## 2 Experimental Test Overview
### Experimental Results  
Table 2 summarizes the results of the visual inspections, which identified damage to the specimen following the resonant frequency search and the limit state seismic simulation tests. The resonant frequency search test is referred to as RES, and the limit state seismic simulation test as EQ throughout this study. The resonant frequency was determined using Equation (1) by deriving the transfer function (\(T_{ab}\)), which represents the ratio of the acceleration response at each measurement point to the input acceleration. It is defined as the frequency at which the peak magnitude and the phase angle shift (\(\pm\)90\({}^{\circ}\)) coincide; if they do not, it is defined as the frequency corresponding to the peak magnitude. In this context, \(P_{aa}\) denotes the power spectral density of the input signal, and \(P_{ba}\) represents the cross power spectral density between the input and output signals.  
\[T_{ab}(f)=\frac{P_{ba}(f)}{P_{aa}(f)} \tag{1}\]  
Before conducting EQ1, the resonant frequencies of the specimen with maintained structural integrity, measured during RES1, were recorded as 16.75 Hz in the X direction and 15.50 Hz in the Y direction. These values were within the target natural frequency range, indicating that the dynamic characteristics of the specimen appropriately reflected the design of the electrical cabinet model. No structural damage was observed through EQ2. However, during EQ3, two anchor bolts occurred plastic deformation and torque loosening. Approximately 5 mm of plastic deformation was confirmed by comparing the post-test bolt lengths to their original dimensions. The bolts were retightened to the initial torque value, and testing was resumed. RES4, conducted after the observed damage, reduced more resonant frequencies of 1.5%, 8.4%, and 0.6% in the X, Y, and \(Z\) directions, respectively, compared to RES1. These changes are graphed in Figure 7. Notably, the frequency variation in the horizontal directions was more than 10 times greater than that in the vertical direction, confirming that the dominant dynamic behavior of the cabinet was governed by global horizontal modes [24; 25]. The test was ultimately terminated during  
Figure 6: Experimental procedure and method.  
EQ4 due to the failure of three anchor bolts, following the earlier damage. The damage and failure patterns of the specimen are captured in Figure 8.  
\begin{table}
\begin{tabular}{c c c c c} \hline \multirow{2}{*}{**Test ID**} & \multicolumn{2}{c}{**Resonant Frequency (Hz)**} & \multirow{2}{*}{**Remarks**} \\  & **Side-Side** & **Front–Back** & **Vertical** & **(Visual Inspection)** \\  & **OO** & **(Y)** & **(Z)** & \\ \hline RES1 & 16.75 & 15.50 & 40.50 & - \\ \hline EQ1 (100\%) & & - & & - \\ \hline RES2 & 16.75 & 15.50 & 40.50 & - \\ \hline EQ2 (200\%) & & - & & - \\ \hline RES3 & 16.75 & 15.25 & 40.50 & - \\ \hline EQ3 (300\%) & & - & & - Damage to anchor bolts \\  & & - & & due to plastic deformation \\  & & & (2 units) \\ \hline RES4 & 16.50 & 14.25 & 40.25 & - \\ \hline EQ4 (350\%) & & - & & - Failure of anchor bolts (3 \\  & & - & & units) \\  & & & - Termination of the test \\ \hline \end{tabular}
\end{table}
Table 2: Shaking table test results.  
Figure 8: Failure mode of specimens.  
Figure 7: Changes in resonant frequency due to damage.