## 3 Experimental Results and Analysis
### Strain Analysis  
By processing the strains of the reinforcement bars numbered A1 to A4, the specific strain changes of the vertical distribution bars of the wall slab could be observed, as shown in Figure 12 below.  
(1) The strains of specimen W-1 remained essentially the same as those of A2 in the early stage of stressing, A3 had the second largest values, and A4 was located on the central axis with the smallest strain. In the later period, A1 bore more tension and the strain increased, while A3 bore more pressure and the negative strain increased, indicating that the specimen was shifted westward in the neutral axis in the later period of loading, which made the area of the pressure zone decrease and the tension zone increase for the positive loading. The opposite occurred for the negative loading. The observation of the maximum strain value could also be found in that only A1 yielded in tension, indicating that the westward offset of the neutral axis in the late stage of loading caused the difference in the force situation between the east and west sides of the wall plate, so the strain of A1 in compression was less than that of A3.  
(2) The W-2 specimen kept the maximum strain of A2 for both positive and negative loading in the early stage, and the maximum strain of A2 in tension in the late stage. A1 started to take effect and the strain gradually increased, and the specimen had the maximum strain of A3 in compression. This meant that W-2 also had the situation of neutralizing the axial westward movement. Additionally, observation of the maximum strain value could be found regardless of the fact that the tensile and compressive tendons had not yielded. After the concrete was crushed, the compressive longitudinal tendons still had not yielded, indicating that the utilization rate of the longitudinal distribution tendons was not ideal. While the strain patterns of the reinforcement in specimens W-3 and W-4 were similar to those in W-1, A1 in specimen W-3 also yielded in tension, while W-4 was similar to W-2 in that it yielded in both tension and compression. This indicated that the higher the strength of the wall panel was, the lower the utilization of the steel reinforcement was for the height to width ratio as well as the reinforcement scheme designed in this study.  
(3) W-5, as a solid wall panel, was more uniformly stressed, and it essentially maintains the rule that the strain of the longitudinal bars decreased from the outside to the inside and  
Figure 11: Comparison chart of stiffness degradation.  
the strain of the outermost longitudinal bars was the largest, but the maximum strain of W-5 did not reach the yield strain due to the limitation of the height-width ratio.  
The valid data before the failure of the concrete strain gauges were selected and the strain curves of the reinforcement-concrete were plotted, as shown below, by specifically observing the synergy of each specimen. Firstly, when comparing Figure 13a with Figure 13e, it was obvious that the fitted length of the two materials was significantly shortened after adding the insulation board, which more intuitively indicated that the sandwich wall panels were less able to work together. Secondly, Figure 13a-c shows that the integrity of the W-2 specimen was significantly improved, while the change of W-3 was not significant,  
Figure 12: Longitudinal strain diagram.  
indicating that the fiber doping of 0.3% was more beneficial for improving the integrity of the specimens than the fiber doping of 0.4%. Finally, the difference between the fitted lengths of W-4 and W-1 was not significant, which indicated that the two load-bearing materials selected in this research had less influence on the integrity of the test wall panels.  
Figure 13: Steel-concrete strain diagram.