# Experimental Investigation into Failure Modes of Low-Yield-Point Steel Plate Shear Walls
## 2 Horizontal Cyclic Loading Test
### Experimental Results  
#### 2.2.1 Description of Failure Phenomenon  
A horizontal low cyclic load was executed on specimen 1. The loading process in this direction was called forward loading when the actuator was pushed against specimen 1, and the structure produced a displacement of more than zero, whereas the opposite operation was called reverse loading and the structure generated a displacement of less than zero. The forward loading displacement was measured to be 0.17 mm and the reverse loading displacement was also 0.17 mm upon being loaded to the first level load of 50 kN without apparent phenomenon in the loading process of the structure. The frame columns and the LYP infill panel yielded no visible out-of-plane displacement. The displacement of forward loading was 0.48 mm, whereas the displacement of reverse loading was 0.46 mm when the second stage load was 100 kN with an out-of-plane displacement of 0.08 mm at the center for the infill panel. The displacement returned to zero when the loading was returned to zero, which showed that the structure was in the elastic stage at that moment. The forward loading displacement was estimated to be 1.3 mm and the reverse loading displacement was 1.1 mm at the third load level of 200 kN. A slight sound emerged during the loading process and the maximum out-of-plane displacement of the center for the infill panel was 0.1 mm. The forward loading displacement was detected as 1.8 mm and the reverse loading displacement was 1.5 mm for the fourth level of 250 kN; however, the structure remained in an elastic state. At the fifth load level of 300 kN, the forward loading displacement was 2.4 mm and the reverse loading displacement was 1.8 mm. Moreover, the infill panel started to enter the yielding state with the maximum out-of-plane displacement of 0.14 mm. It was found that the hysteresis curve of the structure occurred in an obvious non-linear phase by observing the force-displacement records in the main control room, and hence the loading regime of the actuator was adjusted from force control to displacement control for the subsequent loading levels. Measured displacements under the first five loading levels are shown in Table 4. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Levels**} & \multirow{2}{*}{**Load (kN)**} & \multicolumn{2}{c}{**Displacement (mm)**} \\ \cline{3-4}  & & **Forward** & **Reverse** \\ \hline
1 & 50 & 0.17 & 0.17 \\
2 & 100 & 0.48 & 0.46 \\
3 & 200 & 1.3 & 1.1 \\
4 & 250 & 1.8 & 1.5 \\
5 & 300 & 2.4 & 1.8 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Measured displacements under the first five loading levels. Figure 12: Drawing grid lines of infill panel for specimen 1. At the sixth loading level, the maximum reaction force of the actuator forward loading was 320.8 kN and the displacement was 2.9 mm, whereas the reverse loading was 398.2 kN and the displacement was 2.7 mm. Four slight sounds appeared during the loading process and there was no significant variation in the shape of the structure (Figure 13). The frame column was not yielded, whereas all four corners of the infill panel started to enter the yielding state and the shear panel had the maximum out-of-plane displacement of 0.17 mm at the center. The maximum reaction force of the actuator forward loading was 385.3 kN during the seventh loading stage and the displacement measured from the displacement meter was 3.7 mm, while the maximum reaction force of the reverse loading was 462.1 kN and the displacement was 3.0 mm. A slight sound from the structure was accompanied by the loading process, and the middle-upper part of the infill panel gradually entered the yielding stage, at which time the maximum out-of-plane displacement at the center of infill panel was 0.22 mm. At the eighth loading level, the maximum reaction force of the actuator forward loading was 423.5 kN with a displacement of 4.3 mm, while that for reverse loading was 530.4 kN with a displacement of 3.5 mm.