Composite frame of circular CFST column to steel-concrete composite beam under lateral cyclic loading

In this paper we investigate the performance of composite frames composed of circular concrete-filled steel tubular (CFST) columns connected to steel-concrete composite beams subjected to a constant axial load and a cyclic lateral load. Seven single-story and single-bay in-plane frames were fabricated and tested. The effects of the slenderness ratio (lambda), the axial compression ratio (n), and the beam-to-column linear stiffness ratio (k) on the seismic performance of the composite frame were studied. The experimental results, including damage development and stiffness degradation, load-deformation responses, energy dissipation capacity and ductility are discussed. It was found that these composite frames exhibited satisfactory seismic performance. Furthermore, a finite element (FE) model was developed and validated by comparisons with the experimental results, considering both material and geometrical nonlinearity for confined concrete and steel. The results obtained from the FE modeling were in good agreement with the experimental results in terms of failure modes, load-displacement hysteretic curves, and skeleton curves.