Behavior of Concrete-Filled Steel Tube Beam Columns

The behavior of concrete-filled circular and square steel tubular (CFT) beam columns with a variety of material strengths was investigated experimentally. The main test parameters are steel strength (400, 590, and 780 MPa), diameter- (width-) to-thickness ratio of steel tube, and concrete strength (40 and 90 MPa). The interior beam-column models were tested under constant axial compression and cyclic horizontal load with incrementally increasing lateral deformation to clarify the effects of the test parameters on the behavior. The exterior beam-column models were laterally loaded under variable axial load, including axial tension. The behavior of square beam columns subjected to biaxial bending was also investigated. The test results show that higher strength and thicker steel tubes give better overall behavior of the beam column, while higher strength concrete has an adverse effect on the behavior. Furthermore, computer simulations for the hysteretic behavior of CFT beam-column specimens are presented here. The analytical results show excellent agreement with the test results except for a few cases.