# Study on New Bolted T-Stub Connection with Inserted Plates under Axial and Cyclic Loads
## 4 Test Observations, Results and Analysis
### Cyclic Test  
#### 4.3.1 Test Results  
For evaluating the dissipative capacities of the T-stub connections with inserted plates and investigating the optimum width of plates, a total of 11 specimens were tested under the low-cycle loading conditions. The states of four representative specimens after loading are given in Figure 9. The deformation of the traditional specimen TC-P-50-0-H was limited when subjected to compression, and the main yielding was located at the flange-to-web connection, where cracks could be clearly identified, although no other obvious failure could be detected (see Figure 9a). \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Specimen** & **P\({}_{y}\) Test Results/kN** & **F\({}_{c,bd}\) Theoretical Results/kN** & **Difference** \\ \hline TC-P-50-38-C & 29.91 & 28.14 & 5.93\% \\ TC-P-50-40-C & 34.12 & 32.58 & 4.50\% \\ TC-P-50-42-C & 36.19 & 34.20 & 5.49\% \\ TC-P-60-40-C & 38.86 & 37.05 & 4.65\% \\ WA-P-50-40-C & 33.83 & 31.91 & 5.67\% \\ WA-P-50-46-C & 43.84 & 43.00 & 1.91\% \\ WA-P-50-52-C & 68.56 & 65.91 & 3.87\% \\ WB-P-75-40-C & 202.4 & 185.02 & 8.59\% \\ WB-P-75-46-C & 346.6 & 326.77 & 5.72\% \\ WB-P-75-52-C & 714.62 & 766.19 & \(-\)7.22\% \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Comparison of compressive bearing capacity. Figure 9: Failure modes of four representative specimens of three different groups under cyclic loads: **(a)** TC-P-50-0-H, **(b)** TC-P-50-40-H, **(c)** WA-P-50-40-H and **(d)** WB-P-75-40-H.  
All other specimens in group TC and WA demonstrated the bidirectional deformation of tension and compression, and experienced uplift or depression alternately under hysteretic loads, which can be confirmed by the wave deformation on each flange and through the cracks adjacent to the flange-to-web connections that gradually emerged (see Figure 9b,c). At the end of the loading, specimens finally fractured at the flange-to-web connections, due to the expansion and propagation of cracks. Further, the bulge of flange sections above the inner side of the plates and the hollow of flange sections perpendicular to the bolt centerline pointed out the other two locations of plastic hinges. It was found that there was only a minor abrasion on the inside of the bolt hole, with no necking observed in the bolts, and that the inserted plates remained in good condition by disassembling specimens. In contrast, the cracks on the flange-to-web connections in group WB were conspicuous, but the overall deformation of the flange sections was far less obvious than that of specimens in the other two groups. There was almost no shaped wave and only an insignificant convex or concave on the flange surface. The high-strength bolts showed a necking phenomenon in the thread section, which can be concluded by the clear gap between the flange and the inserted plates seen in Figure 9d. The force-deformation hysteretic curves obtained from four representative specimens are depicted in Figure 10. The traditional specimen TC-P-50-0-H dissipated energy only under tensile force, as shown in Figure 10a, while the other specimens with inserted plates were capable of dissipating energy in two directions. Moreover, the load bearing capacity and stiffness of all innovative specimens were relatively higher when subjected to a compressive direction relatively higher than those under tensile one. The hysteresis loops of specimen TC-P-50-40-H in Figure 10b and specimen WA-P-50-40-H in Figure 10c were full and stable, generally belonging to a classical fusiform curve. Neither showed a pinch effect with the increment of cycles. Furthermore, the hysteresis loops of the former were less  
Figure 10: Relation curves between cyclic force and displacement of four representing specimens, they are (**a**) TC-P-50-0-H; (**b**) TC-P-50-40-H; (**c**) WA-P-50-40-H; (**d**) WB-P-75-40-H, coming from three groups respectively. plump than those of latter, indicating specimens made of welding had a better overall elastoplastic performance.