Research On Seismic Bahavior Of Composite Concrete-filled Steel Tubular Columns

Researches have shown that the bearing capacity,rigidity and deformation ability of the steel-concrete composite column are superior than that of the reinforced concrete column.It is beneficial to the rapid restoration after the earthquake and can meet the needs of large span,towering and heavy load of modern engineering structures.Therefore,the steel-concrete composite column is widely used in high-rise buildings,underground structures and bridges.Among them,the composite-sectioned concrete filled steel tubular column is a new type of column used by setting up circular steel pipe in the center of concrete filled square steel tube column,which is particularly suitable for the frame column of the bottom floor of the super-high-rise structure.However,there are few researches on this new type of column at home and abroad presently.In this paper,refined finite element analysis was conducted to composite concrete-filled steel tubular column by using finite element analysis software ABAQUS,push-over analysis was conducted by using SAP2000.The seismic behavior of composite concrete-filled steel tubular column was researched in this paper,and it can provide some basis for its engineering design and application.The main research work of this paper could be summarized as follows:(1)The calculation of confinement coefficient of composite-sectioned concrete filled steel tubular columns is suggested through the analysis of the mechanism of the increase of strength of concrete-filled steel tube.Based on the existing test of composite-sectioned concrete filled steel tubular columns,the finite element models of composite-sectioned concrete filled steel tubular columns are established by general nonlinear finite element software ABAQUS.On the basis of the good agreement between the finite element analysis results and experimental results,we get the key parameters that influence axial force redistribution and ductility of composite column between the outer concrete and the core concrete by analyzing the influence of design nominal axial compression ratio,diameter width ratio,confinement coefficient and some other parameters to the displacement ductility coefficient of composite-sectioned concrete filled steel tubular column.The simplified calculation formula of displacement ductility coefficient of composite-sectioned concrete filled steel tubular column,which reflects the influence of key parameters,is proposed by regression analysis and it can provide a reference in the displacement ductility coefficient calculation of the composite-sectioned concrete filled steel tubular column design.(2)In order to study the deformation capacity of composite columns,The influence of the parameters on the ultimate displacement angle of the composite column was analyzed.The formula of the yield displacement angle and the ultimate displacement angle of the composite column is proposed by the general displacement analysis method and the data regression analysis,which can provide a reference for the engineering seismic design.(3)The analysis model of 15 story concrete-filled steel tubular column frame structure and composite-sectioned concrete filled steel tubular column frame structure were established by using structure analysis software SAP2000.The natural vibration periods,base reaction-vertex displacement curve,structural performance point and some other information were obtained by push-over analysis,and evaluate the seismic performance of structures with these information.The seismic performance of composite-sectioned concrete filled steel tubular column frame structure were evaluated by comparison of push-over analysis results between the two frame structures,and it can provide a reference in the seismic design and application of composite-sectioned concrete filled steel tubular column.