# A Study on the Seismic Performance of Steel H-Column and T-Beam-Bolted Joints
## 3 Seismic Performance Analysis  
### Failure Mode and Stress Development  
Based on the analysis of the BASE node, in the elastic stage, the displacement at the column end gradually increases while the stress at the beam end shows no significant change. The stress in T-part 1 develops rapidly, whereas the stress development in T-part 2 is not evident. These constraints reduce T-part 2's rotational demand, minimizing its participation in moment redistribution. As a result, T-part 2 experiences minimal stress compared to T-part 1, which is exposed to higher bending stresses at the beam-column interface (Figure 8). When the displacement is loaded to approximately 42 mm, the load reaches 374.04 kN. This load is a lateral-load applied in the orthogonal-alternate loading mode, which means it is applied alternately in the X-direction and the Z-direction. At this moment, the stress of the section at the position of the bolt holes in the first row of T-shaped part 1 exceeds the yield stress of the steel, indicating that the joint has yielded. Stress concentration occurs at 246 mm from the end of the steel beam, and the stress at the edge of the bolt hole and the corner of the joint domain is higher than the yield strength. Most of the other areas remain in the elastic stage.  
The yield stage then transitions into the elastoplastic stage. When the first-round positive displacement is loaded to 83.2 mm, the bolt hole on the tension side of T-part 1 experiences slight buckling and reaches the tensile strength. The horizontal load at the column end reaches 493.36 kN, and the bearing capacity of the joint attains its peak state. At this point, the stress in most sections of the node domain has not exceeded the yield strength and remains in the elastic stage. However, the stress in the T-parts, bolt holes of the column walls, and their edge corners are relatively high.  
During the loading process, obvious buckling occurs on the web plate of T-part 1. When the positive displacement of the node in the first cycle is loaded to 104 mm, the buckling of the column wall is further intensified. Meanwhile, obvious buckling takes place on the web of T-part 1, and its stress far exceeds the tensile strength of the steel, leading to the damage of T-part 1. The entire failure process unfolds as follows: First, there is slight buckling on the web of T-part 1, followed by slight bulging of the column wall and higher stress at the compression flange of the beam end. Then, more obvious buckling occurs on the web of T-part 1, which further intensifies. Eventually, the first row of bolts on the web of T-part 1 reaches its ultimate tensile capacity and breaks.  
The final failure mode of the node is the buckling failure of the web plate of T-part 1, as illustrated in Figure 8, the stress unit is MPa. It can be observed that in the failed state, the stress at the connection between the web plate and the flange of T-part 1 is relatively high. The stress and plastic strain of T-part 1 is mainly concentrated at the joint of the web and the flange, extending to the first row of bolt holes on the web.