# Shake Table Testing of Standard Cold-Formed Steel Storage Rack
## 3 Test Results
### Results of Phase Two: Shake Table Tests (Non-Scaled in The Time Domain)  
Figure 11 shows the structural responses under 20% to 80% intensity of the El-Centro earthquake record without scaling the time domain in terms of accelerations in the top and bottom levels and the lateral displacement of the rack frame. The experimental data of the back frame are only shown in this figure since the results of the front and back frame were almost identical, indicating that no rotation occurred during the tests. It was decided not to subject the specimen to a record greater than 80% of the El-Centro earthquake as the recorded acceleration of the top-level indicated a peak acceleration near \"1.0 g\", which was close to the capacity of the shake table under a 4-tonne structure. As shown in Figure 12, pallet sliding occurred in all specimens; however, no significant pallet movement was observed during the tests with intensities of 20% and 40%. Sliding was much more pronounced for intensities of 70% and 80%, with maximum sliding of around 27 mm and 18 mm in the top pallet, respectively. For this reason, the top pallet acceleration (Effective Design Acceleration (EDA) started to deviate from the acceleration that was recorded from the accelerometer mounted to the upright, as shown in Figure 12.  
Measured peak responses of the rack structure under seismic actions are tabulated in Table 3. A comparison between first and second level accelerations and displacements as well as the base shear of the rack system is also provided in Figure 13. The deformation of the structure under seismic actions indicates that the inter-storey drift of the first level is significantly higher than the second level inter-storey drift. This trend becomes more obvious by increasing the seismic intensity, which was indicative of a soft storey failure mode of the structure [43; 44; 45]. The base shear shown in Figure 13 is also calculated from the two accelerometers placed on the pallets at two levels times the mass of the pallets (rack mass is negligible). The base shear results demonstrate that the rate of increasing base shear is lower at higher intensities, though the base shear is generally enhanced by increasing the earthquake intensities. The difference between pallet and rack accelerations, presented in Table 3, is mainly due to the sliding of the pallet on the frame where this difference is more significant at higher intensities (owing to greater sliding of the pallet).  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Intensity** & **Top Level Disp.** & **1 st Level Disp.** & **Top Level Acc.** & **1 st Level Acc.** & **Top Level Pallet** & **1 st Level Pallet** \\
**(\% ELC)** & **(mm)** & **(mm)** & **(a/g)** & **(a/g)** & **Acc. (a/g)** & **Acc. (a/g)** \\ \hline
20 & 16.4 & 10.0 & 0.15 & 0.086 & 0.15 & 0.083 \\ \hline
40 & 47.5 & 39.1 & 0.31 & 0.23 & 0.33 & 0.23 \\ \hline
60 & 60.6 & 47.7 & 0.52 & 0.29 & 0.5 & 0.285 \\ \hline
70 & 68.4 & 52.6 & 0.61 & 0.35 & 0.54 & 0.327 \\ \hline
80 & 76.2 & 58 & 0.69 & 0.425 & 0.545 & 0.396 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Peak responses of rack structure under seismic actions—Non-Scaled in time domain.  
Figure 11: Structural response under 20–80% intensity of El-Centro (ELC) earthquake record—Non-Scaled in time domain: (**a**) accelerations in first level, (**b**) accelerations in top level, (**c**) displacements in frame.