Finite Element Analysis And Comparison Of The Axial Compression Behavior Of Two New Concrete Filled Steel Tubular Short Columns

Through the restraint(hoop)action of the steel tube on the core concrete,the concrete filled steel tube makes the core concrete in the state of three-dimensional compression,which can effectively improve the compressive strength and compression deformation ability of the concrete,not only greatly improve the plasticity and toughness of the concrete,but also avoid or delay the local buckling of the steel tube.The new type of concrete-filled steel tubular column has a good bearing capacity under axial compression and has a good development prospect in the future engineering construction.This paper study a new type of circular concrete-filled steel tube column and composite T-shaped concrete-filled steel tube column,in which the main feature of the new round concrete-filled steel tube column is that there is a section of welded outer steel pipe in the middle,which further enhances the restraint effect on the core concrete;the T-shaped steel pipe is welded with rectangular steel tube and U-shaped steel pipe,which greatly reduces the difficulty of manufacture and reduces the influence of negative angle on the steel pipe.This paper first analyzes the test process of two kinds of ordinary concrete-filled steel tubes.By changing the friction coefficient of steel tube and concrete and the viscosity coefficient of concrete,and comparing the analysis results with the test results,the optimal friction coefficient and bond coefficient of two kinds of concrete-filled steel tubes are determined.On the basis of these,ABAQUS is used to establish 5 groups of finite element models of new fabricated circular concrete-filled steel tube short columns to study the optimal structure of core concrete,7 groups of finite element models of new fabricated circular concrete-filled steel tubular short columns were established to study the optimal length range of the outer steel tube,and 10 groups of finite element models of new fabricated circular concrete-filled steel tubular short columns were established to study the effects of steel tube thickness,slenderness ratio,concrete strength,steel tube strength and other parameters on the axial compression performance.9 groups of composite T-shaped concrete-filled steel tubular short columns were established to study the slenderness ratio,steel tube strength The influence of four parameters,steel tube thickness and concrete strength,on the axial compressive behavior of composite T-shaped concrete filled steel tubular short columns.The effects of slenderness ratio,steel tube strength,teel tube thickness and concrete strength on the mechanical properties of composite T-shaped steel tube short columns are analyzed.The results show that when the length of the interface between the upper concrete and the outer casing steel pipe accounts for 1/3 of the total length of the interface between the concrete and the outer casing steel pipe,and the length of the outer casing steel pipe is 1/12 of the column length,it is the optimal structure.The composite T-shaped concrete-filled steel tubular short columns have good axial compression performance,deformation capacity and ductility performance,and under axial compression,the longitudinal stress and circumferential stress of the steel pipe,the longitudinal stress and circumferential stress of the outer steel pipe and the longitudinal stress of the concrete are evenly distributed.The greater the steel pipe thickness,concrete strength and steel pipe strength,the greater the ultimate bearing capacity of the new fabricated circular concrete filled steel tubular short column;The greater the steel pipe thickness and concrete strength,the greater the initial stiffness of the new fabricated circular concrete filled steel tubular short column;The greater the slenderness ratio,the smaller the ultimate bearing capacity and initial stiffness of the new fabricated circular concrete filled steel tubular short columns.The greater the steel pipe strength,concrete strength and steel pipe thickness,the greater the ultimate bearing capacity of composite T-shaped concrete filled steel tubular short columns;The greater the concrete strength and steel pipe thickness,the greater the initial stiffness of composite T-shaped concrete filled steel tubular short columns;The larger the slenderness ratio,the smaller the ultimate bearing capacity and initial stiffness of the new fabricated circular concrete filled steel tubular short columns.Increasing the length of specimens is the most obvious way to reduce the stiffness of composite T-shaped concrete-filled steel tubular short columns;the restraint degree of T-shaped steel tube to concrete is greater than that of rectangular steel tube to concrete.When the section area of the short column is the same,the steel ratio,slenderness ratio,concrete strength and steel pipe strength are also equal,the ultimate bearing capacity and initial stiffness of the new fabricated circular concrete filled steel tubular short column are greater than those of the composite T-shaped concrete filled steel tubular short column.