Experimental study on axial compressive behavior of concrete-filled double-skin thin-walled steel box columns with and without PBL

Abstract

To study the axial compressive behavior of concrete-filled double-skin thin-walled steel box (CFDTSB) columns and the effects of PBL ribs and cross-sectional hollow ratio, seven CFDTSB columns with or without PBL were tested under axial compression. By comparing the failure modes, initial stiffness, ultimate load and strength index, ultimate displacement and ductility, and strain distribution on the surface of the outer steel box of each specimen, the improvement of axial compressive behavior due to PBL ribs at different hollow ratios were investigated. The results showed that the greater of hollow ratio, the more obvious of steel box local buckling, and the weaker of interaction between steel box and concrete. PBL ribs effectively relieve the local buckling of steel boxes and enhance the participating degree of outer steel boxes in bearing axial forces; and improve the interaction between steel boxes and concrete and increase the confinement of steel boxes on concrete. In addition, the beneficial effect of PBL ribs is more obvious when the hollow ratio is larger. Therefore, compared with CFDTSB columns without PBL, CFDTSB columns stiffened with PBL have higher stiffness, axial compressive capacity, and deformation capacity. Based on that, axial compressive bearing capacity calculating formulas for CFDTSB columns with or without PBL were developed considering the local buckling and confinement of steel boxes and the effects of PBL ribs on them. The verification results proved that predicted values agree well with the experiment results.