Seismic performance and design method of T-shaped CFST column to U-shaped steel-concrete composite beam joint with vertical stiffeners

Special-shaped concrete-filled steel tubular (CFST) columns and cold-formed U-shaped steel-concrete composite beams (CUCB) have recently been developed for efficient steel-concrete composite construction. In this study, five half-scaled T-shaped multi-cell CFST columns to CUCB joint specimens with different vertical stiffener dimensions were designed for pseudo-static test. The seismic performance of the proposed joints was analyzed based on the failure modes, hysteresis curves, ductility, and stress distribution. The experimental results show that joints with vertical stiffeners exhibit favorable seismic performance and can be considered rigid joints in a braced frame according to Eurocode 3. A finite element (FE) model for the joint was developed using ABAQUS and verified with the available experimental results. Furthermore, a parametric study was conducted to explore the effects of the vertical stiffener dimensions on joint strength and stiffness. The numerical results indicate that the vertical stiffener dimensions can significantly enhance joint strength and stiffness. A design method of such joints was proposed for practical engineering applications, including calculation formula for joint flexural capacity as well detailing for joint stiffness.