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摘要
Recently, the concrete-filled elliptical steel tube (CFEST) members have been widely applied in engineering practice due to their outstanding mechanical performance. However, relative research and design have never considered the effect of gap imperfections. Herein, this paper designed and produced 10 CFEST short columns with circumferential gap and investigated the influence of steel strength and gap ratio on their failure patterns, axial compressive resistance, initial stiffness and ductility by axial compression tests. The CFEST short columns axial compression typical load-displacement curves and circumferential gap influence characteristics were revealed respectively. The experimental results indicated that the circumferential gap caused the steel tubes to be caved and buckled locally due to the lack of concrete’s supporting action. And the weakening of the restraint effect caused the brittle collapse and shear failure of the concrete, which leaded to the significant decrease of the bearing capacity, stiffness and ductility of the specimens. The axial compressive strength, initial stiffness and ductility of CFEST short columns are respectively reduced by 20. 6%-34. 5%, 10. 8%-17. 8% and 8. 0%-30. 4%, owing to existing of the circumferential gap defects (the gap ratio ranging from 2. 1% to 6. 5%). The finite element (FE) model using the software ABAQUS was established and verified to simulate the axial compression behavior of CFEST short columns with circumferential gap. And a systemic parametric investigation based on test results was developed to explore the impact of material and geometric parameters on the axial compression performance of the columns. The influencing mechanism on the effect of circumferential gap on the contact stress between the elliptical steel tube-concrete interface was figured out. The analysis results show that the axial compressive strength and initial stiffness of CFEST short columns decrease significantly with the increase of gap ratio, but the decrease was no longer significant once the gap ratio was greater than 0. 5%. Finally, a formula for calculating the axial bearing capacity of CFEST short columns with circumferential gap was proposed this paper. And the accuracy of the formula was verified by experiments and finite element parameter analysis, which would provide a reference for theoretical research and design of concrete-filled elliptical steel tubular short columns with circumferential gap. ? 2023 Science Press.
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