Numerical analysis of rectangular double-skin concrete-filled steel tubular slender columns incorporating interaction buckling
Rectangular double-skin concrete-filled steel tubular (RDCFST) slender columns made of non-compact or slender steel sections under axial load and bending may undergo local–global interaction buckling, which is rarely considered in existing fiber-based nonlinear modeling procedures for RDCFST columns. In this paper, a new computational model is presented, which can simulate the load–deflection responses of uniaxially loaded thin-walled RDCFST slender columns that are discretized into fiber elements. The important features associated with thin-walled RDCFST slender columns are explicitly accounted for in the computational model, including the interaction between the local buckling of outer and inner steel tubes and the column global buckling, initial geometric imperfections, material nonlinearities and second order effects. An incremental-iterative computational algorithm is developed to capture the nonlinear buckling displacements of RDCFST columns. The nonlinear equilibrium equation generated at each iteration is solved by means of implementing Müller's numerical scheme. The computational model, which is verified by experimental results, is utilized to investigate the interaction buckling responses of RDCFST columns loaded eccentrically, considering a wide range of design parameters. It is demonstrated that the developed computational modeling and simulation technique can detect the initial local buckling of double-skins and capture the influences of the interaction of localized and global instability on the performance of nonlinear RDCFST slender columns. The benchmark numerical results obtained from the parametric study provide a new insight into the interaction buckling behavior of RDCFST columns.
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