Local buckling in steel tubes was observed to be capable of reducing the ultimate loads\nof thin-walled concrete-filled steel-tube (CFST) columns under axial compression. To strengthen\nthe steel tubes, steel bars were proposed in this paper to be used as stiffeners fixed onto the tubes.\nStatic-loading tests were conducted to study the compression behavior of square thin-walled CFST\ncolumns with steel bar stiffeners placed inside or outside the tube. The effect and feasibility of steel\nbar stiffeners were studied through the analysis of failure mode, loadâ??displacement relationship,\nultimate load, ductility, and local buckling. Different setting methods of steel bars were compared as\nwell. The results showed that steel-bar stiffeners proposed in this paper can be effective in delaying\nlocal buckling as well as increasing the bearing capacity of the columns, but will decrease the ductility\nof the columns. In order to obtain a higher bearing capacity of columns, steel bars with low stiffness\nshould be placed inside and steel bars with high stiffness should be placed outside of the steel\ntubes. The study is helpful in providing reference to the popularization and application of this new\nstructural measure to avoid or delay the local buckling of thin-walled CFST columns.
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