Test Of Defects In Concrete Filled Steel Tube And The Analysis Of Its Influence On Mechanical Properties

The concrete-filled steel tube structure has high bearing capacity,ductility,and seismic performance.It has the advantages of simple structure,convenient construction,etc.The mechanical properties of its components meet the needs of the current engineering structure such as long-span bridges,towering buildings,and heavy loads.Because concrete pouring of steel pipe concrete components is a concealed project,internal defects caused by construction cannot be avoided.Therefore,the mechanical properties of concrete-filled steel tube members are weakened to varying degrees,directly affecting their bearing capacity,and reducing the quality of the structure has serious safety hazards.In order to study the direct influence of construction defects on concrete-filled steel tubes,the actual bearing capacity and safety performance are evaluated.Through a large number of experimental analysis,the following issues are mainly explored for the defects of steel pipe concrete:(1)Quantitative studies on flaws in ultrasonic testing.Based on the propagation law of ultrasonic waves,the propagation path and acoustic time of ultrasonic waves in flaws of steel tubes were analyzed.On the basis of detection,the quantitative calculation formula for the central flaw of a steel pipe concrete was deduced according to the first-wave acoustic time method,and the applicable conditions were analyzed in depth.When the conditions were not satisfied,the mobile probe symmetrical detection method could be used for quantitative detection.In the presence of defects on the side of the pipe wall,the defect was quantified using the sector detection method.(2)Through the qualitative analysis of the mechanical properties of concrete-filled steel tubular members with different defect rates and locations,the larger the defects,the more obvious the decline in bearing capacity of the specimens,and the shorter the course of the elastic-plasticity stage;the smaller the void ratio,The less obvious the descending segment,the axial compression curve of the short column is serialized with the change of the void ratio,and the working performance of the steel tube concrete that changes with the change of the defect rate is continuous.The mechanical properties of the steel pipe concrete component after the defect occurred and the mechanical properties after the secondary replenishment were compared.After the secondary replenishment,the mechanical properties of the concrete component could be basically restored.(3)The finite element software ABAQUS was used to establish the defective steel pipe concrete component model.The model and the test sample were chosen in the same size and material properties.The influence of the defect on the mechanical properties of the steel pipe concrete component was analyzed.For rams,the larger the evacuation rate,the lower the bearing capacity.The deficiencies are believed to reduce the cuffing effect of the steel pipe on the core boring and the cross-sectional area of the contact surface of the core boring,resulting in a reduction in the bearing capacity of the overall steel pipe truss structure.