## 2 Structural Parameters and Simulation Model
### Simulation Model  
A simulation model of the suspended filter capacitor was established by ABAQUS software v6.14.3, as shown in Figure 3. The structures which include the door-type gantry and the support frame used for the capacitors are simulated by B31 beam elements because they have obviously larger lengths than the cross-sectional dimensions. The simulation details of only the filter capacitor are shown in Figure 4. For the suspended insulators, they have less cross-sectional sizes, and only the three translational degrees of freedom of their two ends are restricted. Their ends can freely rotate which exhibits the significant axial stiffness, so truss elements are suitable for the simulation. In each layer of the filter capacitor, the capacitor modules that are installed on the support frame have a large stiffness with a high natural frequency. This research considers only their mass effect, since they exert weights to the suspension insulators through the frame, and this study focuses on the seismic responses of the suspension insulators instead of the capacitor modules. The stiffness influence of the capacitor modules is thus ignored. Hence, the capacitor modules are simplified as the lumped masses that are uniformly attached to the support frames, as shown by the green points in Figure 4.  
The steel gantry is composed of Q345 steel with a density of 7850 kg/m\({}^{3}\), an elastic modulus of 206 GPa, and a Poisson's ratio of 0.30. Its constitutive adopts a bilinear model with a yield platform, as shown in Figure 3b. It should be mentioned that the stress of the gantry induced by earthquakes generally would not exceed the yield strength because the possible local instability will occur prior to the yielding. Typically, there is no local instability for the components of the steel gantry unless the extreme strong earthquakes occur. Moreover, the composite insulator rods have a significantly lower safety factor \begin{table}
\begin{tabular}{c c c c} \hline \hline \multicolumn{2}{c}{**Component**} & \multicolumn{1}{c}{**Section Shape**} & \multicolumn{1}{c}{**Section Profile (Unit: mm)**} \\ \hline \multirow{3}{*}{Gantry beam} & Main beam & Pipe-shape & \(\Phi\)304\%6 \\ \cline{2-4}  & Braces & L-shape & L110810 \\ \cline{2-4}  & Suspended & T-shape & Web: L250810; Flange: L125510 \\ \hline \multirow{3}{*}{Gantry column} & Main column & Pipe-shape & \(\Phi\)304\%6 \\ \cline{2-4}  & Braces & L-shape & L110810 \\ \hline \multirow{3}{*}{Suspended insulators} & Top & Circle & \(\Phi\)30 (Effective diameter) \\ \cline{2-4}  & Middle & Circle & \(\Phi\)45 (Effective diameter) \\ \cline{2-4}  & Bottom & Circle & \(\Phi\)30 (Effective diameter) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The cross-section information of the overall filter capacitor. than the steel members. Therefore, this study considers only the failure of the insulators. For the steel materials, a bilinear constitutive model was employed for simplifying the computations, which also can accelerate the computation process. For the GFRP composite insulators, the density is 2160 kg/m\({}^{3}\), the elastic modulus is 60 GPa, and the Poisson's is also 0.30. Its constitutive adopts a linear-elastic model due to its brittle performance, as shown in Figure 3b, which has been approved in relevant literature about substation equipment modelling [3; 7; 14; 43; 44]. The overall damping ratio of the model is set to 0.02 according to the relevant literature [4; 7; 14] and codes [49; 50]. Some interactions should be provided to make the parts a whole. The horizontal parts and the vertical parts of the gantry are connected using Beam connectors because of the restriction for all degrees of freedom. Nevertheless, the suspension points of the filter capacitor on the gantry are set to MPC pin connections that only restrain the translational displacements. Furthermore, this type of connection is also employed for simulating the nodes between interlayered insulators.