Behavior Of Prestressed Stayed Circular Concrete Filled Double Skin Steel Tubular Columns Under Axial Compression Load

Prestressed stayed circular concrete filled double skin steel tubular columns are a new type of prestressed composite members,which are formed by setting horizontal struts and tensioning prestressed cables outside the columns.Compared with ordinary circular concrete filled double skin tubular column,the use of cable-braced system provides lateral elastic support for the columns,which reduces the effective length of the columns,and greatly improves the buckling capacity.Compared with prestressed stayed columns,the concrete in the composite columns can limit the local buckling of steel tube and enhance the fire performance of the composite columns.More importantly,the bearing capacity of the composite columns is higher than the simple superposition of the two materials.The consumption of steel can be effectively decreased at the same bearing capacity level,thus reducing the overall cost of the structure.Therefore,the new composite columns has considerable economic benefits.In terms of the increasing research on prestressed stayed columns and the increasing practical applications,prestressed stayed circular concrete filled double skin steel tubular columns have significant research value and application prospects as a new type of prestressed composite columns to improve and complement prestressed stayed columns.Therefore,this paper aims at studying the axial compressive behavior of prestressed stayed circular concrete filled double skin steel tubular columns.The main contents and results are as follows:(1)Based on the finite element software ABAQUS,a finite element model of prestressed stayed circular concrete filled double skin steel tubular columns was established.The reliability of the model was verified by the axial compression test data of circular concrete filled double skin steel tubular columns and prestressed stayed columns completed.It lays a foundation for the finite element analysis of the axial compressive behavior of prestressed stayed circular concrete filled double skin steel tubular columns.(2)Based on the established finite element analysis model,the economic benefits of prestressed stayed circular concrete filled double skin steel tubular columns were compared with prestressed stayed columns,and the economic differences of using different metal materials were analyzed.The effects of cable diameter,nominal steel ratio,hollow ratio,slenderness ratio,relative length of struts,columns diameter and initial prestress on the axial compressive behavior of prestressed stayed circular concrete filled double skin steel tubular columns were studied.Meanwhile,a comparative analysis with the same parameters of prestressed stayed columns was carried out to verify the rationality of the parameter analysis results and obtain the difference between the new prestressed composite columns and the traditional prestressed stayed columns.Finally,influences of parameters on the axial compressive behavior of prestressed stayed circular concrete filled double skin steel tubular columns were discussed and the recommended values were proposed.(3)The influence of buckling modes on the buckling capacity was analyzed theoretically,and a stiffness ratio ? was introduced to estimate the buckling modes and structural efficiency of columns.Finite element analytical results were used to confirm feasibility of ?=2 as the critical value of the buckling mode transition.The linear calculation formulas of the axial compressive bearing capacity and the optimum initial prestress of prestressed stayed circular concrete filled double skin steel tubular columns were derived theoretically.By comparing with the results of finite element analysis,a practical formula for calculating the buckling capacity and the actual optimum initial prestress values were recommended.A practical design method of prestressed stayed circular concrete filled double skin steel tubular columns was proposed.