Cyclic behaviour of novel blind bolted joints with different stiffening elements

Because of the difficulty of accessing the interior of structural hollow sections, emerging technology using blind bolts has been recently developed for fabricating connections to concrete-filled steel tubular (CFST) columns. However, two issues limit the structural benefits of this joint system including the limited transfer of hogging moment and high susceptibility of the steel tube to local failure. Therefore, the authors proposed four methods to enhance the CFST column's stiffness in the connection region, namely, using inner binding bars, welding two internal rings, externally welding two C-shaped channels, and internally embedding a short segment of I-section in the steel tube. A total of 6 joints were tested under cyclic loading accordingly. The experimental results are analysed in this paper to evaluate the efficiency of different stiffening methods. It indicates that the C-shaped channels and embedded I-section are very effective in enhancing the performance of the joint, and the joint's strength and deformation capacity can be significantly improved with large bending deformation developed in the end plate. In contrast, welding binding bars or internal rings has only moderate influence on the joint performance.