## 3 Shaking Table Tests
### Test Results and Analysis  
The damage of RC models was first assessed by their natural vibration characteristics after the structural models were subjected to all the earthquakes. Table 9 shows the first natural period values before and after the earthquakes for both models. For the story isolation model and non-isolated model, the first natural period respectively increased by 10.4% and 15.6% after the earthquakes. \begin{table}
\begin{tabular}{c c c} \hline \hline \multirow{2}{*}{**Model**} & \multicolumn{3}{c}{**The First Natural Period (s)**} \\ \cline{2-3}  & **Before Earthquake** & **After Earthquake** \\ \hline Story isolation Model & 0.77 & 0.85 \\ Non-isolated Model & 0.64 & 0.74 \\ \hline \hline \end{tabular}
\end{table} 
Table 9: Analysis results of first natural periods of the models. Figure 16: Hysteresis curve of rubber bearings: (**a**) LRB; (**b**) LNR. Table 10 shows the average peak acceleration values of each story at its mass center measured after both models were subjected to four consecutive earthquakes with PGAs of 0.30 g and 0.40 g. The two models present different acceleration values due to the influence of the isolation layer. Compared to the non-isolated model, the isolation model has much lower acceleration values regardless of PGA level (Figure 17). As expected, the first floor below the isolation layer has a negligible variation of acceleration, while the floors above the isolation layer have significant decreases in accelerations by more than 68%. It was also found that the PGA had a minor influence on the decreasing ratio of accelerations. Interestingly, it was found that, with the increase of PGA from 0.30 g to 0.40 g, the acceleration value of the story-isolated structure at each story generally increased much less than that of the non-isolated structure, as shown in Figure 18.  
Table 11 shows the average inter-story displacement values of each two stories at its mass center measured after both models were subjected to four consecutive earthquakes with PGAs of 0.30 g and 0.40 g. The two models present different inter-story displacement values due to the influence of the isolation layer, as shown in Figure 19 where the decreasing ratios of displacement values of the story isolation model when compared to the non-isolated model are presented. The results show that the displacement values of the story-isolation structure are significantly decreased from 74.2% to 91.2% (0.30 g) or from 69.6% to 92.3% (0.40 g), indicating a good damping effect due to the isolation layer. The maximum decrease of displacement was found between the base ground and the first  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Story**} & \multicolumn{2}{c}{**0.30 g**} & \multicolumn{2}{c}{**0.40 g**} \\ \cline{2-5}  & **Isolation Model (g)** & **Non-Isolated Model (g)** & **Isolation Model (g)** & **Non-Isolated Model (g)** \\ \hline
7 & 0.176 & 0.764 & 0.302 & 1.160 \\
6 & 0.159 & 0.648 & 0.246 & 1.071 \\
5 & 0.169 & 0.573 & 0.233 & 0.934 \\
4 & 0.145 & 0.532 & 0.191 & 0.813  
floor. Similar to the case of acceleration, the PGA also has a negligible effect on the decreasing of inter-story displacement. Further analysis shows that, under the PGA of 0.30 g and 0.40 g, the displacements of the substructure in the non-isolated model are both large. The corresponding displacement angles are 1/107 (i.e., 8.94/960) and 1/68 (i.e., 14.19/960), indicating a large horizontal displacement of the first story subjected to the earthquakes. The displacement angle value of 1/68 in the first floor when the