Seismic Performance of Joint between Locally Reinforced Multichamber Concrete-Filled L-Shaped Steel Columns and H-Shaped Beams

Owing to their irregular geometry, L-shaped steel-tube concrete column frame joints are prone to stress concentration at corners and welds, and the torsional performance of L-shaped columns is poor, which may lead to structural instability in torsion. Therefore, it is necessary to adopt a reinforcement method that enables easy fabrication and effective load transfer. In this paper, locally reinforced multichamber concrete-filled L-shaped steel columns and H-shaped beam (LRMCLSC-HB) joints are introduced. Three LRMCLSC-HB joints with different specifications in the beam–column joint area were subjected to quasistatic tests. Test findings reveal that the dominant failure mechanism was the formation of plastic hinges in the steel beam flanges. The hysteresis curves exhibit a full shape, demonstrating good seismic performance. A joint-reinforced column significantly enhances the specimen’s mechanical performance indicators, including energy dissipation capacity, load-bearing capacity, and stiffness, by enhancing the wall thickness of the steel tube in the joint zone. Although extending the height of the stiffened column zone produces similar reinforcement effects, the degree of improvement remains relatively limited compared with that achieved through wall thickness augmentation. Additionally, the installation of a rectangular stiffener causes the plastic hinge to shift outwards. Finite element joint models were built in ABAQUS to corroborate the experimental findings. A subsequent parametric study evaluated the impact of different specifications of the joint-reinforced column and the thickness and arrangement of the vertical stiffener on the mechanical performance of the joints. The simulations show that increasing the thickness and height of the joint-reinforced column improves the seismic performance of the samples; however, the height increase has relatively limited effects. The arrangement of the vertical stiffener enhances both the shear strength and stiffness of the core zone. When the vertical stiffener is aligned with the long side rather than the short side of the rectangular chambers, the bearing capacity, initial stiffness, and energy dissipation capacity of the joint significantly improve. On the basis of the experimental and simulation analyses, a force transfer mechanism and a calculation formula for the ultimate flexural load capacity of this type of joint are proposed.