Experimental Research And Finite Element Analysis On Seismic Behavior Of Special Shaped Column Composed Of Concrete-Filled Steel Tubes And Steel Beam Frames

Special shaped column composed of concrete-filled steel tubes frames was gradually used in multistory building during rencently years.In order to clear its seismic performance, three single span two-storey SCFST column-H steel beam frames was tested under a constant axial load on columns and a lateral cyclic load on the frame. The impact of different axial compression ratio and beam-column linear stiffness ratio was studied for seismic properties. The result of test shows that the energy dissipation capacity and ductility of the frames are adequate and the strength and stiffness degradation is not obvious, which prove the excellent seismic performance. The increase of axial compression ratio will weaken the energy dissipation capacity and ductility and improve the bearing capacity.The increase of beam-column linear stiffness ratio will improve the energy dissipation capacity and ductility and weaken the bearing capacity. The stiffness degradation of the frames with different beam-column stiffness are not obvious.And the increase of the axial compression ratio will intensify the stiffness degradation slightly.The finite element model(FEM) with contact element and without contact model were established to compare with the result of test. By comparsion, we found that the stress of two types of FEM was coordinating, which meet the failure mode that yielding first appeared on the beams end, and then column ends. The calculation of FEM with the contact element is more accurate than that of the FEM without contact element, which matches the results of the test better. Then three FEMs without contact element were established to compare with the test which are identical with the test specimens. Generally, the FEM meet the test result well, but the bearing capacity and ductility were a little higher than the test.While the calculation time for the FEM with contact element is 5 times more than that of the FEM without contact element. Therefore, calculation accuration and time should be considered when selecting the calculation model.The FEM verified by the test was build to analyze the seismic performance of SCFST frames under different axial compression ratio, and all the frames have adequate energy dissipation capacity and ductility.But when the axial compression ratio reaches 0.6, the yield of column end will appear earlier than than of beam end. With the increase of the axial compression ratio the energy dissipation capacity and ductility will decline.The beam-column linear stiffness ratio of FEM was changed by different span and beam size.The comparsion of 6 SCFST frames with different beam-column linear stiffness ratio shows that the the bearing capacity and ductility improve with the increasing of beam-column linear stiffness ratio. It also indicates that increasing the height of beam is an effective way to improve the bearing capacity of the frame, and the effective way to improve the ductility is decreasing the span of the beams. The analysis of five frames with different stiffener distance under hysteresis load shows that large area of the connection plate will yield while there is a long stiffener distance. And the short distance of the stifferner will cause nonuniform stress of the connection plate which is higher in the connection of beam and column. Therefore the analysis results show that the best ratio of stiffener distance and the width of connection plate is about 1.75.