## 2 Experimental Overview  
### Test Specim Design and Fabrication  
The dimensions of the beam-column joints were designed according to the requirements in the code [34]. The overall strength, stiffness, and stability of the joint core were ensured to meet the requirements. The precast columns of two specimens were made of concrete with strength class C80, with a height of 4200 mm and a cross section of 750 mm \(\times\) 750 mm. The precast beams were both made of concrete of strength class C40, with a beam length of 3800 mm, a beam cross section of 400 mm \(\times\) 750 mm, and a beam enlarged end cross section of 750 mm \(\times\) 750 mm. The precast beam and column were connected by 8 bolts with a diameter of 28 mm (the first group) or 24 mm (the second group) through the reserved hole at the enlarged end of the beam. The details of the precast specimens are shown in Tables 1 and 2, with the haunched plate and compression plates made of Q345 steel. The longitudinal reinforcement for the precast columns and beams was HRB400 Grade III steel (symbol \(\varphi\)) with diameters of 25 mm and 22 mm, respectively, with the same reinforcement in both groups. The specific dimensions and reinforcement of the specimens are shown in Figures 1 and 2.  
The test specimens were fabricated at the Anhui Key Laboratory of Building Structure and Underground Engineering, Anhui Jianzhu University. A joint seam of 20 mm-25 mm was reserved in the spliced part of the core zone of the connection node, and the precast beams and precast columns were connected by bolts; see Figure 3 for the specific connection method.  
The process for making the new precast concrete frame beam-column joint specimens is shown in Figure 4.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Specimen** & **Concrete Grade** & \begin{tabular}{c} **The Thickness of the** \\ **Concrete Protection** \\ **Layer (mm)** \\ \end{tabular} & \begin{tabular}{c} **Cross-Sectional** \\ **Dimensions (mm)** \\ \end{tabular} & \begin{tabular}{c} **Length** \\ **(mm)** \\ \end{tabular} \\ \hline \begin{tabular}{c} Precast concrete \\ beam \\ \end{tabular} & C40 & 25 & \
\begin{tabular}{c} 400 \(\times\) 750 \\ (exlarged end: \\ 750 \(\times\) 750) \\ \end{tabular} & 3800 \\ \hline
\begin{tabular}{c} Precast concrete \\ column \\ \end{tabular} & C80 & 25 & 750 \(\times\) 750 & 4200 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Details of precast specimens.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Number** &
\begin{tabular}{c} **Type of Joint** \\ **Construction** \\ \end{tabular} & **Bolt Grade** & **Bolt Diameter (mm)** \\ \hline J1 & with haunched plates & Q345 & 24 \\ J2 & with haunched plates & Q235 & 24 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Specim types and sizes.  
Precautions for making test pieces: firstly, the bolt holes are produced in strict accordance with the bolt holes corresponding to the respective required connection positions, with precise dimensions (error in millimeters), otherwise it will affect the smooth butt joint of bolt connectors during splicing; secondly, pay attention to the protection of steel strain gauges. Before steel binding, the position of strain gauges must be predicted to avoid collision with formwork and vibrators; finally, the precast beams and precast columns are assembled by bolt splicing, and the splicing is calibrated with a laser level.  
Figure 1: Design of the specimen.  
Figure 3: Precast beam–column connection joints. (**a**) Splice in precast beams and columns; (**b**) splice in precast beams and columns after grouting.  
Figure 2: Specim reinforcement arrangement.