| Different from traditional concrete filled steel tube column,the tubed steel reinforced concrete column has its special characteristic.Steel tube in the joint area is off its outsourcing,and the steel tube does not directly bear the vertical loads.Transverse effect between steel tube and concrete,which makes concrete in the state of three-way compressive stress,and the concrete strength and bearing capacity of the components may be improved.At present,the domestic and foreign research on this aspect is relatively lacking,especially in the performance of joints.In this paper,according to the existing research,finite element models of T-shape joint of tubed steel reinforced concrete column to steel beams and traditional joint for construction are established based on ABAQUS.The seismic performance and parameter analysis of two kinds of joints are studied.Finally,based on the results of element analysis,the restoring force models of joints are obtained.In this paper,the main research results are as follows:(1)The key problems in numerical simulation of tubed steel reinforced concrete column and steel beam joints in ABAQUS software are studied,including the determination of the material,constitutive element selection,meshing principle,interaction and contact problems and load boundary conditions etc.according to two test results of short columns of circular tube confined steel reinforced concrete and circular concrete-filled steel tubular column to steel beam joint with external diaphragm,analysis of the load and longitudinal strain test results and hysteretic curves and failure modes are compared with experimental results.And also the reliability of finite element modeling is verified.The finite element method provides well conditions for parameters analysis of tubed steel reinforced concrete column and steel beam joint.(2)Based on the verified finite element method,T-shape joint of tubed steel reinforced concrete column to steel beams(J-1 joint)and traditional joint for construction(D-1 joint)are designed and simulated.The failure modes,hysteretic behavior and energy dissipation characteristics of two joints are analyzed.It shows that the J-1 joint has more advantages in the bearing capacity,hysteretic behavior and seismic energy dissipation than traditional joint.(3)In order to study the seismic performance of the new joint,the parameters analysis are established based on finite element analysis,including axial compression ratio,concrete strength,size of ring plate,tube thickness in joint domain.Studies have been shown that:1)The joint effect of hysteresis curve under axial compression ratio is not obvious.When under the small axial compression ratio,the hysteretic curve may be express relatively full,and also,with the increase of axial compression ratio,the stability of the hysteresis curve will become worse.Strength and stiffness degradation can accelerate the speed of the joints of the initial stiffness and ultimate bearing capacity will reduce.2)The increase of concrete strength grade influence on flexural bearing capacity is limited;it is only slightly impact for the initial stiffness.However,in order to ensure a good bond between concrete and steel,concrete strength is not less than C40.3)With the increase of ring plate width,the flexural bearing capacity of the joint and the initial stiffness has a corresponding increase,but the overall growth rate is not particularly evident,and the change tendency of the flexural bearing capacity of the initial stiffness change is obvious.In general,the bigger the ring width,the constraints of nodes become stronger and will make the deformation of the node is reduced,but its contribution to the seismic performance of the node is limited.4)With the change of tube thickness in joint domain,the initial stiffness and ultimate bearing capacity are changed;the performance of the initial stiffness and bearing capacity of change is more obvious.In addition,with the increase of the thickness of the steel tube,the growth effect will gradually fade and be integrated.(4)Based on the numerical simulation and the researches of the existing restoring force models,the restoring force model of tubed steel reinforced concrete column to steel beams joint is proposed.The model is a tri linear model considering stiffness degradation.At the same time,the stiffness expression of each stage of the skeleton curve,the degradation rule of the positive and negative unloading stiffness and the specific loading and unloading hysteretic rules are provided.The research results will provide support for further theoretical research. |
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