## 2 Experimental Plan  
Figure 1 and Table 1 show the fabricated eight RC column specimens having stubs at the ends. The main variables were configuration of transverse reinforcement (tie: H-series, spiral reinforcement: S-series), yield strength of transverse reinforcement (Normal: 453 MPa, Ultra: 1053 MPa), and axial force ratio (20%, 30%). The specimens were named in the form of NH20 (example), as shown in Figure 2. Here, N is the yield strength of transverse reinforcement, H is the transverse reinforcement of ties, and 20 represents an axial force ratio of 20%. The concrete used to fabricate the specimens had a compressive strength of 35 MPa; the longitudinal reinforcement was 12-D10 (71.3 mm\({}^{2}\)) with a yield strength of 300 MPa. The transverse reinforcement used in specimens was D6.1 (28.27 mm\({}^{2}\)) regardless of \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multirow{3}{*}{**Specimens**} & \multirow{3}{*}{\(f_{e}\) **(MPa)**} & \multicolumn{3}{c}{**Longitudinal**} & \multicolumn{3}{c}{**Transverse Reinforcement**} & \multirow{3}{*}{\(A_{e}\)**} & **Axial** \\  & & \multicolumn{3}{c}{**Reinforcement**} & & & & \\ \cline{3-10}  & & \(A_{l}\) & \(f_{yl}\) & \(A_{t}\) & \(S\) & \(f_{yt}\) & \(\rho_{t}\) & \(\rho_{t/yt}\) & **(mm\({}^{2}\))** & **(km)** \\  & & **(mm\({}^{2}\))** & **(MPa)** & **(mm\({}^{2}\))** & **(mm)** & **(MPa)** & **(\%)** & **(MPa)** & **(MPa)** \\ \hline \multirow{4}{*}{
\begin{tabular}{c} Hoop \\ type \\ \end{tabular} } & NH20 & & & & & 453 & & 5.43 & & 450 \\  & NH30 & & & & 63.3 & 453 & & 5.43 & & 675 \\  & UH20 & & & (\(S_{l}=1680\) mm) & 1050 & & 12.6 & & 450 \\  & UH30 & & 71.3 & 300 & 28 & & 1050 & 12.6 & & 675 \\  & NS20 & & & (12-D10) & (\(e_{y}=0.0017\)) & (D6.1) & & 453 & & 5.43 & & 450 \\ Spiral & NS30 & & & & 45.3 & 453 & & 5.43 & & 675 \\  & US20 & & & & (\(S_{l}=754\) mm) & 1050 & & 12.6 & & 450 \\  & US30 & & & & 1050 & & 12.6 & & 675 \\ \hline \hline \end{tabular} \(A_{l}=\) Area of longitudinal reinforcement; \(A_{t}=\) Area of transverse reinforcement; \(A_{e}=\) Effective area of cross-section; \(f_{t}^{\prime}=\) Compressive strength of concrete (MPa); \(f_{yl}=\) Yield strength of longitudinal reinforcement (MPa); \(f_{yt}=\) Yield strength of transverse reinforcement (MPa); \(s=\) Spacing of transverse reinforcement (mm); \(s_{l}=\) Perimeter of transverse reinforcement per 1 pitch (mm); \(\rho_{t}=\) Transverse reinforcement ratio (\(A_{t}\cdot s_{l}/A_{e}\)); \(\rho_{t/yt}=\) Amount of transverse reinforcement.  
\end{table} 
Table 1: Properties of specimens (1 MPa = 145 psi, 1 mm = 0.0394 in.). configuration, and the yield strengths of the transverse reinforcement were 453 MPa and 1053 MPa, respectively, as shown in Figure 3.  
As shown in Figure 1, the square cross-sections measure 250 \(\times\) 250 mm, and the height of the experimental section was set as 1500 mm for a shear span-to-depth ratio (a/D) of 3.0. The H-series were spaced at 63.3 mm intervals in the experimental region, and the S-series were spaced 45.3 mm intervals. The total length of transverse reinforcement per spacing was 1680 mm for the H-series, and 745 mm for the S-series. That is, the S-series had 55% less transverse reinforcement. The loading was designed with an antisymmetric flexural moment to simulate seismic loads. A constant axial load was applied using an actuator of 1000 kN capacity, as shown in Figure 4a, and lateral load was applied twice according to the drift angle using an actuator of 500 kN capacity, as shown in Figure 4b. Figure 1: _Cont._  
Figure 1: Details of specimens: (**a**) H-series; (**b**) S-series (1 mm = 0.0394 in.). Figure 2: Name of specimen. Figure 4: _Cont._  
Figure 3: Stress–strain relationship of reinforcement. The drift angle was calculated based on displacement (\(\Delta y\)) of specimens at the time of yield of longitudinal reinforcement.