## 3 Experimental Phenomena and Their Analysis
### Analysis of Experimental Phenomena  
As can be seen from Figure 14, the damage forms of J1 and J2 are mostly the same. There are no cracks in the precast column and the corbel, and the final damage was caused by the precast beam and the bolt, which follows the design concept of these new joints. The cracks on the top surface of the precast beam are distributed at the intersection of the enlarged end and the core of the joint, and there are almost no cracks far from the core of the joint. The bottom surface of the precast beam is cracked near the corbel, but no cracks are produced at the enlarged end. This shows that the presence of the corbel inhibits the generation of cracks in the precast beam to a certain extent and prevents damage to the joint under seismic action. The cracks in the sides of the precast beams are mostly located in the core of the joints, and there are no cracks in the areas away from the core of the joints. The crack distribution in J2 is more dispersed than that in J1, and the cracks in the precast beams are more dispersed along the surface of the beams, with a wider distribution area than in J1. This shows that the energy dissipation of J2 bolts is higher than that of J1 bolts, which improves the energy dissipation capacity of the beam in the joint core area, and the stress concentration phenomenon in the joint core area of J2 is smaller than that of J1. \begin{table}
\begin{tabular}{c c} \hline
**Position** & **Test Phenomenon** \\ \hline \multirow{8}{*}{Side of beam} & \(-\)50 mm: 35 cm from the edge of the column, length of 8 cm, seam width of 0.07 mm \\ \cline{2-3}  & \(-\)55 mm: 30 cm from the edge of the column, length of 30 cm, seam width of 0.14 mm; 5 cm \\ \cline{2-3}  & from the contact surface of the beam–column joint at the side of the enlarged end of the beam from the bottom up, length of 6 cm, seam width of 0.07 mm \\ \cline{2-3}  & \(-\)60 mm: the side of the enlarged end of the beam is carried out parallel to the face of the bearing plate at a distance of 4 cm from the face of the bearing plate, with a length of 74 cm and a seam width of 1.3 mm; at a distance of 45 cm from the edge of the column, with a length of 26 cm and a seam width of 0.1 mm \\ \cline{2-3}  & \(-\)70 mm: 58 cm from the edge of the column, length of 25 cm, seam width of 0.1 mm \\ \cline{2-3}  & \(-\)75 mm: 35 cm from the edge of the column, length of 20 cm, seam width of 0.1 mm \\ \hline \multirow{8}{*}{The top surface of the beam} & \(+\)35 mm: 25 cm from the edge of the column, length of 20 cm, seam width of 0.9 mm \\ \cline{2-3}  & \(+\)50 mm: the top surface of the expanded end of the beam, 5 cm, 14 cm, and 23 cm from the edge of the column, length 40 cm, 42 cm, and 40 cm, respectively, seam width 0.2 mm, \\ \cline{2-3}  & \(0.11\) mm, and 0.22 mm, respectively \\ \cline{2-3}  & \(+\)55 mm: 35 cm from the edge of the column, length of 15 cm, seam width of 0.12 mm \\ \cline{2-3}  & \(+\)60 mm: 65 cm from the edge of the column, length of 13 cm, seam width of 0.1 mm \\ \cline{2-3}  & \(+\)70 mm: 65 cm from the edge of the column, length of 20 cm, seam width of 0.09 mm \\ \cline{2-3}  & \(+\)80 mm: 56 cm from the edge of the column, length of 18 cm, seam width of 0.07 mm \\ \hline \multirow{8}{*}{The bottom surface of the beam} & \(-\)10 mm: 40 cm and 65 cm from the edge of the column, lengths of 40 cm and 20 cm, respectively, with seam widths of 0.13 mm and 0.08 mm, respectively \\ \cline{2-3}  & \(-\)30 mm: 32 cm from the edge of the column, length of 40 cm, seam width of 0.1 mm \\ \cline{1-1} \cline{2-3}  & \(-\)50 mm: 20 cm, 65 cm, and 98 cm from the edge of the column, lengths of 30 cm, 10 cm, and 18 cm, respectively, seam widths of 0.1 mm, 0.2 mm, and 0.2 mm, respectively \\ \cline{1-1} \cline{2-3}  & \(-\)55 mm: 3 cm from the edge of the column, length of 10 cm, seam width of 0.1 mm \\ \hline \end{tabular}
\end{table} 
Table 8: Test phenomena of specimen J2. Figure 12: Joint damage image. (**a**) Precast column damage image after loading; (**b**) precast beam damage image after loading.