Effect of Rib Stiffeners on End-Plate Connections of Concrete-Filled Steel Tubular (CFST) Columns and I-Section Beams

This study aims to analytically investigate the effect of rib stiffeners on through-bolt end-plate connections of concrete-filled steel tubular (CFST) columns and I-section beams. For this, 3D finite element (FE) models of the CFST column-I beam connections were generated. The FE models were validated with test results of similar connections published previously in literature. To examine the influence of the rib stiffeners, FE models of the stiffened connections were created by adding rib stiffeners of different thicknesses, slopes, and steel quality to the validated FE models. FE analyses considering both material and geometrical nonlinearities were performed under cyclic loading. The results of the analysis showed that the ultimate strength of the CFST column-I beam connection was affected by the slope of the rib stiffener rather than its thickness, but was not affected by its material quality. Although the rib stiffeners significantly increased the ultimate strength, they were unable to prevent local buckling in the beams, and therefore, no significant improvement in the ductile behavior of the connections was achieved. Additionally, it was seen that the rib stiffeners enhanced equivalent plastic strain (PEEQ) and had the effect of reducing relaxation of through bolts.