Nonlinear analysis of rectangular concrete-filled double steel tubular short columns incorporating local buckling

Abstract

Rectangular concrete-filled double steel tubular (CFDST) columns with inner circular steel tube possess higher structural performance than conventional concrete-filled steel tubular (CFST) columns. However, the local buckling of the outer steel tube of thin-walled rectangular CFDST columns has not been accounted for in the existing fiber element models and design codes that may overestimate the column ultimate axial strengths. This paper describes a computationally efficient fiber-based modeling technique developed for determining the behavior of concentrically-loaded rectangular CFDST short columns including the local buckling effects of the external steel tube and the confinement offered by the internal circular steel tube. The effective width concept is used to simulate the post-local buckling of the outer steel tube. Comparative studies are undertaken to verify the fiber-based model with the relevant test results. The computational model is then employed to investigate the axial load-strain responses of rectangular CFDST short columns with various key design variables. A design equation is developed for computing the ultimate axial loads of short rectangular CFDST columns and compared with design methods given in several international design codes. It is shown that the fiber-based modeling technique and the proposed design model predict well the structural performance of short CFDST columns.

Experimental and numerical studies of square concrete-filled double steel tubular short columns under eccentric loading

“…However, the core concrete is confined by the internal circular steel tube in a square CFDST column and this confinement is recognized in the material stress-strain relations for coreconcrete in the present study. The material constitutive models for sandwiched-concrete and core-concrete in rectangular CFDST columns have been validated against experimental data by Ahmed et al [27]. The general stress-strain curves for both confined concrete and unconfined concrete are schematically illustrated in Fig.…”

“…The effects of local buckling on the structural performance of concrete-filled steel tubular composite columns have been investigated by a number of researchers [21][22][23][24][25][26][27][28]. A fiber-based modeling technique has been proposed by Ky et al [29] for the response predictions of axially loaded concrete-encased composite (CEC) short and slender columns.…”

Numerical analysis of axially loaded rectangular concrete-filled steel tubular short columns at elevated temperatures

“…Although local buckling could be included in the finite element analysis of rectangular CFST columns in fire, the development and computational cost of the finite element model is highly expensive compared to that of the fiber element model [31,39]. The comparative study conducted by Ahmed et al [39] demonstrated that the total time for creating and analyzing the finite element model of a concrete-filled double steel tubular short column was 2640 s while the total time for creating and analyzing its fiber element model was only 25 s. Moreover, there are relatively limited studies dealing with rectangular short CFST columns under fire loading.…”

Buckling Analysis and Stability of Compressed Low-Carbon Steel Rods in the Elastoplastic Region of Materials

“…e value of the critical stress-σ crt was solved from quadratic equation (16) and substituted in equation (13), and thus, the adjusted formula for calculating the critical stresses was obtained in the elastoplastic working region of the material.…”

“…In the literature [16,17], researchers presented a numerical method for computing the load-de ection relationships of loaded square columns with various geometric parameters, loading eccentricity, and column slenderness ratios.…”