Study On Seismic Behavior Of Concrete-filled Steel Tubular Column-steel Beam Joints With High Strength Core Columns

With the rapid development of modern economy,the low and multi-storey buildings in the past have been unable to meet the demand for buildings in the current era,so the high-rise and super-high-rise buildings emerge at the historic moment,and the research on new materials and new structural forms is inevitable.In recent years,FRPsteel tube-concrete composite column is widely concerned,especially in the design of aseismatic structure,because of its various composite forms and excellent ratio of strength to weight.Of this new type of composite structure of the column and beam node seismic performance research into the application of the composite column form one of the key issues,however,at home and abroad to this new combinations of steel girder cross section column node study also is less,this paper designs a built-in high strength core column of square steel tube concrete composite column,and the connection with steel beam node seismic performance was studied,the specific work as follows:(1)Using finite element analysis software ABAQUS to establish the built-in high strength core column of square steel tube concrete column and H type steel beam end plate finite element model of bolt node,the failure mode of the model are analyzed and the distribution of stress and strain state,and the failure modes of the finite element model of CFST column with the same size parameters are compared and analyzed,the results show that the model has a typical elasticity,yield and failure stage,is proved that the finite element model on the choice of specimen size,model creation methods of interface interaction between the rationality of the Settings and so on,And the design of the joints conforms to the requirements of the seismic design code for the joints.Furthermore,the aseismic test of joint specimens of the same specification is designed and made,and the relevant practical specimen fabrication process and the details needing attention are described.(2)The effects of axial compression ratio,bolt diameter,end plate thickness,steel tube thickness,FRP layer number and core column changes on the hysteretic curve,skeleton curve,ductility,energy dissipation capacity and stiffness degradation of joints are further analyzed.The analysis results show that the axial compression ratio greatly affect the bearing capacity and ductility and energy dissipation capacity of nodes,bolt diameter and the thickness of the endplate is within a certain range of change will have bigger effect on seismic performance of nodes,blindly increasing bolt diameter or thickness of end plate can not enhance the seismic bearing capacity and seismic performance of structures,The increase of steel tube thickness makes the linear stiffness ratio of beam-column too large.For the high-strength column in this paper,the increase of column stiffness makes the seismic performance of joints worse.The increase of the number of FRP layers increases the ductility and energy consumption of the joints to some extent.(3)By means of theoretical analysis,the contribution of each part of the joint area to the shear capacity of the joint area is analyzed,and a five-fold line model of the shear-shear strain relation curve of the model selected in this paper is presented.By using the boundary conditions,the shear capacity of the nodal area under the peak load in the finite element analysis is obtained.With the calculation formula of shear bearing capacity of the damage state were compared,it can be concluded that the shear capacity of the node area under the limit state of actual loading can not reach the value of the shear capacity of the node area under shear failure,the general structure under seismic loading are in the process of damage due to failure by the node area,and so will the ultimate shear capacity of nodes in the node area node failure and damage under the two states of the upper and lower limits of the middle.