## 3 Experimental Program  
### Specimen Details  
This research aims to assess the structural behavior of RC beams contingent upon the module dimensions and the existence or nonexistence of interconnections within the modularized steel plate. To achieve this, one non-retrofitted specimen and three specimens retrofitted using modularized steel plates were fabricated. The specifics of these specimens are detailed in Table 1 and illustrated in Figure 3. While the modularized steel plate is intended to encase both the slab and beam in real onsite applications, this investigation solely concentrated on the RC beam behavior. Hence, the steel plate was designed to wrap solely around the beam, as depicted in Figure 3.  
All specimens comprised RC beams measuring 300 mm in width, 350 mm in height, and 4000 mm in total length. The depth of the beam retrofitted with steel plates was set at 100 mm to prevent the retrofitted RC beams from becoming a deep beam. The thickness of the Z-shaped side plate and vertical grid was 3 mm. In contrast, the L-shaped lower plate and bottom plate, which directly impact ductility, were designed with thicknesses of 5 mm. Chemical anchors, utilized to secure the existing structure and the steel plate, were spaced at 300 mm intervals and had a diameter of 16 mm. The joint width between steel plates was 50 mm with a bolt spacing of 90 mm. High-strength bolts with diameters of 16 mm were employed for the connections. The size of one unit was categorized into two types. Type 1 comprised steel plates of lengths of 1.1 m, 1.8 m, and 1.1 m, whereas type 2 consisted of lengths of 1.5 m, 1 m, and 1.5 m. This distinction was important, as the overall structural behavior of the steel plate varies based on the joint's position relative to the load application point. Notably, type 1 lacks a joint within the load application area, while type 2 possesses a joint at this location. Figure 4 is notation of specimens.  
To validate the structural behavior of RC beams retrofitted with modularized steel plates, the tensile reinforcing bar and stirrups were designed to ensure that bending failure preceded shear failure. The incorporated tensile reinforcing bar was a deformed bar with a diameter of 19 mm, while the stirrups were constructed using a deformed bar with a diameter of 10 mm. The concrete used in specimen fabrication had a compressive strength of 23 MPa, the tensile reinforcing bar had a yield strength of 400 MPa, and the steel plate had yield strength of 275 MPa.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**No.**} & \multirow{2}{*}{**Name**} & \multirow{2}{*}{**Retrofitted Method**} & \multirow{2}{*}{**Bolted Connection Detail**} & \multicolumn{2}{c}{**Length of Modularized Steel Plate (m)**} \\ \cline{5-6}  & & & & **Left** & **Middle** & **Right** \\ \hline
1 & CB & None & None & None & \\ \hline
2 & MSP-NC & & Absence & 1.1 & 1.8 & 1.1 \\ \hline
3 & MSP-C & & Presence & 1.1 & 1.8 & 1.1 \\ \hline
4 & MSP-L & & Absence & 1.5 & 1 & 1.5 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Details of the specimens.  
**[Retrofitting method]**  
CB: Control beam  
MSP: Modularized steel plate  
**[Connection type]**  
NC: Non-connection  
C: with Connection  
L: Long length of modularized steel plate  
**Figure 4. Notation of specimens.**  
Figure 3. Details of the specimens (mm): (**a**) CB, (**b**) MSP-NC, (**c**) MSP-C, and (**d**) MSP-L.