EXPERIMENTAL STUDY ON MECHANICAL BEHAVIOR OF STEEL REINFORCED CONCRETE STOCKY COLUMN WITH MONOSYMMETRIC CROSS-SHAPED STEEL UNDER AXIAL COMPRESSION

To investigate the axial compression behavior of the composite column with monosymmetric cross-shaped steel, 9 stocky columns were tested under axial compression. The experimental parameters were the cross-shaped steel eccentricity ratio, concrete strength, steel ratio and volume-stirrup ratio. The failure pattern, the load-deformation curves, the law of strain change of the specimens were obtained by the test. The stress mechanism and the influences of four parameters on axial compression behavior of the composite columns were analyzed. Based on Mander model, a calculation method of axial bearing capacity for the composite column is proposed by partitioning different confined areas of concrete. The experimental results show that the specimen failure was concentrated in the reverse cross-shaped steel eccentric direction. The steel profile, longitudinal bar, stirrup and concrete can work together, and the strength of them can be mobilized. The axial compressive bearing capacity and ductility of the specimen decrease with the increase of eccentricity and stirrup spacing of cross steel. Increasing the concrete strength and the steel ratio can enhance the axial bearing capacity of the specimens. However, increasing the concrete strength reduced the ductility of the specimens. The axial bearing capacities of the specimens calculated by the JGJ138-2016, EC4 and ACI318-14 are relatively conservative. Calculation results from the axial bearing capacity formula proposed for the composite column under axial compression agree well with the test results.