## 4 Analysis and Comparison of Results
### Comparison of Acceleration Response Spectra  
FRS were calculated at locations A2 to A4 in each axial direction from the acceleration response time history to analyze and compare the seismic behavior of the electrical cabinet model between the experimental and numerical results. These were then analyzed using a damping ratio of 5% and a 1/12 octave bandwidth. Figures 20-22 present the FRS results along with those of the input seismic motion: black lines indicate the experimental results, red the numerical results, and blue the input seismic motion. In EQ1 (Figure 20), the experimental and numerical results had good agreement across all three directions. The FRS increased with height, particularly in the resonant frequency range of the horizontal directions (X and Y). In EQ2 (Figure 21), where no damage occurred despite increased input seismic motion, the experimental FRS exhibited greater amplification than the numerical FRS. While the vertical FRS remained consistent with the input seismic motion, the horizontal FRS exhibited notable amplification within the resonant frequency range, excluding low- and high-frequency ranges. Results from EQ1 and EQ2 demonstrated that amplification within the resonant frequency range generally increases with height. As represented in Figure 22, for EQ3--where damage occurred to the specimen--the experimental FRS showed greater amplification variations than the numerical FRS in the horizontal directions within the resonant frequency range. Moreover, the experimental FRS exhibited significant amplification across all three axes in the high-frequency range. Notably, whereas high-frequency amplification in the horizontal directions had increased gradually with input seismic motion, the vertical direction showed a sharp increase only during EQ3. Since global horizontal modes govern the cabinet's dynamic behavior, horizontal responses increased linearly with seismic motion in most frequency ranges, excluding low-frequency ranges. However, anchorage damage and impact effects contributed substantially to high-frequency and vertical amplification. These findings align with NUREG CR-5203, stating that vertical excitation rarely amplifies low frequencies but strongly affects high frequencies due to local modes and impacts [31]. Figure 19: Percentage difference of RMS ratio and RMQ ratio in A4: (**a**) \(R_{\text{RMS}}\); (**b**) \(R_{\text{RMQ}}\). Simply comparing the peak values of FRS may not be sufficient to evaluate the dynamic characteristics of electrical equipment under seismic loading. According to IEEE Std 693, ZPA represents the maximum acceleration in the high-frequency range beyond the RRS [56]. This study defined ZPA based on the highest frequency of the RRS and the performance capacity of the shaking table. Considering the shaking table's performance and the FRS octave bandwidth, the spectral acceleration at 45.25 Hz was adopted as the ZPA [10]. Additionally, using average and peak values within defined frequency ranges offers a practical means of evaluating acceleration amplification [31; 57]. However, if the frequency range is set too broadly, these values may be distorted and misrepresent actual system behavior. Thus, defining an appropriate frequency range is essential. Three frequency ranges were defined in this study for calculating average and peak values based on the frequency content of the input seismic motion and the cabinet's resonant frequencies: 1-10 Hz (low frequency), 10-20 Hz (resonant frequency), and 20-50 Hz (high frequency). According to Equation (6), the amplification ratios of the average value (R\({}_{\text{Avg}}\)), peak value (R\({}_{\text{Peak}}\)), and ZPA (R\({}_{\text{ZPA}}\)) were calculated for each defined frequency range and are summarized in Tables 9-11. As in Equation (5), these ratios indicate the response at each cabinet floor level (A2-A4) relative to the shaking table base (A1).