test results are less persuasive.Therefore,based on this,another two sets of a total of 10 prefabricated square steel pipe reclaimed concrete column beam joint finite element model,with different thickness of the outer partition and the external partition elongation as the control variables,The effect of external diaphragms on the seismic performance of joints was investigated.The results indicates:(1)By comparing the numerical simulation results with the experimental results,the difference between the two results is small,indicating the feasibility of the finite element model analysis.The finite element software can be used to expand the study of the experiment.(2)Compared with the nodes without external partitions,the seismic capacity,hysteric performance,energy dissipation capacity and deformation capacity of joints are significantly improved when the node area has an outer partition.(3)The hysteresis curves of the prefabricated square steel tubular reclaimed concrete column beams are full of shuttle-shape,and the joints have good seismic performance.There are three stages in the node stress process: elastic working stage,yield strengthening stage and failure stage;(4)Within a certain range,the seismic bearing capacity of the joint increases with the increase of the extension length of the diaphragm,while the thickness of the outer diaphragm has little influence on the a seismic bearing capacity of the joint.The seismic performance of prefabricated square steel tubular reinforced concrete column-beam joints is good.The conclusions of this paper can provide theoretical references for the engineering practice of such joints and recycled concrete;The outer partition can restrain the deformation of the drum zone in the core area of the node,so it has a great influence on the hysteretic performance,ductility and energy dissipation capacity of the node;The outer partition can improve the bearing capacity of the joints.At the same time,the installation of the outer partitions is not affected by the sectional size of the steel pipe columns.The construction is convenient and often used in practical projects.In this paper,the conclusions about the influence of the thickness of the external partition and the external elongation on the seismic performance of the joint can provide reference for the design of the external partition of the actual project.