Experimental investigation and theoretical analysis of axially-loaded concrete-filled elliptical tubes with circumferential gaps

摘要

This paper herein conducts an experimental investigation on the axial compression behaviour of the concrete -filled elliptical steel tubular (CFEST) short columns offering circumferential gaps (CFEST-CG) and explores the influence of gap ratio and steel strength on their failure modes, axial compression resistance, initial stiffness and ductility, etc. Moreover, a finite element (FE) model is built and validated by the test observations. A systemic parametric investigation is presented to explore the impact of geometric and material parameters on the axial compression properties of CFEST-CG short columns. The influencing mechanisms of the circumferential gap on the typical load-displacement curve, the stress response and the contact stress are figured out. Two simplified calculation approaches for estimating the axial compression strength of CFEST-CG short columns are proposed in accordance with the unified theory and the simple superposition principle. The research results indicate that the existence of circumferential gap defects may result in failure patterns, such as the brittle cracking of the concrete, the inward and outward bulges in steel tube, due to the weakened steel confining effect and concrete supporting action. And the significant decrease in the axial compressive strength, initial stiffness and ductility of the columns is obtained as well. The accuracy of the design methods is verified by experiments and FE parameter analysis, which would provide a reference for theoretical research and design of CFEST-CG short columns.