Numerical and theoretical investigation on the cyclic behavior of self-centering CFDST column-steel beam joints

Abstract

In this paper, a self-centering joint between the concrete-filled double steel tubular (CFDST) column and the steel beam is proposed. The joint was self-centered by prestressed strands when unloading, and energy was dissipated during loading by friction. This work is a numerical and theoretical exploratory study based on a modeling approach already validated by experiments, aiming to investigate the mechanical behavior of the novel self-centering joint and optimize its design parameters. The reasonableness of the joint model was verified by numerical simulation with ABAQUS finite element software, and the damage modes, hysteresis curves, and energy dissipation capacity of the joint were analyzed. A mechanism-based semi-theoretical restoring force model was established. Performed a parametric analysis on the primary factors influencing the mechanical behavior of the joint. The results indicated that there was a contradiction between self-centering performance and energy dissipation in the joint, and the ratio β between the moment resistance provided by the strands and that provided by the friction devices in the decompression moment of the joint played a key role in moderating the relationship between the two. A value of β between 1 and 1.5 was recommended for a balance between the two. The restoring force model of the joint provided a well-predicted mechanical behavior of the joint. The modified rigid model was more consistent with the numerical results. This study provided theoretical support and optimized design parameters for the design of CFDST column-steel beam joints with favorable self-centering performance and energy dissipation capability. The parameter analysis showed that increasing strand prestress increased the bearing capacity but potentially resulted in stress loss; an increase in friction force improved the bearing capacity and energy dissipation capacity, yet it augmented residual deformation; and an enlargement of the cross-sectional area bolstered both the bearing capacity and stiffness, albeit it also led to stress loss.