## 4 Numerical Simulation Analysis
### Seismic Response Influence of Structure-Electrical Equipment Interaction
#### 4.3.2 Displacement Responses  
Time-history curves of displacement on the top floor in M1 and M2 under El-Centro motion and Lanzhou motion are shown in Figure 22. Layer drift and layer drift angle of each layer under 0.40 g are shown in Table 11.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multicolumn{2}{c}{**Acceleration Amplification Factor**} & \multicolumn{1}{c}{**Soil Surface**} & \multicolumn{1}{c}{**Roof**} & \multicolumn{1}{c}{**Floor 3**} & \multicolumn{1}{c}{**Floor 2**} & \multicolumn{1}{c}{**Floor 1**} & \multicolumn{1}{c}{**Equipment Top**} \\ \hline \multirow{3}{*}{El-Centro motion} & \multirow{3}{*}{Structure} & X-direction & / & 0.817 & 0.82 & 0.823 & 0.824 & 2.600 \\  & & Y-direction & / & 0.498 & 0.582 & 0.661 & 0.728 & 1.194 \\  & & X-direction & 0.752 & 0.810 & 0.985 & 1.064 & 1.219 & / \\  & & Y-direction & 0.594 & 0.780 & 0.817 & 0.841 & 0.864 & / \\ \hline \multirow{3}{*}{Lanzhou motion} & \multirow{3}{*}{Structure} & X-direction & / & 0.805 & 0.828 & 0.845 & 0.865 & 2.554 \\  & & Y-direction & / & 0.502 & 0.515 & 0.545 & 0.599 & 1.096 \\  & & X-direction & 0.812 & 1.287 & 1.327 & 1.319 & 1.457 & / \\  & & Y-direction & 0.788 & 0.822 & 0.836 & 0.829 & 0.845 & / \\ \hline \multirow{3}{*}{Taft motion} & \multirow{3}{*}{Structure} & X-direction & / & 0.90 & 0.924 & 1.047 & 1.070 & 3.518 \\  & & Y-direction & / & 0.69 & 0.759 & 0.807 & 0.954 & 1.494 \\ \cline{1-1}  & & X-direction & 1.267 & 1.342 & 1.551 & 1.583 & 1.772 & / \\ \cline{1-1}  & & Y-direction & 1.021 & 1.036 & 1.049 & 1.093 & 1.177 & / \\ \hline \hline \end{tabular}
\end{table}
Table 10: Acceleration amplification factors.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & \multicolumn{2}{c}{**El-Centro Motion**} & \multicolumn{2}{c}{**Lanzhou Motion**} \\ \cline{3-5}  & & **M1** & **M2** & **M1** & **M2** \\ \hline \multirow{3}{*}{Floor 3} & layer drift in the X-direction & 3.110 & 2.737 & 2.949 & 2.598 \\  & layer drift angle in the X-direction & 1/1640 & 1/1863 & 1/1729 & 1/1970 \\  & layer drift in the Y-direction & 8.074 & 6.803 & 5.373 & 4.611 \\  & layer drift angle in the Y-direction & 1/632 & 1/750 & 1/949 & 1/1106 \\ \hline \multirow{3}{*}{Floor 2} & layer drift in the X-direction & 2.984 & 2.623 & 2.808 & 2.463 \\  & layer drift angle in the X-direction & 1/1609 & 1/1830 & 1/1709 & 1/1949 \\  & layer drift in the Y-direction & 7.660 & 6.454 & 5.185 & 4.510 \\  & layer drift angle in the Y-direction & 1/627 & 1/744 & 1/926 & 1/1064 \\ \hline \multirow{3}{*}{Floor 1} & layer drift in the X-direction & 3.135 & 2.754 & 2.952 & 2.610 \\  & layer drift angle in the X-direction & 1/1531 & 1/1743 & 1/1626 & 1/1839 \\ \cline{1-1}  & layer drift in the Y-direction & 8.132 & 6.796 & 5.402 & 4.621 \\ \cline{1-1}  & layer drift angle in the Y-direction & 1/590 & 1/706 & 1/889 & 1/1039 \\ \hline \hline \end{tabular}
\end{table}
Table 11: Layer drift (mm) and layer drift angle (rad).  
From Figure 22 and Table 11, it can be seen that layer drift and layer drift angles of M1 are larger than those of M2 under 0.40 g. The reason is mainly that electrical equipment produces additional inertial force and extra relative displacement, which leads to structure displacement increasing at the same time. Therefore, the interaction of structure-equipment should be involved in seismic design. Only when the effect of electrical equipment is taken into account is the seismic design of an underground substation safe.