| Research Abstract |
The concrete-filled steel tubular(CFST) structure has been recognized as an earthquake-resistant structure, and the investigation of the effects of several factors on the strength and deformation capacity of CFST members and connections have been investigated : axial force ratio, width-thickness ratio of steel tube, concrete strength, strain-hardening of steel, and interaction between steel and concrete, that is, confining effect on concrete by steel tube, and restraining effect of cencrete on the local buckling of steel tube. However, there have been no research found on the three-dimensional behavior of a frame consisting of CFST columns under the severe earthquake, in which the column behavior under the bi-axial bending and the connection behavior under the three-dimensional loading may appear. From this point of view, three-dimensional subassenblages consisting of a concrete-filled steel tubular column and four H-shaped beams were tested under a constant axial load on the column, constant beam loads in the minor direction, and alternately repeated beam shear in the major direction simulating the earthquake loading, and the effects of the following experimental parameters on the elasto-plastic behavior were investigated : shapes of specimen (three-dimensional and planar frame specimens simulating subassemblages around exterior and corner columns) ; failure types (panel failing type and column failing type) ; and pattern of the long-term loads on the beams in the minor direction. New findings obtained from the experimental study on the elasto-plastic behavaior of three-dimensional concrete-filled steel tubular subassemblages are as followa : (1)The maximum, strengths of panel-failing specimens were almost the same, and the effects of neither the three-dimensional loading nor the biaxial bending were observed. On the other hand, both the three-dimensional loading and the bi-axial bending reduced the maximum strengths of column-failing specimens (2)Beam-to-column c
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