## 4 Experimental Results and Discussion
### Energy Dissipation Capacity  
The cumulative dissipated energy at each loading drift, i.e., the sum of all the energy dissipated until a certain loading drift, was calculated for the three tests, as shown in Figure 13a. At the beginning of the three tests, the specimen remained elastic, and the cumulative dissipated energy remained almost unchanged. Before the 0.67% drift level, the cumulative dissipated energy of Test RW1-1 was slightly higher than that of the other two tests because the infill grout at the wall-footing connection played a role in improving the energy dissipation capacity of the system for the first minor earthquake attack. Since the quantities of energy dissipaters in Tests RW1-2 and RW1-3 were more than that of Test RW1-1, their cumulative dissipated energy became higher after the yielding of the steel energy dissipaters. Local damage actually weakened the energy dissipation capacity; as a consequence, Test RW1-3 remained lower than Test RW1-2 in terms of cumulative dissipated energy. Figure 11: Degradation of stiffness. Figure 12: Degradation of strength. (**a**) Second loading cycle; (**b**) Third loading cycle. The equivalent viscous damping ratio, \(\zeta_{\rm eq}\), is widely employed to evaluate the energy dissipation capacity of members in many structural seismic experiments [5,16]. In this study, \(\zeta_{\rm eq}\) is employed and calculated for the first hysteresis loop at each drift level of the tests, as shown in Figure 13b. Test RW1-1 exhibited high \(\zeta_{\rm eq}\) in the early stage due to the effect of the infill grout. In the later stage, more energy dissipaters in both Tests RW1-2 and RW1-3 helped to increase \(\zeta_{\rm eq}\) rapidly, which meant that the energy dissipation of the system was mainly concentrated in the energy dissipaters. At the end of the test, the \(\zeta_{\rm eq}\) values of Test RW1-2 showed no noticeable decrease, indicating a high energy dissipation capacity. This indicates that an appropriate delay in the timing of partial energy dissipaters into operational status could improve the energy dissipation capacity of the system under major earthquake effects. The values of \(\zeta_{\rm eq}\) in Test RW1-3 were marginally higher than those in Test RW1-2 at the initial loading stage because the MBSFs in Test RW1-3 functioned earlier than those in Test RW1-2. However, due to local concrete crushing, \(\zeta_{\rm eq}\) of Test RW1-3 dropped significantly compared with that of Test RW1-2. The lateral displacement of the wall top was contributed to by both the flexural-shear deformation and the rigid body rotation of the wall panel [44]. The local concrete crushing before RW1-3 and Test RW-3 was conducted on the damaged wall panels. Therefore, compared with RW1-2, the contribution of the flexural-shear deformation of the wall panel to the lateral displacement of the wall top increased in Test RW 1-3, and the rigid body rotation decreased. Under the same loading drift level, the angle of rigid body rotation in RW1-3 was less than that in Test RW1-2, i.e., the uplifting height of the wall toe was less than that of Test RW1-2, the deformation of MBSFs was smaller, and the energy dissipation capacity was not developed sufficiently. The cumulative dissipated energy and equivalent viscous damping for the above-mentioned maximum story drift level of 1% [33] and limit drift level of 2.5% are summarized in Table 4. The cumulative dissipated energy of RW1-2 and RW1-3 showed little difference from that of RW1-1 at the drift level of 1%, whereas the difference was significant at the drift level of 2.5%, which indicated that MBSFs possessed considerable potential for enhancing the structural energy dissipation under extremely rare earthquakes. The comparison of \(\zeta_{\rm eq}\) demonstrated that the energy dissipation capacity of the structure achieved a superior level at 1% drift level. Although Belleville springs were incorporated into the MBSFs in RW1-2, the \(\zeta_{\rm eq}\) was 17.6% greater than that of RW1-1 at the drift level of 1% and 34.8% at the 2.5% drift level.