# Experimental Investigation into Failure Modes of Low-Yield-Point Steel Plate Shear Walls
## 2 Horizontal Cyclic Loading Test
### Experimental Results
#### 2.2.3 Strain  
Three-dimensional strain rosettes were arranged at its corners and center to investigate the shear characteristic of infill panel. The strain gauges were fixed on the flange of column at the top, middle, and bottom locations to obtain the tensile or compressive performance of frame columns. The distribution of strain gauges is shown in Figure 19.  
Figure 19: Strain gauge arrangement in specimen 1. Figure 18: Change in bearing capacity after yielding for specimen 1. Due to the damage of a few strain gauges and collection channels, those strain gauges that were along the 45\({}^{\circ}\) direction at the three corners of infill panel, at the middle location of infill panel, along the 45\({}^{\circ}\) direction at the middle and lower part of left column web, and at the lower part of left column flange were extracted and analyzed to derive their alterations with increasing load. Table 5 summarizes the strain values at different locations for the specimen at each level of peak load(units: \(\mu\epsilon\)). The yielding strain value of the infill panel, beam, and column can be calculated according to Equation (1):  
\[\sigma=E\epsilon \tag{1}\]  
A low-yield-point infill panel was adopted as the steel of LYP100 with a nominal yield strength of 100 MPa and the measured yielding strain derived from the material test was as follows in Equation (2):  
\[\epsilon_{y}=\frac{f_{y}}{E}=\frac{95.4\times 10^{6}}{202782.4}=470.4\ \mu\epsilon \tag{2}\]  
Q235 steel with a nominal yield strength of 235 MPa was used for frame beams and columns, and the corresponding measured yielding strain was the following in Equation (3):  
\[\epsilon_{y}=\frac{f_{y}}{E}=\frac{234.91\times 10^{6}}{200152}=1174\ \mu\epsilon \tag{3}\]  
The variations of strain with the number of loading levels during forward and reverse loading for the infill panel are shown in Figure 20. It can be observed from the figure that the measured strain values of infill panel developed relatively smoothly before the eleventh loading level, whereas those strain values developed extremely rapidly when the eleventh loading level was reached, which was consistent with the observed suddenly increasing trend of the out-of-plane deformation of infill panel. The strain increasing development in the upper-right corner and lower-left corner of the infill panel was identical in the process of forward and reverse loading, and was more rapid than that in other positions, which was due to the deformation of the infill panel towards one side in the last few loading levels. The strain variation of infill panel was larger in the reverse loading than in the forward loading, which was attributed to the fact that the forward loading had failed at the thirteenth load level and the bearing capacity decreased, while the structural bearing capacity was invariably increasing in the reverse loading. The variations of strain with the number of loading levels for the left column during forward and reverse loading are shown in Figure 21. It can be seen from the diagram that the strain values in the middle and lower part of the web for the left column had similar development trends under forward and reverse loading, and developed toward one side after the eleventh loading level with significantly increased development speed. The strain value of the right flange increases with the number of load stages and the change accelerates after the eleventh stage. The trends of strains at the left flange developed in