Axial Compressive Behavior of Thin-Walled Concrete-Filled Double-Skin Steel Tubular Stub Columns with Connecting Strips

Concrete-filled double-skin tubular (CFDST) columns have high fire resistance, and are widely used in the construction of electrical towers and bridges. However, previous research showed that the buckling of steel tubes can be significant in noncircular CFDST for nonuniform confinement or a large width-to-thickness ratio. The authors proposed a novel stiffened thin-walled CFDST column with steel strips welded on both inner tube and outer tube to form several closed cavities to fully utilize material strength. This paper presents an experimental study on the axial compressive behavior of this new type of stiffened thin-walled CFDST column; tests were conducted on six thin-walled CFDST columns and two steel tubes. The test results confirm that the stiffened CFDST columns have higher strength and better deformation capacity than the control columns. Moreover, the finite element (FE) model was developed to simulate the interaction between steel tubes and concrete. The average error of the FE analysis when predicting the column bearing capacity was 1.3% compared with experimental results. Finally, a strength design formula was proposed to predict the compressive strength of the stiffened thin-walled square CFDST column, which is recommended for design purposes.