# Experimental Investigation into Failure Modes of Low-Yield-Point Steel Plate Shear Walls
## 4 Conclusions  
The LYP SPSW is a novel kind of lateral force resisting system with excellent development potential. Two reduced scale specimens of single-story single-span LYP steel plate shear wall were fabricated to investigate the seismic performance and deformation characteristic of the LYP SPSW structure with consideration of various loading factors. The horizontal low cyclic loading test was executed for specimen 1, whereas the vertical loading experiment was implemented for specimen 2. Through the horizontal cyclic loading test of the low-yield-point steel plate shear wall, the study focused on the failure phenomenon of this structure, the change in bearing capacity after yielding, the strain variation, and the inclination angle of the first principal stress of the wall panel, so as to make a reasonable evaluation of the seismic performance for the specimen. In addition, the deformation characteristics of the LYP SPSW structure were evaluated by applying vertical loading to specimen 2 with a compression-shear machine, which was regarded as an exploratory research test for this structure since few experimental investigations on SPSW structure have been conducted by vertical loading. The different failure phenomena and performance of this structure under the two different loading actions were analyzed in detail from various perspectives. The detailed contents and major observations were as follows. 1. Specim 1 was loaded with a mixed force-displacement system. The infill panel entered the yielding state at the end of the first five loading levels with the maximum out-of-plane displacement of 0.14 mm, and then the infill panel started to appear with a slight bulge at the eleventh loading level and the maximum out-of-plane displacement of 3.7 mm. The infill panel severely bulged and the column base was significantly distorted up to the fourteenth loading level. The maximum out-of-plane displacement at the center of the infill panel reached 31.8 mm. 2. Specim 1 was further loaded by applying the controlled displacement that increased from 1.74 to 3.28 times the yield displacement after yielding. The structural bearing capacity decreased extremely slowly and the specimen still possessed a relatively high strength, which indicated that the ductility of this structure was excellent. 3. The overall strains of the infill panel and frame columns continued to grow smoothly with the increasing forward and reverse loading levels. The increasing rate of strain developed rapidly until the fourteenth loading level, and the measured maximum strains respectively reached 11,735 \(\mu\epsilon\) for the infill plate and 13,117 \(\mu\epsilon\) for the frame column, which was significantly higher than the yielding strains of 470.4 \(\mu\epsilon\) and 1174 \(\mu\epsilon\) derived from the material tests of LYP steel and ordinary Q235 steel. 4. The results obtained by the vertical loading experiment for specimen 2 indicated that the maximum deformation of both infill panel and frame columns occurred at the middle-upper part of members. The dramatic out-of-plane bulging phenomenon developed along the width of the infill plate under the vertical load, whereas the seriously torsional deformation occurred at the frame column. The maximum out  
Figure 34: Out-of-plane deformation of the column flange along the height in specimen 2.  
of-plane deformations were 95 mm at the center of the infill panel and 70 mm at the flange of the frame column, respectively. * The inclination angle of the first principal stress in the wall panel was analyzed, and in overall terms, the inclination angle of the shear panel varied from 8\({}^{\circ}\) to 45\({}^{\circ}\). Writing--review and editing, Q.L. ; visualization, Q.L. ; conceptualization, J.S. ; validation, J.S. ; investigation, J.S. ; supervision, J.S. ; methodology, B.T. ; validation, B.T. ; investigation, B.T. ; data curation, B.T. ; writing--original draft, B.T. ; resources, Z.W. All authors have read and agreed to the published version of the manuscript.