## 3 Experimental Program  
### Specimen Descriptions  
The proposed NoWS system is a seismic retrofit method using CFST with bolted connections--not welding. Bolted connections have many advantages over welding. However, they also suffer from issues such as bolt loosening. In order to investigate the capacity of seismic resistance and assess bolt loosening of the NoWS system, full-scaled members were manufactured, and cyclic loading tests were conducted. Experimental results were compared with those obtained from previous research [24] which explored the CFST seismic retrofit method using welding. Therefore, details of specimens and test setup were the same as in previous research [24]. In this experiment, the non-retrofitted reinforced  
Figure 2: Retrofitting procedure using the NoWS system. **(a)** Cleaning the surface of the existing RC frame; **(b)** attaching the C-shaped steel channel to the surface; **(c)** bolting between the steel channel and cover; **(d)** and finishing off the retrofitted surface. concrete moment frame specimen is named ERC (existing reinforcement concrete), and a specimen that was applied with the NoWS system is named NoWS. Each specimen consisted of two columns, beams, and a foundation. The reinforced concrete frame was chosen as a benchmark structure which had dimensions and reinforcement details similar to a typical elementary school built between 1980 and 2000 in Korea. The exterior elevation and benchmark structure are shown in Figure 3; the target span in Figure 3 was a span located on the exterior first floor and referenced to manufacture specimens. The size of the members and details of the reinforcements are given in Table 1. The beam dimensions were 250 mm \(\times\) 450 mm \(\times\) 3200 mm, and the column dimensions were 350 mm \(\times\) 500 mm \(\times\) 2850 mm. The benchmark material properties were obtained by drawing. The specimens were fabricated based on material properties of the benchmark structure; the compressive strength of concrete was 21 MPa. Longitudinal reinforcements and transverse reinforcements with yield strengths of 400 MPa were used, and steel channels with a yield strength of 275 MPa were used in CFST members. The compressive strength of the mortar which was injected in steel channels was 24 MPa. The drawings of each specimen are shown in Figures 4 and 5. Installation of the CFST frame in the NoWS specimen is shown in Figure 6. First, the finishing materials on the surface of the existing RC frame were removed (Figure 6a). After drilling for attaching steel channels to the outside of the columns, chemical anchors were constructed to integrate with existing concrete (Figure 6b). After bolting the covers onto the steel channels (Figure 6c), mortar was injected (Figure 6d). It took five days to install the CFST frame. Compared to welding [24], the construction period was shortened by about twofold when using bolted connections. Figure 3: Benchmark structures. (**a**) Exterior elevation; (**b**) floor plan (mm). \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Members**} & \multirow{2}{*}{**Dimension (mm)**} & \multicolumn{2}{c}{**Reinforcement**} \\ \cline{2-3}  & & **Longitudinal** & **Transverse** & **Section (mm)** \\ \hline Column & 350 \(\times\) 500 \(\times\) 2850 & 8-D19, 2-D16 & D10@300 mm & 8-D19 \\ \hline Upper beam & 250 \(\times\) 450 \(\times\) 3200 & 6-D22 & Mid: D10@300 mm & 6-D22 \\ \hline Lower beam & 350 \(\times\) 600 \(\times\) 3200 & 6-D22 & Mid: D10@300 mm & 6-D22 \\ \hline Lower beam & 350 \(\times\) 600 \(\times\) 3200 & 6-D22 & Mid: D10@300 mm & 6-D22 \\ \hline \hline Foundation & 800 \(\times\) 500 \(\times\) 4350 & 45-D22 & D16@130 mm & 45-D22 \\ \hline CFST & 300 \(\times\) 300 \(\times\) 12 & - & - \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Lists of members. Figure 4: Drawing of the ERC specimen (mm). (**a**) Front view; (**b**) vertical cross-section. Figure 5: Drawing of CFST attached to the NoWS specimen (mm).