# Resilience Assessment of Beijing Subway Lines under Extreme Precipitation Weather
## 4 Case Study
### Risk Analysis of Changping Line  
#### 4.2.1 Operating Parameter Importance Evaluation  
The function decomposition of the subway system is mainly carried out from the level of its equipment structure. Electromechanical equipment can be divided into nine subsystems, the signal system can be divided to sixteen subsystems, the communication system can be divided into nine subsystems, the power supply system can be divided into four subsystems, the line system can be divided into three subsystems, and the vehicle system can be divided into eight subsystems. Each subsystem has a corresponding function, which has the corresponding operating parameters.  
Figure 6: Schematic of the results of the subway line resilience assessment.  
In order to obtain the operating parameters, a failure mode and failure cause analysis should be conducted. In the process of failure mode analysis, referring to the current failure data recording in the subway system, the possible failure modes of the sub-systems in extreme rainfall are determined. In this case study, we analyze the failure data of the Changing Line in the Beijing subway, and the characteristics of each station are not considered. Thus, only the failure caused by extreme weather is considered.  
Combined with the failure data and failure modes, we can obtain the full set of the operating parameters corresponding to the sub-functions in extreme weather. In this case, we regard the sub-functions as the operating parameters. The relationship between failure modes and operating parameters of the electromechanical system is shown in Table 3. The rest of the failure modes analysis results of the Changping Line are shown in Appendix A.  
After clarifying the failure modes and corresponding failure causes, combined with the sub-functions of the subway system, the relationship of these parts of the electromechanical system can be obtained as shown in Table 4. The rest of the relationship results can be seen in Appendix A.  
\begin{table}
\begin{tabular}{c c c} \hline
**First Level Subsystem** & **Secondary Sub-Function** & **Failure Mode** \\ \hline \multirow{8}{*}{**Electromechanical system**} & Environment and equipment monitoring system & \multirow{2}{*}{Environment control failure} \\ \cline{2-3}  & Integrated monitoring system & \\ \cline{2-3}  & Escalators, moving walks, and barrier-free access & Elevator failure \\ \cline{2-3}  & Low-voltage lighting & Lighting failure \\ \cline{2-3}  & Automatic fire alarm system & Fire alarm failure \\ \cline{2-3}  & Water supply and drainage and fire & \\ \cline{2-3}  & extinguishing system & Failure of fire extinguishing equipment \\ \cline{2-3}  & Platform door & Platform door failure \\ \cline{2-3}  & Access control system & Water supply and drainage failure \\ \cline{2-3}  & Ventilation air conditioning and heating & HVAC equipment failure \\ \hline \end{tabular}
\end{table}
Table 3: The failure mode analysis results of the electromechanical system—examples.  
Figure 7: The structure of the subway system.  
After obtaining the sub-function and the corresponding failure modes, the importance evaluation of the sub-function is conducted. The importance evaluation of each sub-function is scored by experts on the Beijing subway system. Combined with the failure data in the past years and the expert experience during the subway operation, the score of the sub-function is obtained.  
Combined with Tables 3 and 4 and expert scoring, the importance evaluation results of the operating parameters can be obtained in Table 5. The rest of the scoring results can be seen in Appendix A.