Numerical and experimental investigation of the seismic behavior of rigid steel beam-to-hollow circular column connections using a steel box

Rigid beam-to-circular steel column connections have always attracted the attention of researchers and design codes due to their geometric complexity and construction challenges. In this study, the use of a steel box at the connection region is proposed for joining I-shaped sections to hollow circular columns. This method offers advantages such as simplified detailing and eliminates the need for continuity plates or doubler plates. The initial design of the experimental specimens was performed numerically, and then three specimens exhibiting superior performance were selected for experimental investigation. The experimental studies examined the effect of the configuration of column-to-box and beam-to-box stiffeners on their seismic performance. Subsequently, further numerical studies were conducted on the experimentally superior specimen. After validating the numerical model, the effect of the steel box thickness on the connection with various beam and column sections was evaluated. The aim of this part was to determine the minimum required thickness for the steel box, beyond which further increases would not affect the results. Additionally, the rigidity of the connection was also investigated. The experimental results indicated that the model with internal box stiffeners aligned with the beam flanges provided the highest strength, ductility, and elastic stiffness. Parametric analyses indicated that rigid behavior and full beam capacity can be ensured when the steel box thickness is at least 1.4 times the beam flange thickness.