## 3 Experimental Results and Discussion
### Displacement Responses  
The maximum relative displacements at each story and inter-story drift ratios of the specimen were derived from the data collected by displacement sensors installed at each floor for the different earthquake intensity levels. Only the displacement data within the PGA of 1.0 g were recorded because one part of the displacement sensors mounted on the steel column fell down when PGA reached 1.0 g. The collected time-history inter-story displacements of the test model at the bottom story under the PGA of 0.5 g, as an example for three seismic waves, are shown in Figure 19. Although the PGA was scaled to the same level for different seismic waves, the peak inter-story responses of the specimen subjected to the El Centro, Kobe, and Taft waves were still inconsistent and reached 0.53, 0.64, and 0.6 mm, respectively. This indicates that the influence of different seismic waves, possessing individual dynamic characteristics, on the structural performance varies from each other.  
The measured maximum inter-story drift ratios of the specimen, which are obtained by dividing the relative lateral displacements of two adjacent floors by the corresponding story height, for three seismic waves under different earthquake intensity levels are summarized in Table 9. The drift ratios at each story exhibited a gradually increasing trend with PGA growth. The average peak drift ratio of the test model subjected to a frequent earthquake (PGA = 0.35 g) was between 1/2310 and 1/1742, which was far less than the elastic limit value of 1/250 for the multi-story steel structure given by the GB 50011-2010. This indicates that the test structure meets the specific seismic fortification goal of \"no damage under minor earthquakes\". Furthermore, the corresponding value subjected to a rare  
Figure 18: Acceleration amplification factor. (**a**) El Centro wave; (**b**) Kobe wave; (**c**) Taft wave.  
earthquake (PGA = 1.0 g) was 1/233, indicating a satisfactory performance within the elastic-plastic allowable limit value of 1/50 described in this code. This also indicates that the structure meets another required goal of \"no collapsing under strong earthquakes\".  
The above results clearly reveal that the test model sufficiently satisfies the design requirements of the seismic code and possesses a significantly high structural safety reserve even when subjected to a strong earthquake, which is attributable to the abundant lateral stiffness and remarkable energy dissipation of the structure provided by the energy absorbers installed on the inner braces. It can be concluded that the prototype structure, as a novel horizontal lateral force-resisting system, is highly applicable to high-intensity seismic fortification areas.  
Figure 20 presents the variation trends of inter-story drift ratios at the top and bottom floors under different intensity levels of three seismic waves. It was found that the differences of drift ratios between the two stories under the lower intensity, before PGA < 0.7 g, were quite small; however, by further increasing the intensity level of the input seismic wave, these differences became more significant, and the measured drift ratios at the bottom story were dramatically higher than those at the top story. This indicates that the structural stiffness and strength at the bottom story are more flexible compared to the top story under the high-intensity level. In conclusion, it is recommended that the steel members at the lower stories be appropriately strengthened, by increasing the cross-sectional areas or adding more LYP plates in energy absorbers, to assure the uniform distribution of lateral stiffness along the vertical height direction for all stories, in order to avoid the occurrence of weak floors when performing the seismic design.  
Figure 19: Inter-story drifts at the bottom floor under PGA of 0.5 g for three seismic waves. (**a**) El Centro wave; (**b**) Kobe wave; (**c**) Taft wave.