LOCAL BUCKLING OF CONCRETE FILLED CIRCULAR STEEL TUBE COLUMN

Local buckling of concrete filled steel tube column (CFT column) is analyzed on the upper bound theorem of the limit analysis. The collapse mechanism of the analysis is assumed on the basis of CFT column test under monotonic and repeated load. The load deformation relations of many CFT columns designed under quite different conditions are calculated by the proposed analysis method. The plastic deformation capacity until the local buckling of CFT column which is closely related to the crack of steel tube is also obtained by it. From the calculated results it is shown that the local buckling of CFT column is significantly effected not only by the well known diameter to thickness ratio of steel tube but also by the axial force ratio, the aspect ratio and the strength ratio of concrete to steel tube.