Study On The Mechanical Properties Of Steel Tubular Columns Filled With Steel-Reinforced High-Strength Concrete

Through investigating the damages caused by earthquakes, people have realized the design of columns plays a key role in preventing the collapse of building in strong earthquakes. In particular, with the increase of height and span of building, columns have to bear higher and higher axial load. So the columns are required to have high strength as well as high ductility. Based on the summary about the present research on steel reinforced concrete columns and concrete-filled steel tubular columns, a new type of steel-concrete composite column, steel tubular column filled with steel-reinforced concrete, has been presented in this paper. In this type of steel-concrete composite column, steel section is inserted into concrete-filled steel tubular column. Based on experiment and theoretical analysis, the mechanical properties of high-strength concrete-filled circular steel tubular column into which +-shaped steel section is inserted are researched. The major contents are summarized as follows:Experiments of the short composite column under axial compression are carried out to investigate the mechanical properties of working feature, load-carrying capacity and ductility etc. The effects of main factors on these properties are also discussed. According to the test results, formulas used for predicting the ultimate bearing capacity of the short composite column are proposed. The calculated results show good agreement with the test data.Based on the analysis of the experimental results about short steel tubular columns filled with steel-reinforced high-strength concrete and high-strength concrete filled short steel tubular columns under axial compression, the constitutive relationship of the core high-strength concrete in composite column is established. With deformation compatibility conditions and equilibrium conditions, load-deformation curves of short composite column subjected to axial compressive load is worked out by integral method. The calculated and experimental results agree very well. The working mechanics of the composite column are also discussed based on the calculated results.On the base of experiments and calculations, the mechanical properties of the axially loaded slender composite columns are studied. Furthermore, formulas used for predicting the ultimate bearing capacity of slender composite column subjected to axial compression are deduced. The results from formular calculation are in good agreement with the results of numerical calculation and experiment.The mechanical properties of the composite member subjected to pure bending moment are studied by numerical analysis. The analytical results have been verified by experiment studies. Finally, formulas used for the evaluation of flexural capacity are proposed.According to the results of experiments and numerical calculations, the mechanical properties of the composite columns subjected to compression and bending moment areinvestigated. The main factors affecting the mechanical properties are analyzed and interaction equations of the ultimate bearing capacity for compression-bending composite column are established. The advantages of circular steel tubular columns filled with steel-reinforced concrete are discussed by comparison to bar-reinforced concrete columns.Through a series of experiments, the behaviors of the composite column subjected to low frequency cyclic loading are also investigated. The results show the composite column has higher ductility and higher vertical residual load-carrying capacity after failure. These features of the composite column will prevent the collapse of buildings in strong earthquakes. So this type of composite column can be used in structures of strong seismic intensity zone.