Numerical investigations of circular double-skin steel tubular slender beam-columns filled with ultra-high-strength concrete

Abstract

The use of ultra-high-strength concrete in double-skin concrete-filled steel tubular (DCFST) composite columns has received considerable attention in recent years. However, no numerical study on the behavior of eccentrically loaded circular DCFST slender beam-columns made of ultra-high-strength concrete has been reported. This paper proposes computational modeling procedures for accurately predicting the axial load–deflection responses and axial load-moment interaction diagrams of circular DCFST slender beam-columns filled with ultra-high-strength concrete when subjected to the combined action of bending and axial compression. The computational procedures based on the fiber element methodology incorporate the effects of concrete confinement, second-order and initial geometric imperfection on the behavior of DCFST slender beam-columns. The enhanced King-Werner’s algorithm is implemented in the fiber-based procedures to solve the nonlinear moment equilibrium equation. The accuracy of the present model is verified with experimental results published in the literature and finite element analysis results. The numerical results reveal that the confined concrete model can capture the response of ultra-high-strength concrete with a sudden drop after reaching the peak load and the ductility in the softening branch. The significance of several influencing factors on the structural behavior is investigated in the comprehensive parametric study including 154 specimens with a wide range of column geometric and material properties. The design of circular DCFST slender beam-columns with ultra-high-strength concrete in accordance with Eurocode 4 is discussed. The artificial neural network (ANN) model is developed to propose new empirical formulas for evaluating the member resistance of DCFST slender beam-columns. The proposed equations give accurate and reliable predictions of the column’s resistance and can be employed in practical design.