# Experimental Study of High-Strength Concrete-Steel Plate Composite Shear Walls
## 2 Experimental Investigation
### Analysis Methods for Experimental Observations  
Key information was inferred from the instrumentation recordings in the reversed cyclic load test to evaluate the seismic performance of shear walls, including hysteresis curve, skeleton curve, ductility, energy dissipation ability, etc. Figure 6a presents a typical hysteresis curve that is directly obtained by the lateral force and displacement readings from the load cell and LVDT, and the skeleton curve is determined from the hysteresis curve by joining the peak-load tips of each primary loop. Ductile structures are preferable in the earthquake-resistant design. Structural members are required to undergo large amplitude lateral deformations without the substantial loss of strength and also dissipate significant amounts of energy in those cyclic deformations. A displacement ductility factor, \(\mu\), is defined as the ultimate displacement, \(\Delta_{u}\), to the displacement at yield, \(\Delta_{y}\), and it is given by  
\[\mu=\frac{\Delta_{u}}{\Lambda_{y}} \tag{2}\]  
where the ultimate displacement (\(\Delta_{u}\)) is defined as displacement value that corresponds to 85% of peak load on descending branch of the skeleton curve as specified in Chinese Specification for Seismic Test of Buildings [36] and suggested by [PERSON] [11], [PERSON] [12], and [PERSON] [37]. The yield displacement (\(\Delta_{y}\)) is determined with the method that [PERSON] recommended [38], which will be described in detail later. The definition of the yield point in the skeleton curve often causes difficulty in the calculation of ductility factors. Figure 6b illustrates three alternative definitions of the yield displacement and the corresponding yield strength. [PERSON] [38] suggested that the yield displacement be determined by the equivalent elasto-plastic system with the secant stiffness at 75% of the peak lateral load, \(P_{max}\) (Figure 6b1). [PERSON] [39] proposed the use of the equivalent elasto-plastic system with the same energy  
Figure 5: Cyclic Displacement History for Quasi-static Test of Shear Wall Specimens. \(\Delta y\) indicates the lateral displacement when the wall specimen shows yielding behavior. absorption from the origin to the peak lateral load level, as shown in Figure 6(b2)). In ASTM E2126 [40], an equivalent energy elastic-plastic (EEEP) is defined as an elastic-plastic curve that circumscribes an area that is equal to the area enclosed by the skeleton curve between the origin, the displacement axis, and the ultimate displacement (Figure 6(b3)). [PERSON] [41] claimed that the first definition is the most realistic option to determine the yield displacement for reinforced concrete structures, which will be used herein to calculate the displacement ductility factors of test shear wall specimens. Figure 6: Analysis Methods for Experimental Observations (**a**) Hysteresis Curve and Skeleton Curve; (**b**) Yield Strength and Yield Displacement; and, (**c**) Equivalent Viscous Damping Coefficient. As shown in Figure 6a, structural members have some deformation capacity beyond the peak lateral load, \(P_{max}\), with undergoing a small reduction of strength. Thus, it is reasonable to recognize part of the post-peak deformation capacity, and the ultimate displacement is defined herein as the point when the load carrying capacity drops below 85% of the peak strength on descending branch of the skeleton curve, or when severe collapse failure takes place in the specimen, whichever occurs first. The ductility factor is defined in terms of deformation, which provides no indication regarding the energy dissipation capacity of the structural members. The equivalent viscous damping (EVD) coefficient is considered to be a critical parameter in evaluating the energy dissipation ability of given structural members.