## 3 Results
\begin{table}
\begin{tabular}{c c c} \hline \hline \multirow{2}{*}{**Component**} & **Failure Mode I** & **Failure Mode II** \\  & **(Specimen ST-1, ST-2, and ST-5)** & **(Specimen ST-3, ST-4, and ST-6)** \\ \hline Anchored blind bolt & Partial pull-out & Bolt rupture \\ Column wall & Bulging deformation & Slight bulging around the bolt holes \\ Core concrete & Severely damaged & Local concrete crushing \\ Steel beam & No obvious local beam buckling & No obvious local beam buckling except ST-6 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Typical failure modes of the specimens. in the beam compression flange, as presented in Figure 7d. The bolts of specimen ST-6 fractured at a larger drift ratio of 6%, compared with specimen ST-3, indicating that the steel beam section can also affect the deformation capacity of the specimens and that use of the weaker steel beam can improve the deformation performance. Observations of the exposed concrete after cutting open the steel tube show that, as presented in Figure 7g, the concrete infill in the panel zone remained basically intact, and only local crushing around the bolt hole was observed. As the expanding sleeve, a part of the blind bolt, was pulled outwards, the surrounding concrete was likely to crack locally when the connections were under tension. The intact concrete could effectively restrain the pull-out of the blind bolts, causing rupture failure of the blind bolts. In the two failure modes, as shown in Figure 8, the anchored blind bolts embedded in the concrete basically remained intact, despite the different failure patterns exhibited by the blind bolts. However, scratches were clearly observed at the anchor nut, undoubtedly caused by the mechanical anchorage against the concrete. In addition, throughout the loading process, no welding fracture occurred in the fillet weld and plug weld between the steel tube and the C-shaped channel. According to the observations on the deformation conditions around the bolt holes, as shown in Figure 9, the square steel tube and the C-shaped channel fit closely together, indicating that the steel tube wall and the C-shaped channel can work well together. The observed results demonstrate that the two proposed methods can both be effective and provide stability to the performance of connections under cyclic loading. Figure 6: Failure mode I (specimens ST-1, ST-2, and ST-5). (**a**) ST-1; (**b**) ST-2; (**c**) ST-5; (**d**) tube wall in specimen ST-1; (**e**) core concrete in specimen ST-2. Figure 8: Embedded extension of blind bolt. Figure 7: Failure mode II (specimens ST-3, ST-4, and ST-6). (**a**) ST-3; (**b**) ST-4; (**c**) ST-6; (**d**) steel beam in specimen ST-6; (**e**) fractured blind bolts; (**f**) tube wall in specimen ST-3; (**g**) core concrete in specimen ST-3. Figure 9: Bolt holes in specimen ST-3. The steel tube thickness in the panel zone of the connection and the anchorage method of the blind bolt directly determine the connection failure mode. The use of thicker steel tube walls and blind bolts with anchor nuts can change the failure mode of an anchored blind bolt connection to CFST column from mode I to mode II. Therefore, when modified anchored blind bolts (Hollo-Bolt) and a locally strengthened steel tube (C-shaped channels) are used in the panel zone, the proposed connection demonstrated its ability to reach the ultimate strength of the blind bolts, exhibiting favorable flexural resistance and stiffness. The end-plate thickness and the steel beam section mainly affect the deformation capacity of the connections. In the proposed connection, the use of thinner end-plates and weaker steel beams can result in favorable deformability of the test specimens and avoid premature brittle failure.