# Shaking Table Tests of Suspended Structures Equipped with Viscous Dampers
## 4 Experimental Results and Discussion
### Displacement Response  
By analysing the data collected, the relative displacement of each layer can be obtained. Figure 10 shows the maximum relative displacements of each layer under three earthquake waves. The maximum relative displacement is the maximum difference between the displacement of each layer and the displacement of the shaking table under the same case. It can be seen that with the increase of the peak acceleration input and the height of the model structures, the relative displacement of each layer gradually increased. The comparison and analysis \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Seismic Input** & **PGA/g** & **Conventional Structure** & **Damping Structure** & **Reduction Effect (\%)** \\ \hline \multirow{3}{*}{El Centro} & 0.0525 & 0.70 & 0.09 & 87.14 \\  & 0.105 & 1.47 & 0.17 & 88.44 \\  & 0.210 & 3.00 & 0.35 & 88.33 \\  & 0.0525 & 0.51 & 0.09 & 82.35 \\ \multirow{3}{*}{Taft} & 0.105 & 1.28 & 0.12 & 90.63 \\  & 0.210 & 2.84 & 0.23 & 91.90 \\ \multirow{3}{*}{artificial wave} & 0.0525 & 0.84 & 0.12 & 85.71 \\  & 0.105 & 1.64 & 0.20 & 87.80 \\ \cline{1-1}  & 0.210 & 3.81 & 0.38 & 90.03 \\ \hline \hline \end{tabular} Note: Besides to the \(\%\) data and the gal added in the above table, the remaining data units are all m/s\({}^{2}\).  
\end{table} 
Table 6: Acceleration of first suspended floor. Figure 10: Maximum relative displacements of model structures. (**a**) Under El Centro; (**b**) under Taft; (**c**) under artificial wave. showed that under 7 and 8 frequent earthquakes, the relative displacement of each layer was not much different. However, under 9 frequent and 7, 8 rare earthquakes, the relative displacement of each layer increased significantly, and the difference was large. Furthermore, the response under the Taft wave was slightly larger than those of the other two waves, according to the maximum relative displacement of the same floors, and the maximum relative displacement of the tenth layer under 8 rare earthquake (PGA = 0.600 g) was 7.94 mm (Figure 10b). It can also be seen that the damping suspended structure (DSS) had a smaller relative displacement compared with that of the conventional suspended structure (CSS). Through analysis and calculation of the data in the above figure, it was found that: (i) the reduction effect of displacement at the model structure's top was 10.08-49.55%. This meant the dampers installed between the mega columns and suspended floors can help the primary structure to dissipate a lot of the input earthquake energy. Furthermore, displacement can also be considerably reduced. (ii) Different seismic wave inputs had different reduction effects. The damping suspended structure had the best reduction effect under 7 frequent earthquake of the Taft wave, while under 8 rare earthquake of the El Centro wave had the worst reduction effect. The reason may lie in the frequency characterization of the input earthquake excitation. Table 7 lists the maximum inter-story drift angles at different earthquake levels. Combined with Figure 10, it can be analysed that the positions of the maximum inter-story drift angle were mostly on the fifth floor. Additionally, the maximum inter-story drift angles of DSS were moderately less than those of CSS, except for the 7 frequent earthquake. The maximum inter-story drift angle was 1/724 when the conventional suspended structure was subjected to frequent earthquakes. The value exceeded the limit value of frame-core tube (i.e., 1/800 pursuant to GB50011 (2010)). However, for DSS, the value was reduced to 1/856, which met the limit requirement. Even under a rare earthquake, the corresponding value was 1/196, which was well within the limit value (i.e., 1/100). [PERSON] and [PERSON] (1976) studied 10 storey frames and found only small increases of displacements and inter-story drifts when p-delta effects were considered. The maximum inter-storey drifts under a rare earthquake in Table 7 were 1/138 and 1/196 respectively, which was far less than a maximum inter-story drift of only 1.2% of the story height.