## 3 Experiments
### Test Result
The moment-displacement hysteresis curve is shown in Figure 30. The maximum moment was 982.012 kN-m (push: 999.17 kN-m, pull: 964.85 kN-m), which is 98.5% of the maximum moment of SP-0 (996.92 kN-m). For the push-over of the actuator against the specimen, the maximum moment of SP-W was larger than SP-0. Therefore, the specimen using the Type-W joint had enough strength to exert equal performance to the single-body specimen. Connection using a Type-W joint could be applied to the modular DSCT wind  
Figure 28: Load–displacement hysteresis curve of SP-H.  
Figure 27: Buckling failure of outer tube of SP-H.  
Figure 28: Load–displacement hysteresis curve of SP-H.  
turbine tower. The maximum lateral displacement at the loading point was 82.185 mm, which is almost the same as that of SP-0. Table 3 shows the summary of test results. In the cases of SP-S and SP-H, the specimens did not exert their performances, which the authors had expected, because of the early failure of the connections. For these two cases, the experiments were stopped early, and the results were not analyzed in detail. In this study, the results for SP-W specimen and SP-0 were mainly compared and analyzed. The load-displacement envelope curves are compared in Figure 23:0 The envelope curves were plotted by using averaged measured values for both push-over and pull-over. As mentioned previously, the maximum loads in SP-0 and SP-W were similar and equal to 486.30 kN and 479.03 kN, respectively; their behaviors were analogous to each other until the maximum displacement. In the cases of SP-S and SP-H, the behavior of the connection plate was expressed as the governing behavior because the lateral load was not completely transferred to the lower module by the premature failure of the connections. Figure 23:1 Load–displacement envelope curve. Figure 23:2 Load–displacement hysteresis curve of SP-W. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & \multicolumn{3}{c}{**Maximum Load**} & \multicolumn{3}{c}{**Maximum Displacement**} \\ \cline{2-6}
**Specimen** & \begin{tabular}{c} **Moment** \\ **(kN-m)** \\ \end{tabular} & \begin{tabular}{c} **Lateral Force** \\ **(kN)** \\ \end{tabular} & \begin{tabular}{c} **Comparison** \\ **(kN)** \\ \end{tabular} & \
\begin{tabular}{c} **Lateral** \\ **Displ. (mm)** \\ \end{tabular} &
\begin{tabular}{c} **Comparison** \\ **Comparison** \\ \end{tabular} \\ \hline SP-0 & 996.83 & 486.26 & 100\% & 82.195 & 100\% \\ SP-S & 583.25 & 284.51 & 58.5\% & 123.275 & 150\% \\ SP-H & 541.04 & 263.92 & 54.3\% & 102.885 & 125\% \\ SP-W & 982.01 & 479.03 & 98.5\% & 82.185 & 100\% \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Test results. As a result of calculating the yield displacement and ultimate displacement by using the method suggested by [PERSON] [18], the yield displacement, ultimate displacement, and displacement ductility of SP-0 were 15.7 mm, 52.3 mm, and 3.33, respectively. For SP-W, the yield displacement was 15.6 mm, ultimate displacement was 69.9 mm, and displacement ductility was calculated as 4.48, which is larger than that of SP-0. This results from the larger moment resisting capacity of SP-W after peak load. Figure 32 shows the energy dissipation with drift ratio; it can be observed that SP-W similarly dissipated energy with SP-0.