# A Study on the Seismic Performance of Steel H-Column and T-Beam-Bolted Joints
## 4 Parametric Analysis
### Parameter Analysis of T-Part 1
These values were consistent across multiple test specimens, validating the reproducibility of the failure threshold. Figures 11 and 12 shows the stress distribution in the T-part at the moment of failure, clearly indicating the regions of high stress concentration that led to failure. Based on these data, the critical failure threshold of the T-part can be accurately defined, providing a solid foundation for future research and design. Figures 13 and 14 show the skeleton curve of the T-part 1 when the web and flange change. When the web thickness of T-part 1 increases from 14 mm to 18 mm, its flexural stiffness increases, resulting in a change in the stiffness distribution in the joint area. According to the component method theory [22], the increased stiffness of T-parts enables them to bear greater bending moments, thereby reducing the risk of local buckling of column walls. At the same time, the force flow path of the node domain gradually shifts from the \"T-part-column wall\" leading role to the \"beam-T part\" synergistic role. At this time, the bending moment of the beam end increases due to the stiffness of the T-shaped part. When the ultimate bending strength of the beam is not enough to match this demand, the plastic hinge will be formed at the flange of the beam. This process shows that the stiffness balance  
Figure 11: A total of 13 and 21 web thickness T-part 1 stress. (**a**) BT1F-1. (**b**) BT1F-5. Figure 12: A total of 20 and 28 flange thickness T-part 1 stress. (**a**) BT1Y-1. (**b**) BT1Y-5. controls the failure mode: the stiffness threshold of the T-part determines whether the joint will undergo brittle failure (T-part fracture) or ductile failure (beam plastic hinge). As is evident from Figure 12, when the flange thickness is relatively small, the junction between the web plate and the flange of T-part 1 is the first location where plastic deformation takes place. As the thickness of the flange of T-part 1 increases, the yield area of the tension zone at the flange of T-part 1 gradually diminishes. Moreover, the degree of deformation of the flange of T-part 1 continuously weakens, and its stress level decreases correspondingly. The increase in the flange thickness of T-part 1 has a negligible impact on the buckling of the column wall. As the flange thickness increases, the development of joint stress and deformation is not significant. Therefore, the flange thickness can be reasonably controlled. When the web thickness of T-part 1 increases, the yield load and bearing capacity of the space nodes are significantly enhanced. Compared with the BASE nodes, the yield load and bearing capacity of the BT1F-6 nodes increase by approximately 12% and 16%. However, when the web thickness reaches 21 mm, the growth rate of the nodes' bearing capacity gradually diminishes. As the flange thickness of T-part 1 increases, the yield load and bearing capacity of the space nodes show no obvious variation. Specifically, the yield load and bearing capacity of the BT1Y-5 nodes are less than 1% higher than those of the BASE nodes. Compared with the BT1Y-1 node, the yield load and bearing capacity of the BT1Y-5 node are not significantly improved, with an increase of less than 3%. The stiffness of the joint rises as the thickness of the web plate and flange of T-part 1 increases. For instance, the stiffness of the BT1F-6 node is approximately 4% higher than that of the BASE node, and the stiffness of the BT1Y-5 node is about 6% higher than that of the BASE node. Figure 14: Node skeleton curves of different T-part 1 flange thicknesses. Figure 13: Node skeleton curves of different T-part 1 web thicknesses. As the web thickness of T-part 1 increases, the joint-yield displacement rises while the ductility coefficient decreases markedly. Because when the web thickness is relatively large, the joint failure mode shifts from the failure of the T-part to the plastic-hinge failure at the beam end. Additionally, the increase in the joint-bearing capacity hastens the failure of the beam end.