# A Study on the Seismic Performance of Steel H-Column and T-Beam-Bolted Joints
## 4 Parametric Analysis
### Parameter Analysis of T-Part 1  
A comparison is made regarding the changes in the web thickness and flange thickness of T-part 1, with 10 groups of variables set. Specifically, five groups are designed to explore the influence of the web thickness of T-part 1 being 14 mm, 16 mm, 18 mm, 20 mm, and 22 mm on the nodes, and BT1F is used to denote the variation in the web thickness of T-part 1. In the other five groups, variable parameters of the flange thickness of T-parts are investigated, with the values being 20 mm, 22 mm, 24 mm, 26 mm, and 28 mm, respectively. BT1Y represents the change in the flange thickness of T-shaped parts 1. The model parameters are presented in Table 5.  
Obviously from Figure 11, when the web thickness is 16 mm or less, T-shaped part 1 yields first, with relatively high stress, and the joints exhibit failure of the T-part. However, when the web thickness of T-part 1 increases to 18 mm, the joint failure mode shifts from T-part failure to beam plastic-hinge failure. As the web thickness of T-part 1 continues to increase, the joint failure mode evolves as follows: First, T-part 1 is damaged due to excessive deformation in the first row of bolt holes; then, T-part 1 is damaged due to excessive stress at the junction between the web and the flange; finally, T-part 1 is damaged when an obvious plastic hinge is formed by the buckling of the beam flange. In the damaged state, the stress of T-part 1 gradually decreases, and the yield area of the tension zone at the bolt hole becomes smaller as the web thickness of T-part 1 increases. Increasing the thickness of the web plate of T-part 1 can enhance the resistance to column-wall buckling. As the web thickness of T-part 1 rises, the joint stress of the beam gradually develops further. The yield area in the joint region expands, and the stress on the beam flange at a position 426 mm from the end of the steel beam becomes higher. Nevertheless, once the web thickness of T-part 1 reaches a certain level, the development of joint stress and deformation becomes less apparent, and the bearing capacity does not improve significantly. Consequently, it is essential to control the thickness of the web of \begin{table}
\begin{tabular}{l l} \hline
**Abbreviation** & **Implication** \\ \hline SCBB & Square steel tube column-bolted beam \\ BT1F & Different web thicknesses T-part 1 \\ BT1Y & Different flange thicknesses T-part 1 \\ BT2F & Different web thicknesses T-part 2 \\ BT2Y & Different flange thicknesses T-part 2 \\ BZB & Base joint with bolted connection \\ BZY & Bolted joint with different axial load ratios \\ JD-FSH & Joint with different flange thickness of steel H-section \\ JD-YJL & Joint with different web thickness of Y-shaped steel \\ BYJL & Bolted joint with different yield preload levels \\ \hline \end{tabular}
\end{table} 
Table 4: Abbreviated definition. \begin{table}
\begin{tabular}{c c c c c c} \hline Model number & BT1F-1 & BT1F-2 & BT1F-3 & BT1F-4 & BT1F-5 \\ Web thickness (mm) & 13 & 15 & 17 & 19 & 21 \\ Model number & BT1Y-1 & BT1Y-2 & BASE & BT1Y-4 & BT1Y-5 \\ Flange thickness (mm) & 20 & 22 & 24 & 26 & 28 \\ \hline \end{tabular}
\end{table} 
Table 5: T-parts 1 node model parameters of different thicknesses. T-part 1 reasonably. When the web thickness of T-part 1 increases from 14 mm to 18 mm, the initial stiffness is increased from 11.2 kN/mm to 13.5 kN/mm (based on the slope of the linear section of the skeleton curve), an increase of 20.5%. When the web thickness of T-part 1 increases from 14 mm (BT1F-1) to 18 mm (BASE), the ductility coefficient decreases from 3.2 to 2.8 (\(\Delta_{\rm u}/\Delta_{\rm y}=104/37.1\)), a decrease of 12.5%. T-part failure was observed when the load reached a certain level, indicating a critical failure threshold. Through finite-element analysis, we obtained the necessary numerical evidence. The maximum von Mises stress in the T-part reached 380 MPa at the onset of failure, as determined by strain-gauge readings at the most stressed regions. The corresponding maximum principal strain was measured as 0.0035.