Parametric Study and Design of a Novel Bolted Endplate Rigid Connection Between CCFT Columns and Wide-Flange Beams

This study proposes a design method for a novel bolted endplate rigid connection between circular concrete-filled steel tube (CCFT) columns and wide-flange (WF) steel beams, with particular emphasis on the parametric behavior governing joint performance. Based on the preliminary quasi-static tests, finite element simulations are conducted to evaluate the flexural behavior and failure mechanisms under beam-end maximum moment, followed by an extensive parametric study examining the effects of square tube dimensions, high-strength grout, and column axial load. The numerical results show that the wall thickness of the square steel tube significantly affects grout indentation. A 60% reduction in wall thickness led to a 503% increase in indentation. In contrast, variations in tube dimensions, grout strength, and column axial load within the studied range caused less than a 16% change and did not influence the flexural performance. These results indicate that the constraints on tube dimensions and axial load may be relaxed. The proposed connection effectively overcomes the limitations of conventional CCFT-to-beam joints, including unfavorable stress transfer, complex detailing, and construction inefficiency, by modifying the load-transfer mechanism and reducing the demand on tensile-critical welds, thereby enhancing ductility. Based on the parametric findings, a design method is established, and theoretical analysis confirms that the proposed connection satisfies the stiffness requirements for fully rigid connections. Future quasi-static tests with different member sizes are recommended to validate these findings.