Research On Seismic Behavior Of Large Depth-to-width Multi-core Concrete-filled Steel Tube Column

Concrete filled steel tube(CFST)is widely used in high-rise buildings because of its high bearing capacity,good ductility,convenient construction and good economy performance.In this paper,based on MCFTS(Concrete Filled Steel Tube System)high-rise steel structure residence system,a new type of concrete filled steel tube structure is proposed-Large depth-to-width multi-core concrete-filled steel tube column(LCFST).It is a new type of vertical component with good mechanical properties,which has the advantages of simple structure,convenient construction and shows good bearing capacity,deformation capacity and energy dissipation capacity under the action of vertical force and lateral force.It overcomes the defects that the traditional CFST bulges from the room corner so that influence the use of the building.Based on the result experimental research,numerical analysis and theoretical analysis,the seismic behavior of CFST is studied.The main contents include:(1)A total of 1 presudo-static experiment has been concucted for LCFST.The hysteretic behavior,ductility,energy dissipation capacity,bearing capacity and stiffness degradation are studied.The result shows that the failure modes of the MCFST are the buckling of the web,the buckling of the steel plate,the tearing of the longitudinal weld and the compression failure of the concrete.The load-displacement hysteretic loops are stable,the displacement ductility coefficient is close to 3 and the equivalent viscous damping coefficient of the failure point is 0.326.The result shows that LCFST has good bearing capacity,ductility and energy dissipation capacity,the degeneration of which stiffness and bearing capacity are stable.(2)Using the nonlinear finite element software ABAQUS to establish the model,the finite element simulation under monotonic loading and low cyclic loading are carried out.The result shows that the failure phenomenon is consistent with the test,the load-displacement curve of the finite element and experiment are in good agreement of the elastic and elastic-plastic period.Based on the results of finite element analysis,the internal force distribution of steel tube and concrete is analyzed according to the aspects of stress,strain,damage and contact.(3)The parametric studies are conducted to investigate the influence of axial compression ratio,slenderness ratio,steel strength,concrete strength,steel ratio by using the nonlinear finite element software ABAQUS.(4)Based on the experimental results and finite element results,a practical formula for calculating the ultimate bearing capacity of the LCFST is proposed,the results are compared with the experimental results,the finite element results and the specifications calculation results,the result shows that the calculation results are more secure.Introducing the engineering practice and engineering application of LCFST,which can provide reference for engineering design.