# Experimental Investigation into Failure Modes of Low-Yield-Point Steel Plate Shear Walls
## 1 Introduction  
Steel plate shear wall (SPSW) structure was a new type of lateral force resisting structural system when it was developed in the 1970s. Steel plate shear walls, consisting of embedded steel plates, vertical edge members (columns), and horizontal edge members (beams), have been adopted as one of the lateral load resisting systems in high-intensity seismic areas for the past 40 years. The excellent performance of steel plate shear walls in improving structural bearing capacity, stiffness, ductility, and energy dissipation capacity led to the widespread application of this system and different academic scholars have conducted experimental studies [1, 2, 3] and abundant simulation research [4, 5, 6, 7] on steel plate shear walls, which was tremendously applied in engineering practice [8, 9, 10]. Various seismic structures and energy dissipation materials, such as foamed aluminum [11, 12] and low-yield-point steel [13], which replaced the traditional reinforced concrete construction [14, 15, 16, 17], have been discovered and utilized as scholars continued their research on seismic performance. Low-yield-point (LYP) steel, as a new material with better inelastic deformation capacity, superior elongation, and low yield-strength ratio, has been increasingly utilized and developed in energy dissipation and vibration damping structures such as steel plate shear walls and dampers [18, 19, 20]. The low-yield-point steel exhibits2 to 3 times the elongation of ordinary structural steel, possesses a lower yield-strength ratio, and has significant strain hardening characteristics in the post-yield phase. Therefore, low-yield-point steel plate shear walls have high ductility and energy dissipation capacity to meet the developing requirements of high-rise steel structures. Most of the domestic and international investigations on steel plate shear walls made of ordinary steel in the past 30 years were divided into two diverse sorts according to the different design methods, which include the prevention of infill panel buckling for thick plates and utilization of strength after buckling for thin plates, while a relatively few investigations were focused on low-yield-point SPSW [21]. Therefore, research on structural characteristics including the failure modes and seismic performance of LYP SPSW under horizontal low cyclic loads and vertical loads will be helpful to fill this deficiency. The LYP SPSW structural system consists of an infill panel made of low-yield-point steel and an external frame [22; 23], which possesses the lower yielding characteristic and higher buckling capacity of the infill panel, and prominent lateral resisting stiffness and excellent ductility performance of an overall system [24; 25; 26]. The low-yield-point steel appears to have extremely low-yield strength, which could dissipate the abundant seismic energy by plastic deformation earlier under the action of an earthquake [27; 28; 29; 30; 31]. The internal wall panel that behaved just like a \"fuse\" in buildings will significantly yield and dissipate energy before the external frame when subjected to the numerous lateral forces, which is extremely beneficial to guarantee the safety of the overall structure and satisfied the design principle of multiple seismic defense lines for a double lateral force-resisting system. At present, almost all the research about the low-yield-point steel plate shear walls has been focused on or restricted to the investigation into seismic performance under horizontal loads, rather than vertical loads. However, the whole steel elements in the SPSW structure were inevitably subjected to vertical loads such as dead load, live load, snow load, etc., in practical service conditions. In addition, even if the steel plate shear wall was under horizontal loads, the column would undergo a certain compression deformation, which apparently causes the vertical deformation of the steel plate connected to the column, resulting in compressive stresses within the infill panel.