Effect of vertical stiffeners on the seismic performance of T-shaped CFST column to steel beam joint

Special-shaped concrete-filled steel tubular (SCFST) columns have recently been developed for efficient steel-concrete composite construction. In this study, a novel vertical stiffener joint for the SCFST column and steel beam frame structure is proposed. Five SCFST columns with H-section beam joints were investigated under cycling loading. The test parameters mainly consider the column stiffening form, vertical stiffener type, and the column axial load. The failure pattern, hysteretic curves, and strain development of specimens are analyzed. Experimental results demonstrate the proposed joint with vertical stiffeners can develop the steel beam's full plastic flexural capacity and exhibit favorable seismic performance. In addition, a finite element (FE) model is developed to explore the effects of the following parameters on the hysteretic performance: vertical stiffener sizes, width-to-thickness ratio of column steel tube, and the column axial load. Based on the experimental and FE analyses, a stress and deformation model of the joint steel tube was established. To facilitate the practical applications, a calculation formula for joint strength was also put forward, considering the contribution of vertical stiffener, and front and side steel plates of the joint steel tube.