# Experimental Study of High-Strength Concrete-Steel Plate Composite Shear Walls
## 3 Experimental Results and Discussions
### Force-Displacement Responses  
Figure 10 presents the hysteresis curves (blue line) and skeleton curves (red line) for the shear specimens. Significant \"pinching\" effects were observed in the hysteresis loops of RCSW shear specimens. With the embedment of the steel plate, the hysteresis curves appear in a plumper shape with higher peak lateral load capacities, which indicated that RCSPSW specimens have better seismic performances. Figure 11 shows comparisons among the skeleton curves of all shear specimens. The blue, red, and green lines in Figure 11a,b represent skeleton curves of specimens under the axial compression ratio of 0.33, 0.45, and 0.50, respectively. The dash and solid lines in Figure 11c show the curves of the RCSW and RCSPSW specimens. It is evident that the use of embedded steel plate significantly increased the lateral load capacity, but a severer and quicker post-peak strength and stiffness degradation was observed in the RCSPSW specimens as compared to RCSW specimens under same axial compression ratios. In terms of the RCSPSW 1-1 specimen, it shows better deformation capability than other RCSPSW specimens, which is attributed to a lower axial compression ratio. Additionally, the positive lateral load re-increased after the strength decay in the previous step, which may result from the hardening of the steel plate. Figure 12 shows the hysteresis and skeleton curves for flexure specimens. Overall, the RCSW specimens show a S-shaped hysteretic behavior with a \"pinching\" phenomenon. The hysteresis curves of RCSPSW specimens appear in a full bow shape, which indicates that mixed flexure-shear failure mechanisms exist in the damage progression of flexure specimens. From the results that are presented in Figure 12, it is evident that \"fatter\" hysteresis loops were obtained for specimens when they were subjected to lower axial compressive loads. Figure 13 presents the comparative results of skeleton curves for different flexure specimens. As compared to the RCSW specimens (dash lines), the RCSPSW specimens (solid lines) show higher lateral load capacities. The skeleton curves with the same color represent specimens subjected to the same axial compressive load. With the increase of the axial compressive load, the peak lateral load increased, but the ultimate lateral displacement decreased. A severer and quicker strength and stiffness degradation was observed for RCSPSW specimens with an axial compression ratio higher than 0.50. Figure 10: Hysteresis and Skeleton Curves for Specimens with Aspect Ratio of 1.5 (**a**) RCSW Specimens and (**b**) RCSPSW Specimens. The key characteristics were summarized for all shear wall specimens with considerations of the damage progression and force-displacement responses, although differences do exist among their skeleton curves. Figure 13(a) shows the skeleton curve of RCSW 1-1 specimen as a representative example, where five critical points are defined, including crack point, yield pint, peak point, failure point, and collapse point. Each critical point represents an event when the specimen's behavior is significantly altered. The crack point corresponds to the load step when the first web inclined shear crack or boundary horizontal flexure-tension crack is observed. The determination of yield point, peak point, and failure point has been described in the previous section. The collapse point indicates the tip of last load cycle if the post-ultimate load capacity (\(0.85P_{max}\)) exists. It is worth mentioning that the yield point and failure point in the load-displacement skeleton curve (Figure 13(b)) can be determined while using alternative approaches. [PERSON] and [PERSON] [47, 48] suggested the equivalent elastoplastic line determine the yield displacement with the secant stiffness at two-thirds of the peak lateral load. As for the failure load, [PERSON] and [PERSON] [47, 49] recommended the use of 80% of the peak lateral load, resulting in a relatively larger ultimate displacement as compared to the \(0.85P_{max}\) defined herein.