STABILITY LIMIT AXIAL FORCE AND ALLOWABLE ROTATION ANGLE OF STEELCONCRETE COMPOSITE COLUMNS

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Sreel-concrete composite columns have been used as the beam-column members of high-rise building in Japan. The columns of lower stories of high rise building are subjected to both high axial compressive force and repeated bending under the earthquake excitation. It is indicated that the effect of vertical force on the inelastic behavior is very large, and for this Steel Reinforced Concrete Standard of AIJ prescribes a limiting value of axial load for a beam-column which requires the deformation capacity.The objectives is to study the strength and behavior of steel-concrete composite columns subjected to constant compressive load and repeated bending. As the main test parameter, axial load ratio on a column was selected.Thirty-six concrete filled steel square and forty concrete filled steel circular tubular columns are tested. The steel portion of a specimen is a cold-formed square and circular section. In addition to the axial load ratio, width-thickness ratio and diameter-thickness ratio are selected as the experimental parameters.Twenty-two SRC columns are tested. In addition to the axial load ratio, steel area ratio is selected as the experimental parameters.From the test results, inelastic behavior, maximum strength, energy dissipation capacity and deformation capacity are discussed. We have shown relations between axial load ratio and critical rotation angle of a column.