Behavior of through-core bolted connections between CFDST columns and steel or composite beams subjected to cyclic loading

Abstract

The cyclic performance of through-core bolted connections between CFDST columns and steel or composite beams has been rarely studied. To address this gap, an experimental study was performed to investigate the effects of different parameters. An innovative multi-chamber system was developed by incorporating vertical clip-type transverse plates between the inner and outer steel tubes, which effectively enhances structural integrity, reduces interface slip, delays steel tube buckling and significantly improves construction efficiency. Four specimens of the interior joint at 1/2 scale of the actual specimen were designed and tested under cyclic loading conditions. The main design parameters were the column hollow ratio, the cross-section shape of inner steel tube, and the type of beam section. Lateral load vs displacement and strain vs displacement hysteresis responses were then obtained. The experimental results were analyzed, including failure mechanisms, ultimate strength, damage development, stiffness degradation, strength degradation, energy dissipation capacity, ductility and strain responses. The results of the experiment showed that the proposed composite beam-column joints had good cyclic performance. Characters of hysteresis curves of the specimens were show two forms: anti-S-type of composite beams and spindle-type of steel beams. Two typical failure modes were also observed from the conducted tests, which included buckling and tearing failure at steel beam flange and web for specimens with steel beams, as well as bolt slip and concrete cracks in concrete slab for specimens with composite beams. The cyclic performance of specimens with composite beams was better than that of specimens with steel beams. The outcomes of this study improve the practice design and implementation of semi-rigid CFDST frames in active seismic areas.