Static And Dynamic Performance Research Of Bar-reinforced Concrete Filled Steel Tubular Component

The concrete filled steel tubular (CFT) component has been widely used in themulti-storey, high-rise and large-span structures because of its good stressperformance. In recent years, due to its good fire resistance, the bar-reinforcedconcrete filled steel tubular (RCFT) has been more and more used in multi-storeyand high-risestructures. But only a few researches on the static and dynamicperformance of the bar-reinforced concrete filled steel tubular under roomtemperature have been done, so the author studied the static performanceandductility coefficient of the bar-reinforced concrete filled steel tubular from thefollowing aspects: the theoretical analysis, the finite element simulation and theexperiment.The paper studied the stress performance of the materials of the bar-reinforcedconcrete filled steel tubular, awaring that the stress performance of the longitudinalreinforcements in the reinforced concrete structures is the same with that in theconcrete filled steel tubular. The paper argues that the bar-reinforced concrete filledsteel tubular is assembled by the longitudinal reinforcements and the concrete filledsteel tubular equipped with stirrups. The paper regarded the core concrete equippedwith multi-layer stirrups as equivalent plain concrete with the same strength, andthen calculated the combined strength of the equivalent concrete filled steel tubularaccording to the "unified theory".According to the superposition principle, the bearing capacity of thebar-reinforced concrete filled steel tubular member under axial load is derived bysuperposing the bearing capacity of the equivalent concrete filled steel tubularmember under axial load and the bearing capacity of the longitudinal reinforcementsunder axial load. The paper obtained the position of the neutral axis of the memberby the flexural capacity formula of the concrete filled steel tubular, and then derivedthe flexural capacity of the longitudinal reinforcements, on which the flexuralcapacity of the bar-reinforced concrete filled steel tubular is obtained bysuperposing the flexural capacity of the equivalent concrete filled steel tubular.Based on the analysis of the parameters by ABAQUS finite element software,three parameters has been determined for the experiment. Axial compression testsfor twelve bar-reinforced concrete filled steel tubular short columns and three longcolumns, one bar-reinforced concrete filled steel tubular short column and one longcolumn have been carried out. The tests compared the different stress performanceand failure modes between the bar-reinforced concrete filled steel tubular columnsand the concrete filled steel tubular columns. A series of parametric analysis are conducted on the load-displacement curve, such as the reinforcement ratio, thereinforcement strength and the stirrup ratio.Simulation of the bar-reinforcedconcrete filled steel tubular short column under axial load and compression-bendingload has been done by the ABAQUS software, together with the experimental valuesto verify the reasonableness of the theoretical formula.The hysteretic behavior of the bar-reinforced concrete filled steel tubularcompressive-bending member is analyzed by using Rayleigh-Ritz method and thelimit equilibrium theory. A curve model is provided, and the calculation of thedisplacement ductility factor is given.