Research On Hysteretic Performance Of Inner Tube Ribbed Round-sleeve Hollow Sandwich Steel Tube Column-steel Beam Joint

Compared with the ordinary concrete-filled steel tube column-steel beam node,the hollow sandwich concrete-filled steel tube column-steel beam node has the advantages of lighter weight and better bending resistance.However,when the inner tube and the steel beam are not connected at the node,the inner tube often buckles locally.The force transmission method of the node area mainly relies on the interface bonding between steel pipe and concrete.If there is void phenomenon,it will cause problems in the force transmission path,and the advantages of high rigidity and high bearing capacity of the concrete-filled steel tube column-steel beam joint will be weakened.In order to ensure the coordinated work of the inner and outer steel pipes and the sandwich concrete,the internal force is transmitted by ribbing the inner pipe in the node area.In this paper,an experimental study on the inner tube ribbed round-sleeve hollow sandwich concrete-filled steel tube column-steel beam joint is carried out and the ABAQUS software is used to establish a finite element model for calculation to explore the hysteretic performance of this type of joint.The main contents of this paper are as follows:（1）This paper conducts low-cycle reciprocating tests on 5 inner tube ribbed round-sleeve hollow sandwich steel tube concrete column-steel beam joints.The strength degradation,stiffness degradation,ductility and energy dissipation capacity of the joint specimens under reciprocating loads are analyzed to obtain relevant laws.The test results show that the hysteresis curve of each test piece is relatively full,no pinching phenomenon occurs,and it is in the shape of a shuttle,showing a good energy consumption capacity.（2）This paper uses ABAQUS finite element software to establish this type of node model.According to the properties of different materials such as steel tube concrete and steel beams,the corresponding constitutive relations are introduced respectively,and the contact between various materials is set to simulate the frame structure The way of combining each component,setting appropriate boundary conditions and loading method,and comparing the calculated finite element analysis results with the test results,the two are more consistent.The finite element simulation verifies that the hysteresis curve fits well with the monotonic curve,and its various properties can be studied through the joint force under monotonic load.（3）In this paper,the static performance of the joints under the three parameters of stiffener length,width and strength is studied.The results show that the length of the stiffener has a certain degree of improvement in the bearing capacity of the joint,but the increase is not large.When β=1,the bearing capacity reaches the highest,which is greatly improved compared with the ductility of non-rib joints.When the rib width increases,the ultimate bearing capacity increases slightly,and reaches the highest when k=0.5.The ductility increases in proportion to the rib width when k=0.5 or more,and the ductility increases slowly.The strength of the rib has little effect on the peak load and ductility,and the overall increase in the flexural capacity and the shear capacity increases with the increase of the rib strength.After carrying out the parameter analysis of the length and width of the stiffener,the length of the stiffener and the height of the steel beam were selected.By changing the axial compression ratio,the hollow ratio,the strength of the inner steel pipe,the strength of the outer steel pipe,the strength of the concrete,the strength of the steel beam,the analysis of these The influence of parameters on the mechanical properties of the ribbed square-sleeve-circular hollow sandwich concrete-filled steel tube column-steel beam joint.（4）A more detailed analysis of the force mechanism of this type of node is carried out,and the stress state of the outer steel pipe,core concrete,inner steel pipe and steel beam at the characteristic points of the node during the loading process is analyzed in detail.The working mechanism is studied through stress cloud diagrams taken out of three characteristic points.The study shows that when there are no stiffeners,the maximum stress is concentrated on the surface of the steel pipe in the joint area.When the inner pipe is ribbed,the maximum stress is distributed on the ribs and the inner steel pipe respectively;The ribbing of the steel pipe in the core area increases the deformation resistance of the inner steel pipe.（5）By calling the python interface of abaqus,it realizes the parameterized automatic modeling and the plug-in that extracts the skeleton curve,strength degradation,stiffness degradation,and energy consumption data from the hysteresis curve.Perform a black box verification test on the parameterized function module and analyze the verification results.It can be seen that the developed parametric modeling plug-in and post-processing plug-in program can achieve the required modeling and data processing functions.