Study On Mechanical Behavior Of The Circle Steel Tube Confined Reinforced Concrete Stub Columns With Fly Ash Under Axial Compression

Along with the modern civil construction to develop in the direction of tall and super-tall,the structure of the vertical load is bigger, cross-sectional dimensions of the column areincreasing and easy to form a reinforced concrete short and ultra short column，they are difficultin practical engineering use, tube confined reinforced concrete column as a novel combinationof components emerged in recent years and it has been applied in the "Dalian City Stadium"and other large construction projects. Pulverized coal combustion fly ash is discharged back aclay pozzolan, incorporation of fly ash in concrete has the advantages of economy,environmental protection.In this paper, fly ash concrete within a certain dosage were poured into the tube, formingcircular steel tube restraint reinforced fly ash concrete members, with steel tubediameter-to-thickness ratio and fly ash replacement rate as parameters, circular steel tubeconfined reinforced fly ash concrete experimental research on axially loaded. It analyzed thefailure mode, ultimate bearing capacity, strain variation of the steel tube and lateral deformationcoefficient of the class members to study the component’s performance with the influence ofdiameter-to-thickness ratio and fly ash replacement rate, and practical engineering applicationrecommendations of diameter-to-thickness ratio and fly ash replacement rate were given. Thewhole process of stress of the test specimen was simulated by using the finite element analysissoftware ABAQUS, and the results were compared with the test results. On the basis ofexperiment and finite element analysis, limit capacity formula of the circular steel tube confinedreinforced fly ash concrete short column was suitably proposed.The results show that: The failure mode of the circular steel tube restraint reinforced flyash concrete axial compression short column specimen was shear failure of concrete, specimendamage when steel tube outer convex or tear, longitudinal reinforcement buckling. Steel tubediameter-to-thickness ratio and fly ash replacement rate had obvious influence on the bearingcapacity and ductility of the specimens, but for the influence of specimen failure mode was notobviously, and the restriction in steel tube on core concrete was most fully after the peak load.This article suggested that：the mechanical properties of circular steel tube confined reinforcedconcrete under axial compression were optimal when the fly ash replacement rate was less than 30%and steel tube diameter-to-thickness ratio was less than100. Finally, based onexperimental research, theoretical analysis and finite element analysis, the bearing capacitycalculation method of circular steel tube constraint reinforced fly ash concrete axialcompression short column was put forward, and it could provided a reference for follow-upstudy of this kind of components.