Abstract
The objective of this study was to investigate the composite behavior of rectangular concrete-filled cold-formed steel (CFS) tubular stub columns under axial compression. A fine finite 3D solid element model of rectangular concrete-filled cold-formed steel tubular stub column was established by ABAQUS, which utilized a constitutive model of cold-formed steel considering the cold-forming effect and a triaxial plastic-damage constitutive model of the infilled concrete. Good agreement was achieved and the average discrepancy between the experimental and FE results was less than 5%. Based on the verified models, a further parametric analysis was carried out to reveal the influence of various factors on the strength and behavior of the concrete-filled rectangular cold-formed steel tubular stub columns. The factors included constitutive models adopted for cold-formed steel, length over width ratio of the rectangular section, wall-thickness and width, and concrete strength and yield strength of the cold-formed steel. A total of 144 FE models were analyzed. The stress nephogram was reasonably simplified in accordance with the limit state and a theoretical formula considering confinement coefficient was proposed to estimate the ultimate bearing capacity of concrete-filled rectangular cold-formed steel tubular stub columns using the superposition method. The calculated results showed satisfactory agreement with both the experimental and FE results, which proved the validity and accuracy of the formula proposed in this paper. In the proposed formula, the confinement coefficient of square concrete-filled cold-formed steel tubular stub columns is larger than that of hot-rolled steel counterparts but smaller than that of the stainless steel counterparts.
Highlights
Concrete-filled steel tube (CFST) is a preferable combination of steel and concrete materials, which can make the most use of the compressive strength of concrete and the tensile strength of steel
Zhu et al [13] explored the influence of stiffeners on the mechanical performance of square concretefilled cold-formed steel tube (CFCFST) stub columns through experimental studies and the calculated results using different codes were compared with the test results, which showed that the calculated results in the current codes are conservative
Based on triaxial plastic-damage constitutive relations with features of the parameter certainty for the infilled concrete and a rational constitutive model for cold-formed steel, a fine finite 3D solid element model of CFCFST stub columns was established, which takes into account the composite behavior of cold-formed steel tube and core concrete
Summary
Concrete-filled steel tube (CFST) is a preferable combination of steel and concrete materials, which can make the most use of the compressive strength of concrete and the tensile strength of steel. (2) Based on the numerical model that was verified against experimental results, a parametric study was performed and the composite behavior of cold-formed steel tube on concrete with different sectional sizes, steel ratios, steel yield strengths, and concrete strengths was investigated. The mechanical properties of rectangular CFCFST stub columns under axial compression based on different constitutive models of cold-formed steel were investigated. (3) According to the results of parametric study and the equilibrium theory at limit state, a practical design formula considering the confinement coefficient was proposed to predict the ultimate bearing capacity of the rectangular CFCFST stub columns under axial compression. The incremental iterative method was used to consider structural nonlinearities during the analysis
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