## 4 Results and Discussions
### Comparison of Seismic Demands by Different IGM Selection Procedures  
Figures 4-7 present the floor displacements, inter-story drift ratio, shear force, and bending moment computed by the IGMs from motion sets 2. The mean seismic demands of the set plus and minus one standard deviation of the demands, denoted as Mean + \(\sigma\) and Mean \(-\)\(\sigma\), are also plotted. It is clear from Figures 4-7 that the ratio of one standard deviation of seismic deformation to the mean deformation is much larger than that of seismically induced force. As a result, the seismic deformation is more sensitive to the variation of IGMs, compared with seismically induced force.  
As shown in Figure 4, the IGMs selected by the MGMS procedure and CM procedures caused a less and more conservative prediction of the floor displacement for all the stories of W1, respectively. Displacement calculated with UW-CM selected IGMs matched the best with the mean displacement of the set. When calculating the floor displacement of W2, NLRHA with IGMs chosen by all the selection methods led to an overestimated floor displacement of the set. The results of the two methods are shown in Figure 5. The comparison of the floor displacement of the set is shown in Figure 6. The comparison of the floor displacement of the set is shown in Figure 7. The comparison of the floor displacement of the set is shown in Figure 8.  
displacement. Still, the displacement by the MGMS-IGMs approximates the reference displacement the best. Floor displacement of W3 under motion set 2 calculated by IGMs selected by all the selection procedures is conservative. The displacements of MGMS-IGMs and VW-CM-IGMs are similar and close to the benchmark displacement.  
Considering the inter-story drift ratio of W1, the UW-CM selected IGMs led to the most reliable computation of the drift ratio, although the drift ratio computed with UW-CM-IGMs is conservation. The MGMS selected IGMs and VW-CM selected IGMs induced an under- and overestimation of the inter-story drift ratio of W1, respectively. The results of the MGMS-IGMs are closer to the mean drift ratio of the set. As for W2 and W3, inter-story drift ratios were overestimated by IGMs selected by all the IGM selection methods, but those computed with the MGMS-IGMs matched the best with the reference drift ratio. Comparing the inter-story drift ratio of W2 and W3 calculated by the CM procedures, the results from NLRHA with VW-CM selected IGMs have better approximations to the benchmark drift ratio.  
It can be found in Figures 7 and 8 that IGMs of MGMS and both CM procedures could ensure shear force and bending moment of all the RC shear wall structures approximate the reference forces well in the upper floors. For shear force at lower stories, the UW-CM selected IGMs, VW-CM selected IGMs and MGMS-selected IGMs led to the most reliable computation of shear force of W1, W2 and W3, respectively. The bending moment of W1 at lower stories computed with UW-CM-IGMs is the closest to the reference bending moment, and the bending moment of W2 and W3 at lower floors from NLRHA with MGMS-IGMs has the best approximation to the mean moment of the set.  
By comparing the seismically induced deformation and force of the wall structures under motion set 2, it is found that both MGMS procedure and CM procedures can select IGMs that ensure the seismic demands close to the mean demands of NLRHA with IGMs  
Figure 8: Deviations between the seismic demands from different IGM selection procedures and benchmark demands.  
of the whole motion set. Additionally, MGMS-IGMs tend to provide a more reliable estimation of the seismic demands than CM procedures selected IGMs.